I won't go into all of the details, and the problem is fixed now. But
this morning when my daughter's alarm clock went off, the electricity
was off in some rooms of the house (including the master bedroom).
some rooms had plenty of juice. One room had 2 computers running.
They are on UPSs, but the UPSs weren't beeping.

Nothing on 240V that I tested was working, except that the clothes
dryer would spin (I don't know if it was heating). Our water pump (on
120V, I think) was not working. I checked the circuit breakers, and
they were OK. After I did that, the lights came back on in 3 rooms
that had not had electricity. A TV started repeatedly trying to turn
itself on, but it couldn't, and each time it caused the lights to
blink elsewhere. I had to unplug it.

Upstairs there was a UPS, but the computer was off. The UPS had
almost no load on it, just two wall warts, I think. I noticed that if
I turned on the overhead light in the adjoining room, the UPS would
start beeping.

Some of the electrical outlets showed their usual 120V and some of
them showed only 110V.

I called the electric company and reported a partial outage. They
found the problem, saying something about "dropping a leg", and dug up
the cable in the yard and fixed the problem.

What is "dropping a leg"?

As I understand it, you have 3 wires, two of them carry 240V and the
third is a ground back to the power company. You get 120V between
either of the hot wires and the ground. Is dropping a leg related to
that?

Why would some rooms have electricity and others not, in a situation
like this?

---
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According to Jud McCranie :
As I understand it, you have 3 wires, two of them carry 240V and the
third is a ground back to the power company.

I wouldn't describe it quite that way. You have a 240V circuit, with
a centre tap (normally called neutral, the fact that it's also grounded
isn't relevant in this context). You get 120V between either hot and
neutral. Each 120V circuit is the neutral plus a connection to one
or the other of the two hots.

Is dropping a leg related to that?

Yup. You lost one of the hot legs. 120V circuits "on that side" failed.
Since you only had one working conductor in your 240V circuits, they
didn't work either. Your dryer spun because the motor is 120V
(and it was on the working side), but the heating element didn't, because
one end of the element was disconnected.

Why would some rooms have electricity and others not, in a situation
like this?

Simply depends on which 120V "leg" they were attached to.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.

Someone named Jud McCranie
Proclaimed on Tue, 21 Sep 2004 15:25:20 -0400,

What is "dropping a leg"?

As I understand it, you have 3 wires, two of them carry 240V and the
third is a ground back to the power company. You get 120V between
either of the hot wires and the ground. Is dropping a leg related to
that?

Why would some rooms have electricity and others not, in a situation
like this?


A leg is 120V feeding your house, you have two. To get 220V (your
dryer) both are used. Usually half of the house is run on one (phase)
and the other is split. There is no method set in stone to distribute
the legs.

As to your voltage readings, that will fluctuate throughout the day
110 is the lowest it should go, but testing the circuit again at 3:00
AM would probably yield a reading of over 120 VAC. It is dependant on
usage in the area. The one constant is time, measured in Hertz, which
is 60 cycles per second, that is VERY accurate and the electric
company works hard to maintain (your analog clocks rely on it).

-Graham

On 21 Sep 2004 19:30:43 GMT, (Chris Lewis)
wrote:

Why would some rooms have electricity and others not, in a situation
like this?

Simply depends on which 120V "leg" they were attached to.

OK, so part of the 120V in the house could be on one leg and part on
the other, and that is why part of the house was working and the other
wasn't.

A related question: what kind of wave is on the 240V line - sine,
square, or other? IS the 120V the same, or is it only one side of the
240V wave?
---
Replace you know what by j to email

Interesting problem. First it sounds as if one of the hot legs is open. Then
you say the lights come on and turning one other devices causes lights or
other devices to be effected. That sounds like neutral problem - or the open
hot somehow reconnected, but in a high resistance state causing the odd
behavior.
John

"Jud McCranie" wrote in message
...
I won't go into all of the details, and the problem is fixed now. But
this morning when my daughter's alarm clock went off, the electricity
was off in some rooms of the house (including the master bedroom).
some rooms had plenty of juice. One room had 2 computers running.
They are on UPSs, but the UPSs weren't beeping.

Nothing on 240V that I tested was working, except that the clothes
dryer would spin (I don't know if it was heating). Our water pump (on
120V, I think) was not working. I checked the circuit breakers, and
they were OK. After I did that, the lights came back on in 3 rooms
that had not had electricity. A TV started repeatedly trying to turn
itself on, but it couldn't, and each time it caused the lights to
blink elsewhere. I had to unplug it.

Upstairs there was a UPS, but the computer was off. The UPS had
almost no load on it, just two wall warts, I think. I noticed that if
I turned on the overhead light in the adjoining room, the UPS would
start beeping.

Some of the electrical outlets showed their usual 120V and some of
them showed only 110V.

I called the electric company and reported a partial outage. They
found the problem, saying something about "dropping a leg", and dug up
the cable in the yard and fixed the problem.

What is "dropping a leg"?

As I understand it, you have 3 wires, two of them carry 240V and the
third is a ground back to the power company. You get 120V between
either of the hot wires and the ground. Is dropping a leg related to
that?

Why would some rooms have electricity and others not, in a situation
like this?

---
Replace you know what by j to email

From: Jud McCranie



On 21 Sep 2004 19:30:43 GMT, (Chris Lewis)
wrote:

Why would some rooms have electricity and others not, in a situation
like this?

