heatrae sadia immersion heater fault

[69xians]

Hello,

I have a Heatrae Sadia Megaflow immersion heater with off peak and peak rate supply. Got back from holiday recently switched the off peak switch back on but the following morning no hot water. The peak (24-hour supply) works fine. Thinking that it must be the thermostat for which there are 2; one for the off peak and one for peak supply, I replaced the thermostat, it's a cotherm 11" if that makes any odds but it still doesn't work. There is definitely power reaching the thermostat but thereafter I don't know what could be wrong. Any thoughts? I'm satisfied that everything up to and including the thermostat is in working order and the replacement thermostat is definitely the correct part - like for like and as I say prior to my 2-week holiday everything was in working perfectly.

Thanks for any help.[/u]

 

[Agile]

There is not point in replacing parts unless they are faulty.

Almost certainly the element has failed.

You need to measure the voltage across it when powered and next you check its resistance which should be about 18 ohms. These tests should only be done by a competent person!

We used to charge £106 to replace the elements but found that was insufficient due to all the complications we encountered and the inability of users to understand how the system is supposed to work.

Tony

 

[69xians]

Many thanks for your comments, I'm no expert but I'm not convinced that it's the heating element because the immersion still heats with the 24-hour supply.

 

[joe-90]

Is it a dual element?


joe

 

[69xians]

the installation diagram depicts and mentions only one heating element. Cheers

 

[Agile]

Most have an on peak element nearer the top and an off peak at the bottom!

Regardless, you need to measure the voltage and resistance to get any idea of what the problem is.

Tony

 

[69xians]

cheers for that but the diagram definitely says one heating element, think I'll have to call someone in to look at it. Thanks for the efforts tho.

 

[Agile]

Its more relevant what the cylinder has.

If its a single element then its even odder that you decided to change the thermostat as that will be common to on/off peak heating. In that case there is usually a switching box with, often, a rocker switch to select on/off peak.

The selector switch often fails or there may be a breaker tripped in your off peak circuit or maybe the off peak is not switching on?

Tony

 

[Softus]

...Thinking that it must be the thermostat for which there are 2; one for the off peak and one for peak supply, I replaced the thermostat...

Therefore it's a dual element immersion heater.

If one element has failed, which is certainly the concensus view on this topic, then you need to replace the entire dual element package.

They're available from QVS Direct, amongst others.

 

[Agile]

Back to ages ago!

You MUST measure the resistance of the off peak element to see if its failed ! If NOT then measure the voltage across it when its expected to be powered.

Tony

 

[ChrisR]

69xians - you're saying that you have one heating element with two thermostats. Sounds very unlikely. Are you sure its a Megaflo?
If you have a timer box which switches different stats on, that could of course be faulty.
As has been explained it only needs basic voltage resistance measurements to see what's going on but if you can't do that you'll have to get someone in.

 

[69xians]

Definitely a megaflo, has it stamped on the cylinder and I have all the original documentation for it too and it says megaflo everywhere. The diagrams in the manual match my boiler also but according to the paperwork it only mentions 1 element but I'll bow to the superior knowledge that 2 thermostats = 2 elements. As much as I am tempted to tinker myself and probably blow myself sky high in the process I'm going to call in an expert. At least the on peak element is working and I have plenty of hot water it's just not the cheapest way of heating my water.

Cheers guys

 

[Softus]

This is going nowhere fast - please could you post a photo showing the position the two thermostats?