All,

Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9
volts difference between phases when a 120 V 1.3 kW microwave is
running. Is this excessive, or acceptable?

Long story:

For the past few mornings, the UPS (APC Smart-UPS 600) in my office has
been switching on to battery power for a few minutes, even when the
lights in the rest of the house hadn't flickered or gone out. I
finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the
UPS while the UPS was running and found out it was probably tripping
on _over_voltage: the wall socket was delivering over 130 volts!

After a bit of experimentation, I discovered that the voltage went up
when the microwave in the kitchen was running, which is why it happened
in the mornings when the other half was making tea. The microwave is on
one of the 20 A kitchen circuits, while my office is on a 20 A
receptacle circuit with a couple of other rooms. It's a GE microwave,
about 10 years old, 120 V 1300 W per the nameplate. I also noticed that
the voltage rise was less pronounced when the central air conditioner was
running. The compressor is 240 V and is fused and breakered at 40 A.

Suspecting a loose neutral, I inspected the breaker panel. Nothing
looked out of place. I tried tightening all of the screws on the
neutral/ground bus bar. They all took a bit of tightening - less than
1/8 turn - but none were really badly loose. I made very sure that the
neutral coming in from the meter was tight at the bus bar. I have the
US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus
panel. It is original to the house (1969), although the breakers have
all been replaced. To my knowledge, the kitchen circuits are two
separate 20 A circuits with their own NM cable, not split like a
Canadian kitchen circuit.

After I tightened the screws, I went around in the house and made sure
most things were turned off. There were still a few computers running,
but the TV, stereo, lights, etc were all off. The air conditioner was
also shut off. I measured the voltage between the neutral/ground bus
bar and each hot lug with the microwave off and then with the microwave
running, heating about 8 oz (230 mL) of water in a coffee cup. I then
turned the A/C on and tried again. Results...

A/C uWave left right l-r notes
off off 122.5 123.2 -0.7 run 1
off on 126.3 117.6 8.7

off off 121.9 121.3 0.6 run 2
off on 126.1 116.7 9.4

on off 119.6 123.3 -3.7
on on 123.7 118.5 5.2

I know that the two sides of the service will very rarely be in exact
balance, but the 8 to 9 V difference seems somewhat high. Is this
considered within reasonable bounds, or should I have the power company
out? Or should I chase the wiring in the house further? When I moved
into the house 5+ years ago, most of the receptacles were original and
back-wired. I changed all of them that are regularly used for new spec
grade side-wired receptacles.

Out of curiosity, I measured the voltage drop across each breaker. This
was with most of the loads shut off, so it may not be too useful, but I
found no breaker over 100 mV and most under 40 mV.

Let me know if you need more information. Thanks for your help!

Matt Roberds

The gain on the hot leg opposite the microwave is about 1/2 the loss on the
microwave side. This make sense because the the neutral leg is 1/2 the
circuit for the microwave.

Let me get this straight - you are measuring at the panel? If so, the gains
and drop seems excessive.
John

wrote in message
news:Xiroe.12325$Wr.100@fed1read04...
All,

Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9
volts difference between phases when a 120 V 1.3 kW microwave is
running. Is this excessive, or acceptable?

Long story:

For the past few mornings, the UPS (APC Smart-UPS 600) in my office has
been switching on to battery power for a few minutes, even when the
lights in the rest of the house hadn't flickered or gone out. I
finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the
UPS while the UPS was running and found out it was probably tripping
on _over_voltage: the wall socket was delivering over 130 volts!

After a bit of experimentation, I discovered that the voltage went up
when the microwave in the kitchen was running, which is why it happened
in the mornings when the other half was making tea. The microwave is on
one of the 20 A kitchen circuits, while my office is on a 20 A
receptacle circuit with a couple of other rooms. It's a GE microwave,
about 10 years old, 120 V 1300 W per the nameplate. I also noticed that
the voltage rise was less pronounced when the central air conditioner was
running. The compressor is 240 V and is fused and breakered at 40 A.

Suspecting a loose neutral, I inspected the breaker panel. Nothing
looked out of place. I tried tightening all of the screws on the
neutral/ground bus bar. They all took a bit of tightening - less than
1/8 turn - but none were really badly loose. I made very sure that the
neutral coming in from the meter was tight at the bus bar. I have the
US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus
panel. It is original to the house (1969), although the breakers have
all been replaced. To my knowledge, the kitchen circuits are two
separate 20 A circuits with their own NM cable, not split like a
Canadian kitchen circuit.

After I tightened the screws, I went around in the house and made sure
most things were turned off. There were still a few computers running,
but the TV, stereo, lights, etc were all off. The air conditioner was
also shut off. I measured the voltage between the neutral/ground bus
bar and each hot lug with the microwave off and then with the microwave
running, heating about 8 oz (230 mL) of water in a coffee cup. I then
turned the A/C on and tried again. Results...

A/C uWave left right l-r notes
off off 122.5 123.2 -0.7 run 1
off on 126.3 117.6 8.7

off off 121.9 121.3 0.6 run 2
off on 126.1 116.7 9.4

on off 119.6 123.3 -3.7
on on 123.7 118.5 5.2

I know that the two sides of the service will very rarely be in exact
balance, but the 8 to 9 V difference seems somewhat high. Is this
considered within reasonable bounds, or should I have the power company
out? Or should I chase the wiring in the house further? When I moved
into the house 5+ years ago, most of the receptacles were original and
back-wired. I changed all of them that are regularly used for new spec
grade side-wired receptacles.

Out of curiosity, I measured the voltage drop across each breaker. This
was with most of the loads shut off, so it may not be too useful, but I
found no breaker over 100 mV and most under 40 mV.

Let me know if you need more information. Thanks for your help!

Matt Roberds

wrote in message
news:Xiroe.12325$Wr.100@fed1read04...

I know that the two sides of the service will very rarely be in exact
balance, but the 8 to 9 V difference seems somewhat high. Is this
considered within reasonable bounds, or should I have the power company
out? Or should I chase the wiring in the house further? When I moved
into the house 5+ years ago, most of the receptacles were original and
back-wired. I changed all of them that are regularly used for new spec
grade side-wired receptacles.

It is too high but I doubt the power co will help and they may cause you
more problems. I'd try to find a smart, honest electrician.

N

ees right! run the romex to the ground on the other side of the box
from where the wires come out of the box. Romix is tricky tho, so run a
wire from the one wire that is hooked to the romix in the box where the
other wires are.

Then hook it in somewher to an outlet somewher but not before the place
where an outlet hooks to something, and make double sure you dont hook
it to something that hooks to something before the box with the wires
in it hooks up to the other thing.

wrote:
All,

Short story: On a US-standard 240/120 100 A service, I am seeing 8 to
9 volts difference between phases when a 120 V 1.3 kW microwave is
running. Is this excessive, or acceptable?

Long story:

For the past few mornings, the UPS (APC Smart-UPS 600) in my office
has been switching on to battery power for a few minutes, even when
the lights in the rest of the house hadn't flickered or gone out. I
finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the
UPS while the UPS was running and found out it was probably tripping
on _over_voltage: the wall socket was delivering over 130 volts!

After a bit of experimentation, I discovered that the voltage went up
when the microwave in the kitchen was running, which is why it
happened in the mornings when the other half was making tea. The
microwave is on one of the 20 A kitchen circuits, while my office is
on a 20 A receptacle circuit with a couple of other rooms. It's a GE
microwave, about 10 years old, 120 V 1300 W per the nameplate. I
also noticed that the voltage rise was less pronounced when the
central air conditioner was running. The compressor is 240 V and is
fused and breakered at 40 A.

