Immersion faulty???

Peter1891 · Jan 20, 2021

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.

brianmoooore · Jan 20, 2021

Timbo said:
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 · Jan 20, 2021

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 · Jan 20, 2021

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 · Jan 20, 2021

Peter1891 said:
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 · Jan 20, 2021

snowhead said:
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