RCD Tripping - Electrician can't help!!

[vincentbrown]

Hi, sorry if this end up a little long but hopefully, with all the info, somebody may be able to help.

Our house was built in 1995 and had fitted from new a 'Square D 10 way' consumer unit. However, we had a conservatory built in February of last year (2006) and at the same time I had my electrician upgrade the consumer unit (Protek 16 way) as we had filled up the existing. He also did some earth bonding in the bathrooms in order to be able to certificate the work.

During the next few weeks, the new RCD tripped a couple of times but we thought nothing of it. However, when we returned from our Summer holiday in the August, the RCD had tripped again and we returned to find my daughters tropical fish had died and two warm freezers full of food!!

The electrician advised that he would not be able to trace the fault and it is a case of leaving appliances turned off to see if we can isolate the cause. We have been doing this for the last eight months and it's driving us mad!!!

Over recent weeks we thought we had traced it down to the tumble drier as we found that it was always on when the RCD tripped, although this doesn't explain the tripping whilst on holiday. I have put the drier on an extension so that it can be unplugged when not in use and I though I had found the cause.

Before replacing the drier however, I thought it worthwhile exchanging the RCD in case the original was a little too sensitive. This was done on Thursday of this week and all has been ok untill it tripped in the middle of last night (Friday night) - the tumble drier was unplugged at the time!!

To me, this suggests that there is something else causing the fault and that the tumble drier is the 'straw that breaks the camels back'???

The previous RCD, before the electrician fitted the new consumer unit, was a Square D unit with an 80A / 30mA RCD. This RCD never ever tripped during the 11 years that we had it. Both of the new RCD's have been 63A / 30mA.

Is it true that an electrician with the right kit wouldn't be able to even identify the circuit that the fault is on?

The problem we have is that we have had several weeks with no problems, and then it will trip several times over a course of a few days followed by a calm period again!!

Due to the extended time between trips that we sometimes have, it would be dificult to turn off individual circuits at a time to try to isolate the fault.

Sorry for the extended post, but if anybody could give any advice that may help, I would be most apprciative, this is driving us nuts!!!!! Thanks.

 

[sparkydude]

A decent electrician will be able to carry out a series of proper tests on your RCD and the associated circuits connected to it. By the way a Protek board is the cheapest of the cheap , and certainly was a step down from your old square D board. Ask your electrician to carry out a full inspection on all of the circuits connected to your RCd and see what he reckons. It could be a faulty appliance yes, but it could more likeley be a faulty circuit on your fuseboard. Did you have any problems with the RCD tripping before you had a new board and your conservatory fitted?

I would suggest its more likeley a fault with the new circuit s than the old if this is the case

Nick

 

[JohnD]

Are you paying for this rectification work? If so, could I ask how much it is costing you?

Do you have any spare ways on the CU, on the non-RCD side? If you can say what are the circuits on the CU (RCD and not) it might trigger some ideas.

Do the intermittent trips have any correlation with weather conditions? E.g. rain causing trips if it gets into an outdoor circuit, cold if it is a heater or the CH pump). Have you seens any signs of mice?

I will probably make some smart-alec remark about the benefits of RCBOs, later (sorry).

 

[vincentbrown]

Thanks for the responces. Firstly, there was never any problem before the new CU was fitted. There is currently no rectification work being carried out because we don't know what to rectify!. As far as weather etc is concerned, there is definitely no correlation, this is happening at different times of the day and night and has also happened throughout the year.

RCD circuits are:

Cooker
Conservatory Sockets
Garage (and room above) Sockets
Kitchen/Utility Room Sockets
Main House Sockets
Shower
Immersion Heater
Spare

The non RCD side consists of different lighting circuits, Fridge, boiler and a separate one for the smoke detectors plus one spare.

The house is relatively modern being just 12 years old and certainly there is no evidence of mice.

 

[Lectrician]

Immersions have no need to be on the RCD side.

