Small tank in loft boiling

[mcmoby69]

How much did the pump fitter spank them for?
I guess that they tried to fix a fault by fitting a new pump rather than diagnose the problem correctly. IE blocked pipe as mentioned earlier.

If you have the energy for a fight ring them back.

 

[bernardgreen]

did you not read Old Buffy's post?

No I had not.

The first mention of a gas boiler was after my post. Hence I was considering the immersion heater and / or a back boiler as the source of heat.

Pump fitted the wrong way round is a possible reason for the over heating as the boiler's temperature sensor and over heat safety cut out will be monitoring the water returning to the boiler and not the water leaving the boiler.

 

[FiremanT]

Vent pipe may be below the level of the water in the F & E tank and the water circulating bu syphonic (?) action.

Could be. If the SMALL tank was the CWS which is unlikely

 

[FiremanT]

No I had not.

The first mention of a gas boiler was after my post. Hence I was considering the immersion heater and / or a back boiler as the source of heat.

Pump fitted the wrong way round is a possible reason for the over heating as the boiler's temperature sensor and over heat safety cut out will be monitoring the water returning to the boiler and not the water leaving the boiler.

Except, Bern, the OP mentioned the seller of 2 tanks.

But I will allow that you may, and probably were, writing as OB was posting