Nucience Tripping Help

justjust1 · May 22, 2011

Hi all,

I am just finishing my Level 3 City and Guilds, 17th edition and Test and inspection at collage.

I have a problem!!!
I have replaced the consumer unit in my house with a Hager split load, with a main switch and 2 RCDs. One of the ring circuits has a large Samsung American style fridge freezer, washing machine, tumble dryer and a microwave (this is all situated in the laundry room).
The last 2 sunday nights the RCD has tripped on that side of the consumer unit. Only the oven (40amp MCB) and the ring circuit (32amp MCB) are on that side of the split loaded board.
I am not really sure when the trip happened but it was some time after using the grill in the oven (40ampMCB) but the MCB did not trip just the RCD. The only other thing i can think that it would be is the fridge giving me nuisance tripping via an earth leakage.

The previous CU was a old re-wirable fuse type! Never had this issue but then i have heard on the grape vine that they are not very sensitive plus it did not have an RCD.

Insulation resistance tests @ the consumer unit are coming back ok!

Anyway i can find out if the fridge is omitting earth leakage?

Anyone have any idea on what i could do to find where the problem is?

Cheers
JG

telectrix · May 22, 2011

i might add though, that as has been said, it could well be the cooker.

justjust1 · May 22, 2011

@ Telectrix haha i see what you mean now! Just me being dumb!

justjust1 · May 22, 2011

telectrix said:
i might add though, that as has been said, it could well be the cooker.

Yeah thats why im going to move the laundry room ring circuit to the other RCD, see if it trips then. If not then i know its a problem with the oven!

My theory is that its he grill, the oven is about 8 years old! Fridge is brand new!

Goody · May 22, 2011

Filthy grill; check the electrics on the oven. May be it's time to say goodbye to the cooker.

telectrix · May 22, 2011

can't say goodbye to my cooker. she'd kill me

truckster · May 23, 2011

As said before I have had a few where the fault is nly apparent when the heating element is switched on, i.e. an electric grill. Can be a bit of a pain to isolate the fault. Good luck

BlueToBits · May 23, 2011

My money is on the cooker. Heating elements are like MICC (Pyro). When cold the IR tests out OK, but when hot, it can fall to a fraction of the cold value. This type of fault is not uncommon.
if the RCD won't hold in to heat up the element, it may be difficult to confirm this fault without using a heat gun or blowlamp.
Isolate the cooker and set tp IR tester to continually display IR for the appliance N-E. Whilst watching the meater reading, heat up one end of the first element with the heat gun (blow lamp) and move the heat along the length of each element in turn. It does not need to get very hot, 100 deg C will probably do. The IR reading will drop as you heat up the point fault. If you find such a point, keep heating it until the element glows red and note the IR reading.

If the reading remains constant for all elements, check that the neutrals of all elements are connected together and that each element has continuity across it. If this is the case, your cooker is not the cause of the probelm.
Obviously, there are safety precautions to take here such as isolation, working with heat etc. It is a lot easier to have someone read out the IR values as you watch what you are doing with the heat gun.
Only try this on naked elements. I would imagine it could cause damage and risk if you did it on solid plates, ceramic/glass hobs and halogen elements.