storage heaters

CSP2012 · Jun 24, 2014

Hi all. I hope you're all well.

I was wondering if anyone could help me.
I've been asked to look at some storage heaters that are tripping. Council have recently upgraded consumer units. It's now a main RCD switch protecting 3 circuits. The RCD trips at random times. Not when the storage heaters come on but before. I have insulation resistance tested all 3 circuits and all clear. Lowest reading was 800 off M ohms.
The one thing I did notice though was there was 5 volts on neutral and earth. So I assume this is causing an imbalance... The tenant wasn't in so couldn't get to the incomer. Does anyone know what would cause this? I the off peak usually has it's own neutral but so could it be that it's sharing the neutral with the 24/7 supply?
Any help would be great. Thanks

Welchyboy1 · Jun 24, 2014

CSP2012 said:
Hi all. I hope you're all well.

I was wondering if anyone could help me.
I've been asked to look at some storage heaters that are tripping. Council have recently upgraded consumer units. It's now a main RCD switch protecting 3 circuits. The RCD trips at random times. Not when the storage heaters come on but before. I have insulation resistance tested all 3 circuits and all clear. Lowest reading was 800 off M ohms.
The one thing I did notice though was there was 5 volts on neutral and earth. So I assume this is causing an imbalance... The tenant wasn't in so couldn't get to the incomer. Does anyone know what would cause this? I the off peak usually has it's own neutral but so could it be that it's sharing the neutral with the 24/7 supply?
Any help would be great. Thanks

Have you got a milliamp meter to test with

have you tested the heaters individually IR between LN and earth

failing that shut one down at a time for a few days and see what one stops tripping it(ensure its on a DP switch and not a single pole spur)

can you install rcbos if they are all leaking a little bit

Are they old heaters, may be circuit board

have you ramp tested rcd, is that ok

doubt its the meter as it would be upstream of the rcd

CSP2012 · Jun 24, 2014

Thanks for the reply welchyboy.

See I didn't think it'd be the incomer but just had that 5volts which made me think..

The storage heaters arnt new but I've seen older.
I have got the tenant isolating all individually. He did it at the breakers and now I've got him doing it through the dp switches but still no good.
I thought it was more than likely one of the heaters but isolating them has ruled that out.
I IR'd all individually aswel as together.

So all in all I'm pretty stumped now. Only thing I can think is faulty RCD?
But now you've said accumulative leakage could be the problem.. But again 2 have been isolate leaving 1 open and it's still tripped..

Richard Burns · Jun 24, 2014

Since the heaters are not at fault there may be rodents eating a cable even one with exposed live conductors would give a good IR reading, up until the mouse nibbles it!

CSP2012 · Jun 24, 2014

It's a downstairs flat (purpose built) so I doubt it. Think the supplies were even surface in trunking...

R G · Jun 24, 2014

Storage heaters are notorious for RCD Nuisance tripping ,especially when first switched on after the summer , I would try and avoid RCDs if you can , i.e. surface wiring and no cables buried in walls and not in special location , thats if everything tests out o/k though , if you have a leakage fault thats gotta be rectified whatever , the only way is a clamp meter that registers milli amps , test for leakage down the earth when live ..