Honeywell CMT927 range - Any experience

[WHPES]

I've got a system on a 12 bedroom country house to re-jig. We are wanting to fit CMT927 wireless stats in the zones to transmit to a boiler house adjacent to the main house. Does anyone have any idea of the sort of realistic ranges you can expect one to transmit bear in mind its an old stone built Georgian property with 10ft ceilings and thick walls.

 

[Billy Bob Bob]

you will have problems what ever rf you use they cant hack a signal trough stone walls faced this hassle when zoning a large church ended up going wire free,it sound like in your case near impossible to get cables in but imho i dont think rf will work regardless of the make

 

[WHPES]

I will try one out as a temporary set-up at the farthest end of the property and if it doesn't work we will work out a way of getting the receivers inside the main part of the house.

 

[doitmyself]

I will try one out as a temporary set-up at the farthest end of the property and if it doesn't work we will work out a way of getting the receivers inside the main part of the house.

That's sensible. Don't forget that the relay boxes provided with each CM927 will control just the motorized valve for the zone. The boiler is controlled by a separate relay box, which is synchronised via the "master" controller.

Honeywell will supply you with the necessary information as it's not given in the instructions provided with each CM927. However the instructions for the earlier version, CM67NG, are Here.

 

[WHPES]

All the zone valves are located in the boiler house.

The electrician is designing his own relay control box for the boiler. It is a complex system with three separately pumped systems each with two zones fed from one massive boiler and three corresponding 2 channel programmers so that the boiler will come on for one or more programmer. It has 6 zones in total, one of which is the hot water calorifier and the rest will have wireless stats on.

 

[doitmyself]

The electrician is designing his own relay control box for the boiler. It is a complex system with three separately pumped systems each with two zones fed from one massive boiler and three corresponding 2 channel programmers so that the boiler will come on for one or more programmer. It has 6 zones in total, one of which is the hot water calorifier and the rest will have wireless stats on.

It might be a good idea if you installer ran their proposal past the tech department at Honeywell. The CM927 is a programmable PI thermostat which expects to be able to control the boiler directly.

Other option to consider are the Honeywell Hometronic and Honeywell Smile.

 

[WHPES]

My electrician has done stuff like this before and can build his own control units so knows what he is doing.

The CMT927 can only control one channel in any case so with a system boiler you still need a separate timeclock to run the channel for the hot water cylinder circuit.

 

[doitmyself]

My electrician has done stuff like this before and can build his own control units so knows what he is doing.

Be interesting to know how he deals with one circuit trying to reduce the boiler output while another one is trying to increase it.

The CMT927 can only control one channel in any case so with a system boiler you still need a separate timeclock to run the channel for the hot water cylinder circuit.

So why do you need three 2-channel timers?

A single channel timer will do the hot water (make sure it has a Boost button) and the heating circuits can be handled by CM927 programmable thermostats.

 

[WHPES]

You've got the pumps to contend with - due to the size there are three of them with each pumped circuit split into 3 zones and its no good pumping against a closed zone valve!

 

[doitmyself]

You've got the pumps to contend with - due to the size there are three of them with each pumped circuit split into 3 zones and its no good pumping against a closed zone valve!

So you control the pump and the associated motorized valve from the same programmable thermostat.

I'm getting confused! Three pumps with three zones each requires nine controllers. Assuming one zone is HW, that leaves eight heating zones. But earlier you said there were six zones in total, five heating and one HW.

Can you post a drawing showing the proposed layout?

 

[WHPES]

The water from the boiler splits 3 ways. Each split has a pump on it which after the pump splits into 2 zones hence 3 x 2 =6.

Basically its a 2 channel programmer for each pump. When the programmer wants the boiler on it activates a relay to power the boiler circuit. The boiler circuit can be powered when one of the programmer circuits activates its boiler circuit relay.

You can't have just one pump to work all 6 channels like you would a standard domestic system with 2 channels as a large pump will be overloaded if you only have 1 zone open and a smaller pump will be too small for all 6 zones on.

 

[doitmyself]

The water from the boiler splits 3 ways. Each split has a pump on it which after the pump splits into 2 zones hence 3 x 2 =6.

So you were correct the first time!

Basically its a 2 channel programmer for each pump. When the programmer wants the boiler on it activates a relay to power the boiler circuit. The boiler circuit can be powered when one of the programmer circuits activates its boiler circuit relay.

Still don't see why you cannot use the CMT927 programmable stats for the CH and a single channel programmer for the HW to control both pump and motorized valves.

You can't have just one pump to work all 6 channels like you would a standard domestic system with 2 channels as a large pump will be overloaded if you only have 1 zone open and a smaller pump will be too small for all 6 zones on.

What about using a variable speed pump, such as the Grundfos Alpha or Magna?
With multiple pumps, sometimes all working at the same time, sometimes individually, how are you going to ensure the correct flow rate through the boiler and rads at all times? Are balancing valve incorporated in the system?

 

[Gray0689]

I agree to use 3 pumps is very old fashioned plumbing go for a grundfos magna these can be set to work on automatic variable speed