RCD tripping in Consumer Unit

[blackbirdxx]

Hi,
My house was totally rewired about 18 months ago. The new consumer unit has 2 RCD's, one of which started to trip intermittently last night. Circuits on this RCD include the kitchen and 1st floor ring mains along with the ground floor lighting circuit. No MCB's are tripping.
There are 2 fridge freezers, a washing machine and a tumble dryer connected to separate sockets on the kitchen ring main and an outside security light connected to the ground floor lighting circuit.
My gut feeling (based on not alot) is that its the o/s security light causing the problem after all the heavy rain we had the other night but everything seems very watertight.
In the meantime, I'm connecting the freezers, one by one, to the non tripping ring main on the other RCD by means of an extension lead to see if either of these appliances are the source of the problem.
Nothing has tripped today which may imply the problem has now dried out but what can I do to the outside light to rectify the problem as its on the same RCD as the freezers? Is just turning the security light off at the wall switch adequate to stop the RCD tripping (assuming that is the problem of course??)
Is there anything else I can do to isolate which appliance/lamp is causing the RCD to trip?? Having 2 fridge freezers on this tripping RCD is quite concerning as you can imagine. All appliances are less than a year old except the washing machine.
Thanks in advance for any assistance.

 

[ericmark]

Main reason why I had an all RCBO consumer unit was this problem. If the fault is line - earth turning it off will stop the problem, but if neutral - earth then any heavy load is likely to cause it to trip.

When my fuse box and consumer unit (CU) was swapped for a new CU I found a problem with the lights, so the idea of DIY working in a CU is not a good idea, it needs some one with the test gear to modify it.

Outside lights should have double pole isolating switches in doors, but mine haven't. You can get 10 mA RCD's which should trip first, but I would say get an electrician to swap the RCD for an isolator and fit all RCBO's in that side.

Note RCBO is a RCD and MCB combined.

 

[blackbirdxx]

Thanks for the info. I guess an RCBO CU should have been the way to go in retrospect.

If I understand you correctly, checking the colour of the wiring in the security light wall switch will confirm line - earth or or neutral - earth. If its line - earth, I can turn the security light off at the switch (if the light is the tripping problem of course)?

You suggest the way to go is to get an electrician to replace all the mcb's on the tripping RCD side with RCBO's, yes? Sorry to reiterate what you have already said but just need to get my head around what's required.

That said, am I overloading the kitchen ring by having both a fridge freezer and a freezer on it? Is this a likely cause of the tripping, although its never happened before?

 

[EFLImpudence]

Thanks for the info. I guess an RCBO CU should have been the way to go in retrospect.

Not really.

If I understand you correctly, checking the colour of the wiring in the security light wall switch will confirm line - earth or or neutral - earth.

No. It depends whether the fault is from the Line or Neutral to earth.

If its line - earth, I can turn the security light off at the switch (if the light is the tripping problem of course)?

Yes - but then - you might have a double pole switch.

You suggest the way to go is to get an electrician to replace all the mcb's on the tripping RCD side with RCBO's, yes?

It depends what you want to spend your money on. You might then get a fault on the other side.
When you cure the fault it will be cured.

That said, am I overloading the kitchen ring by having both a fridge freezer and a freezer on it? Is this a likely cause of the tripping, although its never happened before?

It's nothing to do with overload.

It's probably just a tiny 'fault' caused by something like moisture or even a slug or similar.

Just a disadvantages of RCDs.

 

[blackbirdxx]

Not sure where I should go from here?
Nothing has tripped today so I'm guessing whatever was damp (or whatever) has dried out and is currently not a problem. What I'm concerned about now is the problem reoccurring and I loose the contents of the 2 freezers, especially not knowing where the original problem was.

Thanks for the ongoing help..

 

[crystal ball]

Had a call today to RCD tripping in an unoccupied granny flat, the owner went through what he thought had caused it, failing bulbs, leaky roof, I had look outside and spotted a Wiska box hanging off the fascia with a hole in one of the blank membranes (Blue Tits?). Full of water

 

[blackbirdxx]

Not in my case....
The security light was professionally installed as part of the new wiring installation. The plastic junction box is water tight and everything looked completely dry.

 

[Harry Bloomfield]

Nothing has tripped today which may imply the problem has now dried out but what can I do to the outside light to rectify the problem as its on the same RCD as the freezers? Is just turning the security light off at the wall switch adequate to stop the RCD tripping (assuming that is the problem of course??)

No, if that is the problem, then the only way is to fully isolate it - both the L and N to it, need to be disconnected. The usual advice is to wire such items via a double pole switch, but the default is usually a single pole switch, which only isolates the L.

 

[blackbirdxx]

Still not 100% sure that the security light is the problem? I have to ask again whether its OK to run a fridge freezer and another freezer continually on the 32A ring? Obviously all the other appliances are only in operation when required.

 

[Harry Bloomfield]

Still not 100% sure that the security light is the problem?

The only way to find out, is by completely isolating one thing at a time.

I have to ask again whether its OK to run a fridge freezer and another freezer continually on the 32A ring? Obviously all the other appliances are only in operation when required.

Both on one 32amp ring is not a problem, just an amp or two each.

 

[blackbirdxx]

aah good to know I'm not overloading the main.....

Knowing what you know about my electrics, would it be a good idea to get an electrician to provide an RCBO for just the kitchen ringmain to stop unwanted trips from the o/s security light, for example, tripping the RCD and causing the 2 freezers to fail??

 

[ericmark]

I lost two freezers full of food, which is why when I moved I went all RCBO, however even then can still loose them.

 

[Harry Bloomfield]

aah good to know I'm not overloading the main.....

Knowing what you know about my electrics, would it be a good idea to get an electrician to provide an RCBO for just the kitchen ringmain to stop unwanted trips from the o/s security light, for example, tripping the RCD and causing the 2 freezers to fail??

There is no fool proof system using RCBO's, they can still trip with just fridge/freezers on them. If there were concerns - The advice used to be, to have these on separate circuits and not on an RCBO - but I don't think you can do that now. Certainly you can reduce the chances of them tripping, if they are on their own separate circuit.

You can also buy battery powered alarms, which plug in to the freezer circuit and warn you when power is lost.

 

[plugwash]

There is no fool proof system using RCBO's, they can still trip with just fridge/freezers on them. If there were concerns - The advice used to be, to have these on separate circuits and not on an RCBO - but I don't think you can do that now.

IIRC it's still possible but a lot more awkward than it used to be. IIRC the exemptions from the rule for RCD protected sockets are now limited to non-domestic premises so you would have to hard wire the equipment and you would also have to comply with the modern rules for non-rcd protected wiring (which would probably mean running the circuit in SWA).

 

[blackbirdxx]

So can I assume its not a straightforward exercise to put the kitchen ring onto a RCBO in a CU full of MCB's and 2 RCD's - shame!

Alarms on the freezers sound good although the real problem is when you are away from home.

Any other ideas gratefully received....