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

[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

 

[KEV 1 N]

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

The impression I got was that they swapped things at the DBs. The OP doesn’t mention anything about boosters, not all E7 installations have that feature.

 

[elsparko]

The impression I got was that they swapped things at the DBs. The OP doesn’t mention anything about boosters, not all E7 installations have that feature.

most of the bigger heaters ive worked on had a booster feature

 

[Toneyz]

What is the modal number and KW rating of this storage heater and how is the circuit connected to the 24Hr consumer unit?You state that the E7 consumer unit has 15A MCB's what is the rating of the 24Hr MCB it was put on?

 

[lurch]

any idea what the heater is pulling (amps)

 

[elsparko]

either way, something is wrong and should have been figured out on the first visit before changing the heater then backtracing from there

im betting your old storage heater has made its way to the skip, or been crushed beyond repair in the back of a van

the OP is too unclear to make sense of, you need a site visit by a competent sparky

 

[elsparko]

any idea what the heater is pulling (amps)

a new heater has been installed and also trips, but it only trips the E7, it is unclear if the link has been made at DB or at 24h/e7 outlet beside heater

the only way to truely diagnose is to be on site

 

[buzzlightyear]

The OP has suggested that this storage heater ijn particular trips any of the E7 MCB's .............. so if its not the MCB, or the heater it has to be the cable and / or connections between the 2!

that's in possible
if theirs a fault on any heaters it would only knock out that mcb .

 

[Deleted member 9648]

Assuming all testing has been carried out effectively and shows no issues. Based on the info the OP has given I would suggest running a temporary new supply cable from the off peak board mcb to the new storage heater and see if it still trips. If it does it must be the heater, if it doesn't it must be the circuit cable.

 

[elsparko]

that's in possible
if theirs a fault on any heaters it would only knock out that mcb .

yes but it sounds like they have connected the faulty circuit into all the other mcbs and has tripped those

 

[elsparko]

Assuming all testing has been carried out effectively and shows no issues. Based on the info the OP has given I would suggest running a temporary new supply cable from the off peak board mcb to the new storage heater and see if it still trips. If it does it must be the heater, if it doesn't it must be the circuit cable.

a permanent temporary?

 

[ipf]

We all know that the fault is probably quite simple, when found, at least. Until visiting site and having personal experience of the situation, I find some of the confident posts a little presumptuous. I don't tend to criticize other tradesmen without that personal involvement. Sorry if it upsets anyone but let's not presume we're talking about simple cockups (even if we are).

 

[Deleted member 9648]

a permanent temporary?

no a temporary temporary....it'll prove a point. Just chuck a bit of T/E round for a night or two and disconnect the circuit cable feeding the offending heater

 

[elsparko]

We all know that the fault is probably quite simple, when found, at least. Until visiting site and having personal experience of the situation, I find some of the confident posts a little presumptuous. I don't tend to criticize other tradesmen without that personal involvement. Sorry if it upsets anyone but let's not presume we're talking about simple cockups (even if we are).

the replacing of the heater was a bit cart before the horse

it should not take 5 visits to be in the same/worse situation than you started with

 

[buzzlightyear]

no a temporary temporary....it'll prove a point. Just chuck a bit of T/E round for a night or two and disconnect the circuit cable feeding the offending heater

what a good idea Stanley

 

[Deleted member 9648]

We all know that the fault is probably quite simple, when found, at least. Until visiting site and having personal experience of the situation, I find some of the confident posts a little presumptuous. I don't tend to criticize other tradesmen without that personal involvement. Sorry if it upsets anyone but let's not presume we're talking about simple cockups (even if we are).

Indeed....I spent 8 hours over 3 visits last week to trace what turned out to be an intermittent lighting fault.

 

[KEV 1 N]

what a good idea Stanley

Maybe these were two of the five electricians?

 

[telectrix]

Indeed....I spent 8 hours over 3 visits last week to trace what turned out to be an intermittent lighting fault.

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

 

[ipf]

the replacing of the heater was a bit cart before the horse

it should not take 5 visits to be in the same/worse situation than you started with

As regards the heater, maybe.....but how do you know it's state, or whether previous tests were or were not carried out.
Five visits seems excessive but how do we know what they involved or how long they took?

 

[elsparko]

no a temporary temporary....it'll prove a point. Just chuck a bit of T/E round for a night or two and disconnect the circuit cable feeding the offending heater

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

a farmer i know supplied one of his sheds with steel fence wire, over about a kilometer nailed directly to the top of fence posts

basically a 230v electric fence, cant remember what sort of animal was unfortunate enough to land on said fence but it blew the main fuse

 

[KEV 1 N]

a farmer i know supplied one of his sheds with steel fence wire, over about a kilometer nailed directly to the top of fence posts

basically a 230v electric fence, cant remember what sort of animal was unfortunate enough to land on said fence but it blew the main fuse

Would have been fine if the fence posts were taller!

 

[elsparko]

Would have been fine if the fence posts were taller!

i think it was a deer but may have been a cow, this is war story that was swapped so never seen it first hand

 

[KEV 1 N]

i think it was a deer but may have been a cow, this is war story that was swapped so never seen it first hand

I can believe it, it’s the sort of thing a farmer would do as opposed to spending money!

 

[elsparko]

I can believe it, it’s the sort of thing a farmer would do as opposed to spending money!

why should he shell out for insulated copper when he has an almost infinite supply of steel fence wire?

bloody farmers...

 

[KEV 1 N]

why should he shell out for insulated copper when he has an almost infinite supply of steel fence wire?

bloody farmers...

Haha! There’s a bloke at our place keeps horses (or used to when there was money in them!) He fitted some lights in a farmers barn......his payment?
Three bails of hay!

 

[buzzlightyear]

this post is now getting like one that flew over the cuckoos nest.

 

[KEV 1 N]

this post is now getting like one that flew over the cuckoos nest.

A classic!

 

[SparkyChick]

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.

 

[buzzlightyear]

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.

how can 5 sparks not work out were the fault lies .not very good is it .

 

[Bob Geldoff1234]

If i was trying to fault find this i would do the following.
1.Clamp meter the live cable feeding the heater to find out the current it is pulling.
2.Change the 20 amp switch.
3.Change the flex feeding the heater.
4.Depending on the current try fitting a 20 amp breaker instead.

The other difference between day time running and night is the temperature drop during the night.It might have something to do with it?Maybe not.

From what i can read from this,then my guess is that the day time running(when its not tripping) is not run for long enough for the fault to develop.ie. 3 hours into the night the breaker trips.Day time half an hour running everything seems ok.
Like others have said failing all the above,run a temporary wire to the heater to see if this helps and if so then rewire it.

 

[marconi]

Reading the symptoms and what has been tried out I reckon the problem is the MCB for the large NSH (3.4kW) is of inadequate rating for the load current 14A at 240V. The E7 board does not take into account derating of this MCB for grouping and ambient temperature. In service it has too low a rating for its load current and its situation alongside 3 other MCBs through which steady currents of circa 10-14A are flowing for prolonged periods. It is not surprising they are getting warm, and that the one that trips first is the one through the highest current is flowing for the large NSH.

Switching the large NSH to the 24/7 board I guess powers it from an MCB which is situated alongside only lightly loaded MCBs - it can more readily dissipate the Ohmic heat and thus has a higher in-service rating.

The answer if possible is to swap the MCBs for 20A ones - a study will have to be done on the E7 cabling and its installation method to ensure this is safe to do.

see this piece on Hager MCBs for more information:

 

[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.