Combi - Using for Hot Water with empty CH system?

OscarFoxtrot · 8 Jul 2010

Long story short.

Towel rail in bathroom is corroded and leaking slightly (getting gradually worse every day).

I turned the rad valves off but one of them leaks badly when turned to off.

I'm going to replace the radiator and the valves but the rad won't be here for a few days.

Off on holiday next week so thinking off draining the system before I go in case the leak gets worse (live 2nd floor of a flat).

With the likelihood of it being a few days after I get back that the new rad is fitted is it safe to run the combi for HW only with the CH system empty. Will it work at all?

Cheers

trbod · 8 Jul 2010

what boiler isit ?

mylocalgasman · 8 Jul 2010

No it wont work for hot water, without the system being full,if the boiler has an internal bypass you could close the isolation valves to the heating fill the boiler only and it would probably work. You would need to keep the temprature setting very low so that it does'nt overheat.

mysteryman · 8 Jul 2010

Isolate the boiler from the central heating with the system pressure OK, select 'hot water only' and you should be alright.

OscarFoxtrot · 8 Jul 2010

It's a Heatline Compact 24

danhiltonplumbingservices · 8 Jul 2010

the heating system needs to have water in as this is what heats the hot what in the heat exchanger under the boiler should be some valves close the valves for the central heating and the hot water will work but only for a short time as the ch temp will rise quickly therefore turning the ch off as no depend is needed

ianniann · 8 Jul 2010

select 'hot water only' and you should be alright

It's a combi?

the hot water will work but only for a short time as the ch temp will rise

You lost me. I'm guessing you lost the OP too. Why should the CH temp rise simply because the pipes and radiators are bypassed? So long as only HW is drawn then the flow should be entirely within the boiler anyway.

This subject has been discussed any number of times here. Details depend on your boiler design. At best, you can just use the hot water with the heating empty. On the majority of newer combis, you need to have a minimal central heating circuit filled with water, sometimes minimal being only as far as an internal bypass.

mylocalgasman · 8 Jul 2010

Addition to previous post, if it's a HeatLine I wouldn't bother if you try to turn the heating isolation valves off, they will either not turn off or you will snap the valve handle.

OscarFoxtrot · 9 Jul 2010

Cheers for the replies.

I'll drain the system before I go on holiday and fit the radiator as soon as I get back.

No showers until the new rad is fitted should be enough motivation

mylocalgasman · 9 Jul 2010

If you are going to drain the system anyway ,get a couple of speedfit cap-ends cut the pipe below valves, fit the blanks and re-fill the system. You can re-fit the rad anytime then.

twgas · 10 Jul 2010

why not stick new valves on, when you've drained it. That way you will be able to refill so showers are not a problem, and you can connect your replacement without draining again.

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Combi - Using for Hot Water with empty CH system?

mysteryman

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