Here's a bit of an old chestnut - but with a responsibility angle.

My girlfriend lives in a Housing Authority house.
Those nice people have done a bit of updating, including the consumer
unit.

Now, when she puts the washer on, the CU frequently trips.
The housing authority say, it's her appliance(s).
She says it didn't happen before.

I was thinking of measuring the current in the appliance earth cables
- suspecting capacitors included in radio interference suppression
components ???

I was also thinking of changing the RCD from 30mA to 100mA. I think
that is legal and would likely stop it ???

By the way, I think that a 30mA trip could just about prevent a lethal
shock, wheras 100mA would not.
[I don't really fancy the "responsibility" of changing a "safety"
component in a rented house.]
But (at least to me), a 30mA RCD seems to offer NO protection against:
1. right hand on live.
2. left hand on neutral.
i.e. current through the heart, not shoes to earth when wearing
seriously insulating shoes (eg rubber soled trainers).

Any comments.

Happy Christmas

Dave

In article , Dave
scribeth thus
Here's a bit of an old chestnut - but with a responsibility angle.

My girlfriend lives in a Housing Authority house.
Those nice people have done a bit of updating, including the consumer
unit.

Now, when she puts the washer on, the CU frequently trips.
The housing authority say, it's her appliance(s).
She says it didn't happen before.

Well if there wasn't an RCD then it could not have happened;!"..

I was thinking of measuring the current in the appliance earth cables
- suspecting capacitors included in radio interference suppression
components ???

I was also thinking of changing the RCD from 30mA to 100mA. I think
that is legal and would likely stop it ???

DO NOT do this you'd be leaving yourself open to all sort of
liabilities.

An 30 ma RCD should work fine in domestic environments even with
dishwashers and the like on the go .. Theres one on our gaff thats fine
and in some others we have all ticking just so.

Its quite possible that they might have an obscure earth to neutral
wiring fault or indeed her machine could be playing up it needs someone
who knows what their doing and regretfully a lot of sparks don't
understand quite how RCD's work and nuisance trip.

But just don't change it yourself grumble and complain is the best bet..

If you find no trips with a large other load on the RCD protected
circuits then its not likely to be a wiring fault. If it only plays up
when her washer on then its likely it has a faulty heating element...

By the way, I think that a 30mA trip could just about prevent a lethal
shock, wheras 100mA would not.
[I don't really fancy the "responsibility" of changing a "safety"
component in a rented house.]
But (at least to me), a 30mA RCD seems to offer NO protection against:
1. right hand on live.
2. left hand on neutral.
i.e. current through the heart, not shoes to earth when wearing
seriously insulating shoes (eg rubber soled trainers).

Any comments.

Happy Christmas

Dave

--
Tony Sayer

snip

DO NOT do this you'd be leaving yourself open to all sort of
liabilities.

I'm NOT going to - it was just a passing thought as a "brute force"
way to stop this.
I agree I definately don't want the liability of changing a safety
related component on a house I don't even own.

I will do some checking though on earth current on a few appliances.

Cheers.

"Dave" wrote in message
...

snip

DO NOT do this you'd be leaving yourself open to all sort of
liabilities.

I'm NOT going to - it was just a passing thought as a "brute force"
way to stop this.
I agree I definately don't want the liability of changing a safety
related component on a house I don't even own.

I will do some checking though on earth current on a few appliances.

Cheers.

The wasing machine would apear to be the culprit from what you have
told us.
Not sure how you intend measuring leakage current though.

You may well see the leakage safely by unplugging it and measuring
the resistence on a multimeter between the earth and live and/or
neutral pins of the plug, If the reading is less than in than 1 Megohm,
then you can try to isolate suspect components of the machine.

I would try the following
main motor (carbon debris on brush carrier tracking to metal frame)
pump (close to moisture)
heater element (same reason)

In each case isolate both terminals,
--
Graham.

%Profound_observation%

snip
The wasing machine would apear to be the culprit from what you have
told us.
Not sure how you intend measuring leakage current though.

I was thinking of (me, not her) lifting the earth connection in the
plug and *very carefully* switching it on with a milliammeter in the
earth lead.

