can I get hot water when the radiators are drained?

[wic]

This could be fun.

I have a combi boiler. I have to do some work on the heating system which might take a few days.

I have a notion to shut the CH service valves before I drain the radiators, leaving the boiler pressurised, in the hope that I will be able to use the boiler for hot water only.

Is there a reason why I shouldn't do it?

 

[muggles]

In general the answer is no, a few boilers will take it but quite a lot would be killed to death if you tried that

 

[cantaloup63]

As you are doing some work that will take a few days, can you not temporarily plumb in one rad to allow flow through the CH system which will enable you to complete your work and flush it all through before reconnecting?

 

[wic]

Thank you for your replies, muggles and cantaloup63.

Muggles: what causes the boiler death? Mine's a Vaillant Ecomax 835/2, by the way.

Cantaloup63: Why would I want to connect a radiator to flush through? I will flush the whole lot after I've finished the repairs.

I'm not asking anybody to say that my proposal is ok. I'm asking for specific objections - something like "the service valves can't stand the differential pressure when the boiler is pressurised and the heating circuit is not". If nobody can think of any particular disaster waiting to happen, I will go ahead and try it.

 

[cantaloup63]

What I meant was that you can work on the rest of the system and flush this out thoroughly before you reconnect it to the boiler. Creating a single temp circuit with a single rad will act as a backup bypass and remove any doubt of potential damage to the boiler. For the sake of an hour's work and peace of mind, it seems to be a sensible thing to do.

 

[wic]

Thanks again, Canatloup63.

I see what you mean now and it does sound like a good safety measure although in my case ('coz I'm slow) it might take a lot more than an hour.

As it happens, I have done something that I should have done at the start: I asked Vaillant . They say that it's ok to do what I intended, with certain provisos. Obviously, one should not automatically assume that the advice applies to any other boiler model.