Our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area. This Question of the Day, concerning a difficult to detect intermittent fault in a house, is answered by the ECA:
Now that the RCBOs have been fitted, we now know that the fault is on the downstairs ring. We carried out insulation tests on the ring main and found no fault. We unplugged everything so that the only item remaining was the central heating, which is off the ring main. The customer said that the boiler had been serviced, so there should have been nothing wrong with that - she thinks that it is our fault.
I know that service engineers don't carry out insulation tests. What is the best way to test the heating to eliminate the fault?
In the past, I have isolated the pump and the fault was found. Also, on another job, I found it was m/valve, but both of the above were easy to detect as the RCD would not re-set. However, with this fault, the problem is that as soon as the customer switches the RCBO back on, it is OK for a few days before it trips again!
Answer: One way is to isolate the heating system from the ring main and temporarily connect to another circuit to see if same thing happens. Alternatively, inspect, check and disconnect the electronic devices of the heating system and carry out insulation tests on the same.
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