Control System for 3 zone Central heating?

[George Kaplan]

HI folks, this post is a follow up to my post relating to my single pipe heating system. In summary, I have a house built in 1980 (I bought it 2 years ago) that had a single pipe heating system but over the years there have been some changes made to the system that meant it didn't work. I have now removed the old system entirely and have repiped it in 3 separate 2 pipe circuits so I can control 3 different areas of the house independently. I now have some questions that I was hoping someone might be able to help with.

I now have 3 pairs of 22mm pipe that all converge on the area where the boiler is located. I assume I will need three motorised valves, one on each flow pipe, which I need to control.

I will need a thermostat in each of the three areas (I can run cable so wireless is not essential). I assume I will need a programmable thermostat in each that then feeds back to the boiler. However how does each thermostat interface with the boiler? Do I need a control unit between the three room 'stats and the boiler and if so what is recommended?

The boiler is a Worcester Bosch Greenstar 550 Highflow. There is currently a single "dumb" room thermostat. I say single, there is in fact two of them but only one controls the heating. I am not sure what the other one does but we also have a Brookvent Aircycle system in the house so maybe the second one is to do with that. (see attached picture)

I do get a large discount of Worcester Bosch products so if there is a product by Worcester Bosch than that would be good but not essential. I also get a discount on Hive products but again I am not tied to either of those brands except its nice to save a bit of cash.

Any feedback/comments are very welcome.

Thanks

P.S. I have just realised that there is a Controls section on here so my apologies for putting this in the wrong section.

 

[fowlerboi]

The wiring works in a series of switches starting with:

1. Power from the fused spur (should supply your entire heating system including the boiler)
2. Power goes to programmer(s)
3. Programmer calls for heat based on time schedule or overide and sends power to room thermostat
4. Room thermostats then send power to the motorised valves when the temperature gets to below the set threshold
5. Motorised valve opens the circuit which then switches a microswitch to send power to the boiler and pump

Basically you just need those 3 components for each circuit: Programmer/thermostat/motorised valve
Alternatively a programmable room thermostat would combine the first two.

I've no knowledge or what Worcester provide for heating controls not intergrated to the boiler but I would be fitting Honeywell if it was my house. Honeywell don't make a 3 channel programmer (3 zones) unless you go with something like evohome which would allow you to control it from your phone. For me I would pick the Honeywell T3 which can come in a wireless version if you would prefer.

 

[George Kaplan]

Thanks fowlerboi. I had previously assumed that the room 'stat just provided a control signal. I didn't realise that the full current to power the motorised valves went to and from them. Obviously wireless room 'stats must work differently.

In my case the longest path to the furthest 'stat is circa 20m so in total the circuit for the power to the motorised valve will be 40m. Looking at some random valves online they say they all are 5w or 6w "Power Consumption" but then say that they draw up to 3A which is clearly not the same as 6w.

I assume that a normally closed valve uses 6w in the open position and draws 3A when actually opening or closing?

40m at 3A means I need 1.0mm2 cable so what cable is recommended for this application?

I will do some reading up on the one you mention and also see what Worcester and Hive have to offer.

Thanks.

 

[fowlerboi]

Have no idea on cable sizing as I'm just a plumber.

In regards to wireless stats the wiring is the same just you wire it to the reciever instead of the stat

 

[George Kaplan]

I had a very busy day so not much time to look at options but I did speak to Worcester Bosch Technical help line. They suggested that any "inteligent" controller would be fine such as Hive or Nest which was refreshing as they didnt try to sell me a Worcester product. It was only when I asked about Worcester products did the guy suggest that I could use a single "Easy Control" and three Worcester Bosch programmeable thermostats.

Next will be to compare the other products with the Worcester ones both function and price. I can buy Worcester Bosch products for a large discount to the best prices online so price might also be a consideration.

 

[Last Plumber]

It doesn't matter I know but a one pipe system in 1980?

This is a combi so it needs to be boiler plus compliant. Have you taken that into account?

 

[George Kaplan]

It doesn't matter I know but a one pipe system in 1980?

This is a combi so it needs to be boiler plus compliant. Have you taken that into account?

Hi Last Plumber. Yes it is (was) a single pipe system from 1980. I am not sure of the rationale for that but it may be related to the house being a Scandinavian kit house, or maybe not. For 1980 the house is very well insulated.

The system will be Boiler Plus Compliant. As far as I know the boiler has to be of a certain efficiency (although I assume that only applies to new boilers?). No matter, my boiler is not that old and the same as the current model offered by Worcester Bosch. I also need to comply with one of the four listed requirements. Because I am fitting "smart control" then I will be compliant with one of the four so I am compliant even though I am not changing the boiler.

 

[ShaunCorbs]

Combi or heat/ system boiler ?

 

[George Kaplan]

Combi or heat/ system boiler ?

Its a Combi. Its a Worcester Bosch Greenstar 550 High Flow.