In the only property (flat) I let, I had an old electrical consumer unit which my electrician had been telling me would benefit from upgrading to all RCDs instead of the existing MCBs. Now when it came to the EICR test time, I asked him if it was necessary to replace the consumer unit and he said yes. This was before I booked him to do the Eicr. So I trusted him and got him to do both. About a month since then, the tenants reported an RCB in the kitchen had tripped which had the fridge on it. They tried to turn it back on and it came back on. A couple of days later same thing happened and when they tried it didnât reset till about an hour later. When the electrician came to check he said there was nothing he could do while the RCB hasnât tripped. He recommended putting back an MCB into the circuit which had the fridge to avoid the nuisance trips. Since he said it was safe, I let him do that. Now a month on another RCB has tripped in the kitchen this time on the circuit that has the oven on it and nothing else. Tenants themselves reset it but this time the electrician is saying the oven must be faulty. I pushed back on this saying suddenly all kitchen appliances canât end up being faulty after the consumer unit change. He has offered to come in but if he again says thereâs no current fault what do I do? Are there tests he should be performing?
When he replaced the consumer unit should he have run some tests to find such issues? Or could the kitchen have existing issues in wiring which may intermittently trip RCBs but not MCBs?
I am so annoyed that I trusted the electricianâs word that I needed to change the unit when it may not have been necessary to pass the EICR and heâs created a bunch of issues for me. How should I proceed?
MCB s i have in a couple of places . Still got a pass. . An faulty appliance will trip a breaker, but if the appliance IS faulty it will not reset. The cynical may say that it was all not needed at all.
Annoyingly before replacing the unit he said to me the current one doesnât meet the standards so needs replacing. Once replaced he said existing MCBs arenât a problem so it wasnât an issue to put back an MCB. Mainly looking for some guidance on what tests that should be done by this guy when he comes back to find out whatâs causing these intermittent trips in more than one circuit. Can the RCBs themselves be faulty?
RCB S are very sensitive I have never had a faulty one but possibly wrong RCB in place?
What do you mean by âwrong RCBsâ?
For example a 20 in instead of a 32
RCDs and MCBs do different things https://www.mybuilder.com/electrical/articles/rcd-vs-mcb - even if the sparkyâs work has revealed other problems you werenât aware of and thatâs frustrating.
2. A modern RCD is pretty much essential to protect tenants and my understanding is most electricians wonât issue EICRs without them and almost all domestic properties need them
https://certifiedelectrician.co.uk/rcd-protection-guide/
3. You may just have old wiring or faulty kitchen appliances and the new rcb is more sensitive to them. And nothing done wrong by the sparky. You can of course check his qualifications⌠which you should have done before employing him. You can also ask on electricians forum like on diynot. But sounds like a good one not necessarily a cowboy as coming back. How old is the oven and how old is the fridge? How many years since the property was last re-wired?
4. One thing to be aware is that ovens can often trip if not used for a while due to moisture buildup inside. Most people use ovens rarely these days - air fryers and combi microwaves do the same job quicker and cheaper by heating a smaller space. So ask tenants if theyâd used oven at all or recently before it tripped. The solution is to use the oven on a low temperature for a while first then gradually increase the temperature.
"Immediate Actions to Take
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Dry it out: If you have just turned it on and it tripped, try resetting the breaker and immediately setting the oven to a low temperature (\(50^{\circ }\text{C}\)â\(80^{\circ }\text{C}\)) for 30â60 minutes to dry out the heating elements.
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Gradual heating: Run the oven on low heat, then gradually increase it over several hours, letting it run at high temperatures to expel all moisture."
Good luck
Nope. Thatâs not accurate. Best get the spark to inspect the circuit thoroughly
what is not accurate?
You are advocating changing a breaker value when you donât know if it can be. Thatâs dangerous
No I never did Gk said it had tripped .I said maybe there is a wrong size breaker in it. I never told him to change it
No, Earth Leakage is supposed to trip the Residual Current Deviceâs -RCDâs, (RCBOâs in your consumer unit for each circuit )So the oven has occasional / intermittent earth leakage?, most likely the heating element which is least used if there are 2 in a single oven with a grill element as well as the oven element. The tiniest earth leakage from Line (Live) to Earth will do it. Anything with electronics inside (Microwave, Fridge?) or a heating element - Kettle, Washing M/c, D/Washer, Oven. Sparky will have provided you with a report showing his readings which includes Insulation Resistance of the existing cables. If these are failing due to age this could also provide a leakage path of current which would trip the sensitive RCD on that circuit. A clamp meter on the meter tails (for the total mA leaking) and then on each circuit will show if there is one circuit being âleakyâ more than others by monitoring the difference in current btw Line and Neutral. If there is a difference in 10âs of milliAmps its going somewhere - to earth via the CPC wire (Earth connection)
MCBâs - plain old circuit breakers only trip with overcurrent of 1.5 times their rating or so. They do not monitor or trip for any minor leakage to earth. RCDâs are designed to do both and are called RCBOâs when fitted to an indidual circuit in a C/U.
How have you now proceeded with your Sparky?
What else was on the fridge circuit, was it the kitchen ring which would serve all the sockets by any chance? So a kettle or an Air Fryer used on that circuit with the Fridge on it would trip if âleakyâ Its just the way of things these days. The Cooker is always served by its own radial feed and MCB.