Totally stumped. Night Storage Heater tripping out MCB, but ok on daytime circuit.

[Steve Poulton]

Please help. I have a basic understanding of electirics, but 5 Electricians are stumped and I don't know where to go next. My mother in law heats her house by 4 Night Storage Heaters, all of which are wired to a Economy 7 supply/fuse board, with no RCD just MCB. The largest of the Night Storage Heaters began to fail and trip the MCD. To cut a long story short, she ended up having a new one fitted. Unfortunately this new one also now trips the MCB. The electricians have tried swapping the various supplies to the various heaters around in the E7 fuse board and the same heater is tripping the different MCB. It would be an obvious thing to consider that there is a fault on the circuit between the board and the night storage heater. However, they have now wired it into the day time board and it is not tripping. Has anyone got any ideas as we need to get it wired back into the E7 circuit??

 

[Steve Poulton]

Murdoch. The same company that supplied the heater are trying their hardest to solve, not asking others to solve. I am seeking suggestions. I think the only thing to do is to fit a new E7 fuse board with RCD. But that still doesn't make sense if all the other heaters work in what ever MCB they are in and to repeat there is no fault with the circuit to the problem heater as it works fine on the normal supply.

 

[AJshep]

There's not much to a storage heater, In your case probably 3 elements and 24 bricks.

If they have "fully" tested the circuit, the heater including all the elements and it is ok, then the only other thing it could be is a loose connection somewhere creating a high resistance or what Buzz mentioned, a faulty mcb.

 

[Dave OCD]

3 elements would be 12 bricks and 4 elements [The largest conventional NSH at 3.4kW] would have 16 bricks.

 

[Octopus]

Murdoch. The same company that supplied the heater are trying their hardest to solve, not asking others to solve. I am seeking suggestions. I think the only thing to do is to fit a new E7 fuse board with RCD. But that still doesn't make sense if all the other heaters work in what ever MCB they are in and to repeat there is no fault with the circuit to the problem heater as it works fine on the normal supply.

So that wouldn't be a sensible idea .

When the circuit trips, the RCD will shut off ALL the E7 circuits, so your mum will be without any heat..

Its never a good idea to change a fuseboard when there are problems...

If the heater works for a while, then it may well suggest a problem with heat build up in the cable - you state that the heater works on normal rate electricity, but how long did they leave it on for?

I'm guessing that they added a temporary link from the 24x7 board to the cable in the E7 board to said heater? Were you there when this was done?

 

[westward10]

So that wouldn't be a sensible idea .

When the circuit trips, the RCD will shut off ALL the E7 circuits, so your mum will be without any heat..

Its never a good idea to change a fuseboard when there are problems...

If the heater works for a while, then it may well suggest a problem with heat build up in the cable - you state that the heater works on normal rate electricity, but how long did they leave it on for?

I'm guessing that they added a temporary link from the 24x7 board to the cable in the E7 board to said heater? Were you there when this was done?

See #36 and #38.

 

[Strima]

Could be a short on the cable that only occurs when it gets up to operating temperature. IR @500v for a few minutes may show a short somewhere.

 

[static zap]

The answer envolves a patient late night electricain and a current clamp.

 

[paul291277]

Please confirm:

Each Storage Heater has its own MCB on the E7 board and all are the same rating?

Same heater will trip any MCB on the E7 board?

You say it's the largest heater which rings bells for me

E7 MCB appears to be tripping a few hours into night storage heater charge. it is not overheating as it does not trip RCD on main board when wired to that.

RCD will not trip if it gets too hot, MCB will!

But it will operate for hours on all MCB's in normal CU?

Are the MCB's in the main CU the same rating as the E7 one?

 

[Octopus]

See #36 and #38.

We don't know how they achieved the link from the 247 board to the heater ..........

 

[ipf]

We don't know how they achieved the link from the 247 board to the heater ..........

Is it a split board? If so, I don't doubt the simplicity.

 

[Steve Poulton]

It cant be the cables as they work fine when wired into the daytime supply. I will suggest that the guys to replace the E7 MCB unit's. my hunch is that because its an old E7 unit and the main unit is newer. The MCB's may have failed and are too sensitive and need upgrading, hence the heater not tripping the normal MCB when wired into that.
Thanks everyone who offered useful advice.

 

[Taylortwocities]

I didn’t spot this in the missives above.
What is the make, model and power rating of the heater?

 

[KEV 1 N]

It cant be the cables as they work fine when wired into the daytime supply. I will suggest that the guys to replace the E7 MCB unit's. my hunch is that because its an old E7 unit and the main unit is newer. The MCB's may have failed and are too sensitive and need upgrading, hence the heater not tripping the normal MCB when wired into that.
Thanks everyone who offered useful advice.

That’s what I’m thinking. Older mcbs in your E7 are more sensitive

 

[elsparko]

at first i thought he had put the "faulty" + new heater onto the 24hour supply and that they worked fine, and that this was done at the outlet rather than the db

if this is the case then its the e7 circuit that is faulty, and they have been using the 24h outlet next to the e7 outlet to test, sounds like they do not have the correct test instruments if this is how they are conducting their fault finding

buying new accessories comes after fault finding, not before.

 

[elsparko]

That’s what I’m thinking. Older mcbs in your E7 are more sensitive

im thinking the way they have connected the booster+storage heaters into the 24hour supply and it now works

i dont think they have taken the circuit from the e7 board and tried it on the 24h supply

rather they have taken the 24hour supply and put the storage heaters on that circuit outlet

thats all that i can gather/make sense of