Strange immersion heater / CU problems, help please!

[MrTM]

I've added a clearer pic.

I'm 100% positive that switch 2 (the broken one) is wired to an MCB in the standard CU and that switch 3 is wired to an MCB in the Eco 7 CU. I'm not quite sure how I will verify which element they control as the wiring is out of sight and awkward, but I'll give it a go.

If Switch 2 and Switch 3 both operate the lower heater, and one is wired to the Eco 7 CU but the other is wired to the normal CU, that is WRONG and DANGEROUS.

You've got me worried now. I guess the best case is that I have two switches that do the same thing i.e. heat the top element on demand (1 & 3), which seems strange but possible, and that only the MCB is broken (which incidentally is 20A anyway).

After the heater went dead I looked through my energy bills and realised that eco 7 is incredibly expensive for me, so I've arranged to go onto a 'normal' tariff. As a result someone will be replacing my meter tomorrow - this should give me an opportunity to find out a bit more about the wiring, though I'm sure the engineer wont want to waste any time fiddling around with my dodgy immersion heater!

Thanks to all for the advice so far. I'm keen to at least work out what is wrong before calling in an expert.

 

[JohnD]

. I'm not quite sure how I will verify which element they control as the wiring is out of sight and awkward, but I'll give it a go.

Once you have bought your multimeter, you can test by turning on one at a time, them probing the terminals in the switch and on the immersion.

Be aware that it is very dangerous to work live especially when you are around earthed copper pipes and cylinders. If you are not confident and competent, ask around for a local well-recommended electrician

Look for a meter with probes that are quite long and have a finger-guard to keep your fingers well away from the live point.

I use a Steinel indicator, this might be a bit expensive for you (you can get a Digital Multimeter for £10 or so)

Edited:
this budget version might do the trick, what do others think? Simpler than a multimeter, no chance of mis-plugging it, better quality probes and leads than a cheap DMM
http://www.toolbank.com/p/C4014/STI1129

 

[MrTM]

try disconecting the element before reseting mcb and switching on (see pic) if the mcb holds and the switch lights up when disconected then the element is gone

Only problem is that the MCB is definately broken. I could switch it with the MCB that controls the working switch and try this though to ascertain if top element is broken.

next question, are you absolutly sure that the switch in the airing cupboard is for the top element? you mentioned earlier about flow increasing when switched on, is this not operating a pump?

Time for one of those head in hands, Victor Meldrew "I don't believe it" style breakdowns. I now think the mysterious switch 1 is actually just a switch that in some way controls the shower. I can't locate any fuses/switches in the bathroom for the shower and this would explain the increase in waterflow/pressure to the shower whilst its on. Having run out all of the hot water in the tank there now appears to be no affect on the heat of the water. Any previously percieved increase in heat must have been imagined or incidental.

That would also indicate that the problems with the immersion heater are far more mundane - definately a broken MCB, probably caused by a faulty/corroded on demand top element. I'm sorry I've fed everyone duff information and feel well and truly like a View media item 23320
Sigh. What an idot.