Central Heating Controllers

[bryno]

Just starting winter in our new house. CH system has a Honeywell ST9400C programmable controller and where the Thermostat is there is a Siemens REV 22 controller. Both these controllers are programmed to time (and a max temp) All Rads have Thermostatic valves.

What I would like is a programmer that can be set to drive the boiler on Thermostat Temp eg switch off at say 21 deg and switch on at 17deg. Is there such a device available and where do I get one from? I've searched a bit but not found anything, if they are not available why not, these sort of controllers are widely available in industry?

 

[D_Hailsham]

Why do you want such a wide differential between on and off temperatures? Modern thermostats are designed to have a differential of about 1degC as anything greater is noticeable , so people are continually turning the thermostat up and down to try and stay warm.

 

[bryno]

Can you recommend a thermostat/controller which does what you say?

 

[D_Hailsham]

Can you recommend a thermostat/controller which does what you say?

Your Siemens REV22, should do that.

What, exactly, is the problem you are having?

Was the ST9400C already there and all you did was to swap the existing thermostat for the REV22?

 

[bryno]

Thanks for the reply. Whe I moved into the house the ST9400C is in the kitchen adjacent to the boiler. The previous owner had replaced the thermostat in the hallway with the Siemens Rev22. I have a detailed guide for the ST9400C but only a slip of paper for the Siemens but its probably got enough info to set it up.

What I would like is for the temperarure in the hallway to drive the central heating eg switch it off when it gets to say 21 degC and swtich it on again when it gets to another temp say 18degC. Looking at the Siemens I can set a time period for operation as I like and set a max temp to drive the central heating to, then presumably I have to set the Honeywell to "continuous" driven by the set up of the Siemens.

What I am trying to do is have a system which irrespective of time switch on at say 17degC and switch off at 21 deg C or any temperatures of my choice.

What we find with the system driving to 21deg the boiler just keeps working and the house gets really warm so we manually switch it off then when it gets down to about 17deg we switch it on manually, I want it to do that automatically irrespective of time.

 

[MJN]

What I would like is for the temperarure in the hallway to drive the central heating eg switch it off when it gets to say 21 degC and swtich it on again when it gets to another temp say 18degC.

Why do you want it to do that? It would make for an extremely uncomfortable environment with such massive temperature swings.

If your ideal temperature is, say, 21decC then surely you want your stat (and heating) to maintain it as close to that as possible?

Mathew

 

[D_Hailsham]

What we find with the system driving to 21deg the boiler just keeps working and the house gets really warm so we manually switch it off

Are you saying that, when the house reaches 21deg, the boiler does not go out but continues running, so the house gets even hotter?

If so, there is something wrong with the wiring.

 

[kevplumb]

dave as an "armchair advisor" are you sure you should be advising on this

you obviously don't know as much as some on here think they do

 

[bryno]

Dave Thanks for your help, today I have set the Siemens to 21 deg and the Honeywell to "continuous". The Boiler cuts in at 20.2 deg and cuts out at 21.8 deg which is fine as I reckon with the ambient today of about 9 degrees its taking about an hour for the hallway temp to fall from 21.8 to 20.2 which is acceptable to me and the house is quite pleasent. AS the ambient drops no doubt the hallway temp will fall quicker but at the moment on today's performance we are content.