What have I done wrong to immersion heater

[musicjunkie]

I have a problem and would much appreciate any help. I have an immersion heater which is heated overnight on Economy7 tarriff and has a separate control box for a 2hr boost when needed outside theses times. I foolishly turned the boost switch on whilst it was being heated by Economy7 and it tripped out in the fuse box. I put switch back into on but still tripped. Only way I could get power back to fridge etc was to turn off immersion heater power in it's cupboard. Haven't a clue what's happened - anybody any ideas please. Thanks

 

[AndyPRK]

Pics always help. Eg immersion heaters. Are there 2?

What has tripped? A wide rcd with test button ?
Or MCB marked b16 ?

 

[RF Lighting]

Does your cylinder have one or two heating elements in it?

 

[musicjunkie]

Immersion has just one element goin in at the top...The ciruit board feed that keeps tripping is marked MCB B16 61/B16.

There are 2 switches in the airing cupboard one is marked 'off-peak'.... the booster is Pactrol WHB2

Thanks

Read more: //www.diynot.com/forums/electrics/immersion-heater.406708/#ixzz36gSuHzjB

 

[westie101]

Check (or get checked) the connections in the two switches that there is not a live neutral cross somewhere

 

[EFLImpudence]

If there are two elements (a dual) then the MCB would trip if both were turned on.
This would indicate that the wiring is not correct or the Pactrol is faulty.

Are there two cables going to the element?

Is it 'back to normal' now with the boost turned off?

 

[JohnW2]

Immersion has just one element goin in at the top...The ciruit board feed that keeps tripping is marked MCB B16 61/B16. There are 2 switches in the airing cupboard one is marked 'off-peak'.... the booster is Pactrol WHB2

What sort of Economy 7 setup do you have? Does it simply give you cheap rate for everything in your house during the night, or is there a dedicated supply for the immersion which is only 'live' during the night-time hours? If the former, where is the time switch or controller which makes the immersion only work at night?

Kind Regards, John

 

[JohnW2]

If there are two elements (a dual) then the MCB would trip if both were turned on. This would indicate that the wiring is not correct or the Pactrol is faulty.

You will see that I've just asked the OP a question - and there may be 'follow-up questions'!. The whole idea of the Pactrol MHB2 is that it switches the element between a low-rate-only and permanently-on supply, so that one can power the heater (for up to 2 hours) when the low-rate supply is 'off'. If it were wired like that, there would have to be a second supply, presumably with its own separate MCB.

There are, of course, other ways in which it could have been wired - but, as you suggest, I can only see it producing an overload problem if the MHB2 powered a second (never normally used) element from the low-rate-only supply - which would be a rather odd way to wire it!

Kind Regards, John

 

[musicjunkie]

Yes there are 2 cables goint to the element. Both the supply switches are on but not the Pactrol. If I attempt to switch on the 2 hr Pactrol boost it trips out and I also lose power to fridge and some other mains plugs.

 

[musicjunkie]

I should add that I have replaced the pactrol unit with identical but fault persists.

 

[JohnW2]

Yes there are 2 cables goint to the element. Both the supply switches are on but not the Pactrol. If I attempt to switch on the 2 hr Pactrol boost it trips out and I also lose power to fridge and some other mains plugs.

What device is actually tripping? Does it trip immediately you switch on the boost, or only after a period of time?

Kind Regards, John

 

[westie101]

The ciruit board feed that keeps tripping is marked MCB B16 61/B16.

Seems clear enough to me what device is tripping!

But as it seems to feed a fridge and a number of other plugs there is certainly, if the wiring to the immersion heater is correct, something else odd with the wiring

 

[JohnW2]

The ciruit board feed that keeps tripping is marked MCB B16 61/B16.

Seems clear enough to me what device is tripping! ... But as it seems to feed a fridge and a number of other plugs there is certainly, if the wiring to the immersion heater is correct, something else odd with the wiring

Yes, my question was very badly worded (my brain knew what I wanted to type ) - for the reasons you mention above, what my brain wanted was to ask the OP to confirm that it really was the B16 (and only the B16) that was tripping! As you imply, to have an immersion heater and socket circuit(s) all on one B16 would clearly be very wrong!

Kind Regards, John

 

[kai]

Could it be due to a failing immersion element??, the off-peak immersion in my old flat popped out the off-peak B16 Breaker whenever the night supply came on each night, until I bought a new immersion element to replace it.
Funnily enough, the 13amp fuse in the off-peak fuse-connection unit remained intact, whilst the main B16 breaker popped off instead!

 

[JohnW2]

Could it be due to a failing immersion element??

If, as seems probably (since there are two cables going to it), it is a dual-element immersion, and the 'boost' one is rarely used, then that is certainly a possibility. However, there seem to be a lot of odd things about the story as a whole which we don't yet really understand.

Funnily enough, the 13amp fuse in the off-peak fuse-connection unit remained intact, whilst the main B16 breaker popped off instead!

That's far from unusual, particularly if the degree of overload is 'moderate'.

Kind Regards, John