In article ,
Dave wrote:
Now, when she puts the washer on, the CU frequently trips.
The housing authority say, it's her appliance(s).
She says it didn't happen before.

I was thinking of measuring the current in the appliance earth cables
- suspecting capacitors included in radio interference suppression
components ???

Likely things are a suppressor - or the heating element. Can you try it
with a cold wash so the heater isn't used at all?

--
*If only you'd use your powers for good instead of evil.

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave" wrote in message
...
snip
The wasing machine would apear to be the culprit from what you have
told us.
Not sure how you intend measuring leakage current though.

I was thinking of (me, not her) lifting the earth connection in the
plug and *very carefully* switching it on with a milliammeter in the
earth lead.

On the same circuit, the RCD will trip as soon as you connect
the ammeter

On a non-RCD circuit (if there is one) you will mealy confirm what
the RCD has already told you.

It is true that sometimes the break-down only occurs at mains voltage,
but usually, the safe method I mentioned is good enough.
--
Graham.

%Profound_observation%

"Dave Plowman (News)" wrote in message
...
In article ,
Dave wrote:
Now, when she puts the washer on, the CU frequently trips.
The housing authority say, it's her appliance(s).
She says it didn't happen before.

I was thinking of measuring the current in the appliance earth cables
- suspecting capacitors included in radio interference suppression
components ???

Likely things are a suppressor - or the heating element. Can you try it
with a cold wash so the heater isn't used at all?

The programmer usually only switches single pole (live)
the heater's neutral will still be connected
and the RCB isn't fussy if the leak is N-E so it will still
trip. Don't you agree?

--
Graham.

%Profound_observation%

Dave wrote:

Here's a bit of an old chestnut - but with a responsibility angle.

My girlfriend lives in a Housing Authority house.
Those nice people have done a bit of updating, including the consumer
unit.

Now, when she puts the washer on, the CU frequently trips.
The housing authority say, it's her appliance(s).

They are probably right.

She says it didn't happen before.

Which can be true, but it does not disprove there being a fault that was
undetected before.

I was thinking of measuring the current in the appliance earth cables
- suspecting capacitors included in radio interference suppression
components ???

Not that easy to make direct measurements. A high sensitivity clamp
meter would probably be your best bet.

I was also thinking of changing the RCD from 30mA to 100mA. I think
that is legal and would likely stop it ???

No, this would not be legal. The 17th edition wiring regs require 30mA
RCD protection. It may stop it.

By the way, I think that a 30mA trip could just about prevent a lethal
shock, wheras 100mA would not.

This is generally true. 100mA trip devices are more for equipment and
installation protection rather than personal shock protection. See:

http://www.memonline.com/rcd3.html

[I don't really fancy the "responsibility" of changing a "safety"
component in a rented house.]

Indeed.

But (at least to me), a 30mA RCD seems to offer NO protection against:
1. right hand on live.
2. left hand on neutral.
i.e. current through the heart, not shoes to earth when wearing
seriously insulating shoes (eg rubber soled trainers).

Agreed, there are a bunch of scenarios where the RCD will offer no
additional protection. However there are also plenty where it can make a
significant difference.

Any comments.

For details on RCDs and how to trace these types of trips see:

http://wiki.diyfaq.org.uk/index.php?title=RCD


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Graham. wrote:

The programmer usually only switches single pole (live)
the heater's neutral will still be connected
and the RCB isn't fussy if the leak is N-E so it will still
trip. Don't you agree?

No, because the N-E voltage is (or should be) quite small and it needs a
very much lower impedance leak to trip the RCD than for L-E leakage.

--
Andy

In article ,
Graham. wrote:
Likely things are a suppressor - or the heating element. Can you try it
with a cold wash so the heater isn't used at all?

The programmer usually only switches single pole (live)
the heater's neutral will still be connected
and the RCB isn't fussy if the leak is N-E so it will still
trip. Don't you agree?

I was sort of assuming the leakage - if the heater element - got worse as
it heated up. If not, I'd expect it to be fairly constant and therefore
not cause an intermittent fault. But like all these things it's only a
guess.

--
*If only you'd use your powers for good instead of evil.

