Wireless thermostat to replace one of three wired

[c3iq]

Hello,
I have a Honeywell ST699 programmer and three thermostats. I want to replace the one in the living room with a wireless one (Salus RT300RF). One is in the loft and the other is in the garage next to the boiler.

The Salus needs a permanent live. The living room stat is only live when the programmer is running the central heating/water. The wiring diagram for the ST699 suggests that I could move the live for the stat from '3' to live.

My worry is the other two stats. How are they wired? Are they part a loop that includes the living room stat? Would making the living room stat permanent live make the other two live too? I understand that the stats have a heating mechanism in them (they are old) to make them more accurate. I'm guessing it would be a bad thing to have them live all the time.

I need to have a proper look at the programmer but it will lose it's programming and that's a pain during the evenings.

Any guidance, much appreciated.

 

[flameport]

The loft and garage thermostats are probably for frost protection, and only activate the boiler when the temperature in those places gets to near freezing.

For the living room - the point of a wireless thermostat is to have the receiver unit (which requires a permanent supply) located next to the boiler or wiring centre, and put the battery operated thermostat unit wherever you want it.
If you bypass the programmer to have the wiring at the existing thermostat position permanently live, your heating will be on 24/7 and only controlled by the thermostat.

Would be better if you explained what you are trying to achieve with these changes - that Salus thing is about as basic as you can get and will offer no advantages over your existing thermostat.

 

[c3iq]

We're changing several radiators soon. All radiators will have thermostats. The boiler is 20+ years old and we will change it at some point. That's why I chosen the Salus basic wireless stat. The living room stat is in a better position than the boiler to put the wireless receiver. The boiler is in the garage and I'm pretty sure the signal won't reach the wireless stat everywhere it might be carried. The idea is that the missus switches off radiators everywhere except her office when she is working from home. It will be even simpler when I put programmable TRVs on the radiators.

From the Salus stat point of view, permanently on, when the room becomes cold it will send a call for heat. If the ST699 is "off" at that point will the boiler still come on? I guess that would be similar behaviour to the stats in the garage and loft. If that is the case I would need the model up which is also programmable...

I'm trying to keep things simple as well as cheap until we go for the new system.

 

[jackthom]

As flameport says, to do what you are suggesting with the receiver installed inside the house you really should go for a programmable thermostat. Then just change the wire which is now connected to CH ON in the programmer over to the permanent Live terminal.

 

[c3iq]

Thanks. I understand it now. A project for the weekend.