Suspecting a loose neutral, I inspected the breaker panel. Nothing
looked out of place. I tried tightening all of the screws on the
neutral/ground bus bar. They all took a bit of tightening - less than
1/8 turn - but none were really badly loose. I made very sure that
the neutral coming in from the meter was tight at the bus bar. I
have the US-standard 240/120 service at, I believe, 100 amps, and a
GE split-bus panel. It is original to the house (1969), although the
breakers have all been replaced. To my knowledge, the kitchen
circuits are two separate 20 A circuits with their own NM cable, not
split like a Canadian kitchen circuit.

After I tightened the screws, I went around in the house and made sure
most things were turned off. There were still a few computers
running, but the TV, stereo, lights, etc were all off. The air
conditioner was also shut off. I measured the voltage between the
neutral/ground bus bar and each hot lug with the microwave off and
then with the microwave running, heating about 8 oz (230 mL) of water
in a coffee cup. I then turned the A/C on and tried again.
Results...

A/C uWave left right l-r notes
off off 122.5 123.2 -0.7 run 1
off on 126.3 117.6 8.7

off off 121.9 121.3 0.6 run 2
off on 126.1 116.7 9.4

on off 119.6 123.3 -3.7
on on 123.7 118.5 5.2

I know that the two sides of the service will very rarely be in exact
balance, but the 8 to 9 V difference seems somewhat high. Is this
considered within reasonable bounds, or should I have the power
company out? Or should I chase the wiring in the house further?
When I moved into the house 5+ years ago, most of the receptacles
were original and back-wired. I changed all of them that are
regularly used for new spec grade side-wired receptacles.

Out of curiosity, I measured the voltage drop across each breaker.
This was with most of the loads shut off, so it may not be too
useful, but I found no breaker over 100 mV and most under 40 mV.

Let me know if you need more information. Thanks for your help!

Matt Roberds


I am not sure it is a loose neutral, although it could be. I don't
believe it is just one circuit, as the change is too little for that, it may
be the whole house or maybe the whole circuit with your neighbors. I would
not rule out a couple or more of those back wired devices causing at least
part of the problem. It may well be on the hot side as well as the neutral.

--
Joseph Meehan

Dia duit

Those voltage changes are excessive. Furthermore, those
voltages may have been larger than 9 volts, but for earth
ground which is keeping those voltage differences from
becoming excessive. IOW it may be a human safety problem.
gfretwell has provided an accurate solution that should not be
ignored. You have numbers and can reproduce the problem. The
utility therefore would have no problem finding and fixing the
problem the first time. Symptoms that are unacceptable and
should not be ignored.

This post assumes those numbers were recorded at the GE
panel.

wrote:
Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9
volts difference between phases when a 120 V 1.3 kW microwave is
running. Is this excessive, or acceptable?

Long story:

For the past few mornings, the UPS (APC Smart-UPS 600) in my office has
been switching on to battery power for a few minutes, even when the
lights in the rest of the house hadn't flickered or gone out. I
finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the
UPS while the UPS was running and found out it was probably tripping
on _over_voltage: the wall socket was delivering over 130 volts!

After a bit of experimentation, I discovered that the voltage went up
when the microwave in the kitchen was running, which is why it happened
in the mornings when the other half was making tea. The microwave is on
one of the 20 A kitchen circuits, while my office is on a 20 A
receptacle circuit with a couple of other rooms. It's a GE microwave,
about 10 years old, 120 V 1300 W per the nameplate. I also noticed that
the voltage rise was less pronounced when the central air conditioner was
running. The compressor is 240 V and is fused and breakered at 40 A.

Suspecting a loose neutral, I inspected the breaker panel. Nothing
looked out of place. I tried tightening all of the screws on the
neutral/ground bus bar. They all took a bit of tightening - less than
1/8 turn - but none were really badly loose. I made very sure that the
neutral coming in from the meter was tight at the bus bar. I have the
US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus
panel. It is original to the house (1969), although the breakers have
all been replaced. To my knowledge, the kitchen circuits are two
separate 20 A circuits with their own NM cable, not split like a
Canadian kitchen circuit.

After I tightened the screws, I went around in the house and made sure
most things were turned off. There were still a few computers running,
but the TV, stereo, lights, etc were all off. The air conditioner was
also shut off. I measured the voltage between the neutral/ground bus
bar and each hot lug with the microwave off and then with the microwave
running, heating about 8 oz (230 mL) of water in a coffee cup. I then
turned the A/C on and tried again. Results...

A/C uWave left right l-r notes
off off 122.5 123.2 -0.7 run 1
off on 126.3 117.6 8.7

off off 121.9 121.3 0.6 run 2
off on 126.1 116.7 9.4

on off 119.6 123.3 -3.7
on on 123.7 118.5 5.2
...

Matt,

I think you have a run-of-the-mill power quality issue that your APC caught.
The microwave appears to be causing the problem.

Microwave tubes fire at a very high frequency and can send AC noise back
into the whole system. Your APC is seeing this and reacting.

Solutions: Put the APC or the microwave on a different phase (switch
breakers around) and see if this helps. Otherwise, a more modern microwave
with better filtering maybe in order.

Jake

wrote in message
news:Xiroe.12325$Wr.100@fed1read04...
All,

Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9
volts difference between phases when a 120 V 1.3 kW microwave is
running. Is this excessive, or acceptable?

Long story:

For the past few mornings, the UPS (APC Smart-UPS 600) in my office has
been switching on to battery power for a few minutes, even when the
lights in the rest of the house hadn't flickered or gone out. I
finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the
UPS while the UPS was running and found out it was probably tripping
on _over_voltage: the wall socket was delivering over 130 volts!

After a bit of experimentation, I discovered that the voltage went up
when the microwave in the kitchen was running, which is why it happened
in the mornings when the other half was making tea. The microwave is on
one of the 20 A kitchen circuits, while my office is on a 20 A
receptacle circuit with a couple of other rooms. It's a GE microwave,
about 10 years old, 120 V 1300 W per the nameplate. I also noticed that
the voltage rise was less pronounced when the central air conditioner was
running. The compressor is 240 V and is fused and breakered at 40 A.

Suspecting a loose neutral, I inspected the breaker panel. Nothing
looked out of place. I tried tightening all of the screws on the
neutral/ground bus bar. They all took a bit of tightening - less than
1/8 turn - but none were really badly loose. I made very sure that the
neutral coming in from the meter was tight at the bus bar. I have the
US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus
panel. It is original to the house (1969), although the breakers have
all been replaced. To my knowledge, the kitchen circuits are two
separate 20 A circuits with their own NM cable, not split like a
Canadian kitchen circuit.

After I tightened the screws, I went around in the house and made sure
most things were turned off. There were still a few computers running,
but the TV, stereo, lights, etc were all off. The air conditioner was
also shut off. I measured the voltage between the neutral/ground bus
bar and each hot lug with the microwave off and then with the microwave
running, heating about 8 oz (230 mL) of water in a coffee cup. I then
turned the A/C on and tried again. Results...

A/C uWave left right l-r notes
off off 122.5 123.2 -0.7 run 1
off on 126.3 117.6 8.7

off off 121.9 121.3 0.6 run 2
off on 126.1 116.7 9.4

on off 119.6 123.3 -3.7
on on 123.7 118.5 5.2

I know that the two sides of the service will very rarely be in exact
balance, but the 8 to 9 V difference seems somewhat high. Is this
considered within reasonable bounds, or should I have the power company
out? Or should I chase the wiring in the house further? When I moved
into the house 5+ years ago, most of the receptacles were original and
back-wired. I changed all of them that are regularly used for new spec
grade side-wired receptacles.

