Hi just replaced the main incomer to an rcd 30ma but when connected trips with in a few mins or hours also when tested the unit does not disconnect i initialy thought it was a faulty unit but replaced and still the same any ideas
probs with rcd
- Thread starter paddy12
- Start date
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What was your reason for replacing the incomer?
What testing did you carry out on existing circuits?
Is it a split load board, and, if so, have you split the neutrals correctly?
Is there is outside power and/or lighting?
Do you have any computers connected on the protected side?
Is your earthing and bonding all up to current standards?
What testing did you carry out on existing circuits?
Is it a split load board, and, if so, have you split the neutrals correctly?
Is there is outside power and/or lighting?
Do you have any computers connected on the protected side?
Is your earthing and bonding all up to current standards?
30MA RCD should not be used as the incomer. U should have a split load board.
in addition to Softus's questions, what is the supply type: TT, TN-S, TN-C-S?
in addition to Softus's questions, what is the supply type: TT, TN-S, TN-C-S?
All these questions!
There is little doubt that there is a fault on one of the circuits.
You should be able to get any spark in to locate this fault with his trusty megger.
There is little doubt that there is a fault on one of the circuits.
You should be able to get any spark in to locate this fault with his trusty megger.
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Or a borrowed neutral. IR test wont show that up.
paddy12 said:
Yes
It was not a good idea.
1) most installations have a bit of background earth leakage, mostly on watery appliances like immersion heater, kettle, washing machine and also on heating elements like an electric oven. this background leakage varies, but the chances are that from time to time it will be above the 30mA so all your power will go off. Or it might be above the trip level all the time.
2) having a single RCD as your main incomer means that in the event of a fault, all your circuits will go off, including those which are not faulty. this is always inconvenient, especially as you may have no light to find and correct the fault, and can be dangerous, for example if the lights go out when you are running downstairs, carrying a heavy object, holding a hot chip pan, lifting a child out of bath, up a step-ladder etc.
A borrowed neutral will trip the RCD instantaneously if the circuit is loaded - this trips after minutes. A sure fire pointer to a circuit with low ins res.
And in anycase, this is not a split-load CU is it?
And in anycase, this is not a split-load CU is it?
Softus is right 
RCD trip due borrowed neutral will show on a split load board if (eg) ring final neutral is used on a lighting circuit.
On a board with a 30mA RCD as the incomer, phase & neutral will be in balance even with a borrowed neutral cos all the loads are connected to the RCD.
I'm going to say no more on this thread until we get more input from the OP.
RCD trip due borrowed neutral will show on a split load board if (eg) ring final neutral is used on a lighting circuit.
On a board with a 30mA RCD as the incomer, phase & neutral will be in balance even with a borrowed neutral cos all the loads are connected to the RCD.
I'm going to say no more on this thread until we get more input from the OP.
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