Unvented immersion elements

[pertinky]

The resistance across the element was about 180 ohms (0.018 on 2k)

That's 18Ω which would be correct(ish) for 3kW element.

The resistance across the thermostat terminals was 20 ohms (0.2 on 200)

That's 0.2Ω which doesn't mean much except that they are connected.

I think im reading it right,

Nope.

but it still doesnt help me figure out why its not working!!!

It doesn't but the element would appear to be alright.

Is it worth changing the thermostat first and see if it works before i call out the installer?

No.

Thanks for that. Any actual advice?

I don't think theres anything else I can check without being qualified now...

 

[Agile]

It needs to be checked for applied voltage.

Anyone can do that if they can use a meter correctly.

Tony

 

[pertinky]

It needs to be checked for applied voltage.

Anyone can do that if the can use a meter correctly.

Tony

I bought a multimeter so should be able to do it. Not read up on how to measure that across a heater element yet though!

 

[Agile]

Buying the meter does not buy the knowledge needed to use it!

I would guess that at least half of those fixing boilers are shaky when it comes to using meters correctly.

Your resistance readings were out by a factor of 10 !

Measuring voltages means working on live terminals which is potentially hazardous! I would not advise it to anyone who has not attended a course on the safe use of test equipment.

Tony

 

[pertinky]

Buying the meter does not buy the knowledge needed to use it!

I would guess that at least half of those fixing boilers are shaky when it comes to using meters correctly.

Your resistance readings were out by a factor of 10 !

Measuring voltages means working on live terminals which is potentially hazardous! I would not advise it to anyone who has not attended a course on the safe use of test equipment.

Tony

#

Fair point! Sparky it is then.

 

[pertinky]

Well...we found the thermal cut off!!!

It was very well hidden in between the spades for the element. Barely visible.

And there was me assuming it was on the stat.

Thanks guys for the help on this - only cost me £30 in the end but i've learnt plenty!

 

[Agile]

You may have a faulty stat or scaled up cylinder.

Regardless, to prevent it tripping again you should start by lowering the stat temp.

They often stick and overshoot the expected set temp.

Tony

 

[pertinky]

Sorry for the bump.

I ended up buying a replacement thermostat with thermal cut out and disconnected the spades from the original thermal cut out that was built into the element unit.

It's working, but it seems the temperature isn't anywhere near as hot as before and ive been slowly turning it up on the dial. Is it possible the thermostat is broke!?

I cant think of any other logical reason for this otherwise.

 

[Agile]

The latest stats only go up to a lower temp than the old ones.

To get your 60C it will need to me virtually at maximum.

Tony

 

[pertinky]

The plot thickens - stopped working again.

Took the cap off, the neutral wire (connected to the element) has completely melted and shorted it all out.

I'm starting to hate these cylinders now.

I thought the thermal cut off would prevent this?

 

[EFLImpudence]

No, that will have been due to a loose connection.

 

[Agile]

An immersion heater takes about 12 amps and any poor connection will overheat and cause damage.

The wire needs to be clean as well as tight on the connection.

Spade terminals are not really very suitable.

Tony

 

[pertinky]

I'm thinking its a connection problem. The power draw hasn't changed!

I'll have to replace the flex. I've got some here that was used for storage heaters - would it be suitable?