Out of curiosity, I measured the voltage drop across each breaker. This
was with most of the loads shut off, so it may not be too useful, but I
found no breaker over 100 mV and most under 40 mV.

Let me know if you need more information. Thanks for your help!

Matt Roberds

wrote in message
news:Xiroe.12325$Wr.100@fed1read04...
All,

Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9
volts difference between phases when a 120 V 1.3 kW microwave is
running. Is this excessive, or acceptable?

Long story:

For the past few mornings, the UPS (APC Smart-UPS 600) in my office has
been switching on to battery power for a few minutes, even when the
lights in the rest of the house hadn't flickered or gone out. I
finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the
UPS while the UPS was running and found out it was probably tripping
on _over_voltage: the wall socket was delivering over 130 volts!

After a bit of experimentation, I discovered that the voltage went up
when the microwave in the kitchen was running, which is why it happened
in the mornings when the other half was making tea. The microwave is on
one of the 20 A kitchen circuits, while my office is on a 20 A
receptacle circuit with a couple of other rooms. It's a GE microwave,
about 10 years old, 120 V 1300 W per the nameplate. I also noticed that
the voltage rise was less pronounced when the central air conditioner was
running. The compressor is 240 V and is fused and breakered at 40 A.

Suspecting a loose neutral, I inspected the breaker panel. Nothing
looked out of place. I tried tightening all of the screws on the
neutral/ground bus bar. They all took a bit of tightening - less than
1/8 turn - but none were really badly loose. I made very sure that the
neutral coming in from the meter was tight at the bus bar. I have the
US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus
panel. It is original to the house (1969), although the breakers have
all been replaced. To my knowledge, the kitchen circuits are two
separate 20 A circuits with their own NM cable, not split like a
Canadian kitchen circuit.

After I tightened the screws, I went around in the house and made sure
most things were turned off. There were still a few computers running,
but the TV, stereo, lights, etc were all off. The air conditioner was
also shut off. I measured the voltage between the neutral/ground bus
bar and each hot lug with the microwave off and then with the microwave
running, heating about 8 oz (230 mL) of water in a coffee cup. I then
turned the A/C on and tried again. Results...

A/C uWave left right l-r notes
off off 122.5 123.2 -0.7 run 1
off on 126.3 117.6 8.7

off off 121.9 121.3 0.6 run 2
off on 126.1 116.7 9.4

on off 119.6 123.3 -3.7
on on 123.7 118.5 5.2

I know that the two sides of the service will very rarely be in exact
balance, but the 8 to 9 V difference seems somewhat high. Is this
considered within reasonable bounds, or should I have the power company
out? Or should I chase the wiring in the house further? When I moved
into the house 5+ years ago, most of the receptacles were original and
back-wired. I changed all of them that are regularly used for new spec
grade side-wired receptacles.

Out of curiosity, I measured the voltage drop across each breaker. This
was with most of the loads shut off, so it may not be too useful, but I
found no breaker over 100 mV and most under 40 mV.

Let me know if you need more information. Thanks for your help!

Matt Roberds


sounds very much like a high resistance in the neutral wire to the main
panel to me. id give the power company a shout first. might be a connection
gone bad in the meter or something.

wrote in message
news:Xiroe.12325$Wr.100@fed1read04...
All,

Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9
volts difference between phases when a 120 V 1.3 kW microwave is
running. Is this excessive, or acceptable?

Long story:

For the past few mornings, the UPS (APC Smart-UPS 600) in my office has
been switching on to battery power for a few minutes, even when the
lights in the rest of the house hadn't flickered or gone out. I
finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the
UPS while the UPS was running and found out it was probably tripping
on _over_voltage: the wall socket was delivering over 130 volts!

After a bit of experimentation, I discovered that the voltage went up
when the microwave in the kitchen was running, which is why it happened
in the mornings when the other half was making tea. The microwave is on
one of the 20 A kitchen circuits, while my office is on a 20 A
receptacle circuit with a couple of other rooms. It's a GE microwave,
about 10 years old, 120 V 1300 W per the nameplate. I also noticed that
the voltage rise was less pronounced when the central air conditioner was
running. The compressor is 240 V and is fused and breakered at 40 A.

Suspecting a loose neutral, I inspected the breaker panel. Nothing
looked out of place. I tried tightening all of the screws on the
neutral/ground bus bar. They all took a bit of tightening - less than
1/8 turn - but none were really badly loose. I made very sure that the
neutral coming in from the meter was tight at the bus bar. I have the
US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus
panel. It is original to the house (1969), although the breakers have
all been replaced. To my knowledge, the kitchen circuits are two
separate 20 A circuits with their own NM cable, not split like a
Canadian kitchen circuit.

After I tightened the screws, I went around in the house and made sure
most things were turned off. There were still a few computers running,
but the TV, stereo, lights, etc were all off. The air conditioner was
also shut off. I measured the voltage between the neutral/ground bus
bar and each hot lug with the microwave off and then with the microwave
running, heating about 8 oz (230 mL) of water in a coffee cup. I then
turned the A/C on and tried again. Results...

A/C uWave left right l-r notes
off off 122.5 123.2 -0.7 run 1
off on 126.3 117.6 8.7

off off 121.9 121.3 0.6 run 2
off on 126.1 116.7 9.4

on off 119.6 123.3 -3.7
on on 123.7 118.5 5.2

I know that the two sides of the service will very rarely be in exact
balance, but the 8 to 9 V difference seems somewhat high. Is this
considered within reasonable bounds, or should I have the power company
out? Or should I chase the wiring in the house further? When I moved
into the house 5+ years ago, most of the receptacles were original and
back-wired. I changed all of them that are regularly used for new spec
grade side-wired receptacles.

Out of curiosity, I measured the voltage drop across each breaker. This
was with most of the loads shut off, so it may not be too useful, but I
found no breaker over 100 mV and most under 40 mV.

Let me know if you need more information. Thanks for your help!

Matt Roberds


Hello Matt,

Sounds like a problem at or upstream of your panelboard. Your service
voltage should stay pretty much unchanged if a smallish load like your
microwave goes on or off. You could put a call in to your utility. Under
the circumstances, hopefully they'd send someone to have a look for free.

130V at your outlet is pretty crazy, too. We need a second opinion but I
would think that problems with a neutral connection should not show that
much effect, except maybe at the end of a circuit using that neutral (ie.
the circuit using the neutral or the multiple circuits using it if in fact
it is shared). Again, though, a neutral problem at or upstream of your
panelboard could cause this trouble.

Wait for a few more opinions though. I wouldn't take my word on this stuff.

j

wrote:

All,

Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9
volts difference between phases when a 120 V 1.3 kW microwave is
running. Is this excessive, or acceptable?

Long story:

For the past few mornings, the UPS (APC Smart-UPS 600) in my office has
been switching on to battery power for a few minutes, even when the
lights in the rest of the house hadn't flickered or gone out. I
finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the
UPS while the UPS was running and found out it was probably tripping
on _over_voltage: the wall socket was delivering over 130 volts!

After a bit of experimentation, I discovered that the voltage went up
when the microwave in the kitchen was running, which is why it happened
in the mornings when the other half was making tea. The microwave is on
one of the 20 A kitchen circuits, while my office is on a 20 A
receptacle circuit with a couple of other rooms. It's a GE microwave,
about 10 years old, 120 V 1300 W per the nameplate. I also noticed that
the voltage rise was less pronounced when the central air conditioner was
running. The compressor is 240 V and is fused and breakered at 40 A.

