Immersion Heater Mystery!

[kels bels]

Hi guys

I was called to a clients house today, because for a week they've had no hot water which is supplied by their immersion heater in the loft.

There is 230V L/N going into the timer, 230V L/N going from time to the immersion.

There is 230V L/N going into the thermostat, which is set to 60 degrees, and 230V L/N going to the elements. I turned the power supply off and disconnected the thermostat from the element. Tested the continuity between the elements with a reading of 19 ohms.

As far as I can see, the immersion should be working fine - I sat there for almost an hour with 230V going from the thermostat to the element - still no hot water.

I could hear a light clicking noise coming from inside the cylinder tank.

Has anyone come accross this before, I have no idea what the problem could be! Does anybody have any ideas.

Thank you so much guys!!!!

Kelly x

 

[kels bels]

It's a Redring immersion in a cylinder tank that on it's side. Thanks.

 

[Sparkystu79]

Had a very similar fault once. No obvious cause for immersion to not be working but when tested with a clamp meter it was taking no load. Only solution was to replace the immersion.

 

[sctp]

I would con checked the live and neutral through the thermostat from the fused spur to the immersion heater itself. I have had a few cases where the thermostat has failed with a high resistance.

 

[kels bels]

Great!

Sparkystu - I don't have a clamp meter will keep that in mind as an option though, might pick one up tomorrow. where would i stick the clamp meter? around the cable running from the thermostat to the element?

sctp - sorry i'm bit of a beginner! are you saying to do a continuity check between live and neutral from the spur through the thermostat? what result would i be expecting to receive? Or rather, what would a high resistance be?

 

[Top Cat]

Probably get slated for this but a fool proof method of checking an immersion heater is to take off the neutral connection and put a connector on it, turn power on and put one end of test lamp on the empty neutral connection and one end on neutral connector. If you get a light (240 V) then you know the element is OK.

OK broad shoulders............

 

[sctp]

Great!

Sparkystu - I don't have a clamp meter will keep that in mind as an option though, might pick one up tomorrow. where would i stick the clamp meter? around the cable running from the thermostat to the element?

sctp - sorry i'm bit of a beginner! are you saying to do a continuity check between live and neutral from the spur through the thermostat? what result would i be expecting to receive? Or rather, what would a high resistance be?

The circuit must be dead for test. Yes resistance check from live and neutral through thermostat and immersion heater. Should be around 18-25 ohms for a 3 Kw immersion. If high then do resistance check across immersion heater direct looking for the same. This should show you what is at fault.
usually it's the heater element itself but change both heater and thermostat as a pair to avoid revisit.

 

[Sparkystu79]

Clamp meter goes round the live conductor, doesn't really matter where on the circuit. If is is working correctly you should see around 12amps.

 

[telectrix]

does the element have a thermal cut-out in the element housing and not in the stat.?

 

[Lighthouse Phil]

Is your stat switching both Line and neutral ? It is normally the case that the stat switches only one side of the supply, on a single element heater, the stat would switch the Line supply only. In a dual element heater, the stat controls the neutral.

 

[oldtimer]

It could be that the element is open circuit but if you are hearing a clicking noise then sounds like the heater is working as this is the element heating up in the tank. Plus you cannot really check these without a clamp meter I had one for 25 years and it gave up so I bought a digital replacement for £60 but for you guys starting off Scr3flux were selling them for £8

Just checked they still have it for £9 it also doubles up as a multimeter so enter 13489 into their search banner and then click to see if your local branch has one in stock and then you are looking for about 11-12 amps

Also you need to stick or hook the clamp on to either the live or the neutral cable at the heater not across the flex and not over L&N together

 

[DeanoThePlumb]

Check the neutral, if there’s a switch it may be a double pole and have lost the neutral.

 

[SJD]

Check the neutral, if there’s a switch it may be a double pole and have lost the neutral.

I really hope this got fixed before now!

 

[kropaske]

That must be new record now...

 

[telectrix]

also check the FCU /D/P switch. could have 1 terminal poor contact. 240V on the meter but dropping off under load.