Bringing up an old thread here which is relevant as I used the content to fit a system in an average semi.
I took note of the Intergas combi boiler and the low loss header to give zoning of upstairs and down and independent TRV temperature control in each room with no central thermostat control.
A low loss header was made up using 28mm pipe and fittings like this, but running horizontally under the boiler.
The two heating zones could have different flows through their own circuits, and sometimes very low flows, so the low loss header guarantees a constant high flow through the boiler giving full boiler protection. The flow and returns to each heating zone were 22mm. The two heating flows were taken from one end of the header. The header also had the filling loop attached. I thought the header of 28mm may be too small, and I was prepared to up the size after testing, which would not be a great job to do, but it works fine.
A 40 kilowatt Intergas combi was used. What a superb simple boiler this is and built like a tank!! You can have only the CH filled or the DHW filled and it works. It can operate as a multipoint with the CH section dry and ignored. The pump could even be removed as it only does CH. The CH pump does not come in when the DHW is called. It is very cheap to say a Japanese Rinnai multipoint of the same DHW output. I checked. This delivers hot water superbly just like a cylinder, and fast.
A new 25mm blue plastic water main was run into the house to ensure there was enough flow of water. On the hot and cold water outlets a water restrictor/isolator was fitted to give the required flow for each. The hand wash basin in the small toilet now has a 2 litre per minute flow, and it works well with the combi, and the kitchen hot and cold 6 litres each. Toilets were regulated to 6 litres flow. This was to ensure the water flow was not robbed from the shower which had no restrictors on the hot and cold pipes taking as much as the shower wants.
The hot pipe for the shower was taken from the combi and cold pipe from just before the combi to avoid and pressure fluctuations in the shower. The combi had a dedicated cold supply of 22mm from the 25mm cold water main to ensure it was priority in the cold water supply. It worked. You can be in the shower and a toilet flushed or kitchen tap full on with no effect on the shower.
Two Wilo Smart pumps with flow switches and non-return valves just after the pumps were used for the heating zones off the low loss header. The flow switches were used to switch in the boiler acting as boiler interlocks. An outside weather temperature sensor was used. A Sentinel magnetic filter was used on the return to the boiler.
Each radiator had a TRV. Two simple, cheap, single stage time clocks were used. One for upstairs and one for down. They are easy to use which is important. The integral Intergas boiler pump was set to minimum, which only circulates around the header. The two Wilo Smart pumps were set to minimum.
The heating system works superbly. I noticed that in cold weather when the boiler switches on all the boilers heat is pumped into the two heating flow pipes, maximizing condensing efficiency. When the house warms up the two return pipes get warm and the temperature to the boiler rises. The boiler's controls then drops the flow temperature, correctly assessing the house is nearing the required temperature. When all the TRVs on a heating zone are closed the smart pump winds itself down as it can work on a dead head. The flow switch on the heating zone closes switching out the boiler.
Looking at the operation I concluded that "maybe" the flow switches on the heating zones are not needed as when all the TVRs close down the return temperature rises to the boiler through the low loss header. It switches out anyhow giving its own boiler interlock. The Intergas pump keeps running and it appears to run down in speed with the burner switched out.
This was simple and easy to fit. No expensive zone valves were used and no wiring in a central unneeded room thermostat. Each heating time clock switched in a pump and the flow switch switched in the boiler. Simple. The weather compensator drops the flow temperature accordingly and works well with the flow temperature most of then time quite low producing lot of condensate; a HepVO trap was used for the condensate. It is cheap to run. I would highly recommend using an Intergas combi, smart pumps and a low loss header when using two or more heating zones and TRVs on all radiators eliminating central electric wall thermostat.
