UK Need advise on RCD query

[Hoggyd]

Hi all,
The rcd in my single rcd consumer unit keeps on tripping.
It first happened when I turned the kettle on. It then happened when I turned my shower on. Both of these times my portable radiator has been on. I have tried the kettle and shower both at the same time and individually when the radiator was off and they were fine. With both of those devices off and the radiator on, the RCD trips again after about 20 min. I therefore think it is the radiator causing it to trip. If I buy a portable RCD and plug it in and then the radiator into it, if it trips the portable RCD, would this confirm that it is the radiator at fault?

All sockets in my flat appear to run off this one RCD. I have tried the radiator in multiple sockets and it still happens. Everything was fine until recently. I just don't want to spend on getting an electrician in if its just the radiator being dodgy.

Any advice appreciated.

Thanks

Dan

 

[ipf]

A current leakage causes the RCD to trip, Most connected items will produce some leakage whilst operating. The RCD operates when the leakage reaches a certain level. Your rad may be close to the MCB operating threshold and, as a result, using the shower or kettle may be adding leakage and causing the tripping. When having a shower or sorting a brew, turn the heater off.
This is only a suggestion. You would be best advised having an electrician investigate, especially if it gets worse, as there is obviously some sort of problem.
edit.

 

[telectrix]

my money is on the radiator element breaking down when it gets hot.(20 minutes). easiest option costing nowt is if you could borrow a sililar rad. from family or a mate. if that trips, you may have a wiring problem. if not, it almost confirms that your rad. is the problem.

 

[James]

If the radiator has not been used for a long time, the oil can absorb moisture and cause it to have a higher leakage current than normal.
Leaving it on for a couple of days will gently drive the moisture out if this is the case.

 

[Hoggyd]

Thanks for your advice guys! Pretty much confirmed what I though. I will try and find a similar radiator to test, but I think it is the current rad causing the problem. Its strange that the first time it happened all 3 were on, but now it just happens when only the rad is on and the other 2 are off. Would it be worth me checking all the plug sockets to make sure there is no loose wiring?

 

[Lucien Nunes]

One likely scenario is that you have a neutral-earth fault either in your fixed wiring or an appliance plugged in, not necessarily any of the appliances that you have associated with the tripping. The clue is that tripping occurs when high-wattage heating loads are switched on, which cause more voltage drop in the wiring which drives more leakage current through the fault wherever that is. I would not be surprised to find, for example, a neutral-earth short in your socket-outlet circuit near where the heater is plugged, in, so its load contributes more to pushing the leakage over the trip threshold than other appliances of similar wattage. The shower is likely the heaviest load in the house so that has an impact despite being electrically further from the fault.

This type of fault can be found quickly and easily by an electrician with suitable test equipment. It can also lie low if not provoked, so merely not experiencing a trip does not indicate it has gone away, only testing will confirm that.

Re your plug-in RCD, that's not a very good test as RCDs all have slightly different thresholds, so any or all RCDs in circuit with a load might trip without preference as to the order. Absent a neutral earth fault and supposing the heater to be leaking excessively, I would still expect the RCD in the consumer unit to trip first as that will be subject to additional normal leakage from the rest of the installation, from which you could easily draw the wrong conclusion.

 

[Hoggyd]

One likely scenario is that you have a neutral-earth fault either in your fixed wiring or an appliance plugged in, not necessarily any of the appliances that you have associated with the tripping. The clue is that tripping occurs when high-wattage heating loads are switched on, which cause more voltage drop in the wiring which drives more leakage current through the fault wherever that is. I would not be surprised to find, for example, a neutral-earth short in your socket-outlet circuit near where the heater is plugged, in, so its load contributes more to pushing the leakage over the trip threshold than other appliances of similar wattage. The shower is likely the heaviest load in the house so that has an impact despite being electrically further from the fault.

This type of fault can be found quickly and easily by an electrician with suitable test equipment. It can also lie low if not provoked, so merely not experiencing a trip does not indicate it has gone away, only testing will confirm that.

Re your plug-in RCD, that's not a very good test as RCDs all have slightly different thresholds, so any or all RCDs in circuit with a load might trip without preference as to the order. Absent a neutral earth fault and supposing the heater to be leaking excessively, I would still expect the RCD in the consumer unit to trip first as that will be subject to additional normal leakage from the rest of the installation, from which you could easily draw the wrong conclusion.

Hi Lucien, Thank you for your reply. If I were to check the sockets, would an issue be visible if there is one? I.e. burning on the wire or loose connection?

If the shower is off at the isolator pull cord, does this "remove" it from the circuit? I.e. Can I rule that out as a cause?

Yesterday I had everything plugged in as I normally would e.g. Microwave, Kettle, Tv, Sky box, ect and it was fine all day. I put the rad on at night and it tripped after 20 mins. So it seems that its either a fault with the Rad specifically causing it to trip or its just the straw that's breaking the camel's back.

If I can check the wiring and can see no faults, then the only logical reason is the rad going faulty?

 

[Lucien Nunes]

The neutral-earth fault I mentioned won't be a loose connection. It is more likely to be a screw through a cable in the wall behind a cabinet or a cable trapped against a heating pipe under the floor.

Yes, isolating the shower at the pullcord prevents it contributing leakage.

Your final question is a non-sequitur. Not all faults are visible to the naked eye, and faults caused by cables chafed against back boxes sometimes clear when you unscrew the accessories to have a look. The rad might well be faulty, but without electrical testing anything more is speculation.