how to test if immersion heater is knackered

[fingertight]

Hi Chaps,

How would a sparky test to see if an immersion heater element is knackered? The immesrion is showing power upto the thermostat.. Also live in and live out of stat...is there a resistance test or something that can be done?

Thanks

 

[Steve]

Yes. there is.

someone will be along in a while with details of that resistance.

 

[SparkyNinja]

Do you have an Ohmeter?

If there is continuity across the element in the area of around 18-20ohms then it should be OK.



(Thats the figure I get on my fluke, exact figures I cannot recall)

 

[ColJack]

yes, but you'd need to know the resistance of a healthy element.. and I don't off hand..

should be fairly low though...

about 12-15 ohms if my maths is right??? ( 3000W/230V = 13Ohms )?

you're only talking about £10-15 for a new element so if in doubt, change it..

 

[Taylortwocities]

As well as the continuity test you should also test Insulation Resistance. Between the terminals of the element and earth.
It is possible for the element to be intact (ie showing continuity) but the outer casing can have cracked.

It may only be £10-15 for a new element, but then you've got to plumb it in.

 

[333rocky333]

ohms law,will give you the resistane

watts=volts x amps

amps =watts /volts

resistance =volts /amps

 

[fingertight]

Bloody hell...I wish the Gas lads were that quick with replies LOL .
I just wanted the info for future ref, but on this occasion I will end up changing it,


Many thanks

 

[ColJack]

can't be that hard can it?
drain the tank, unscrew the old one ( after disconnecting it ), screw in the new one and re-connect it.. job done..
might need a turn or two of ptfe tape but everyone has a roll of that and no idea what it's for don't they?
comes as standard in most "Home DIY Toolkit" sets..

 

[333rocky333]

As TTC said it is better to test to earth as that is the most common fault.

Usually best to power off and disconnect the N to prevent false readings, although the supply switch should be double pole anyway.

 

[Taylortwocities]

can't be that hard can it?

Its probably me. I live in a very hard water area.
The last time I tried to cahnge an element it was so encrusted with limescale that I twisted the top of the tank trying to unsrew it.

Result = new tank.

One of the reasons I'm a sparky & not a plumber

 

[ColJack]

quick spray or "cilit bang" and a smear of copper grease on the new threads before fitting would cure that I recon?

 

[SparkyNinja]

I've drained a few but if it's to scaley I get my plumb mate onboard.
When it was introduced that all immersions had to have a thermostat, I was given the task of changing over 300 of the sodding things.

I have seen a plumber fit an element with his belt before

 

[ban-all-sheds]

can't be that hard can it?
drain the tank, unscrew the old one ( after disconnecting it ), screw in the new one and re-connect it.. job done..

1) No need to drain it completely, just enough to drop the water level below where the element fits. OK - that might be at the bottom, I know...

2) Draw a line with a felt tip that runs from the IH to the tank body. As you apply torque to unscrew it, look very closely at the mark. If you feel the element turning, but the marks are still lined up STOP TURNING IMMEDIATELY.

3) Try a smart whack with a hammer on the spanner in a clockwise direction, then anti-clockwise. Repeat a few times.

4) If that didn't work, finish draining the tank and take a torch to the thread - the heat may free it.

5) You're stuffed.

The last time I tried to cahnge an element it was so encrusted with limescale that I twisted the top of the tank trying to unsrew it.

You didn't do (2), did you...

 

[ColJack]

last element I saw changed was Nan's. and she had to have the entire tank taken out to have it done..
the guy who put the tank in did it so that the pipes and everything were easy to get at... and that left the element pointing at a wall about 5 inches away...

 

[ban-all-sheds]

"cilit bang"

Isn't that what S&M lesbians get up to?

Oh - hang on, I'm thinking of something else...