Suspecting a loose neutral, I inspected the breaker panel. Nothing
looked out of place. I tried tightening all of the screws on the
neutral/ground bus bar. They all took a bit of tightening - less than
1/8 turn - but none were really badly loose. I made very sure that the
neutral coming in from the meter was tight at the bus bar. I have the
US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus
panel. It is original to the house (1969), although the breakers have
all been replaced. To my knowledge, the kitchen circuits are two
separate 20 A circuits with their own NM cable, not split like a
Canadian kitchen circuit.

After I tightened the screws, I went around in the house and made sure
most things were turned off. There were still a few computers running,
but the TV, stereo, lights, etc were all off. The air conditioner was
also shut off. I measured the voltage between the neutral/ground bus
bar and each hot lug with the microwave off and then with the microwave
running, heating about 8 oz (230 mL) of water in a coffee cup. I then
turned the A/C on and tried again. Results...

A/C uWave left right l-r notes
off off 122.5 123.2 -0.7 run 1
off on 126.3 117.6 8.7

off off 121.9 121.3 0.6 run 2
off on 126.1 116.7 9.4

on off 119.6 123.3 -3.7
on on 123.7 118.5 5.2

I know that the two sides of the service will very rarely be in exact
balance, but the 8 to 9 V difference seems somewhat high. Is this
considered within reasonable bounds, or should I have the power company
out? Or should I chase the wiring in the house further? When I moved
into the house 5+ years ago, most of the receptacles were original and
back-wired. I changed all of them that are regularly used for new spec
grade side-wired receptacles.

Out of curiosity, I measured the voltage drop across each breaker. This
was with most of the loads shut off, so it may not be too useful, but I
found no breaker over 100 mV and most under 40 mV.

Let me know if you need more information. Thanks for your help!

Matt Roberds

i would check the ground electrode where the fuse box is that goes inside.
make sure it has a good seat to the earth.
secondly, it wouldn't hurt to run another ground rode on the other end
of the house and connect it to the ground in your romix of the outlets
some where but
not to the neutral because that is not legal. the neutral shall only
be reconnected to the earth ground in the box.
unless codes are different where you live!

On Sun, 05 Jun 2005 00:03:03 GMT, wrote:

All,

Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9
volts difference between phases when a 120 V 1.3 kW microwave is
running. Is this excessive, or acceptable?

Long story:

For the past few mornings, the UPS (APC Smart-UPS 600) in my office has
been switching on to battery power for a few minutes, even when the
lights in the rest of the house hadn't flickered or gone out. I
finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the
UPS while the UPS was running and found out it was probably tripping
on _over_voltage: the wall socket was delivering over 130 volts!

After a bit of experimentation, I discovered that the voltage went up
when the microwave in the kitchen was running, which is why it happened
in the mornings when the other half was making tea. The microwave is on
one of the 20 A kitchen circuits, while my office is on a 20 A
receptacle circuit with a couple of other rooms. It's a GE microwave,
about 10 years old, 120 V 1300 W per the nameplate. I also noticed that
the voltage rise was less pronounced when the central air conditioner was
running. The compressor is 240 V and is fused and breakered at 40 A.

Suspecting a loose neutral, I inspected the breaker panel. Nothing
looked out of place. I tried tightening all of the screws on the
neutral/ground bus bar. They all took a bit of tightening - less than
1/8 turn - but none were really badly loose. I made very sure that the
neutral coming in from the meter was tight at the bus bar. I have the
US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus
panel. It is original to the house (1969), although the breakers have
all been replaced. To my knowledge, the kitchen circuits are two
separate 20 A circuits with their own NM cable, not split like a
Canadian kitchen circuit.

After I tightened the screws, I went around in the house and made sure
most things were turned off. There were still a few computers running,
but the TV, stereo, lights, etc were all off. The air conditioner was
also shut off. I measured the voltage between the neutral/ground bus
bar and each hot lug with the microwave off and then with the microwave
running, heating about 8 oz (230 mL) of water in a coffee cup. I then
turned the A/C on and tried again. Results...

A/C uWave left right l-r notes
off off 122.5 123.2 -0.7 run 1
off on 126.3 117.6 8.7

off off 121.9 121.3 0.6 run 2
off on 126.1 116.7 9.4

on off 119.6 123.3 -3.7
on on 123.7 118.5 5.2

I know that the two sides of the service will very rarely be in exact
balance, but the 8 to 9 V difference seems somewhat high. Is this
considered within reasonable bounds, or should I have the power company
out? Or should I chase the wiring in the house further? When I moved
into the house 5+ years ago, most of the receptacles were original and
back-wired. I changed all of them that are regularly used for new spec
grade side-wired receptacles.

Out of curiosity, I measured the voltage drop across each breaker. This
was with most of the loads shut off, so it may not be too useful, but I
found no breaker over 100 mV and most under 40 mV.

Let me know if you need more information. Thanks for your help!

Matt Roberds

I had a similar situation, but even greater voltage difference with
even smaller loads. Found it to be present at the panel. Sure looked
like a loose neutral in the 120/240 service. I was pretty certain it
was power company connections. Called the power company.
Fortunately I was an electrician in a previous career and left a note
on the meter telling sparky what I thought the problem was. I was
real scared that they would blow me off figuring I was some homeowner
nut case. Thank goodness when they came they found the neutral loose
in their meter section and fixed it pronto.

Steve J. Noll | Ventura California
| The Used Equipment Dealer Directory:
| http://www.big-list.com
| The Peltier Device Information Site:
| http://www.peltier-info.com

mrobe:
You should immediately call up your Power Company and have them come
out and check the service to your meter.... they are responsible for
that... and may even check everything up to your breaker box if they
are nice guys.
I had a similar but more catastophic problem with a previous home I
owned; it turned out that their Neutral connections were faulty from
the power pole to the meter.... they did come into the home and check
everything in the breaker box as a courtesy. I was blowing out light
bulbs and eventually blew up a microwave oven.
Don't let this go... it will not get better, but only worse to the
point of destroying some of your appliances and equipment.... call your
power company right away.
electricitym
- - - - -

wrote:
All,

Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9
volts difference between phases when a 120 V 1.3 kW microwave is
running. Is this excessive, or acceptable?

Long story:

For the past few mornings, the UPS (APC Smart-UPS 600) in my office has
been switching on to battery power for a few minutes, even when the
lights in the rest of the house hadn't flickered or gone out. I
finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the
UPS while the UPS was running and found out it was probably tripping
on _over_voltage: the wall socket was delivering over 130 volts!

After a bit of experimentation, I discovered that the voltage went up
when the microwave in the kitchen was running, which is why it happened
in the mornings when the other half was making tea. The microwave is on
one of the 20 A kitchen circuits, while my office is on a 20 A
receptacle circuit with a couple of other rooms. It's a GE microwave,
about 10 years old, 120 V 1300 W per the nameplate. I also noticed that
the voltage rise was less pronounced when the central air conditioner was
running. The compressor is 240 V and is fused and breakered at 40 A.

Suspecting a loose neutral, I inspected the breaker panel. Nothing
looked out of place. I tried tightening all of the screws on the
neutral/ground bus bar. They all took a bit of tightening - less than
1/8 turn - but none were really badly loose. I made very sure that the
neutral coming in from the meter was tight at the bus bar. I have the
US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus
panel. It is original to the house (1969), although the breakers have
all been replaced. To my knowledge, the kitchen circuits are two
separate 20 A circuits with their own NM cable, not split like a
Canadian kitchen circuit.

