Programmer with wireless thermostats to control 3 zones

[gc1234]

I am revamping my central heating system and plan to have installed a new combi boiler heating three separate zones (downstairs, upstairs, office) each with a wall mounted wireless thermostat controlling a motorised valve.

Ideally I would like to buy a single box of electronics which combines a 3 zone programmer/controller with a wireless receiver which is linked to the 3 separate wireless thermostats. Does such a product exist?

The alternative is to buy separately a programmer and 3 wireless thermostats (each with its own separate receiver) and then wire them together but this will take up more room and should in theory be more expensive because of the duplicate electronics (i.e. the extra power supplies, wireless receivers etc.). Is this necessary or does an integrated product exist? I am looking for a low cost solution.

 

[BGEngineer]

http://www.discountedheating.co.uk/shop/acatalog/Horstmann_7_Day_3_Channel_Programmer_H37.html

I am not aware such a product as you described exists. All our large installations incorporate seperate transmitters and receivers.

 

[echoes]

Heatmiser do an 8-zone wireless receiver for their programmable stats - not particularly cheap though. I have their simpler 2-zone receiver and am very pleased with it.

 

[gc1234]

Thanks for your replies. I like the Horstmann products and have used them before so it is a shame they have not built a wireless receiver into any product yet. The Heatmiser looks good too but is too big and over-speced for my requirements.

So I think I am reduced to using 3 separate programmable wireless thermostats. If they each have a 7 day timer then I guess I have no need for any controller - sorry Horstmann!

 

[D_Hailsham]

So I think I am reduced to using 3 separate programmable wireless thermostats.

If you use the Honeywell CM927 7-day wireless stats, you really need an additional relay box (receiver) to control the boiler. The relay boxes provided with the thermostats just control the opening and closing of the zone valves.

The reason for the extra relay box is to prevent the zone valve relay boxes fighting for control over the boiler.

You can read the principles of how the system works in the CM67NG Installation Manual Section D, Multi-zone RF System. The CM67NG is the model before the CM927.

Unfortunately, Honeywell no longer include the configuration info in the literature provided with the CM927. Your installer will have to obtain it from Honeywell.

 

[gc1234]

Thanks for the comment. I was planning to use two port zone valves which have a separate switched output when the valve is fully open. So I think if I wire these three outputs together this will work as the demand to the boiler - if at least one valve is open the boiler will be on.

 

[matt1e]

Thanks for the comment. I was planning to use two port zone valves which have a separate switched output when the valve is fully open. So I think if I wire these three outputs together this will work as the demand to the boiler - if at least one valve is open the boiler will be on.

yup,
3 x 2 port valves and 3 x prog room stats will do you fine (unless you wish to have all the controls central that is)

Matt

edit this will involve 3 recievers if you want to go wireless, I should read the posts properly!!

 

[D_Hailsham]

I was planning to use two port zone valves which have a separate switched output when the valve is fully open. So I think if I wire these three outputs together this will work as the demand to the boiler - if at least one valve is open the boiler will be on.

That's the traditional way of doing it with on/off thermostats. But modern thermostats are more sophisticated. See Honeywell TPI Control FAQ.

This method of control would mean that the motorized valves were continually opening and closing as the boiler demand was changed by the thermostat. This type of valve has a fairly long response time, typically about 30 seconds to open or close. So the valve could have only just reached full open when it receives an instruction to close again. This obviously is not good for the valve. In fact Danfoss recommend turning the TPI feature off if you are using motorized valves.

I emailed Danfoss a couple of years ago and asked their reason for this and they replied:

When the thermostat is using the chrono feature (TPI logic) it breaks the boiler firing time into defined lengths of time.

Sent to chrono six mean that it will fire the heat source up to six times an hour, breaking an hour into ten minute segments.

Simplistically speaking there could be five minutes on and then five minutes off.

It is self adjusting so if it hit its desired temperature it would turn off, and it would reduce the on period.

And if it did not hit its desired setting it would increase the on period, Say to eight minutes on and two minutes off.

Now as the room gets close to the set temperature it could be on for a minute.

Now motorised valve take time to activate ours take approximately twenty seven second some others may be longer, this could cause the boiler which would be switch by the valve to be on for a very short time less than thirty second which they believe may not be good for the actuator or boiler.

Now imagine what will happen if you have two or three TPI controls in parallel issuing conflicting instructions to the boiler. One wants to light the boiler and two seconds later another one wants to turn the boiler off.

By doing it Honeywell's way, the control of the boiler is separated from the control of the motorized valve, so the boiler only received instructions from a single source.

A receiver will cost about £75, but you can pick them up for about £40 on Ebay.

 

[gc1234]

Thanks for your detailed post. I hadn't realised that modern thermostats were using TPI so I can see why my naive approach would not work too well! I will need to look into the Honeywell system in more detail to fully understand what it is doing.