Running boiler for DHW with CH circuit drained?

[NeilPalfreyman]

First an apology; I know this must have been asked a million times before; I did a search but couldn't find an answer.

I have a Worcster 35CDi II combi and am doing some changes to the heating - a couple of replacement radiators and some other changes.

My question is; can I switch the CH off and drain the circuit, leading Domestic Hot Water on so I can still get hot water for kitchen use, showers etc or will this damage the boiler?

 

[Dan Robinson]

You'd need to form a loop of pipe a couple of metres long between the flow and return pipes under the boiler. Both sides need to be pressurised.

 

[NeilPalfreyman]

Thanks for the reply Dan.

The boiler has isolation valves on CH flow and return and an internal CH bypass loop.

Could I just use these?

 

[Dan Robinson]

Don't even think about using those valves.

The fact that you mentioned them is enough to make them leak.

The boiler needs a couple of metres of pipe looped under the boiler.

Which is why I mentioned it in my first post.


It will cook itself otherwise.

 

[Dean744PiN5]

don't get this problem with an intergas

 

[Agile]

I have run many boilers by just turning them off on the CH isolating valves ( when they don't leak ) without any problems.

For many boilers this is no problem.

The point that Dan will make is that some boilers have an over run which aims to dump latent heat in the heating circuit.

Not all boilers do that though and probably most of the non condensing boilers don't.

Tony

 

[Dan Robinson]

don't get this problem with an intergas

Indeed .

The 35CDII is a big brute of a boiler and the little 8mm piece of Bundy tube will do sweet FA to dissipate the latent heat.