Installing a pump over-run

[pendinas]

120/150 Mistral condensing boiler servicing a large barn conversion. Boiler located externally installed summer 2007

When the weather first turned really cold we advanced the boiler thermostat to almost maximum setting (manufacturers recomended winter setting).

Problem the boiler failed to start next programme session as it had tripped itself out. Reset button and away we went until beginning of next programme setting when it had tripped out again.

After several cold early morning excurtions to reset the boiler I discovered that retarding the thermostat overcame the problem. A subsequent discussion with Mistral tells me that when the boiler has finished its programme and it switches off plus the pumps the latent heat in the water raises the temperature in the boiler to a point where for its own good the safety feature of the boiler switches the burner off and requires a manual reset.

However, turning the thermostat back defeats the objective of trying to create more heat because of the cold weather.

Thought, can you wire or programme the pumps to continue operating for say half an hour AFTER the boiler has finished its heating programme in order to disapate the latent heat in the system via the radiators OR is there some other solution?

 

[doitall]

Programming the boiler for longer on periods would have the same affect as turning in up.

Other than that it depends how badly it's been connected, if you had an header for example you could use an shunt pump in the primary circuit.

 

[simond]

I am assuming that the Mistral has no internal pump overrun feature, your post is grabled when you cover this aspect.

It looks like a basic boiler with a manual thermostat, OH thermostat and a Reillo burner.

Normally this type of nuisance tripping is either because the boiler is actually overheating (could be incorrectly set up burner, or restricted flow) or one of the thermostats is incorrectly calibrated.

If it is a DIY job and there is UFH heating involved, we commonly have found the UFH calling for heat when there is no actual demand. The boiler short cycles and eventually overheats. Is there a bypass fitted?

If you are absolutely sure that the controls arecorrectly wired and there is a bypass fitted - then change the OH and manual thermostat.

 

[pendinas]

I am assuming that the Mistral has no internal pump overrun feature, your post is grabled when you cover this aspect.

It looks like a basic boiler with a manual thermostat, OH thermostat and a Reillo burner.

Normally this type of nuisance tripping is either because the boiler is actually overheating (could be incorrectly set up burner, or restricted flow) or one of the thermostats is incorrectly calibrated.

If it is a DIY job and there is UFH heating involved, we commonly have found the UFH calling for heat when there is no actual demand. The boiler short cycles and eventually overheats. Is there a bypass fitted?

Sorry if my post seemed garbled but I am not an expert in these matters.

Your description of Mistral boiler is correct. I have already had the service engineer to check the burner. I'm not quite sure what you mean when you refer to "restricted flow"

Not a DIY job or is the system feeding UFH. What do I look for to see if a bypass is fitted.

If you are absolutely sure that the controls arecorrectly wired and there is a bypass fitted - then change the OH and manual thermostat.

 

[ChrisR]

If you want to add a pump overrun all you need is a pipe stat:

 

[Nixt]

Before any alteration check the control (not the o/heat) stat sensing phial is properly and firmly connected in its correct pocket, they can become dislodged.

 

[Agile]

FREE solution?

Turn the heat control to max during the heating phase but then turn it DOWN just before it is timed to go off !!!

Tony

 

[doitall]

FREE solution?

Turn the heat control to max during the heating phase but then turn it DOWN just before it is timed to go off !!!

Tony

Very tongue in cheek Tony, may as well just reset it time then.