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Topic Title: night storage heater trips RCCB even when turned off
Topic Summary: any advice welcome
Created On: 05 December 2012 02:15 PM
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 05 December 2012 02:15 PM
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thermalCat

Posts: 2
Joined: 05 December 2012

Hi to all,

I have 4 Dimplex night storage wall mounted heaters in the house. Each has a single power switch (in a seperate white box - similar to a domestic 13A outlet, but without the plug&socket). They all go back to a fuse box via a single circuit breaker.

Problem is, the circuit breaker trips at midnight(ish) even when all the heaters are switched off. If the circuit breaker switch is reset during the night, it instantly trips again. If the switch is reset during the day, it trips the following night.

The past few weeks we have gradually incrreased the input setting, while leaving the boost on minimum. The problem seemed to coincide (to within a day) of turning the input setting up a tad.

Any advice gratefully recieved.

Dave

ps. excuse typo's. I'm wearing gloves, for obvious reasons.
 09 December 2012 10:23 AM
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normcall

Posts: 8120
Joined: 15 January 2005

" I'm wearing gloves, for obvious reasons. " (wimp)

It sounds like you have an earth fault - dead short between live or neutral to earth.
The obvious remedy would be to test the insulation resistance between earth and live/neutral.
The second obvious would be to isolate the heaters by turning the heaters off by the switch beside them. This would normally isolate both live/neutral from the supply and then 'simply' wait until the off peak came on, turn each heater on until one tripped the RCD. Leave that one off, the rest should then work normally and the next day, investigate problem with the odd heater.

After that, it could be any number of things from the heaters being damp (have they been off for some time?), the local isolator nor double pole (leaving either live/neutral still connected), a fault nearer the fusebox or just overload if never been used before.

"They all go back to a fuse box via a single circuit breaker. " Not clear about this one as each would normally be a separate circuit back to a separate distribution board and each heater with own overload protection etc.

Just noticed the date, so I expect you have now resolved the problem.

-------------------------
Norman
 09 December 2012 11:56 AM
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thermalCat

Posts: 2
Joined: 05 December 2012

an electrician came round for quick look on friday.
two of the heaters showed an internal fault ( quite possibly damp, as I think the property was empty for a while before we moved in), and the insulation resistance between neutral & earth indicated a fault somewhere between upstairs and the distribution board.

about the single circuit breaker: The NS heaters do indeed have their own distribution board (an old fuse box). and there is a single large circuit breaker mounted next to this board, (which trips just after midnight if I reset it in the day). I have changed my mind about the order - I now think it goes (RCD - fuse box - heaters) rather than (fuse box - RCD - heaters) , but I can't see for sure without fetching floorboards up.

Anyway, it's up to the landlord what he wants to do now, but thanks v much for posting. I Will post the outcome here just for completeness.

Dave
 09 December 2012 03:03 PM
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normcall

Posts: 8120
Joined: 15 January 2005

Generally, the line of command is:
1 - Meter
2 - Time switch
3 - RCD (not strictly necessary as fixed loads, but frequently fitted - ours is 100mA due to the bricks within NSHs do absorb moisture like its going out of fashion, hence the apparent fault.
4 - Fusebox
5 - Off to a number of single circuits.

You are very unlucky if you have an earth fault on all the circuits ( the insulation resistance between neutral & earth indicated a fault somewhere between upstairs and the distribution board.)

May I suggest that your or your landlord have someone familiar with NSHs as many 'new' boys have never seen them.

Sadly, I can recall installing them in the early 1970's in a small workshop where the client supplied the heaters. The bricks were left outside and after the first evening, the heaters were dripping water and about a pint of water all over the floor - that was the worst case, steam is more common, but in those days a RCD were not 'the default' and even then, the now usual 30mA were more like 500mA or usually voltage operated devices.

I've installed them for many years and have 9 myself (bought 2nd hand 30 years ago!), so I know most of the quirks if you have problems.

-------------------------
Norman
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