Installing a combi boiler

[antgel]

Hi all,

My flat doesn't have a combi boiler. It has (what I consider to be) the old-fashioned system where I have to switch the hot water on a while before I need it. More importantly, the system takes up a lot of space I have a boiler and a small tank in the kitchen, and two more tanks in a hall cupboard.

I also have a pump to ensure that the taps are served adequately, as there is not much natural pressure. This is a pain in the a**e as it doesn't always work properly - water coming in (loud) spurts.

How easy / cost-effective is it to replace a system of this ilk with a combi boiler? Would it be possible to install it in the hall cupboard where the tanks are? I'm planning on knocking down the wall between my lounge and kitchen and a noisy boiler would be much better in the hall cupboard than the kitchen.

Antony (no email replies please)

[John Stumbles]

Conventional (non-condensing) boilers need to be on or adjacent to an outside wall. However by the time you get your system changed over condensing boilers will be more-or-less mandatory (from April) and some models can have quite long flues so can be further from the outside (although where the flue is located is somewhat constrained as the plume of water mist from the flue can be an annoyance for neighbours).

[andrewpreece]

As the above post says, flue position is an important factor in positioning a combi. Wickes do an excellent leaflet regarding installing a combi boiler,giving minium distances of flues from windows, neighbours' windows, eaves, corners, the ground etc etc. If you can't get that, then visit the websites of the manufacturers, e.g. vaillant, Worcester-Bosch, and download their flue /combi installation guides ( .pdf format ) for similar info. I believe several metres ( up to 4.5 metres depending on bends etc ) of flue is allowable, certainly for Vaillant conventional combis, but flue ducting costs money so it's best to keep it short as possible.

Combis work on mains pressure, for the hot water anyway, and there is a minimum pressure for correct operation. You wouldn't want to buy a combi capable of delivering hot water 11litres/min at a delta T of 35C only to find your supply won't allow more than, say, 9 litres/min. Again see the specs given on the websites, you could also look at Baxi.

Most sealed boilers/combis can be fitted into a cupboard, but check for the specific model you are interested in: you do need to provide some minimum free space around the boiler for access, depending again on the model.

Bear in mind that your system may core over a combi in some ways: flowrate of hot water may be greater than for a combi, at least until the tank is empty. Also, when you lose those hot water tanks in your cupboards, where are you going to air your clothes! Just some thoughts,

Andy.

[Paul Barker]

You maybe only have a pump because of the low head of your dhw system

Check flow rate of kitchen tap, that should be on the mains. If howeve you do have a water mains problem. Is it old led pipe which might hav suffered a squash here and there? How good at diy are you? Are yo aware of any mains stop c*ck just outside the boundary of your propert which serves you only? Are you in a flat? Depending on the answers consider digging up the ground to the boundary of your property 1 mete deep, join into the led at the furthest point of your land and run 25m blue plastic. Easiest way for diy guy to join to the led is with a bi black plastic led lock obtained from Plumb Centre It has a range o diameter's within which it works. Basically the small one does mos domestic I only used the big one once. Clean the led and find straight portion, push on the device, have two pairs of grips to han and tighten it up like there is no tomorrow (ignore the instruction they don't impress on you how tight it has to be), the other end wil probably be a push fit to 20mm blue mdpe water pipe, get a 20mm to 25m converter and ask them kindly to supply you a small length of 20mm pip for the joining of the two.

Now you can consider a combi.

Do you hjave a loft? Put it up there. Gable end is cheapest but you ca get fertical flue kit and pass it through a special tile (costs more).

Condensate drain can be sump and pumped (special machines mad specially for the job like Rotthenburger for instance) if necessary most cases you can find a way to route it to a hopper, gully or soil stack. McAlpine do both a 22mm (with which you use 3/4 in overflo pipe) inline trap and 22mm boss for soil stack

-- Paul Barker