After I tightened the screws, I went around in the house and made sure
most things were turned off. There were still a few computers running,
but the TV, stereo, lights, etc were all off. The air conditioner was
also shut off. I measured the voltage between the neutral/ground bus
bar and each hot lug with the microwave off and then with the microwave
running, heating about 8 oz (230 mL) of water in a coffee cup. I then
turned the A/C on and tried again. Results...

A/C uWave left right l-r notes
off off 122.5 123.2 -0.7 run 1
off on 126.3 117.6 8.7

off off 121.9 121.3 0.6 run 2
off on 126.1 116.7 9.4

on off 119.6 123.3 -3.7
on on 123.7 118.5 5.2

I know that the two sides of the service will very rarely be in exact
balance, but the 8 to 9 V difference seems somewhat high. Is this
considered within reasonable bounds, or should I have the power company
out? Or should I chase the wiring in the house further? When I moved
into the house 5+ years ago, most of the receptacles were original and
back-wired. I changed all of them that are regularly used for new spec
grade side-wired receptacles.

Out of curiosity, I measured the voltage drop across each breaker. This
was with most of the loads shut off, so it may not be too useful, but I
found no breaker over 100 mV and most under 40 mV.

Let me know if you need more information. Thanks for your help!

Matt Roberds

wrote in news:Xiroe.12325$Wr.100@fed1read04:

Matt, I'd call my utility company and have them check the neutral from your
meter back to the transformer. Had a similar situation with increasing
voltages on one leg, turned out to be a loose neutral at the transformer.


--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

http://www.machines-cnc.net:81/

On Sun, 05 Jun 2005 00:03:03 GMT wrote:

Results...

A/C uWave left right l-r notes
off off 122.5 123.2 -0.7 run 1
off on 126.3 117.6 8.7

off off 121.9 121.3 0.6 run 2
off on 126.1 116.7 9.4

on off 119.6 123.3 -3.7
on on 123.7 118.5 5.2

Go back and do this test again, but this time measure everything at
the breaker box entrance. That will allow you to determine whether the
cause is inside or outside your house.

Be careful!

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

On Sun, 05 Jun 2005 00:03:03 GMT, wrote:

All,

Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9
volts difference between phases when a 120 V 1.3 kW microwave is
running. Is this excessive, or acceptable?

Long story:

For the past few mornings, the UPS (APC Smart-UPS 600) in my office has
been switching on to battery power for a few minutes, even when the
lights in the rest of the house hadn't flickered or gone out. I
finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the
UPS while the UPS was running and found out it was probably tripping
on _over_voltage: the wall socket was delivering over 130 volts!

After a bit of experimentation, I discovered that the voltage went up
when the microwave in the kitchen was running, which is why it happened
in the mornings when the other half was making tea. The microwave is on
one of the 20 A kitchen circuits, while my office is on a 20 A
receptacle circuit with a couple of other rooms. It's a GE microwave,
about 10 years old, 120 V 1300 W per the nameplate. I also noticed that
the voltage rise was less pronounced when the central air conditioner was
running. The compressor is 240 V and is fused and breakered at 40 A.

Suspecting a loose neutral, I inspected the breaker panel. Nothing
looked out of place. I tried tightening all of the screws on the
neutral/ground bus bar. They all took a bit of tightening - less than
1/8 turn - but none were really badly loose. I made very sure that the
neutral coming in from the meter was tight at the bus bar. I have the
US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus
panel. It is original to the house (1969), although the breakers have
all been replaced. To my knowledge, the kitchen circuits are two
separate 20 A circuits with their own NM cable, not split like a
Canadian kitchen circuit.

After I tightened the screws, I went around in the house and made sure
most things were turned off. There were still a few computers running,
but the TV, stereo, lights, etc were all off. The air conditioner was
also shut off. I measured the voltage between the neutral/ground bus
bar and each hot lug with the microwave off and then with the microwave
running, heating about 8 oz (230 mL) of water in a coffee cup. I then
turned the A/C on and tried again. Results...

A/C uWave left right l-r notes
off off 122.5 123.2 -0.7 run 1
off on 126.3 117.6 8.7

off off 121.9 121.3 0.6 run 2
off on 126.1 116.7 9.4

on off 119.6 123.3 -3.7
on on 123.7 118.5 5.2

I know that the two sides of the service will very rarely be in exact
balance, but the 8 to 9 V difference seems somewhat high. Is this
considered within reasonable bounds, or should I have the power company
out? Or should I chase the wiring in the house further? When I moved
into the house 5+ years ago, most of the receptacles were original and
back-wired. I changed all of them that are regularly used for new spec
grade side-wired receptacles.

Out of curiosity, I measured the voltage drop across each breaker. This
was with most of the loads shut off, so it may not be too useful, but I
found no breaker over 100 mV and most under 40 mV.

Let me know if you need more information. Thanks for your help!

Before jumping to any conclusions, I would beg borrow or steal an
analog VOM and retake the measurements. A Simpson 260 leaps to mind.

DMMs sample the waveform and try to calculate the RMS voltage, but
spikes on the waveform can fool the mathematics giving you false
readings.

The power supply in the microwave might be putting spikes onto the
line and the meter is sensing them.

Another thing to try would be to open *all* of the breakers on one
phase so that the only return has to be the neutral. If the voltage
now goes *down* with increased load, i.e. when you turn on the
microwave, then the neutral is suspect.

"operator jay" wrote in message
...
snip

Hello Matt,

Sounds like a problem at or upstream of your panelboard. Your service
voltage should stay pretty much unchanged if a smallish load like your
microwave goes on or off. You could put a call in to your utility. Under
the circumstances, hopefully they'd send someone to have a look for free.

It sounds a lot like a loose neutral. The loose connection could be
anywhere from his panel up to the service transformer, including inside his
service panel.

130V at your outlet is pretty crazy, too. We need a second opinion but I
would think that problems with a neutral connection should not show that
much effect, except maybe at the end of a circuit using that neutral (ie.
the circuit using the neutral or the multiple circuits using it if in fact
it is shared). Again, though, a neutral problem at or upstream of your
panelboard could cause this trouble.

Wrong. I have seen much greater than 130V with loose neutral problems.
Theoretically, you could get nearly 240V on one leg and zero on the other
but realistically it doesn't get that bad.

Have a qualified electrician check the connections in your panel to make
sure they are tightened to the correct torque specifications. If that does
not help, contact your utility. Most will have a device that they can
temporarily put in the meter base to determine if a loose neutral exists on
the service drop. They remove your meter, and plug in the device. It has
two voltmeters (one for each leg) and a large load that they can switch
between the legs. Simple and effective.

Charles Perry P.E.

You have it right on. I also have seen this problem. Another characteristic
is that adding loads cause further unbalance. If you happen to have a couple
of 100W lights on one circuit and a toaster on the other, the voltage
distribution can get quite hairy as you indicate.

--
Don Kelly

remove the urine to answer
"Charles Perry" wrote in message
...

"operator jay" wrote in message
...
snip

Hello Matt,

Sounds like a problem at or upstream of your panelboard. Your service
voltage should stay pretty much unchanged if a smallish load like your
microwave goes on or off. You could put a call in to your utility.
Under
the circumstances, hopefully they'd send someone to have a look for
free.

It sounds a lot like a loose neutral. The loose connection could be
anywhere from his panel up to the service transformer, including inside
his
service panel.

130V at your outlet is pretty crazy, too. We need a second opinion but
I
would think that problems with a neutral connection should not show that
much effect, except maybe at the end of a circuit using that neutral
(ie.
the circuit using the neutral or the multiple circuits using it if in
fact
it is shared). Again, though, a neutral problem at or upstream of your
panelboard could cause this trouble.

