Fitting a new element in my immersion tank

[kimbers]

We no longer have hot water. We have a immersion heater with a wall clock control.

I've tested the wires at the back of the element & it seems there is a current going into the thermostat box but no current coming out.

Its a sealed unit so looks like i need to replace the element. Its an 11inch element but what sealant do i need to put on when fitting the new one? The old one has lots of hard sealant round the outside.

 

[Diyisfun]

It could be the thermostat that is faulty.

 

[Softus]

I don't think you've done enough fault-finding yet - it might not be the element.

It's quite common for the thermostat to be faulty. To check for this, isolate from the electrical supply and test whether this is continuity across the stat. This is easily done with a multimeter.

Then check the resistance of the element - it should be in the 19 to 20 Ohms range.

If you eliminate everything else and decide that you have to replace the element, then there are lots of topics about this. Everyone has their favourite method of sealing, but mine is: fibre washer first, then PTFE tape on the threads, then LSX sealant on the washer where it will meet the face of the boss.

 

[htgeng]

Everyone has their favourite method of sealing, but mine is: fibre washer first, then PTFE tape on the threads, then LSX sealant on the washer where it will meet the face of the boss.

That is a fair method, but what is the purpose of the ptfe tape on the threads?

 

[wilhelm]

cos their aint an olive. I use lsx.

 

[kimbers]

Thanks for all your replies.

I'll need to replace the element anyway as the thermostat is a sealed unit & is part of the element housing so if the thermostat is dud i've got no option but to replace the whole thing.

 

[Balenza]

htgeng wrote

but what is the purpose of the ptfe tape on the threads?

Helps make a seal , much less torque needed when tightning up or undoing and also prevents the threads seizing up in the future and hence aids easy removal in the future by diyers , service engineers or fitters and generally avoids a lot of bad language and damage to cylinders and costly repairs.
Thought that would be obvious to someone of your calibre

 

[htgeng]

Thought that would be obvious to someone of your calibre

Never thought about it in that way but I can see that it may have some benefit to removal. I don't buy the reduced torque argument though.. You have to apply the same amount to tighten it to stop it leaking whether there is nothing on the threads or some amazing lubricant.

 

[Balenza]

hteng wrote

I don't buy the reduced torque argument though

Then you have no understanding of the coefficient of friction and why the tightning torque lowers when you reduce the friction.
The link below gives a brief explanation.

http://www.roymech.co.uk/Useful_Tables/Tribology/co_of_frict.htm

 

[htgeng]

Would you recommend putting ptfe tape on the threads of compression fittings for exactly the same reason?

 

[Balenza]

Would you recommend putting ptfe tape on the threads of compression fittings for exactly the same reason?

No, I would recommend using ptfe spray lubricant though many use ptfe tape on compression fittings.
In fact I did yesterday and it works a treat.

 

[Agile]

Back to the OP !

IF its a single unit then its probably a manually resettable overheat stat.

Look for a very small 2mm diameter reset button!

Then turn down the thermostat setting temperature.

Tony

 

[John M]

Just a side issue here......... Should you replace the unit, please ensure the wiring is fixed properly ....... MAKE SURE ITS GOOD & TIGHT .........

Please check the link wire from the stat to the element too

AND EARTH IT

Ok ok I'll calm down now ....... Where my pills .......... NURSE nurrrrrrrse

 

[htgeng]

No, I would recommend using ptfe spray lubricant though many use ptfe tape on compression fittings.
In fact I did yesterday and it works a treat.

Which was it - you use spray or tape on compression threads? Sorry to re-hijack this post

 

[kimbers]

Managed to sort it. Snipped the wires from the thermostat & removed. Nasty burnt smell. Managed to get a new thermo from B&Q for £8 replaced in 10 mins.