Overheat stat on Grant boiler

[harryarcos]

Thank you for your sensible and useful advice. The last boiler lasted over 30 years and was only replaced because spares were unobtainable and the efficiency of new boilers so much better. It is clearly a problem of when the pump stops, so no matter how large the bypass loop is, it would not reduced the temperature unless it was above the boiler - if there was some electronic device to keep the pump running for a few minutes after the boiler stopped firing, then it would not be a problem.

I have measured the temperature of the water going through the pump and it does not exceed 70°C. Perhaps the answer is to put a small radiator in the loft!

There are plenty of devices like this available from any electrical supplier.

Basic Term - Run on timer.

Most boiler have these built into the PCB or boiler controls.

It's strange that a new boiler doesn't have this pump connection as standard.
Not a big issue to fit one if you require one.
Quite simple to install also

Yes, of course. I did not really think it through before making the statement. Something like that used in bathrooms as below should do it. I believe the pump runs at about .5 Amps - Note the "nuisance trips" of any safety thermostat"! Thank you Oz.

The ROT240X1800 provides simple, low cost run-on / lag off timing functionality for bathroom / toilet exhaust fans where it is desirable to run the fan longer then the room is occupied. Other uses include element heating applications where the fan is continued to be run to remove any residual heat before turning off, therefore helping to prevent "nuisance trips" of any safety thermostat.

 

[gpbeck]

People join these types of Forums for advice and information, not to be insulted. You have no idea how competent I am. Of course the thermostat is a "safety device" even if it is not identified as such.Who said "those who think they know it all, are a constant irritant to those that do"?

Your sensitivity, arrogance and ignorance are a powerful mix. Stay off the flight deck.