Checking an immersion heater.

[peweuk]

When the only form of hot water heating is electric and the water is not getting hot, is there a method and/orequipment to test whether the thermostat or/and the element is/are faulty, or is it a question of trial and error??

Anyone know?

Thanks

 

[flameport]

The usual things to check are
a. is there power at the required times / all the time
b. test thermostat
c. test element.

No electrical work is ever done by 'trial and error'. Errors can result in injury, fire and death.

 

[Taylortwocities]

Yes. Never use trial and error for electrical work.

To determine a fault on an immersion heater you need a multimeter that can measure 230v AC and also an Ohms range.

Do you have one of these? You can get one at Maplin or B&Q etc for a few quid.

 

[ericmark]

One can use all sorts to test. It could be a door bell with integral batteries or a multi-meter question is what have you got to hand.

The neon screwdriver tends to give erroneous results but even they can help.

I like to work dead and be it an old door bell or a buzzer built into a meter or ohm scale on a meter these can all be used to test a thermostat or element.

Working live clearly has some danger, but with care be it a neon tester with 12, 110, 240, 415 neons or a multi-meter one can pinpoint the problem.

In the main if the fuse has blown there is another fault somewhere, be it current or thermal. So listing possible faults.
Main fuse/MCB open circuit. (blown or tripped)
Fused connection unit (FCU) has blown fuse or faulty switch.
Timer has either stopped working or has faulty contacts.
Thermostat is not calling for heat.
Thermal fuse or cut out as blown or tripped.
Immersion heater element has failed.
Other rare fault.
In some cases indicator neons will show power to FCU and there may be no timer involved. Most likely are immersion heater element and thermostat. I hope you can guide us how to help by describing what you have including items to test with.

 

[peweuk]

Tanks guys.

To clarify the reason for my question.

My 87 year old mother called in a local electrician because her she had no hot water - it usually heated up over night.

Day 1:
The electrician arrived, inspected the tank and left again saying he needed to order a part, but as he was off on holiday that night, a colleague would return and fit the part the next day.

Day2:
His colleague turned up and cursed then left without doing anything saying his mate had ordered the wrong part.

Day 3:
The second electrician returned and fitted a part, then before leaving said my mother would have to call in a plumber. As he was going on holiday that night he left her a note with a plumbers number and on the note it also said:
=====
Immersion heater.
Element faulty, needs new element with stat + timer".
======

When my mother rang me and told me the story I was confused as to exactly what had been done (or not done) so I rang the company.
They told me that the electrician had replaced a faulty thermostat, but as soon as he turned on the immersion the stat blew "because the element was faulty and as it had no RCD on it it had blown the stat again. The electricians are not trained to do any plumbing such as draining tanks and replacing immersions, so a plumber is needed".

I find this whole episode rather bizarre and wonder why they did not manage to determine that the element was faulty on the first visit - hence my question asking if it is possible through testing to determine if the element was faulty before replacing the stat and finding it was going to blow because of an element fault.

Any thoughts anyone?

 

[HERTS P&D]

If the immersion is on the top of the cylinder then it can be replaced within the hour.

If the immersion is on the side of the cylinder then you could be looking at 3 hours to drain the cylinder. If it is on the side then there should/could be 2 immersions which when drained down both should be changed.

Andy

 

[Iggifer]

To answer the question, yes it is easy to test the element without resorting to a 'bang test' i.e. powering it up and letting it blow up if it's still faulty

I hope she wasn't charged for 3 visits for an incomplete job?

 

[peweuk]

If the immersion is on the top of the cylinder then it can be replaced within the hour.

If the immersion is on the side of the cylinder then you could be looking at 3 hours to drain the cylinder. If it is on the side then there should/could be 2 immersions which when drained down both should be changed.

Andy

So, surely this should have been established before sending out an electrician at 4.30pm to attend a job that could potentially take up to 3 hours!!!
Although he probably had no intention of seeing the job done as he turned up with no spares of any sort.

To answer the question, yes it is easy to test the element without resorting to a 'bang test' i.e. powering it up and letting it blow up if it's still faulty

I hope she wasn't charged for 3 visits for an incomplete job?

She hasn't had a bill yet, but I will be keeping a close eye on what they do send.
How would they do that test? Does it require expensive specialist equipment, or can it be done with standard 'electricians toolbox' kit.

