Immersion heater control - gone haywire!??!

[davcal]

Hello,

I moved into my flat around 20 months ago (all electric) and soon replaced the Horstmann controller to my immersion heater (Harton) as it had burned out (only able to manually turn it on, not timed).

When replacing it I only had to replace the front cover with a Newlec one (just a modern Horstmann type), plugged the 5 internal connectors together and it worked well up until now (i.e. for the past 17+ months).

NOW when the controller is turned on, irrespective of any timed settings, it will straight away turn on my top element (which starts hissing away) - if the boost is turned on or the time reached for the "timed boost" setting it seems the second element (bottom one) will also turn on and BANG goes my 16amp fuse (i.e. 6kW rather than 3kW) - their both 3kW rated.

I may be stating the obvious - but this is a controller problem and not an element one?? I'm not much of a plumber/electrician, but I took off the caps to the elements just to have a look and all seemed in order (cables, water temperature control).

Could a corroded element cause this problem or do you think its all to do with the controller (though its just under 2 years old!!). Is there some electrical checks I could do??

Any help would be appreciated - Thanks.

 

[RF Lighting]

Is it possible to power the bottom element 'on' on it's own at the moment? If so try this and see if the breaker still trips. When you say "BANG goes my 16A fuse" Does it actually go bang or is this just the way you phrased it? Do you have a seperate off peak supply, economy 7, or a single tarrif meter?

 

[davcal]

Thanks for the quick reponse!!!!

I cant see a way to just power the bottom one if the top one automatically fires up - could I disconnect one of those 5 wires in the controller?? Is that safe??

The BANG is a loud noise and very visible flash at one of the two elements - its happened a third time over the past two evenings when I was foolishly experimenting - it did make me jump each time (even after I was expecting it!!!).

I'm on economy 7 (meter with low and normal readings), though no time controlled switches - I use any power what time I want - if its during the cheap 7 hours I get billed accordingly.

Thanks for any continued comments.

 

[RF Lighting]

If there is a bang and flash then it is more than likely that the element has corroded and is now shorting. If you feel happy to do so then carefully remove the white wire link between the rod stat and the element terminal. This needs to all be done with the power OFF. Then get the bottom element tested out / replaced. This will at least allow you to have some hot water in the mean time.

Rob

 

[davcal]

Thanks for that.

I can get hot water at the moment - just so long as I dont trigger the "boost" (the lower element) - I just manually switch the controller on and off. It could be the lower one is corroded. As the top one is firing up, that element must be alright for the time being.

One thing I'm not certain on is that surely the top element automatically coming on when the controller is switched on is due to there being something wrong with the controller itself? When the controller turns on it should be regulated by stored "on" and "off" times I've entered into the controller (and how they were previously regulated) - but it will just turn on straight away - when it should not come on at all!!

THANKS