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article ,
Graham. wrote:
Likely things are a suppressor - or the heating element. Can you try it
with a cold wash so the heater isn't used at all?

The programmer usually only switches single pole (live)
the heater's neutral will still be connected
and the RCB isn't fussy if the leak is N-E so it will still
trip. Don't you agree?

I was sort of assuming the leakage - if the heater element - got worse as
it heated up. If not, I'd expect it to be fairly constant and therefore
not cause an intermittent fault. But like all these things it's only a
guess.


I could be wrong but heaters not used for a while get moisture in the
mineral insulator. Therefore when hot or regularly used they stay dry.

Dave wrote:
Here's a bit of an old chestnut - but with a responsibility angle.

My girlfriend lives in a Housing Authority house.
Those nice people have done a bit of updating, including the consumer
unit.

Now, when she puts the washer on, the CU frequently trips.
The housing authority say, it's her appliance(s).
She says it didn't happen before.

I was thinking of measuring the current in the appliance earth cables
- suspecting capacitors included in radio interference suppression
components ???

I was also thinking of changing the RCD from 30mA to 100mA. I think
that is legal and would likely stop it ???

By the way, I think that a 30mA trip could just about prevent a lethal
shock, wheras 100mA would not.
[I don't really fancy the "responsibility" of changing a "safety"
component in a rented house.]
But (at least to me), a 30mA RCD seems to offer NO protection against:
1. right hand on live.
2. left hand on neutral.
i.e. current through the heart, not shoes to earth when wearing
seriously insulating shoes (eg rubber soled trainers).

Any comments.

Happy Christmas

Dave

Likely to be a wahsing machine fault, with most likely culprits being
heating element & carbon dust on the motor. Probably worth leak
testing all the appliances with a multimeter on high R range. Unplug
and check R from L&N to E, and look for any with less than stellar
insulation resistance.

Mucking about with the CU isnt the best plan. RCDs reduce a lot of
shocks, but as you say not all.


NT

On Mon, 22 Dec 2008 01:57:01 UTC, "Fred" wrote:

I could be wrong but heaters not used for a while get moisture in the
mineral insulator. Therefore when hot or regularly used they stay dry.

Very true. We moved in and didn't use the oven for over a year. When the
guy came to check my new wiring, he found excessive earth leakage on the
circuit. He connected anyway, ran the oven for a bit and then it was
fine.

--
The information contained in this post is copyright the
poster, and specifically may not be published in, or used by
http://www.diybanter.com

"Andy Wade" wrote in message
...
Graham. wrote:

The programmer usually only switches single pole (live)
the heater's neutral will still be connected
and the RCB isn't fussy if the leak is N-E so it will still
trip. Don't you agree?

No, because the N-E voltage is (or should be) quite small and it needs a
very much lower impedance leak to trip the RCD than for L-E leakage.
--
Andy


I concede!

I was reading to much into the fact that a dead short

N-E will trip the RCD.


--
Graham.

%Profound_observation%

In article , Graham.
scribeth thus


"Andy Wade" wrote in message
...
Graham. wrote:

The programmer usually only switches single pole (live)
the heater's neutral will still be connected
and the RCB isn't fussy if the leak is N-E so it will still
trip. Don't you agree?

No, because the N-E voltage is (or should be) quite small and it needs a
very much lower impedance leak to trip the RCD than for L-E leakage.
--
Andy


I concede!

I was reading to much into the fact that a dead short

N-E will trip the RCD.


As long as there is sufficient current flowing.

Under no/insufficent current conditions it won't!...

--
Tony Sayer

tony sayer wrote:

In article , Graham.
scribeth thus

[snip]

N-E will trip the RCD.


As long as there is sufficient current flowing.

Under no/insufficent current conditions it won't!...

Our previous house had a TN-S earthing arrangement, neutral was usually
floating about a couple of volts above earth. I could guarantee to trip the
RCD by shorting N-E, even with the circuit fuse removed from the consumer
unit, so no current flowing there.

We've got a TN-C-S system in this house so the same problem doesn't arise.

