Combination boiler question

Oct 16, 2004 3 Replies

Hi Everyone I'm installing a new CH system in a barn conversion to supply both the arn and the house; the two are connected via a conservatory. I'd like to use a combi boiler to supply the radiators and DHW in the barn. The house is too far away to sensibly supplt DHW but there is a hot water tank there from the existing, ancient system. Can I use a combi boiler to supply a hot feed to an indirect cylinder via a three way valve along with hot water directly to some taps and the rads. One question, does a combi work directly off mains water or do I need a cold water tank?



Martin E Yorks


Yes. You simply treat the CH side like a conventional boiler, and split it into CH (proper) and HW circuits.

The HW side of a combi heats mains-pressure cold water as it passes through its heat exchanger.

You will still need a cold header tank for the old indirect hot water system.

The primary CH circuit (feeding the radiators and - in your case - the indirect coil) will almost certainly be unvented - and will have a filling loop and pressure vessel rather than a feed & expansion tank.

Does that answer the question?

To explain further

Thanks. Yes it does although I'm unfamiliar with pressure vessels so need to look further.

Thanks anyway I'll post again (probably when I've done more research :-)

To aid your research, have a look at Ed's Sealed System FAQ at

formatting link

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required