Boiler questions.

[Keith Wootten]

Hi

I have a three story house with two rooms on the top floor. I'd like to convert the smaller of these to an extra bathroom.

In the existing first floor bathroom, I'd like to replace the electric shower with something better.

The current central heating boiler is very old and needs replacing. The hot water uses a storage tank.

So, what I'd like to do is put a small combi in the top room, and use this for a top bathroom shower as well as central heating for these two rooms. I'd also like to replace the existing main boiler with a medium sized combi to heat the rest of the house and provide water for a new shower in the existing bathroom as well as domestic hot water.

Qs

Are there any problems with putting a small combi in a fireplace and venting the flu up the chimney? It's on the top floor and so the flue would only be about 2.5 metres long. I'd like to keep the small Victorian fire surround but remove the innards and have the boiler in there. I see the smallest boilers available seem to be about 24kW and there would only be two rooms to heat - could this be an issue?

The other boiler is currently in the kitchen on the ground floor. Any problems with putting a replacement in the cellar to help keep it dry - the flue would have to go up the old coal shute somehow.

The big one...

The existing bath is big, and would take a long time to fill with a combi. The piping isn't a problem, so any way of using both new boilers at the same time to fill it?

Ta everso.

[Set Square]

There are a lot of questions there, and I cannot answer all of them, so here's a few quick thoughts.

Do you *really* want 2 boilers, and both combis at that?

I would have thought that any combi which was big enough to provide a decent quantity of hot water for a shower would be an overkill for heating 2 rooms.

I don't know of a way of combining the output from 2 combis - unless you have separate plumbing - and 2 hot taps - on your bath. In any case, you will probably be limited by the rate at which your mains supply can provide cold water rather than by the rate at which the combis can heat it.

I would personally go for a conventional boiler, stored hot water and booster pumps on the showers. Have you got an attic above the 2nd floor, which houses the header tank for the current hot water system? If not, you could consider a mains pressure hot water system, or perhaps a heat store - and still have stored hot water without head being a problem.

[Ed Sirett]

Please look at the main FAQ and the Sealed CH FAQ - I doubt you really need 2 combi boilers.

Perhaps the issue is that there is no water pressure for a shower? A multipoint water heater might help (assuming that mains unvented is beyound your means).

Off hand I would recommend that you replace the existing convention system with a quality modern boiler and HW cylinder, with sealed primary to feed the top floor radiators.

You can then look at whether a multi-point gas water heater or (spit) electric shower is the best way to go for a good shower on the top floor.

[Keith Wootten]

Thank you both. I'll think about it a bit more and post here again. I thought there had to be such a thing as a combi but without the CH part, but I hadn't heard of 'Multipoint' before.

There's no loft above the top floor, and any cylinder for the first floor bath would have to be big. At the moment, the hot water has to be very hot to provide enough bath water.

I hadn't considered that there may not be enough incoming flow for two instantaneous gas heaters, even if combining their outputs were feasible.

Hmmm.

[Ed Sirett]

If the water mains pressure/flow is very poor you might be looking for a negative head pump for water both H&C from the HW cylinder and CW cistern.