--
Mike Clarke

On Dec 21, 12:16*pm, Dave wrote:
Here's a bit of an old chestnut - but with a responsibility angle.

My girlfriend lives in a Housing Authority house.
Those nice people have done a bit of updating, including the consumer
unit.

Now, when she puts the washer on, the CU frequently trips.
The housing authority say, it's her appliance(s).
She says it didn't happen before.

I was thinking of measuring the current in the appliance earth cables
- suspecting capacitors included in radio interference suppression
components ???

I was also thinking of changing the RCD from 30mA to 100mA. I think
that is legal and would likely stop it ???

By the way, I think that a 30mA trip could just about prevent a lethal
shock, wheras 100mA would not.
[I don't really fancy the "responsibility" of changing a "safety"
component in a rented house.]
But (at least to me), a 30mA RCD seems to offer NO protection against:
1. right hand on live.
2. left hand on neutral.
i.e. current through the heart, not shoes to earth when wearing
seriously insulating shoes (eg rubber soled trainers).

Any comments.

Happy Christmas

Dave

Interesting problem; so this post respectfully offers a side comment.
Sounds like the RCD maybe 'too sensitive'?

Here (In this part of Canada) RCD type breakers are coming into use;
especially for new installations under revised codes.

However for quite a while now individual (duplex) outlets equipped
with RCDs have been recommended and also fitted extensively to
existing installations. We have several locations where we have added
them. We have two more that will be added shortly to this house which
was wired 38 years ago in accordance with the then codes that didn't
even mention RCD/GFIs!

Here the RCD type outlets are called GFI (Ground Fault Interruption)
outlets, the 'ground' something of a misnomer since they operate on
the unbalance of currents in the neutral and live wires; similar AFIK
to how an RCD operates. But the idea seems to be that, like RCDs, it
protects for currents to ground through a human body and this is what
would cause the unbalance and rapidly trip the circuit.

GFI (RCD outlets) can be wired to 'protect' just themselves or;
themselves and all other outlets 'down stream' of them on our radial
type domestic wiring. (Ring mains not used!).

These GFI are either recommended or now mandatory for any outlets in
damp/outdoor locations etc. Garden tools, garages, our bathroom etc.
However; and this is the point of this comment, they are NOT
RECOMMENDED for any appliance that has an electric motor (with
possible exception of lightweight counter appliances such as a food
mixer, blender etc.) . They are not to be used for fridges, freezers
etc. because a) Possible unbalance currents as the motors start up can
trip the GFI/RCD. b) Also a not working fridge/freezer can cause food
spoilage. Fridge motors probably smaller and lower HP than a
washer?

So respectfully suggest that it may be the unbalance due to a motor
starting that may be causing the RCD breaker to trip? Not sure if
that's a potential fault or leakage or the ground and neutral at the
washer in contact with each other?????? Is it kosher to try reversing
live and neutral at the washer? Maybe not cos the switch will, should
be, be in the live wire????

Anyway the point is that it seems to be 'well known' over here (North
America) to not use GFIs on any motor equipped appliance circuits.

For what this is worth all the best for this season. Cheers.

terry wrote:

Interesting problem; so this post respectfully offers a side comment.
Sounds like the RCD maybe 'too sensitive'?

They can be too sensitive in two ways... one being a faulty unit that
trips below its anticipated tripping current, or one that trips when it
should do, but your appliance / circuit has more than expected leakage.

Here (In this part of Canada) RCD type breakers are coming into use;
especially for new installations under revised codes.

However for quite a while now individual (duplex) outlets equipped

"duplex" is what we would call a "double socket" I take it?

with RCDs have been recommended and also fitted extensively to
existing installations. We have several locations where we have added
them. We have two more that will be added shortly to this house which
was wired 38 years ago in accordance with the then codes that didn't
even mention RCD/GFIs!

Yup, here RCDs have been mandated for any circuit which is likely to be
used to power equipment outside for some time. Recent changes to the
regulations require their use on additional circuit types as well - such
that RCD protection will become common for almost all circuits)

Here the RCD type outlets are called GFI (Ground Fault Interruption)
outlets, the 'ground' something of a misnomer since they operate on
the unbalance of currents in the neutral and live wires; similar AFIK
to how an RCD operates. But the idea seems to be that, like RCDs, it

Yup - the same as our RCDs

protects for currents to ground through a human body and this is what
would cause the unbalance and rapidly trip the circuit.

