Scratching my head over immersion heater!

[davesparks]

Ref: # 23: I think I may have worked out what is wrong. I believe the OP may be mistaken about how the electric immersion element is meant to be wired in and controlled.

If I have interpreted correctly what the OP has described, the electric element currently does not have a push on rod thermostat with cutout - the direct heating system. Instead, the element is being controlled by the upper thermostat and cutout which are meant for the indirect system.

If one reads the installation instructions at #23, it describes how to connect up the electric immersion heater with its own stat and cutout, and the indirect stat and cutout to control a boiler. There is a drawing on page 15 and component list which indicates the electric element is meant to have its own stat and cutout. Someone then - the plumber ? - may have discovered the electric element's stat and cutout were defective and co-opted the indirect stat and cut-out instead.

I doubt that the indirect stat and cut-out have the required current rating for the electric element - but may be wrong on this count. Anyway, the indirect stat and cut-out are not designed to control properly and safely the electric element.

What needs to be ordered is the correct stat and cutout for the electric element and it then fitted and wired up as in Fig 7 Page 9. Note Fig 7 shows the upper stat and cutout are not wired to the electric element.

The correct part has this number 95 612 026. See:

Heatrae Sadia - Megaflo Thermostat 11" Rod Type TSE/TSR 95612026 95612599 - Specialists in plumbing & heating spares - https://www.unventedcomponentseurope.com/heatrae-sadia-megaflo-thermostat-11-rod-type-tse-tsr-95612026-95612599.html?utm_source=Google%20Shopping&utm_campaign=Copy%20Unvented%20Components%20Europe&utm_medium=cpc&utm_term=3590&gclid=CjwKCAjwwMn1BRAUEiwAZ_jnEpIuG47ccjQMP8v4i0VP-hIt-MKRx3PP-nXk4_7wkz4vpjQY8pAV6hoCTzEQAvD_BwE

ETTradesmen - hope this helps.

There are different versions of the megaflo, some have the rod thermostat you mention while others have a seperate thermostat unit.

 

[Taylortwocities]

The tank he has Center direct unvented cylinder 150ltr | Wolseley - https://www.wolseley.co.uk/product/centerstore-direct-unvented-cylinder-150-ltr/

Is not a MEGAFLO!!! It’s a Centrestore unvented tank.
Megaflo is the trade name if a company that makes tanks. There are lots of makers.
Like Hoover is the trade name of a company that makes vacuum cleaners.

 

[ETradesmen]

The tank he has Center direct unvented cylinder 150ltr | Wolseley - https://www.wolseley.co.uk/product/centerstore-direct-unvented-cylinder-150-ltr/

Is not a MEGAFLO!!! It’s a Centrestore unvented tank.
Megaflo is the trade name if a company that makes tanks. There are lots of makers.
Like Hoover is the trade name of a company that makes vacuum cleaners.

Correct Taylor, it is a tank made by Heatrae but has a centerstore sticker on it.
Again, going out of way I called Heatrae technical and questioned them and got two possibilities for the cause.

1) dry pocket between the element and stat has failed and both are sitting too close together.

2) if there is a secondary return with a pump to the tank this can also cause nuisance tripping if the pump is running 24/7.

both of the above are out of my comfort level so I’ve passed this information onto the client and wished her luck.