immersion heater thermostat

[crannog]

Hello

During the winter we have an aga heating our water.
During the summer either our solar panels or immersion heater!
A couple of months ago we had our immersion heater changed by a plumber but we could not test it because our aga was on.

Now our aga is i've realized the immersion heater does not work.

Iv'e checked and there's 238V on the flex going into the heater.
0V across the thermostats input and output
238V across the output of the thermostat and ground.

Why doesn't it heat the water?!
Is there a reset on new thermostats going into the tank does it need to be manually reset if it has reached 60 degrees plus?

Thanks

 

[holmslaw]

..

 

[crannog]

Sorry it's wired exactly how you said.

Can you explain how to do a manual reset?

The odd thing is iv'e just measured the resistance of the thermostat and it shows ~0ohm, water is cold, doesn't this mean thermostat is good?

Should i take it out and try measuring the resistance at 60degres plus?

I just measured the resistance of the element - 10ohm this would give 24amp going through the circuit, is this a standard value for a immersion heater or is the immersion heater at fault dead on arrival?

All the values seem to be correct and all the voltages are there so why doesn't it work?!

This pic might help? just taken it!

Untitled

• crannog
• 5 Apr 2011
• 1

Thanks!

 

[holmslaw]

..

 

[crannog]

Yes, it could be the safety cut out has operated due to excessive heat from the AGA heated water, it needs to be manually reset.

Don't quite understand your description of the wiring, it should be, Live - thermostat input - thermostat output to one side of heater element - the other side of heater element to Neutral.

If it has cut-out due to the excessive heat from the aga wouldn't the resistance of the thermostat show a infinite / no value?

Thanks

 

[TicklyT]

I would say the cutout is the round device at about 7 or 8 o'clock in the picture, with two brown wires, connected to the thermostat output and the heater element post.

Check for continuity (power disconnected, please!) between the thermostat output and the heater terminal post.

 

[crannog]

CHEERS GUYS!

So I took holmslaw advice and disconnected everything before measuring continuity's and resistances.

Everything connected i got a reading of 10ohm for the element!
Disconnecting made a big difference! Element showed up as 19ohm!
I thought great, that's better, also testing the thermostat it showed ~0.03ohm

Starting to reconnect i saw a little black knob between the two brown wires presses on it by mistake and thought noting of it! Didn't loot like a switch!

After connecting everything back up and turning mains back on i noticed a slight hum and rattle by the tank! The mains makes the element rattle right? I know have hot water!

TicklyT you where right there is a reset there! But why put it so subtle and in a silly place?!

Thanks both of you!

 

[crannog]

Yes, it could be the safety cut out has operated due to excessive heat from the AGA heated water, it needs to be manually reset.

Don't quite understand your description of the wiring, it should be, Live - thermostat input - thermostat output to one side of heater element - the other side of heater element to Neutral.

If it has cut-out due to the excessive heat from the aga wouldn't the resistance of the thermostat show a infinite / no value?

Thanks

And I should have clicked here that there was no cutout on the thermostat due to 0ohm showing and that there must be somewhere else! on the element!

 

[TicklyT]

TicklyT you where right there is a reset there! But why put it so subtle and in a silly place?!

They intentionally make it inaccessible because it is a safety device that isn't (or shouldn't be) used during normal operation. If it was easily accessible, some may start using the cutout to control the heater after the thermostat fails instead of changing the 'stat.

As we all know, there's nothing as permanent as a temporary solution, so the stat would never get changed until another disaster occurs when the safety cutout fails to operate.