Wrong. I have seen much greater than 130V with loose neutral problems.
Theoretically, you could get nearly 240V on one leg and zero on the other
but realistically it doesn't get that bad.

Have a qualified electrician check the connections in your panel to make
sure they are tightened to the correct torque specifications. If that
does
not help, contact your utility. Most will have a device that they can
temporarily put in the meter base to determine if a loose neutral exists
on
the service drop. They remove your meter, and plug in the device. It has
two voltmeters (one for each leg) and a large load that they can switch
between the legs. Simple and effective.

Charles Perry P.E.

In alt.home.repair wrote:
Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9
volts difference between phases when a 120 V 1.3 kW microwave is
running. Is this excessive, or acceptable?

All,

Thanks for the advice! To clarify something that was asked a few times,
all of the numbers in the chart I gave were measured directly at the
breaker panel. I took the cover off the panel and put one meter lead on
the neutral/ground bus bar and the other meter lead on one of the two
screw terminals where the hot wires from the meter are connected.

If it is a loose neutral, it almost has to be on the power company's
side. My breaker panel is right on the other side of the wall from the
meter... the supply wires into the breaker panel enter through the rear
of the box and I presume they are coming out the rear of the meter can
as well. The neutral connection to the neutral/ground bus bar in the
panel appears to be tight.

I will call the utility in the morning and see what they have to say.
I'll post back with further developments.

Thanks!

Matt Roberds

IMHO: Sounds that you have imbalanced circuit design within the residence
also, along with the possible loose neutral. Most moderately high current
devices in the kitchens and utility areas of a residence have priority
circuits specified to them, and are connected to the service in a way that
they cause minimal un-balancing of the overall system.
wrote in message
news:KTToe.34658$Wr.31578@fed1read04...
In alt.home.repair wrote:
Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9
volts difference between phases when a 120 V 1.3 kW microwave is
running. Is this excessive, or acceptable?

All,

Thanks for the advice! To clarify something that was asked a few times,
all of the numbers in the chart I gave were measured directly at the
breaker panel. I took the cover off the panel and put one meter lead on
the neutral/ground bus bar and the other meter lead on one of the two
screw terminals where the hot wires from the meter are connected.

If it is a loose neutral, it almost has to be on the power company's
side. My breaker panel is right on the other side of the wall from the
meter... the supply wires into the breaker panel enter through the rear
of the box and I presume they are coming out the rear of the meter can
as well. The neutral connection to the neutral/ground bus bar in the
panel appears to be tight.

I will call the utility in the morning and see what they have to say.
I'll post back with further developments.

Thanks!

Matt Roberds

wrote in message
news:KTToe.34658$Wr.31578@fed1read04...

I will call the utility in the morning and see what they have to say.
I'll post back with further developments.

Perhaps you have a grow op next door!

N

"Don Kelly" wrote in message
news:68Loe.1582115$6l.557950@pd7tw2no...
You have it right on. I also have seen this problem. Another
characteristic
is that adding loads cause further unbalance. If you happen to have a
couple
of 100W lights on one circuit and a toaster on the other, the voltage
distribution can get quite hairy as you indicate.


Ditto.

After a truck knocked a ground installed 240/120 transformer for my neighbor
and my house, I was having trouble with lights getting bright when the
furnace started. Called the utility right away, explained that they had
just re-set the transformer the night before, and what my lights were doing.

Service man showed up within the hour. Cut seal on meter and read voltages
there. Had me just turn on the coffee pot. That load was enough imbalance
that he could see there was a problem (and that it was on the utility side
of the service). Whole line-crew showed up within the next hour and found
the problem. A loose neutral when they re-installed the xfmr.

While talking with the guys, mentioned that it was real nice of them to come
out after 6:00 PM and all, but it could have waited. They replied that
faulty wiring on their side is a big liability issue and they had to get to
it ASAP. In the end, didn't cost me a dime.

daestrom

Neutral failed inside pole transformer. Homeowner had a
defective earth ground. Therefore house obtained neutral
through the gas meter - until gaskets eventually failed.
Fortunately no one was home when the house exploded. Neutral
failures and missing/defective earth ground should not be
treated lightly.

daestrom wrote:
...
After a truck knocked a ground installed 240/120 transformer for my neighbor
and my house, I was having trouble with lights getting bright when the
furnace started. Called the utility right away, explained that they had
just re-set the transformer the night before, and what my lights were doing.

Service man showed up within the hour. Cut seal on meter and read voltages
there. Had me just turn on the coffee pot. That load was enough imbalance
that he could see there was a problem (and that it was on the utility side
of the service). Whole line-crew showed up within the next hour and found
the problem. A loose neutral when they re-installed the xfmr.

While talking with the guys, mentioned that it was real nice of them to come
out after 6:00 PM and all, but it could have waited. They replied that
faulty wiring on their side is a big liability issue and they had to get to
it ASAP. In the end, didn't cost me a dime.

daestrom

On Mon, 06 Jun 2005 08:33:46 GMT wrote:

Thanks for the advice! To clarify something that was asked a few times,
all of the numbers in the chart I gave were measured directly at the
breaker panel. I took the cover off the panel and put one meter lead on
the neutral/ground bus bar and the other meter lead on one of the two
screw terminals where the hot wires from the meter are connected.

If it is a loose neutral, it almost has to be on the power company's
side. My breaker panel is right on the other side of the wall from the
meter... the supply wires into the breaker panel enter through the rear
of the box and I presume they are coming out the rear of the meter can
as well. The neutral connection to the neutral/ground bus bar in the
panel appears to be tight.

That was the right way to take the measurements, and you've done the
right thing in calling the utility. Your problem could be in the meter
box or at the pole, but either way, they are the right ones to fix it.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

In alt.home.repair wrote:
I will call the utility in the morning and see what they have to say.
I'll post back with further developments.

Short version: Utility claims they fixed something and the test results
are better (3.1 V difference as opposed to 9.4 V), but I'm still not
sure what exactly they fixed.

Long version:

I called the utility on Monday afternoon about 2 PM, then hung around
the house, hoping to catch the lineman and hear what he found, if
anything. The utility did try to call at 7:03 PM per the Caller ID.
I was in another room and the machine picked up before I did; I stopped
the machine and picked up and got silence. By 9 PM I hadn't heard
anything, hadn't noticed the lights going out, and I hadn't retested,
so I decided to call again today (Tuesday).

I called today at about 2 PM and the call center rep said that they came
out yesterday and "repaired a connection at the weatherhead". To me,
the "weatherhead" is the thing at the top of the conduit running up from
my meter, where the wires make almost a 180 degree turn and go out
through a plastic disc with holes in it. I went out and looked at it
from the ground and couldn't see anything different. I can't see my
connections at the pole very well, so I'm not sure if anything changed
there.

I decided to retest. I measured again at the breaker panel, with most
of the loads in the house shut off except as noted. The results we

A/C uWave left right l-r notes
off off 120.4 118.7 1.7 run 1
off on 120.9 117.8 3.1
on off 118.7 118.2 0.5
on on 119.0 117.1 1.9

off off 121.2 119.7 1.5 run 2
off on 121.5 119.0 2.5
on off 119.5 119.5 0.0
on on 120.0 118.2 1.8

The 3.1 volt spread does seem to be an improvement from the previous
result, which was a 13.1 volt spread (-3.7 to +9.4).

