Finding fault on socket ring

[alexjackson]

We've had an intermittent fault that trips the circuit breaker on the socket ring for quite a few months now. The ring for lights is unaffected.

It usually happens during the day when we are at work and then we come home to a fridge that is starting to warm up.

I've had an electrician test the circuit at the consumer unit and they can find no fault with the wiring. His advice was that it must be an appliance that draws power during the day, with the most likely culprit being the fridge. We recently replaced the fridge freezer (it needed to go anyway) but have now had the problem reoccur.

The last instance was whilst we were on holiday (resulting in the freezer defrosting fully). I had been careful to switch off/unplug all appliances (e.g. internet, TV, etc) other than the new fridge freezer, the oven and a small clock radio.

When we returned home and reset the circuit breaker the alarm went off (it doesn't normally do this if we reset it after coming home from work). We have previously had trouble with the alarm so don't bother setting it.

Given the above, can anyone suggest where to begin with finding this fault? Or where I should be directing an electrician to test?

Any help much appreciated.

 

[Octopus]

From what you describe, you have one of the most difficault faults to locate. By all means call a sparky in but you may end up paying them to do tests and not find anything.

When you went on holiday, what, apart from the new fridge freezer, was plugged in.

Oh and by the way do you mean the MCB or RCD tripped?

 

[SJD]

Just to clarify/confirm - the device tripping is an MCB (which I guess will be 32A) on the socket ring final circuit - due to overcurrent?
I.e. it is not an RCD tripping, or a combined MCB/RCD (known as an RCBO) - these will both have test buttons.
If you are not sure, either post a photo, or if you can't then post a note of markings on the device tripping.

Update: I see Murdoch beat me to it with the question.

 

[Octopus]

Just to clarify/confirm - the device tripping is an MCB (which I guess will be 32A) on the socket ring final circuit - due to overcurrent?
I.e. it is not an RCD tripping, or a combined MCB/RCD (known as an RCBO) - these will both have test buttons.
If you are not sure, either post a photo, or if you can't then post a note of markings on the device tripping.

Update: I see Murdoch beat me to it with the question.

He's only posted once so he won't be allowed to post a photo yet!

 

[telectrix]

a few members in the manc area. sure one of them will be able to sort it .

 

[uksparks]

By any chance, do you have kind of documentation or readings from the last electrician who looked at it? I usually note them down on the receipt in this situation. As others say though, you may end up paying for someone to look and not fix it. Just be careful whoever you call as fault finding is kind of like having a licence to print money.

 

[alexjackson]

Hi all and thanks for the replies so far.

The switch that trips is marked RCCB and cuts out the power to all the electric sockets in the house.

- hopefully you can see this here.

 

[Octopus]

Hum, with an "up front" RCD you can never be sure exactly which circuit the fault is on.

Have you noticed any pattern at all?

 

[alexjackson]

From what you describe, you have one of the most difficault faults to locate. By all means call a sparky in but you may end up paying them to do tests and not find anything.

When you went on holiday, what, apart from the new fridge freezer, was plugged in.

Oh and by the way do you mean the MCB or RCD tripped?

Fridge/freezer, oven, shower, small clock radio in bedroom - that's everything on this circuit.

Although the alarm system went off when we switched the electrics back on. Which makes me think it is also connected.

 

[alexjackson]

Hum, with an "up front" RCD you can never be sure exactly which circuit the fault is on.

Have you noticed any pattern at all?

It is normally during the middle of the day - I'd guess at mid afternoon by the temperature of the fridge/freezer when I've got home from work to find it has tripped. Probably happened 10-12 times over the last 8 months. However, it did happen once on a morning as we were getting ready for work.

Seemed to go every day during a period of hot weather, which made me think it was definitely the fridge being old and over worked. Which is why I was stumped when it happened to with the new fridge.

 

[Octopus]

Fridge/freezer, oven, shower, small clock radio in bedroom - that's everything on this circuit.

Although the alarm system went off when we switched the electrics back on. Which makes me think it is also connected.

Hum, they normally have a battery that will last some time, so that could be a red herring.

 

[telectrix]

what area of manchester? i cover the south and west. then you have PEG and archy strigg in the area as awell.

