Immersion faulty???

[Peter1891]

Hi guys
Customer had no hot water (house has no gas, electric only)
The immersion is on an fcu with timer straight to a 18inch element.

I replaced the element after testing for a good 230v supply across live and neutral and to earth.

the customer has must phoned to say it’s still not heating up.
It’s a simple system with good supply so I’m stumped as to what it could be?
Any ideas?
the timer is ok by the way.

 

[loz2754]

The thermostat?

 

[Peter1891]

Hi guys
Customer had no hot water (house has no gas, electric only)
The immersion is on an fcu with timer straight to a 18inch element.

I replaced the element after testing for a good 230v supply across live and neutral and to earth.

the customer has must phoned to say it’s still not heating up.
It’s a simple system with good supply so I’m stumped as to what it could be?
Any ideas?
the timer is ok by the way.

Hi
I’ve changed the whole element which comes with the stat built in on top.

 

[loz2754]

Wouldn't be the first new thermostat to be faulty out of the box.

 

[Peter1891]

Wouldn't be the first new thermostat to be faulty out of the box.

Yea possibly but just seems too much of a coincidence. But there isn’t anything else it could be is there if it’s getting 230v across live an neutral.

 

[loz2754]

I always put me ear on the tank to check for humming...

 

[Deleted account]

Yea possibly but just seems too much of a coincidence. But there isn’t anything else it could be is there if it’s getting 230v across live an neutral.

This has happened to me. Water was only getting Luke warm. Just needed to turn thermostat up. New immersion and thermostat. It was frustrating .

 

[andyb]

Did you test the old element before replacing it? Have you tested for 230v across the element with the element in place? and have you used a clamp meter to see if it's drawing the correct current? Try switching the stat on and off with the clamp meter on.

 

[Peter1891]

I always put me ear on the tank to check for humming...

Ah ok good idea I’ll try it when I go back tomorrow. Thank you

 

[Peter1891]

This has happened to me. Water was only getting Luke warm. Just needed to turn thermostat up. New immersion and thermostat. It was frustrating .

Do you chaps change the elements or do you test what’s up then throw it over to a plumber?

 

[loz2754]

I used to change elements but I split a tank once. That put me off big time.

 

[SJD]

I would typically test the element resistance back at the consumer unit (assuming any timer can be overridden), to see a complete circuit (typically circa 18 Ohm or so) including the wiring plus any isolating switches/FCUs that might be in circuit. (Also measure insulation resistance (L+N) to E, but maybe not so relevant here). Then when power is applied, check current with a clamp meter.

But no, I would never consider changing an element, I don't do anything that involves getting wet.

 

[littlespark]

Too risky. Get a plumber to change the element, you just wire it up.

out of interest, did you check across the disconnected heater for a reading in Ohms?

if it’s shorted out to zero, or totally open circuit, then it’s goosed. Should read in the tens of ohms

 

[brianmoooore]

If you tested 230 volts directly across the element, and it didn't get hot, you could have a faulty 'stat that's switching as soon as it gets a hint of the warmed water coming off of the element. If you checked that the 230 volts was there all the time that the water was supposed to be heating, then you have a faulty element. It's not unknown for a broken element to read OK when checked with an ohm meter, but then go O/C as soon as expansion occurs when the power is applied.
Another possibility for a cylinder not heating up is a water leak on the hot system, draining the hot water faster than its produced.
The tool you should have used is a clamp meter, checking the current taken by the element.

 

[Timbo]

Hi-limit cut out reset?

 

[brianmoooore]

Hi-limit cut out reset?

These are often open when you take a new immersion out of the box, especially if they're the round type,* separate from the 'stat, but that's not relevant if 230 volts was measured directly across the element terminals.

*These are the type with a small black reset button, located down between two live terminals. Customers don't tend to reset these more than once without turning the power off.

 

[snowhead]

It could be a L or N connection failing in the Fused spur /FCU or in the consumer unit or elsewhere but making enough contact for a meter to read.

Clamping the supply to the heater is essential especially if you aren't going to wait around till it heats up and switches off.

Has it got a second switch somewhere?

 

[7029 dave]

Test across the element dead test L N 17 to 19ohms should get for a good element, then do an IR test between L and E

 

[Deleted account]

Do you chaps change the elements or do you test what’s up then throw it over to a plumber?

Always give to plumber. it’s a nasty job, even plumbers don’t like doing it.

 

[LastManOnline]

It could be a L or N connection failing in the Fused spur /FCU or in the consumer unit or elsewhere but making enough contact for a meter to read.

Clamping the supply to the heater is essential especially if you aren't going to wait around till it heats up and switches off.
Has it got a second switch somewhere?

If their is a high resistance joint somewhere in the supply the voltage tester won't read 230 at the element. If the voltage tester is reading 230 at the element and the water does, nt start to heat after 5 Mins ( usual "hissing" noise will be heard) that the element is gone. This can be confirmed with a resistance test

 

[DefyG]

Reset button popped? per #15

 

[brianmoooore]

Reset button popped? per #15

You won't get 230V across the element.