Simply depends on which 120V "leg" they were attached to.

OK, so part of the 120V in the house could be on one leg and part on
the other, and that is why part of the house was working and the other
wasn't.

A related question: what kind of wave is on the 240V line - sine,
square, or other? IS the 120V the same, or is it only one side of the
240V wave?
---
Replace you know what by j to email

http://encyclopedia.thefreedictionar...ting%20current

On Tue, 21 Sep 2004 22:48:51 GMT, "JohnR" wrote:

Interesting problem. First it sounds as if one of the hot legs is open. Then
you say the lights come on and turning one other devices causes lights or
other devices to be effected.

That's what it was. I'd never heard of that until this morning. I
thought it was either a brown out or a poltergeist :-)

---
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According to Jud McCranie :
On 21 Sep 2004 19:30:43 GMT, (Chris Lewis)
wrote:

Why would some rooms have electricity and others not, in a situation
like this?

Simply depends on which 120V "leg" they were attached to.

OK, so part of the 120V in the house could be on one leg and part on
the other, and that is why part of the house was working and the other
wasn't.

Right.

A related question: what kind of wave is on the 240V line - sine,
square, or other? IS the 120V the same, or is it only one side of the
240V wave?

Both 120V and 240V circuits are sine wave when you compare one lead
to the other. Or when you compare any hot lead to neutral or ground.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.

According to JohnR :
Interesting problem. First it sounds as if one of the hot legs is open. Then
you say the lights come on and turning one other devices causes lights or
other devices to be effected. That sounds like neutral problem - or the open
hot somehow reconnected, but in a high resistance state causing the odd
behavior.

All the symptoms are explainable by a loose main feed hot in the panel (or
upstream) making intermittent (and poor) connection. Consistent with
"dropped a leg" terminology.

If the neutral comes loose, 120V circuits on _both_ legs start behaving
"funny", but 240V circuits are unaffected. By "funny", I mean that
some 120V circuits show low voltage (brownout) and some show high
voltage (lights overbright).

The former isn't very pleasant at all, but unless you're unlucky
(as per the intermittent connection), no damage will be done and
it doesn't present a shock hazard.

The latter can be _extremely_ dangerous when 120V devices try
to cope with anywhere up to 240V. Boom. Flames. Etc.

Not only that, under some circumstances, the entire grounding system in
the house can go "hot".

Whenever you see something this drastic happening, it's time to
kill the main breaker and get help ASAP.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.

Jud McCranie wrote in message . ..
On 21 Sep 2004 19:30:43 GMT, (Chris Lewis)
wrote:

Why would some rooms have electricity and others not, in a situation
like this?

Simply depends on which 120V "leg" they were attached to.

OK, so part of the 120V in the house could be on one leg and part on
the other, and that is why part of the house was working and the other
wasn't.

A related question: what kind of wave is on the 240V line - sine,
square, or other? IS the 120V the same, or is it only one side of the
240V wave?
---
Replace you know what by j to email


Each leg of the 240V service is a sine wave. They are 180 deg out of
phase with each other.

On 22 Sep 2004 04:28:17 GMT, (Chris Lewis)
wrote:

All the symptoms are explainable by a loose main feed hot in the panel (or
upstream) making intermittent (and poor) connection. Consistent with
"dropped a leg" terminology.

The power company dug up part of the cable running to my house and
fixed it there. They said that the cable TV company had cut the wire
and water got in it. (We've had a lot of rain lately.) I assume that
either the cable TV company repaired the cut, but didn't do it
properly to seal out the water, or partially cut it.

The latter can be _extremely_ dangerous when 120V devices try
to cope with anywhere up to 240V. Boom. Flames. Etc.

That's why I got on it right away. I thought it could possibly be
something wrong in my house. I called the electrician, and they asked
if the stove would come on. It wouldn't. They said to have the power
company come out and check it first, and that's what I did.

Whenever you see something this drastic happening, it's time to
kill the main breaker and get help ASAP.

I didn't kill the main breaker (in retrospect I should have). I did
call the electrician ASAP.

---
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On 21 Sep 2004 19:30:43 GMT, (Chris Lewis)
wrote:

Yup. You lost one of the hot legs. 120V circuits "on that side" failed. ...

If it was going bad (i.e. a bad connection), could that have made my
electric bill higher? The last two months it has been somewhat higher
than expected.

---
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From: Jud McCranie


On 21 Sep 2004 19:30:43 GMT, (Chris Lewis)
wrote:

Yup. You lost one of the hot legs. 120V circuits "on that side" failed.
...

If it was going bad (i.e. a bad connection), could that have made my
electric bill higher? The last two months it has been somewhat higher
than expected.


Is your meter before or after the damaged section?

On 22 Sep 2004 22:14:08 GMT, (HA HA Budys Here)
wrote:

Is your meter before or after the damaged section?

The damaged part of the cable was between the house and the
transformer.

---
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According to Jud McCranie :
On 21 Sep 2004 19:30:43 GMT, (Chris Lewis)
wrote:

Yup. You lost one of the hot legs. 120V circuits "on that side" failed. ...

If it was going bad (i.e. a bad connection), could that have made my
electric bill higher? The last two months it has been somewhat higher
than expected.

It's unlikely to have affected your electrical bill, except when it was
actually not connected at all.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.