Strange immersion heater problems, help please!

MrTM

Hello all,

I have a strange issue with my immersion heater. Its a 'super seven' Economy 7 immersion heater, unknown age (could be anything between 1 and 30yrs old) with two horizontal entry heating elements.

The heater is controlled with three flip switches (no timers!). As far as I can tell, one switch inside the heating cupboard controls the 'boost' as this adds extra heat (and waterflow strangely) to the water. The two in my fuse cupboard control the bottom heating element; one switch allows the element to be switched on at any time, the other only gives power to the unit during the economy 7 hours.

A day or two ago the fuse (MCB) went on the switch that controls the on demand lower heater. I turned off the switch, flicked the fuse back and then turned the switch back on. It stayed on for 5 mins or so and then blew the fuse again. Now I can't reset the fuse regardless of whether the switch is on or off.

What is strange is that the element still works when activated using the economy 7 switch! Having scoured all the forums for this kind of issue I have found that in most instances the element is broken and requires replacement - but how can the element be broken on one circuit/switch and not the other?

Having just had a couple of estimates for replacement from plumbers both around £115 and being skint, I'm hoping this isn't the problem! Any help on this would be greatly appreciated.

Thanks!

ormus

maybe the switch itself is faulty?
or the wiring?
does the control box have a PCB?

paddy's_mum

My home burnt down because of a wiring failure on an immersion heater. I was lucky to escape with my life.

Can you afford to avoid a £115 spend but run the real risk of losing just about all that you own?

MrTM

I certainly don't want to risk everything I own (and as I'm on the third floor of a building, everything everyone else owns), but I definately do want to at least diagnose the problem before I call in the tradesman.

I'm beginning to think the switch may be broken - I've tried turning off all power to the CU and resetting the switch but it still wont go. I'm not sure how its happened but perhaps the wiring has gone. The CU has a plastic casing, I could probably unscrew it and have a look at the PCB, but with my limited electrical know-how I wouldn't really know what I'd be looking for.

Now my problems are compounded - I'd need an electrician to look at the CU, but he might not be able/willing to fit a new heating element if one is required (or vice-versa!). I certainly can't afford two call outs...:(

johnnyroper

MrTM wrote: »

I certainly don't want to risk everything I own (and as I'm on the third floor of a building, everything everyone else owns), but I definately do want to at least diagnose the problem before I call in the tradesman.

I'm beginning to think the switch may be broken - I've tried turning off all power to the CU and resetting the switch but it still wont go. I'm not sure how its happened but perhaps the wiring has gone. The CU has a plastic casing, I could probably unscrew it and have a look at the PCB, but with my limited electrical know-how I wouldn't really know what I'd be looking for.

Now my problems are compounded - I'd need an electrician to look at the CU, but he might not be able/willing to fit a new heating element if one is required (or vice-versa!). I certainly can't afford two call outs...:(

could the boost and economy 7 switches operate seperate elements or do they operate the same element but with different feeds?
if there are 2 elements then it could be the element knackered,if just one element then i would say switch burnt out due to use over x amount of years.

dont take any chances get a decent sparky in,you say cannot afford 2 call outs but on the flip side could you afford not to get a sparky in and have a major problem like a fire??

gas4you

I am struggling to understand why there are two switches to the bottom element. I know you say one is for E7, but why?

All you would need to do is have one switch that you turn at what ever time for the bottom element. All I can possibly think is that the E7 switch is wired to a main E7 timer for the whole house, so when you are testing it during the day, there is actually no power to it, to cause it to trip.

Other than that, are you completely sure that these two switches actually control the same element?

Obviously all the above is just plain guesswork from this distance.

MrTM

could the boost and economy 7 switches operate seperate elements or do they operate the same element but with different feeds?

I am struggling to understand why there are two switches to the bottom element. I know you say one is for E7, but why?

Since I moved in a year ago I've been puzzled by the system! There are three switches that control two elements. They all operate independently.

Switch 1, next to the heater, operates 24/7 and I believe acts as the boost / top element as the water heats faster with this activated. Strangely, this is wired into either my cooker or ring main MCB (can't check the cooker cos I'm making dinner!).

Switch 2, next to the CU, operates 24/7 and I believe controls the bottom element. This is the switch that is now inoperable. Its wired to the MCB labelled 'emersion'

Switch 3, next to the CU, only operates during the ECO 7 period (actually as it comes on at 10.30 for seven hours instead of 12.30) and I believe operates the bottom element. I turned it on last night, the little red light lit up, and this morning I had hot water. It has its own MCB also labelled 'emersion'.

My guess as to why switch 3 is there at all: ease of use. Although I don't use the system in this way, it would be possible to leave this switch on all the time, and it would only heat the water at the cheaper rate.

My thinking is now that there is some electrical issue with either the bottom element or the wiring that connects it to the CU. Looks like I can't avoid a call for an electrician!

1984ReturnsForReal_2

If you have 2 top elements its likely that one is Economy 7 & the other is day/override powered.

You have to look at the wiring of the day/override element & see if there are loose wires & replace it if you don't see any loose wires.

If that doesn't solve the problem you need an electrician.

vaio

MrTM wrote: »

I....... I've tried turning off all power to the CU and resetting the switch but it still wont go.......

Assuming you mean the mcb is not resetting even with no power to the CU then I’ll guarantee it’s broken internally and needs replacing.

Make a note of the make, model and rating off the front of the mcb and call an electrician to get a replacement and come and fit it. When he has fitted it he’ll be able to test and diagnose any other faults on the circuit.

From what you’ve said it sounds like the E7 wiring, switch and element are all good so my money would be on the failed mcb being the only fault with a very very outside chance of a fault between the failed mcb and switch No 2.

MrTM

Assuming you mean the mcb is not resetting even with no power to the CU then I’ll guarantee it’s broken internally and needs replacing.

I'm convinced now that at the very least the MCB is broken, my fear still being that it was damaged by some other problem, either in wiring or in the lower heating element.

Come the light of day I'm going to turn off all power with the CU mains switches and have a look inside the caps on both elements for obvious signs of damage, then maybe take the casing off the CU and check for the same...

macman

Post a pic of the control switches so people can see better how it's set up.