new combi boiler for old back boiler

Just some questions about a combi boiler. What is the difference between a condensing combi boiler and just a plain combi boiler . I have an old back boiler behind the fire place that runs the C.H. and heats the hot water cylinder, would a combi do away with the cylinder, do I have to take the back boiler out completly or can it still sit behind the fire place, would the flue liner have to come out of the chimney. Thank you for any help.

Reply to
Jo King
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As I'm going to have to do the same thing eventually (well soon probably) I'd like to tack on another question. Can I do away with the cold water tank in the loft if I have a combi or is there no connection? My instinct tells me that the cold water tank in the loft has nothing to do with the boiler/heating system but as I know naff-all about plumbing I'd thought I'd just ask this one stupid question.

One thing I DO know (I think....) is that the little header tank could be got rid of should I choose to go the combi route. Is there any way to get rid of it with a conventional boiler?

Reply to
Geoffrey

See Main FAQ.

I have an old back

Yes it could. However to combi or not too combi is perhaps the single most contentious question on this group. All I'll say is that combis are about

60% of the boiler market in the UK, give or take. I think the ideal percentage would be less than that and more than zero.

do I have to take the

If the gas fire is to be left then the boiler must be complete drained and the burner removed. The unit will have to stay as it's an integral part with the fire and forms the flue for the fire.

If the fire is going then everything can go and you will be left with a gaping hole in your living room.

Reply to
Ed Sirett

The small tank is a feed and expansion tank for the primary heating system water. It is the water circulated through the radiators, the boiler and the coil in the HW cylinder.

Most new boilers can work with a sealed system which essentially replaces this little tank with a pressure vessel for expansion and a filling arrangement through a flexible hose and non return valve. There are some advantages as explained by the FAQ in Ed Sirett's signature. This is not an issue of whether it's a combi or a system type of boiler which heats a cylinder.

The cold storage tank could potentially be eliminated by the use of a combi.

However there are issues to consider:

- You would get mains pressure hot water which may be attractive, but only if the flow rate of the mains water supply is good (at least 20 litres/minute.) You should measure this at the kitchen cold tap to get a rough idea. Internal plumbing alteration to upgrade pipework may be needed. In the worst case, an upgrade to the service pipe from the street may be required and that can be expensive.

- Unless you get a high flow rate combi of at least 35kW or so, HW flow performance in comparison to the flow rate from a storage tank system can be disappointing. Be especially careful to look at usage requirements in terms of number of baths and showers.

- It may be necessary to upgrade the gas pipework from the meter to the boiler.

None of these are insurmountable issues apart perhaps from an inadequate water supply at the street main, but it does make sense to check before deciding.

Reply to
Andy Hall

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