Adding zone to existig combi heating system

[Bob Smith]

Buying a house that has a combi boiler in the garage.

I will change the house to a programable themostat rather than the current regular themostat.

We are adding a Convervantory, but I want to connect this to the heating (not sure if underfloor yet, or U/F and rads) using a zone, so that we can heat the house and leave the conservatory cold (or on a programmable stat, seperate to the house)

Whilst at it, I am thinking of doing the same with the garage, so that the heating can fire to heat the garage if required (i.e only on a "frost setting" for the garage).

What is the easiest way to acheve this? We are effectivly creating 3 zone, each with there own stats.

[The Natural Philosopher]

Relative piece of cake.

You need one stat (possibly wireless and/or timed) one motorized valve

Some wire.

Insert motorized valve into zone plumbing take switch contacts and wire in parallel with other motorized switch contacts so *any* motorized valve will call for the boiler.

connect local switched fused spur heating live to thermostat and return to motor on valve.

Connect up neutrals.

Done. Unless you have an 'orrid all built=in type combi. There things get more interesting.

[Doctor Drivel]

For the conservatory get a fan conservatory heater run of the CH. Myson sell these. These are much better and have fast recovery times. When off no heat into the conservatory. UFH in a conservatory has long lags of warm up and cool down; not ideal. The high level versions of the Mysons are good as they do not impede furniture. Look at the Myson web site. They can also have the fan turning in summer with the CH off. this stirs the air promoting a lower temp in the conservatory. Have a flow and return back to the boiler, preferably in 22mm most of the way. Have zone valve for this back at the boiler and zone valve for the house CH too. You can have a clock stat for the conservatory and the main house both running independent of each other.

There is no need to have a frost loop in the garage. Does the combi have integrated frost protection? If not just wire up a frost stat on the return pipework and only have the conservatory loop come in when taking the pipe temp up above freezing. Make sure all pipes in the garage are well insulated.

[Ed Sirett]

Nearly all if not all combis have provision for an external thermostat. This is the way to control the heating. There may be some latest model swhich are using something other than a simple on off control but they probably have 'backwards compatible' control terminals even if not clearly indicated.