Heating element tripping the rcd

[pawpaddy]

Hi all

Just after a quick bit of advice please!

Have a towel radiator fixed up to the central heating system but it is also fitted with an electric heating element. The electric element worked for ages and then one day in the spring it just suddenly stopped heating up. I put this down to old age (it must have been at least a couple of years old) and decided to change it for a new one.

I finally got round to installing a new electric element last month and again it worked fine. Until last week, when it started tripping out the RCD as soon as it was switched on. No problem with any other electrics in the house (had it re-wired when we moved in 2 years ago) and no problem with the RCD when the element is switched off - the RCD just trips immediately as the element is switched on at the wall socket.

It was a 'mare having to get the radiator off the wall, etc, to change the element in the first place so I am hoping it is not the element that is faulty. Anyone have any ideas as to what I can do to diagnose the problem?

 

[JohnD]

Assuming you connected it correctly, element sheathing is probably cracked and water has got into the electrics.

Did you add an inhibitor when you refilled the system with water?

 

[pawpaddy]

Pretty new at this DIY malarkey, so no, didn't add inhibitor! Could this have caused the sheathing to crack?

How much do I not want to fit another element?!

 

[ericmark]

these are the testers used to find the type of fault you have. The one shown is a cheap version at around £150 but normally cost a lot more.

Maybe you can hire one. But without a tester of this type you can't be 100% sure you have found the fault.

You can likely buy a cheap multi-meter for a £10 but although you may find the fault it also may fail.

Most likely the element has failed. It is very easy with duel fuel types to force the water out and then overheat and burn out. There are different quality with some having thermostats and some just being very low output.

Unless you are technical minded then likely you are better off getting some one to do the work for you and giving you some warranty so if there is a problem with water draining from system you will not have the bill next time.

 

[JohnD]

CH systems need an inhibitor to prevent internal corrosion. Sentinel and Fernox are the two best-known brands at about £15 a bottle. Cheaper ones may be cheaper ones.

I don't know the quality of sheaths on those rad elements. For immersion heaters you can get Incalloy-sheathed ones which last a long time.

Depending what your system had in it before, and whether you drained it fully, and how old it is, you may need just to add inhibitor, or it might need a clean first. Post on the Plumbing section with those details. Also, do you have to bleed air out of the radiators; have you got a feed and expansion tank in the loft or is it sealed system; what colour is the water; is there mud in the F&E?

BTW, I hope you put the element at the bottom of the rad, not the top?

 

[pawpaddy]

Thanks John D and ericmark.

I'll try cleaning and inhibiting the system to see if that sorts it. But if not it sounds like it will be a problem with the element, which is what I suspected. I will have to invest in a quality element and hope it lasts a bit longer next time.

I will go to plumbing section to see what they advise too.

Cheers

(and, yes, it was fitted at the bottom!)

 

[JohnD]

it will be the element. the absence of inhibitor might have contributed to its early failure. Adding inhibitor will not mend it.

You can ask the plumbers for advice on getting the rad off. Post a pic if you can.

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