Boiler is an Ideal Standard. In normal cold weather it works brilliantly. But it is no good when ice cold?

How many ice cold periods has it not worked perfectly in . Are you sure something hasn't just gone wrong or did it exhibit the same behaviour a year ago. What about the temperature of the pipes leaving the boiler but in close proximity. Do they get red hot?

As an experience diagnostic boiler engineer I find the information you provide puzzling but no doubt there is a rational explanation but you probably need a site visit to look at the possibilities.

I doubt the gas pressure explanation for a few reasons.

If not enough gas pressure the boiler would not heat up and cut out on its own thermostat but stay running. Secondly if the burner pressure of the boiler is 12mb then 17mb on the inlet would be sufficient to achieve this anyway. Thirdly power is proportional to sq rt of burner pressure so even if burner pressure dropped a bit it would not make that much difference to heat output.

What model Ideal is it. If it a condensing boiler perhaps the condense pipe is getting frozen which allows condense to build up back to the boiler and cut it out. At the moment this is the only thing I can think of that would react to very cold weather.

Hello State.

I am prepared to be contradicted, but the fact is that in very cold weather, demand for gas is high.

I have known gas pressure to drop from a norm of 21mb. to 16 or 17 mb.

Especially if you live in a high density area.

Basically you are not getting enough gas to the boiler.

I would like some input from other gas engineers on this subject.

BB.

sounds like you may have a pump problem, is the pump noisy?

hmm...actually the outside temperature will have no effect on the boiler operation, probably just a coincidence now the cold weather is here, i would check the pump is ok first.

I would think the problem is more likely in the thermostat as everything works when it's only normal cold.

sounds like pump problem but first turn all stats up including thermostatic radiator valve bleed stem from radiator check if pump is running.