Cookers are best NOT on the RCD side, but may be put on the RCD side if your cooker control unit has a socket outlet that your electrician decided could possibly be used to supply portable equipment outdoors.

Showers do not need to be RCD protected to comply, but IMO are best protected, and most manuals for showers do tell you to.

I would suggest getting a decent spark in - where are you? It amazes me how many sparks can't fault find, and can't interpret readings from their test kit. Also amazes me how many try to figure out which circuit without disconnecting neutrals.

Try turning the shower, cooker, immersion OFF at their double pole switch when not is use to illiminate them.

A Neutral To Earth fault on an RCD protected circuit can cause funny symptoms. You could find it would be one appliance causing the RCD to trip, and then another, and then another etc etc.

 

[JohnD]

Immersion heaters and cookers often give nuisance trips, especially as they get old. If you can move them to the non-RCD side is may help. I presume they both have a DP switch, if you turn that off, it should prevent them having any effect on the RCD.

Another possible cause is that you have quite a lot of RCD circuits. It is quite common to have a slight and varying leakage on all circuits, when this is added together, it may cumulatively approach the trip point.

Appliances that tend to have leakages are predominantly those that have water, such as washing machines, kettles, immersion heaters, showers. Then it's appliances with heating elements, such as cookers.

Then point of RCBOs is that they give RCD protection to each circuit individually. So in the event of a fault, they only cut power to that circuit, without affecting others. This causes less inconvenience, and also shows you where the fault is coming from. However they are relatively expensive, and I don't know if they are available for your Proteus. I think they're great.

Do you have outdoor circuits? You mention a fishtank, does this have a heater, and is it fed from an isolating transformer?

edited: bah, too slow!

 

[bernardgreen]

Appliances that tend to have leakages are predominantly those that have water, such as washing machines, kettles, immersion heaters, showers. Then it's appliances with heating elements, such as cookers.

And computors and many other electronic equipment with power supplies that have filters on the mains input. These do have live to earth currents due to the live to earth capacitor in the filters and about 10 these power supplies will bring the "leakage" up high enough to trip a 30mA RCD.

 

[ColJack]

it may be down to harmonics..
we had a similar post on here a few week back that kept tripping at the same time every night..


is there any pattern to the trips at all?
all at night?
only on certain days etc?

any neighbours having similar problems?

any large industry nearby?

to find out if it trips at certain times put a small lamp on a rotary timer ( the kind with a dial and pins. not a digital one..) on one of the rcd protected circuits..

 

[Softus]

...probably...

The Pope is probably catholic.

 

[JohnD]

hee hee!

"If you'd had RCBOs fitted in the first place, you wouldn't be having this trouble"

 

[baldelectrician]

An electrician with decent test equipment and the ability to use it well should be able to isolate the fault.

If the firm have a PAT tester they would be able to eliminate all your appliances.

Another point.
If you have one of those kettles that sit on a base then it may be the culprate. The base is still powered if the kettle is not switched on.
The only way to be certain is to unplug the item.

ps switching off appliances may not be enough- unplug to be sure.

 

[ColJack]

further to my other post above, take a look at this post and see if your RCB is one of those types...

if it is then it is a very good posibility that it may be that you have a few extraneous volts on the earth somewhere either from leakage, or capacitive coupling.

do you have a lot of new electronic equipment on the new circuits?

 

[plugwash]

intermittant faults can be a bitch to find because they never show up when you'r looking for them. This applies in any area testers can only show you faults that are giving signs of themselves during the test.

one option is to get the CU changed from a split load to a box with a swtich incomer and RCBOs. This won't be cheap but it will make all circuits independant from each other RCD wise which may solve your problem and if not will at least tell you where to look.

 

[ChrisR]

Is it feasible to use a clamp ammeter on the earth wire from each circuit to see what they are?

 

[luminaire]

It could be something simple like one of the rcd neutrals being put in with the non-rcd neutrals. I have seen that done on many an occasion.