I climbed up on the roof and inspected the connections at the top of the
meter conduit. I have an insulated crimp splice on each hot wire, and
a bare crimp splice on the neutral wire. I'm pretty sure that the hot
wire splices weren't changed, as each one has a small crack in the
insulation that has been there for a while, and I'm assuming the lineman
would have replaced the insulation sleeve if he installed a new
connector. I am not sure if the bare neutral splice was changed; even
though I haven't inspected it carefully in the past, it doesn't _look_
brand new - there are some black spots (oxidation?) on it, and the
engraved markings are easy to read because dirt seems to have
accumulated in the grooves. There weren't any telltale bits of wire
lying on the roof or shiny places on the wire next to the connector,
either. The thing that holds the mechanical tension on the bare netural
wire (basically a ramp on the wire and a mating ramp with a metal loop
around the conduit) hasn't been changed.

I'm also pretty sure that they didn't do anything to the meter. First,
my lights didn't go out. Also, even though I didn't write down the
serial number on the meter seal before I called, it's at least the same
type of seal, and the metal loop through the meter can tab isn't shiny
as I would expect with a new seal.

It's entirely possible that the bad connection was at the pole and I'm
mistaken about where the "weatherhead" is, or that the path from the
lineman to the call center four states away is lossy and noisy. I'm
curious to know what exactly was repaired, but the test results seem
to show an improvement, so maybe I should just be happy.

Thanks to all for the advice and assistance!

Matt Roberds

wrote in message
newsrppe.55421$Wr.10721@fed1read04...
In alt.home.repair wrote:
I will call the utility in the morning and see what they have to say.
I'll post back with further developments.

snip

I called today at about 2 PM and the call center rep said that they came
out yesterday and "repaired a connection at the weatherhead". To me,
the "weatherhead" is the thing at the top of the conduit running up from
my meter, where the wires make almost a 180 degree turn and go out
through a plastic disc with holes in it.

That would be it.

I went out and looked at it
from the ground and couldn't see anything different. I can't see my
connections at the pole very well, so I'm not sure if anything changed
there.

I decided to retest. I measured again at the breaker panel, with most
of the loads in the house shut off except as noted. The results we

A/C uWave left right l-r notes
off off 120.4 118.7 1.7 run 1
off on 120.9 117.8 3.1
on off 118.7 118.2 0.5
on on 119.0 117.1 1.9

off off 121.2 119.7 1.5 run 2
off on 121.5 119.0 2.5
on off 119.5 119.5 0.0
on on 120.0 118.2 1.8

The 3.1 volt spread does seem to be an improvement from the previous
result, which was a 13.1 volt spread (-3.7 to +9.4).

You don't look at the spread as much as the change in voltage when a single
phase load is turned on verses when it is off. If the AC is 240 V, it
really matters little if it is on or off.

The voltages look perfectly normal now.

I climbed up on the roof and inspected the connections at the top of the
meter conduit. I have an insulated crimp splice on each hot wire, and
a bare crimp splice on the neutral wire. I'm pretty sure that the hot
wire splices weren't changed, as each one has a small crack in the
insulation that has been there for a while, and I'm assuming the lineman
would have replaced the insulation sleeve if he installed a new
connector. I am not sure if the bare neutral splice was changed; even
though I haven't inspected it carefully in the past, it doesn't _look_
brand new - there are some black spots (oxidation?) on it, and the
engraved markings are easy to read because dirt seems to have
accumulated in the grooves. There weren't any telltale bits of wire
lying on the roof or shiny places on the wire next to the connector,
either. The thing that holds the mechanical tension on the bare netural
wire (basically a ramp on the wire and a mating ramp with a metal loop
around the conduit) hasn't been changed.

Probably recrimped the neutral connector.


I'm also pretty sure that they didn't do anything to the meter. First,
my lights didn't go out. Also, even though I didn't write down the
serial number on the meter seal before I called, it's at least the same
type of seal, and the metal loop through the meter can tab isn't shiny
as I would expect with a new seal.

New seals need not be shiny. They sit in a bin in the toolbox of a truck
for months or years before installation. Also, he could open your
meterbase, tighten the connections, and close the meterbase without ever
interrupting your power, unless you have a 60amp meter base.

It's entirely possible that the bad connection was at the pole and I'm
mistaken about where the "weatherhead" is, or that the path from the
lineman to the call center four states away is lossy and noisy. I'm
curious to know what exactly was repaired, but the test results seem
to show an improvement, so maybe I should just be happy.

Thanks to all for the advice and assistance!

Matt Roberds


Charles Perry P.E.

wrote in message
newsrppe.55421$Wr.10721@fed1read04...
In alt.home.repair wrote:
I will call the utility in the morning and see what they have to say.
I'll post back with further developments.

Short version: Utility claims they fixed something and the test results
are better (3.1 V difference as opposed to 9.4 V), but I'm still not
sure what exactly they fixed.

Long version:

I called the utility on Monday afternoon about 2 PM, then hung around
the house, hoping to catch the lineman and hear what he found, if
anything. The utility did try to call at 7:03 PM per the Caller ID.
I was in another room and the machine picked up before I did; I stopped
the machine and picked up and got silence. By 9 PM I hadn't heard
anything, hadn't noticed the lights going out, and I hadn't retested,
so I decided to call again today (Tuesday).

I called today at about 2 PM and the call center rep said that they came
out yesterday and "repaired a connection at the weatherhead". To me,
the "weatherhead" is the thing at the top of the conduit running up from
my meter, where the wires make almost a 180 degree turn and go out
through a plastic disc with holes in it. I went out and looked at it
from the ground and couldn't see anything different. I can't see my
connections at the pole very well, so I'm not sure if anything changed
there.

I decided to retest. I measured again at the breaker panel, with most
of the loads in the house shut off except as noted. The results we

A/C uWave left right l-r notes
off off 120.4 118.7 1.7 run 1
off on 120.9 117.8 3.1
on off 118.7 118.2 0.5
on on 119.0 117.1 1.9

off off 121.2 119.7 1.5 run 2
off on 121.5 119.0 2.5
on off 119.5 119.5 0.0
on on 120.0 118.2 1.8

The 3.1 volt spread does seem to be an improvement from the previous
result, which was a 13.1 volt spread (-3.7 to +9.4).

I climbed up on the roof and inspected the connections at the top of the
meter conduit. I have an insulated crimp splice on each hot wire, and
a bare crimp splice on the neutral wire. I'm pretty sure that the hot
wire splices weren't changed, as each one has a small crack in the
insulation that has been there for a while, and I'm assuming the lineman
would have replaced the insulation sleeve if he installed a new
connector. I am not sure if the bare neutral splice was changed; even
though I haven't inspected it carefully in the past, it doesn't _look_
brand new - there are some black spots (oxidation?) on it, and the
engraved markings are easy to read because dirt seems to have
accumulated in the grooves. There weren't any telltale bits of wire
lying on the roof or shiny places on the wire next to the connector,
either. The thing that holds the mechanical tension on the bare netural
wire (basically a ramp on the wire and a mating ramp with a metal loop
around the conduit) hasn't been changed.

I'm also pretty sure that they didn't do anything to the meter. First,
my lights didn't go out. Also, even though I didn't write down the
serial number on the meter seal before I called, it's at least the same
type of seal, and the metal loop through the meter can tab isn't shiny
as I would expect with a new seal.

It's entirely possible that the bad connection was at the pole and I'm
mistaken about where the "weatherhead" is, or that the path from the
lineman to the call center four states away is lossy and noisy. I'm
curious to know what exactly was repaired, but the test results seem
to show an improvement, so maybe I should just be happy.

Thanks to all for the advice and assistance!

Matt Roberds

No your not mistaken on what the weather head is.

