drayton wiser, how can roomstat and radiatorstat work together

[John Driscoll]

This probably applies to other systems to but here goes. I've always understood that a roomstat will switch off the boiler when the temperature in the room will reach the set temp on the stat.
Now with the new smart wireless systems you get a roomstat and so many radiator stats. So if you have a room with a roomstat with no TRV on the radiator and the roomstat switches off then the boiler will switch off and any wireless TRVs in other rooms will not get any heat when they need it. These systems are supposed to allow different temps and times in each room. This I understand but if the roomstat has switched off then so has the boiler! Roomstats call for heat by closing a contact to the boiler, do radiator stats do the same thing? If they do then the radiator stats will do their thing by keeping the boiler on so the room with the roomstat will overheat. The only way I can see this system working is to have radiator stats in every room in which case I would not need a roomstat. Every sytsem I've looked at has a roomstat even when they are selling radiator stats too.

 

[Harvest Fields]

Have you not got a thread going already about this?

 

[John Driscoll]

I started a thread about general info about smart systems. This is specific about wireless roomstats working along side wireless TRV stats rather than recommending any particular brand. Like I said it probably applies to more than one brand.

 

[Chuck]

Roomstats call for heat by closing a contact to the boiler, do radiator stats do the same thing? If they do then the radiator stats will do their thing

Typically, the 'smart' TRVs communicate with a central controller, which is in the same box as the room thermostat. The central constroller tells the boiler what to do.

 

[snowhead]

The Roomstat is Master and will turn the boiler off when the temperature in that room, the one without the TRV meets the setpoint on the Roomstat.

 

[Vee]

Evohome becomes just a central controller and the room stat function can be disabled therefore each room radiator thermostat effectively becomes an interlock. Not sure how other systems do it.

 

[John Driscoll]

Snowhead: That means then that when the roomstat switches the boiler off then the boiler will not respond to the wireless TRVs. So is the best thing to have is all TRVs wireless and disable the roomstat. That way the roomstat will just be a very expensive room thermometer!

 

[Vee]

In case of the Drayton Wiser that appears to be the case. Not sure if you can even disable it on the Drayton. Evohome central controller has many more functions than just being a thermostat.

 

[John Driscoll]

One thing that attracted me to the wiser was the price, the Evohome is much more expensive, is it worth it? I will need 9TRVs.

 

[Bogart]

I too am considering the Wiser as I thought the Evohome expensive especially with my 22 rads. I think if you have the thing zoned ie up and down the fact a room stat will turn the whole zone off is not in my opinion a great problem as the upstairs will be set at a different temperature than downstairs. Problem here is bathrooms where maybe heat is required when say the bedrooms do not need heat. Ideally, in my opinion, each room should have its own smart trv. Not sure if there is a setup that can handle so many inputs. Possibly I am feeling sorry my dog and cat who reside in the utility at nightime, would be nice to keep their bedroom nice and cosey without having the rest of the downstairs beiong on.

 

[John Driscoll]

22 rads, bathrom"s"! Buy the Evo you can afford it. LOL

 

[Bogart]

I might if I could be assured it is what I need. Problem is as far as I can see the it can control up to 12 zones plus water. My problem is I have 16 rooms with 22 rads, with 13 rads downstairs and 9 upstairs, so even if one could run two controllers together, which I think is not possible, it still would not be suitable.

 

[Vee]

You can have two controller set up together. Have a customer who as two controllers set up as upstairs downstairs due to the number of zones required to be controlled.

 

[Vee]

That is for Evohome.

 

[Bogart]

Need to contact Honeywell. If it is possible to run 2 it is what I need. Wonder if the hot water zone could be used as a radiator contol too that would give me full control of the 13 downstairs rads, failing that I have 2 rads in the living room that I could re plumb in series.

 

[John Driscoll]

Getting back to the OP can anybody tell me if the roomstat has turned off the boiler can the wireless radstats call for heat. Because if they cant then I don't see how the system can work.

 

[Vee]

Yes they can on Evohome. They are room stats in their own right and communicate directly with the controller and relay if set up correctly. That's why you don't need to have the controller being a room stat if you don't want to.

 

[John Driscoll]

good, so how about the drayton wiser

 

[fixitflav]

This probably applies to other systems to but here goes. I've always understood that a roomstat will switch off the boiler when the temperature in the room will reach the set temp on the stat.
Now with the new smart wireless systems you get a roomstat and so many radiator stats. So if you have a room with a roomstat with no TRV on the radiator and the roomstat switches off then the boiler will switch off and any wireless TRVs in other rooms will not get any heat when they need it. These systems are supposed to allow different temps and times in each room. This I understand but if the roomstat has switched off then so has the boiler! Roomstats call for heat by closing a contact to the boiler, do radiator stats do the same thing? If they do then the radiator stats will do their thing by keeping the boiler on so the room with the roomstat will overheat. The only way I can see this system working is to have radiator stats in every room in which case I would not need a roomstat. Every sytsem I've looked at has a roomstat even when they are selling radiator stats too.

Hello John
With this system the roomstat is in a room with no TRV, as you say, but you need to ensure the rad in the room with the roomstat is not too powerful, or as you also say, the boiler switches off before the other rooms are warm. The TRVs can only reduce heat, not increase it, and are still wide open at this point. The trick is to ensure that at design stage the rad with the roomstat is smallish relative to the room size. As you're past that point you should throttle the rad down to reduce output, till the TRVs start to do something.
My system has the roomstat in the hall (no TRV!) and no TRVs in the bathroom or utility room. TRVs on the other 7 rads. It works fine.

 

[John Driscoll]

Good news on this thread.
I finally got to talk to a Drayton engineer, not the help desk. It turns out that each radiator stat works very similar to the room stat. This means that if the room stat has turned the boiler off then a room with a radiator stat need heating up the rad stat will send a signal to the hub to CALL FOR HEAT from the boiler. Each rad stat works as a zone and will call for heat regardless of any other zone including one monitored by a room stat. Its important to have A TRV or better still a rad stat in the same room as the room stat. This is because if various rooms are calling for heat reaching the set temperature in the room stat room will not switch the boiler off and the room will over heat. Install rads stats in this room to switch off the radiators while the other rooms do their thing!

 

[fixitflav]

Good news on this thread.
I finally got to talk to a Drayton engineer, not the help desk. It turns out that each radiator stat works very similar to the room stat. This means that if the room stat has turned the boiler off then a room with a radiator stat need heating up the rad stat will send a signal to the hub to CALL FOR HEAT from the boiler. Each rad stat works as a zone and will call for heat regardless of any other zone including one monitored by a room stat. Its important to have A TRV or better still a rad stat in the same room as the room stat. This is because if various rooms are calling for heat reaching the set temperature in the room stat room will not switch the boiler off and the room will over heat. Install rads stats in this room to switch off the radiators while the other rooms do their thing!

Interesting. It sounds like your radstats aren't "traditional" TRVs like mine (which just close above set temp, no electrical contacts). But if there is a radstat in every room you don't need a roomstat at all, do you?

 

[Bogart]

What I was thinking as each trv is in effect a room stat.

 

[John Driscoll]

Exactamundo! If you understand some of the basics of electrics its like all the TRVs and the roomstat are in parallel wirelessly to the hub so any one of them will call the boiler. What I thought before was that all the TRVs where in parallel but then connected in series with the roomstat so if the roomstat switched off the TVRs were isolated, not so!