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??

 

[elsparko]

Could it not be (as @Murdoch has also hinted) that it's simply a case of the MCBs in the E7 board are getting a little past it?

7 hours a day running near the limit for extended periods of time is going to have some effect on the bi-metal strip.

If they've been thorough and the heater checks out, the cabling etc. checks out and it doesn't trip on an MCB in the 24 hour board, really that leaves only one thing... the MCB in the E7 board. Change the one feeding the heater that causes the trips for a new one and see if that solves it.

but all e7 mcbs going at the same time would seem very unlikely, from what i gather they have tried putting the circuit into other mcbs in the e7 board and all have tripped with the troublesome heater/circuit

i think we have all given our fair share of free advice

 

[Toneyz]

Could it not be (as @Murdoch has also hinted) that it's simply a case of the MCBs in the E7 board are getting a little past it?

7 hours a day running near the limit for extended periods of time is going to have some effect on the bi-metal strip.

If they've been thorough and the heater checks out, the cabling etc. checks out and it doesn't trip on an MCB in the 24 hour board, really that leaves only one thing... the MCB in the E7 board. Change the one feeding the heater that causes the trips for a new one and see if that solves it.

Has this not been tried on the using the other MCB's in the E7 board

 

[buzzlightyear]

we are all speculating what if or may be that .if all else fails bin it .

 

[buzzlightyear]

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??

faulty fuse change !

 

[DC-backfrom the past]

If all relevant testing has been done and nothing shows up.
the heater works on other board ok .
then I would try and replace the relevant mcb that's tripping for a new one or one from the other board if it fits. I believe Murdoch has pointed that out already.

this seems to be the most obvious problem that's staring out.....providing all information to date is correct.

 

[Octopus]

Could the op post a picture of the E7 board and the 247 board?

 

[ipf]

Pretty sure its a 15amp MCB. The point is the particular heater trips any of the 15 MCB's on the E7 board they put it into (the other night storage heaters don't), but the heater does not trip any of the 15 amp MCB's on the main fuseboard when they wire it to that.

Just noticed...if they are 15amp breakers, the unit is getting on a bit. Are you sure they aren't 16 amp?

 

[PEG]

Just noticed...if they are 15amp breakers, the unit is getting on a bit. Are you sure they aren't 16 amp?

Bingo! ...and finally,someone spots the detail,that leads me to believe,the OP is a bit more "involved",than we think

 

[dmxtothemax]

If it is an over current situation ? Then maybe the normal system is better able to provide the high currents needed, which is why it does not trip, but the E7 system is clearly struggling, it might be choking a bit causing currents to rise. You need to do a good low resistance check on both systems, i bet the E7 system has a higher reading !
QUOTE - [when you have eliminated the impossible, whatever remains, however improbable, must be the truth ! ]

 

[Deleted member 9648]

is an intermittent lighting fault one that occurs only when switched on but fine if left off. ?

Bang on...(pun intended)...was a big old house, turned out to be a PIR buried under ivy and unknown to the householder, what it switched on was also unknown, but a L-E fault on the switched side led to a JB under the floor where the cable with the fault could be disconnected. Testing at the DB was clear, but every night at some point the mcb would pop when the PIR activated. A poxy job to trace that one.

 

[snowhead]

102 replies, I'm feeling left out..

I'll go with some of the above answers.
The Storage heater is probably close to the 15amp rating of the MCB. If they're 15 amp, then they're fairly old and degrading.

With 4 heaters into the same board, they'll all be getting hot, which will reduce their rating, whereas with just the one in the non E7 board there's no other constant high loads.

I suspect the original heater was O.K, but I wouldn't want to put it back now it's out.

Either put the new Storage heater on a new MCB in the E& board or turn off the other heaters for 1 night and just leave the suspect one on it the E7.

 

[telectrix]

in the time this thread has been going on, could have installed a gas boiler and 6 rads.

 

[Deakon]

Hi, I am one of the electricians looking at this issue. I’m replying here for advice and not criticism. Originally the cable feeding the heater was down to earth. We replaced the cable from fuseboard to heater, new double pole switch and connected to old heater. Customer rang back 2 days later it had tripped again. We tested the heater and it was showing a fault. So we replaced the storage heater and it tripped again. We have done numerous tests on the cable and showing completely clear. (As you would expect with a brand new cable). We also replaced the MCB in the E7 fuseboard twice. Still tripping. Rigged up on temporary 10a lead and didn’t trip. Yet tripped as soon as on 20a mcb in E7 board. I have now connected it into a 16a fuse in the fuseboard which is not E7 and it ha been on for 2 days without tripping. We have done all tests on heater, E7 fuseboard, cable and double pole switch. The only possible thing left is the E7 meter. Any help would be appreciated but not here for criticism.

 

[elsparko]

we are all speculating what if or may be that .if all else fails bin it .

Hi, I am one of the electricians looking at this issue. I’m replying here for advice and not criticism. Originally the cable feeding the heater was down to earth. We replaced the cable from fuseboard to heater, new double pole switch and connected to old heater. Customer rang back 2 days later it had tripped again. We tested the heater and it was showing a fault. So we replaced the storage heater and it tripped again. We have done numerous tests on the cable and showing completely clear. (As you would expect with a brand new cable). We also replaced the MCB in the E7 fuseboard twice. Still tripping. Rigged up on temporary 10a lead and didn’t trip. Yet tripped as soon as on 20a mcb in E7 board. I have now connected it into a 16a fuse in the fuseboard which is not E7 and it ha been on for 2 days without tripping. We have done all tests on heater, E7 fuseboard, cable and double pole switch. The only possible thing left is the E7 meter. Any help would be appreciated but not here for criticism.

brand new cable? so its been re-wired and still tripping?

this thread is too unclear

 

[SparkyChick]

Hi Deakon, welcome to the forums.

Sounds like you're having a fun time with this.

Someone has already mentioned heating... this circuit, is it in the middle of the MCBs on the E7 board? Is it possible that it is overheating with the combined heat from the MCBs either side? Have you tried moving it away from the other MCBs?

And, donning my tin bonnet, I'm just throwing ideas out there because it does sound like they've done everything that's been suggested so far.