Indeed - that is one of the occasions we use RCDs. They are also used
where it is necessary to protect a circuit and the earth fault loop
impedance (i.e. the round trip resistance from supply line to earth) is
too large to reliably trip the circuit protective device. This scenario
is commonly seen where there is no earth/ground provided by the power
company, and a local earth spike is used instead.

GFI (RCD outlets) can be wired to 'protect' just themselves or;
themselves and all other outlets 'down stream' of them on our radial
type domestic wiring. (Ring mains not used!).

You can get sockets like this here - although they usually don't have
the capacity to protect additional sockets (they would obviously be
incompatible with ring circuits). These can be retrofitted to older
installs to provide a safe socket to power garden equipment etc. More
commonly, the RCD is fitted at the consumer unit (fuse board/box) on
modern installs.

These GFI are either recommended or now mandatory for any outlets in
damp/outdoor locations etc. Garden tools, garages, our bathroom etc.

Our regs have not allowed sockets in bathrooms at all until recently.
They still preclude them in small rooms since there are minimum
distances between baths etc and a socket if fitted.

However; and this is the point of this comment, they are NOT
RECOMMENDED for any appliance that has an electric motor (with
possible exception of lightweight counter appliances such as a food
mixer, blender etc.) . They are not to be used for fridges, freezers
etc. because a) Possible unbalance currents as the motors start up can
trip the GFI/RCD. b) Also a not working fridge/freezer can cause food
spoilage. Fridge motors probably smaller and lower HP than a
washer?

Motors are not usually cited as typically causing problems with RCDs
here - although when a RCD is already loaded very closely to its
tripping current, any power surge (as may be caused by motors starting)
can push them over the edge.

With regard to Fridges/Freezers (and anything else you don't want
tripping like the central heating, or your tropical fish tank etc)), it
advisable to place these on dedicated circuits without RCD protection
(or with their own dedicated RCDs). (we have devices called RCBOs which
are circuit breakers and RCDs combined into a single unit - quite handy
for fitting to circuits like this)

So respectfully suggest that it may be the unbalance due to a motor
starting that may be causing the RCD breaker to trip? Not sure if
that's a potential fault or leakage or the ground and neutral at the
washer in contact with each other?????? Is it kosher to try reversing
live and neutral at the washer? Maybe not cos the switch will, should
be, be in the live wire????

Indeed, you should not reverse the L/N connections for the reason you
highlight. The common RCD trip mechanisms in washers tends to be either
internal leaks that are allowing the electrics to become damp, or a
heating element that is close to its end of life - the mineral
insulation can become damp and conductive and hence result in enough
leakage to cause a problem. Regular usage however can mask the fault by
keeping it dry enough to not trip.

Anyway the point is that it seems to be 'well known' over here (North
America) to not use GFIs on any motor equipped appliance circuits.

What trip rating are your GFIs usually specified at? (30mA is typical
for our RCDs that are intended to protect against shock).

I also have a feeling that the standards to which RCDs are designed also
requires a certain amount of harmonic noise interference rejection to
mitigate problems caused by switch on/off surges.

For what this is worth all the best for this season. Cheers.

And to you also! (only six hours to christmas this side of the globe!) ;-)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Mike Clarke wrote:
tony sayer wrote:

In article , Graham.
scribeth thus

[snip]

N-E will trip the RCD.


As long as there is sufficient current flowing.

Under no/insufficent current conditions it won't!...

Our previous house had a TN-S earthing arrangement, neutral was usually
floating about a couple of volts above earth. I could guarantee to trip the
RCD by shorting N-E, even with the circuit fuse removed from the consumer
unit, so no current flowing there.

We've got a TN-C-S system in this house so the same problem doesn't arise.

If you touch the 2 together, with 2v difference and a fraction of an
ohm, clearly many amps will flow. Compare that with a local earth rod
(TT), where earth impedance is fairly high, and way less current
flows.


NT