 

[JohnW2]

How would they do that test? Does it require expensive specialist equipment, or can it be done with standard 'electricians toolbox' kit.

As you've been told, adequate tests in this situation could be done with a £5-£10 Maplin/B&Q/whatever multimeter, which I somehow doubt you would regard as "expensive specialist equipment"!

Kind Regards, John

 

[333rocky333]

Unfortunately like some plumbers struggle with heater wiring, some electricians struggle with plumbing related wiring and most electrical companies do diagnose element faults and pass on the element change to a plumber.

same with water heaters, so always best to ask when calling them out, how far they do go.

There is a risk of twisting the tank, the Boss is sometimes seized in, the Draincock sometimes fails and theres always risk of a lot of water coming out on the side mount ones.

I recall an old boy plumber tapped on the tank ensuring me it was empty, it wasnt.

As an electrician I once diagnosed one and called in a plumber specifically telling him it was a side mount ELEMENT.
He quoted one hour at a reasonable charge, he turned up with a STAT which similar to your case was not the problem.

On telling him he then trebled his quote and went off sheepishly to get an element.

I use a meggar to check continuity and element resistance to earth and a clamp meter to check load once on, you can even clamp at the meter tails as the load is substantial.

Even without any test gear, though not ideal a good electrician could TEMPORARY and safely bypass the stat for 5 minutes just to test the element.

 

[peweuk]

Thanks 333.

That was the info I was looking for.

I do feel that today customer service appears to have just disintegrated (not just in the electrical world).

I would have expected a professional company to have explained the situation much like you have in your response, particularly when an elderly person (who wouldn't know the correct questions to ask) rings up about about a water heating problem which obviously relates to an immersion heater (otherwise why would she call an electrical company).
At least then the caller would have an idea of what to expect.

OK - now at least I can proceed dealing with the situation more enlightened than I was before.

Thanks again for all the assistance..

 

[333rocky333]

Theres no excuse for what happened but in his defence, not all electrical firms would carry all element sizes, you would tend to evaluate the job on arrival and I would attend at 16:30 as too some people hot water is essential, even though we use plumbers for the element side.

occasionally you can sort it yourself and if not then its at clients discretion to pay a premium for a 24 hour plumber or wait next day.

An options calling a plumber first, yes he may have all the parts, but if the wirings poor he may request you get an electrician to disconnect and connect, so similar situation in reverse but could cost you more why the electrician twiddles his thumbs waiting for the plumber to fit it.

Ive often done this for them as its more common in commercial than in domestic work.

Some electricians even plumbers ive known have stuck in whatever Element they have had on the van, sometimes a 12 inch element in the top of a 4 foot tank so sometimes it is better too wait till next day or for them to get the right one.

To sumarize for next time, its better to get a rough size of the tank, note whether element is top or side mounted and enquire whether they do BOTH electrical and water side to resolve the issue, then hopefully they will arrive with an element on the off chance.

As the other poster mentioned earlier if theres 2 elements, then it makes sense to replace both whilst system drained

 

[333rocky333]

I also note you mention a TIMER this proberly blew due to the fault current generated by the faulty element.

however its impossible to prove whether this blew from the INITIAL fault or the second time the thing blew due to there incompetance in testing the element.

An RCD may have saved the timer, but theres millions of circuits with NO RCD and its not always the case there has to be one, so dont let the firm fob you off with that

As the first electrician didnt order a new timer, suggests he was again incompetent and failed to test it, which IS an electrical firms task or that it was ok and the second bufoon blew the timer due to him also failing to test the element.

Is this a big electrical company, (DONT NAME THEM) it seems odd that TWO of there employees appear to not know what there doing and have no test gear or to lazy to use it

 

[peweuk]

I'm not sure of the size of the company - it's one local to whee my mother lives and they have a card up on the board in her block of flats (it's private but restricted to over 60's).

I'm going to go down to see her tomorrow to investigate further and try and sort out the problem.

I'll run a test for output on the timer to check it - it's economy 7 but has a boost on it for daytime use so I should be able to check if its got a live output.

 

[333rocky333]

When elements blow they often blow the timer contacts, not only do they blow open circuit ie NO power out
They sometimes weld closed thus the timer output is constantly ON regardless of settings

Im off to bed now