RCD keeps Tripping, need some Advice

Benjohnson20 · Jan 22, 2022

My RCD began to trip several months ago. I narrowed it down to a fridge/freezer in the garage. However, after turning this off, its now started to trip again due to another fridge/freezer (in the last few weeks). Either I’m incredibly unlucky and both appliances need replacing, or there’s something more sinister causing it to trip. Not sure whether to buy new ones or whether the RCD unit or something else is to blame?

DefyG · Jan 22, 2022

Sounds like you are just incredibly unlucky, if after unplugging the second fridge/freezer the tripping problem has been resolved.
You could get the appliances and RCD tested but my feeling is it will just confirm what you already know.

pc1966 · Jan 22, 2022

It could be a N-E fault, and it is triggered by the compressor kicking in. So any large load would do the same as it causes enough of a volt drop on the neutral so sufficient current is diverted via the earth/CPC for the RCD to notice, and the fault may not be on the circuit you think is causing it if the RCD is also feeding a few other circuits.

If you have anything else with a large-ish motor that starts directly, say an old vacuum cleaner (not one with a soft-start electronic control) you could see if that does the same thing at that socket.

An electrician could run an IR test for such a fault, also they ought to be able to check for obvious faults on the appliance (the "PAT testing" sort of check). They also can test the RCD trip times and ramp-test to see what leakage current it actually trips at.

Replacing things "just in case" can be a more frustrating and expensive approach than methodical testing!

UNG · Jan 22, 2022

How often does the RCD trip if it is every 24 - 48 hours then I would suspect an auto defrost heater element fault on the fridge freezer

brianmoooore · Jan 22, 2022

pc1966 said:
It could be a N-E fault, and it is triggered by the compressor kicking in. So any large load would do the same as it causes enough of a volt drop on the neutral so sufficient current is diverted via the earth/CPC for the RCD to notice, and the fault may not be on the circuit you think is causing it if the RCD is also feeding a few other circuits.

If you have anything else with a large-ish motor that starts directly, say an old vacuum cleaner (not one with a soft-start electronic control) you could see if that does the same thing at that socket.

An electrician could run an IR test for such a fault, also they ought to be able to check for obvious faults on the appliance (the "PAT testing" sort of check). They also can test the RCD trip times and ramp-test to see what leakage current it actually trips at.

Replacing things "just in case" can be a more frustrating and expensive approach than methodical testing!

This! Totally unrelated N-E fault is much more likely than two similarly faulty fridge freezers.
What other circuits are fed by this RCD?

timhoward · Jan 23, 2022

In most situations like this it's less that 2 hours work for a decent sparks to identify what is going on. That would be considerably less than replacing the appliance again.

Benjohnson20 said:
However, after turning this off, its now started to trip again due to another fridge/freezer (in the last few weeks)

You said "after turning this off". To ask a silly question, is it still plugged into the wall with the switch off?

Benjohnson20 · Jan 23, 2022

pc1966 said:
It could be a N-E fault, and it is triggered by the compressor kicking in. So any large load would do the same as it causes enough of a volt drop on the neutral so sufficient current is diverted via the earth/CPC for the RCD to notice, and the fault may not be on the circuit you think is causing it if the RCD is also feeding a few other circuits.

If you have anything else with a large-ish motor that starts directly, say an old vacuum cleaner (not one with a soft-start electronic control) you could see if that does the same thing at that socket.

An electrician could run an IR test for such a fault, also they ought to be able to check for obvious faults on the appliance (the "PAT testing" sort of check). They also can test the RCD trip times and ramp-test to see what leakage current it actually trips at.

Replacing things "just in case" can be a more frustrating and expensive approach than methodical testing!

Typically happened most in the middle of the night (so was easier to assume freezer compressor), but on other occasions it’s just been quite random (definitely not when using another large compliance).

Benjohnson20 · Jan 23, 2022

timhoward said:
In most situations like this it's less that 2 hours work for a decent sparks to identify what is going on. That would be considerably less than replacing the appliance again.

You said "after turning this off". To ask a silly question, is it still plugged into the wall with the switch off?

Yes, plug in but switched off. Does that make a difference?

Benjohnson20 · Jan 23, 2022

UNG said:
How often does the RCD trip if it is every 24 - 48 hours then I would suspect an auto defrost heater element fault on the fridge freezer

Mainly at night, but has also done this on other occasions. With both fridge/freezers off it’s not happened since. Small fridge still works, but now without a freezer

Benjohnson20 · Jan 23, 2022

brianmoooore said:
This! Totally unrelated N-E fault is much more likely than two similarly faulty fridge freezers.
What other circuits are fed by this RCD?

The RCD covers mainly an area that was part of an extension the previous owners did to create a utility room. So sockets, some lights, outside lights, immersion. On the sockets we have the washing machine, dryer, x2 fridge/freezers (utility and in garage). Most of the time it happened at night. I’ve attached photo of fuse box / RCD.

UNG · Jan 23, 2022

Benjohnson20 said:
Mainly at night, but has also done this on other occasions. With both fridge/freezers off it’s not happened since. Small fridge still works, but now without a freezer

So does the RCD trip every night with the fridge freezer switched on,
What make / model is the fridge freezer

brianmoooore · Jan 23, 2022

Benjohnson20 said:
The RCD covers....... outside lights, immersion.

Two very common hunting grounds for N-E faults.

timhoward · Jan 23, 2022

Benjohnson20 said:
Yes, plug in but switched off. Does that make a difference?

Some cheaper socket faces are single pole so the switch would not remove a Neutral-Earth fault. Best unplug it to be sure it's not still involved in the fault.

Benjohnson20 · Jan 23, 2022

UNG said:
So does the RCD trip every night with the fridge freezer switched on,
What make / model is the fridge freezer

No, it’s been inconsistent. Went through a period where it was tripping randomly, then when it got cold happened more frequently until we unplugged the first appliance and then unplugged the second when it started to trip again (which is why it seemed odd). Brands are indesit and maytag.

RCD keeps Tripping, need some Advice

Benjohnson20

DefyG

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pc1966

UNG

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brianmoooore

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timhoward

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Benjohnson20

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Benjohnson20

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