Water Heater tripping fuse on timer

grumbler

Section62 said:

grumbler said:

I know, it's not everyone's cup of tea, but all electric diagrams are there - in the manual. And, as I expected, it's absolutely clear that the control circuit just controls the relays switching the heating elements on and off.

Great.

Now does that information allow you to guarantee that the heater element is to blame (and nothing else), before the OP shells out for a replacement element and someone to fit it?

IMV, the answer to that is 'no'. 

IMO, the answer is 'yes'.

At least the information can be passed to the 'expert' and he can make sure that he has the spare in his van.

And the assumption could unnecessarily cost the OP the price of a replacement element plus labour to drain the water off and fit it. Hence my advice to get someone in who knows what they are doing.

The someone's precious time spent on sourcing the element, if he doesn't have it in his van, is likely to cost much more. And if the element is available at, say, SF, it's easy to take it back if it's not needed.

Section62

grumbler said:

Section62 said:

grumbler said:

I know, it's not everyone's cup of tea, but all electric diagrams are there - in the manual. And, as I expected, it's absolutely clear that the control circuit just controls the relays switching the heating elements on and off.

Great.

Now does that information allow you to guarantee that the heater element is to blame (and nothing else), before the OP shells out for a replacement element and someone to fit it?

IMV, the answer to that is 'no'. 

IMO, the answer is 'yes'.

I would tactfully suggest you can't possibly get to 'yes' without first verifying that the "fuse" which is tripping is indeed a RCD (not yet confirmed as far as I understand).

Then do a resistance check on the immersion element to see if it is abnormal.

And do a visual check (possibly also an IR test) of the wiring, to make sure that the fault isn't there - for example due to the insulation breaking down as a result of exposure to heat.

I'd also do some lateral thinking to make sure that the cause is in fact the water heater, and that the tripping isn't the result of some coincidental factor, for example another appliance coming on at the same time.  Whenever you have a control system you need to think what other things could possibly cause the symptom(s) rather than latching on to the first or most obvious one.

As a test on its own, pulling the supply wires off the immersion heater can't positively prove the fault.  It is evidence which would help support the initial guess of an immersion heater fault, but not proof.

This is why the OP needs someone who knows the system and will apply a methodical fault analysis process, rather than someone who will take the "I think it could be the immersion heater" information and just swap that out as requested.

grumbler

Section62 said:

grumbler said:

Section62 said:

grumbler said:

I know, it's not everyone's cup of tea, but all electric diagrams are there - in the manual. And, as I expected, it's absolutely clear that the control circuit just controls the relays switching the heating elements on and off.

Great.

Now does that information allow you to guarantee that the heater element is to blame (and nothing else), before the OP shells out for a replacement element and someone to fit it?

IMV, the answer to that is 'no'. 

IMO, the answer is 'yes'.

I would tactfully suggest you can't possibly get to 'yes' without first verifying that the "fuse" which is tripping is indeed a RCD (not yet confirmed as far as I understand).

Yes, I assumed this - guilty as charged.

However, this doesn't devalue the suggestion to disconnect two live wires from the heating element to localise the fault .

...the OP needs someone who knows the system and will apply a methodical fault analysis process, rather than someone who will take the "I think it could be the immersion heater" information and just swap that out as requested.

The OP can be lucky to get such an expert, but can get "someone who will swap out a few parts and hope for the best" instead - like I saw many times (admittedly, for different appliances). So called 'engineers' sent by big companies.