 

[SJD]

If the power was off for some time (days) while you were away, likely the alarm battery went flat, and once power was restored, it might well trigger the alarm. As mentioned, this may be a red herring.

When you say you had an electrician test the wiring before, and found no fault, hopefully he/she tested each circuit separately in turn (for all of the 6 circuits that have MCBs on this RCCB). Was everything unplugged from each circuit, or were they tested with stuff still connected? Were there any test results - insulation resistance tests - that you were given? Plus was the RCCB tested - ramp test - with mA that it trips at?

Assuming the fixed wiring is all OK (and I wouldn't assume that unless I was confident it was tested properly), it might be there are a number of appliances contributing leakage that, when it adds up sufficiently, causes the RCCB to trip. For example, I was at a house yesterday, where the dishwasher had 4mA leakage, the fridge about 2mA, then odd 1 or 2mA each from a few other appliances such as the washing machine, dryer, microwave, all adding up to a base leakage of around 10mA. The RCD trips at 21mA, so already the leakage is half way to tripping.

It is fairly easy to put an low-current clamp meter on the earth connection for the various appliances at the plug/connection, or alternatively to do this for each circuit at the consumer unit. But you probably want an electrician to do this for you. The problem is that this will not show intermittent faults.

One option might be to have someone reconfigure the consumer unit, and move one or more socket circuit from the RCCB, replacing it's MCB with an RCBO (which is a combined MCB and RCD) in each case. For example, the circuit with the freezer on it.

 

[telectrix]

i have just the test meter for intermittent faults. an old megger wind up jobbie. sometimes it works and sometimes it doesn't. the secret is to coincide it's working moments with the faulty circuit intermittent fault, and there you find it. :smilielol5::smilielol5::smilielol5:

 

[Octopus]

It could simply be that the RCD is trucked.

Did the sparky ramp test it and do you have the readings?

 

[alexjackson]

Hum, they normally have a battery that will last some time, so that could be a red herring.

Yes I put a new battery into the alarm last winter. But the fact that it goes off when the electrics are switched back on shows that it must be connected somehow? Power to the keypad maybe?

 

[alexjackson]

It could simply be that the RCD is trucked.

Did the sparky ramp test it and do you have the readings?

I don't know what tests the sparky did. He didn't pass on any test results to me.

 

[alexjackson]

If the power was off for some time (days) while you were away, likely the alarm battery went flat, and once power was restored, it might well trigger the alarm. As mentioned, this may be a red herring.

When you say you had an electrician test the wiring before, and found no fault, hopefully he/she tested each circuit separately in turn (for all of the 6 circuits that have MCBs on this RCCB). Was everything unplugged from each circuit, or were they tested with stuff still connected? Were there any test results - insulation resistance tests - that you were given? Plus was the RCCB tested - ramp test - with mA that it trips at?

Assuming the fixed wiring is all OK (and I wouldn't assume that unless I was confident it was tested properly), it might be there are a number of appliances contributing leakage that, when it adds up sufficiently, causes the RCCB to trip. For example, I was at a house yesterday, where the dishwasher had 4mA leakage, the fridge about 2mA, then odd 1 or 2mA each from a few other appliances such as the washing machine, dryer, microwave, all adding up to a base leakage of around 10mA. The RCD trips at 21mA, so already the leakage is half way to tripping.

It is fairly easy to put an low-current clamp meter on the earth connection for the various appliances at the plug/connection, or alternatively to do this for each circuit at the consumer unit. But you probably want an electrician to do this for you. The problem is that this will not show intermittent faults.

One option might be to have someone reconfigure the consumer unit, and move one or more socket circuit from the RCCB, replacing it's MCB with an RCBO (which is a combined MCB and RCD) in each case. For example, the circuit with the freezer on it.

In reply to questions;
- it was tested with appliances still plugged in
- I wasn't given any test results
- Don't know if a ramp test was done or not

In terms of reconfiguring the consumer unit, any indication how successful that is likely to be and roughly how much it would cost?

 

[Octopus]

I don't know what tests the sparky did. He didn't pass on any test results to me.

What did he put on his invoice?

 

[alexjackson]

what area of manchester? i cover the south and west. then you have PEG and archy strigg in the area as awell.

East Didsbury