I once had a ******* open delta service (commercial service) that lost a
leg. It was dam near mid night before the line man showed.
He got out of the truck with an attitude and was going to teach me something
RIGHT NOW. He started spewing out the right way of testing the system as I
kept my temper and held my tongue.
He got the same readings as I had. Lost a phase. Then I turned on the 8 inch
spot light on the roof of my service van. The light went to the transformer
with one of the feeders hanging down cause the terminal on the transformer
was gone. Absolute silence from the line man. They had to replace the
transformer.
Be happy that there is an improvement. Doubtful you will know the truth to
what they really did.
Never got so much as a oops from him.

Kudos. Not that the problem is fixed, but more important,
how you approached the problem. With intent and solutions to
get it solved the first time. Others should appreciate why
your attitude - how problem was addressed - was so
productive. Also important: a (potentially) major problem was
solved before it could happen.

wrote:
Short version: Utility claims they fixed something and the test results
are better (3.1 V difference as opposed to 9.4 V), but I'm still not
sure what exactly they fixed.

Long version:

I called the utility on Monday afternoon about 2 PM, then hung around
the house, hoping to catch the lineman and hear what he found, if
anything. The utility did try to call at 7:03 PM per the Caller ID.
I was in another room and the machine picked up before I did; I stopped
the machine and picked up and got silence. By 9 PM I hadn't heard
anything, hadn't noticed the lights going out, and I hadn't retested,
so I decided to call again today (Tuesday).

I called today at about 2 PM and the call center rep said that they came
out yesterday and "repaired a connection at the weatherhead". ...

wrote in message
newsrppe.55421$Wr.10721@fed1read04...

I called today at about 2 PM and the call center rep said that they came
out yesterday and "repaired a connection at the weatherhead". To me,
the "weatherhead" is the thing at the top of the conduit running up from
my meter

Yup.

N

According to :
In alt.home.repair wrote:
I will call the utility in the morning and see what they have to say.
I'll post back with further developments.

Short version: Utility claims they fixed something and the test results
are better (3.1 V difference as opposed to 9.4 V), but I'm still not
sure what exactly they fixed.

You did exactly the right things.

For future reference: power codes require that the voltage varies no
more than approximately 3-5% from a nominal 240V at the panel under
worst-case conditions (ie: max power on one leg, zero on the other).
Another 3-5% are permitted at the end of the circuits.

[Precise values of permitted variance will change from jurisdiction
to jurisdiction.]

[Note all of the below is assuming you're measuring the voltages on
the main bus bars. If you're measuring at a circuit-end, double them.]

What that means, for example, is that the leg voltage at the panel
on a given leg should drop no more than 4-5 volts even when max power
on that leg, and zero load on the other. Given resistance in the
neutral, _half_ of that would be the neutral "going towards" the
maxed out leg, and half of that would be the maxed out leg "going
towards" neutral.

In otherwords, (100A panel right?), drawing 100A on one leg, zero
on the other, the fully loaded side could drop as much as 4-5 volts
(hot-neutral), leg-to-leg drop by as much as 2-3V, and unloaded side
to neutral voltage could _rise_ as much as 2-3V.

If the neutral-leg voltage varies more than half of the leg-to-leg
does (see (1) below), you have a loose neutral.

All that said, there are several caveats:

1) Extreme caution should be taken when taking the voltage levels
off your voltmeter. There are a number of ways they can misread,
and many voltmeters are simply not that accurate at measuring RMS
volts. So, don't take a few volts either way seriously.

2) While voltmeters can be fooled by back EMI (line noise), for
the most part it will be minor. To minimize these affects, use
resistive loads (rather than motor or electronic). Ie: heaters.

3) While it may seem that you were approximately "on" those
numbers, remember that your test loads were MUCH less than 100A,
so the problem you were seeing was much worse than the allowable
variance. Frankly, if your wiring was good, given the loads
you were able to test with, I'd expect the voltage variation to
be a volt at most, but, generally speaking, you can't rely
on your voltmeter to that high a degree of accuracy.
Most times the variation will be extremely obvious. You were
on the low side of "obvious" [+]

While your "fixed state" is _still_ outside of what I suggested
above, it's a considerable improvement over what it was, and I'd
be doubtful of taking it too seriously. That said, keep an
eye on it.

[+] The high side of obvious is having a lightbulb on one
leg expire with a BRIGHT flash when you try to turn on
something on the other leg - and that "something" doesn't work.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.

I'd recommend, you don't use a UPS, it's useless and a pain in the ass.One
friend of mine who runs a computer shop, told me that a customer had a
kaputt ups after a power outage.When the power came back, the UPS went
poof.All modern hard discs have an auto parking function in case of power
failure, I think, and one should save everything regularly, I think.

--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
Ï Ýãñáøå óôï ìÞíõìá
news:Xiroe.12325$Wr.100@fed1read04...
All,

Short story: On a US-standard 240/120 100 A service, I am seeing 8 to 9
volts difference between phases when a 120 V 1.3 kW microwave is
running. Is this excessive, or acceptable?

Long story:

For the past few mornings, the UPS (APC Smart-UPS 600) in my office has
been switching on to battery power for a few minutes, even when the
lights in the rest of the house hadn't flickered or gone out. I
finally put a meter (Metex ME-11 DMM) on the wall outlet supplying the
UPS while the UPS was running and found out it was probably tripping
on _over_voltage: the wall socket was delivering over 130 volts!

After a bit of experimentation, I discovered that the voltage went up
when the microwave in the kitchen was running, which is why it happened
in the mornings when the other half was making tea. The microwave is on
one of the 20 A kitchen circuits, while my office is on a 20 A
receptacle circuit with a couple of other rooms. It's a GE microwave,
about 10 years old, 120 V 1300 W per the nameplate. I also noticed that
the voltage rise was less pronounced when the central air conditioner was
running. The compressor is 240 V and is fused and breakered at 40 A.

Suspecting a loose neutral, I inspected the breaker panel. Nothing
looked out of place. I tried tightening all of the screws on the
neutral/ground bus bar. They all took a bit of tightening - less than
1/8 turn - but none were really badly loose. I made very sure that the
neutral coming in from the meter was tight at the bus bar. I have the
US-standard 240/120 service at, I believe, 100 amps, and a GE split-bus
panel. It is original to the house (1969), although the breakers have
all been replaced. To my knowledge, the kitchen circuits are two
separate 20 A circuits with their own NM cable, not split like a
Canadian kitchen circuit.

After I tightened the screws, I went around in the house and made sure
most things were turned off. There were still a few computers running,
but the TV, stereo, lights, etc were all off. The air conditioner was
also shut off. I measured the voltage between the neutral/ground bus
bar and each hot lug with the microwave off and then with the microwave
running, heating about 8 oz (230 mL) of water in a coffee cup. I then
turned the A/C on and tried again. Results...

A/C uWave left right l-r notes
off off 122.5 123.2 -0.7 run 1
off on 126.3 117.6 8.7

off off 121.9 121.3 0.6 run 2
off on 126.1 116.7 9.4

on off 119.6 123.3 -3.7
on on 123.7 118.5 5.2

I know that the two sides of the service will very rarely be in exact
balance, but the 8 to 9 V difference seems somewhat high. Is this
considered within reasonable bounds, or should I have the power company
out? Or should I chase the wiring in the house further? When I moved
into the house 5+ years ago, most of the receptacles were original and
back-wired. I changed all of them that are regularly used for new spec
grade side-wired receptacles.

Out of curiosity, I measured the voltage drop across each breaker. This
was with most of the loads shut off, so it may not be too useful, but I
found no breaker over 100 mV and most under 40 mV.

Let me know if you need more information. Thanks for your help!

Matt Roberds