set back stats on underfloor heating.

[thevenin]

I have been told by heatmiser technical that a stat that turns down by 4deg during the night time "off" period will lead to lower running costs than a system that is completely off during that period,if the house is well insulated Is it possible to wire a "master stat" set at say 16deg to bring the ufh system on during the night if there is call for it.Replacing the existing room stats is not an option.
Regards
T

 

[matt1e]

yes, but why is replacing the existing stats "not an option" and what make/model are they?

 

[Dan Robinson]

+1

 

[thevenin]

Mattle,
The existing stats use 3 c & e,the Heatmiser setback stats need 4core cable Regards,T

 

[thevenin]

PS,
They are Honeywell,dial type.
T

 

[Dan Robinson]

CM901 or CM907.

Simples

 

[thevenin]

Thanks for all the replies.Dan,if I were to replace all the 8 stats with cm901,s
it would cost over £400 00.I wondered if it would be an improvement just to have one overide stat set at 16deg to bring the system on during the night?
Regards T

 

[Dan Robinson]

I guess you could with some clever wiring. Kind of defeats the purpose though.

I guess this is a classic example of a system not being correctly specified from the off.

 

[ALEC1]

i thi k its the industries obsession with zones and controls... UFH can be very efifcient but you need to use compensTion controls and weather compensation in particular..then the flow temp runs along at a few degrees above room temperature...highly suitable for condensing boilers...

 

[Dan Robinson]

All depends on the rest of the system though...

 

[ALEC1]

not knowing the history of this install its difficult to say...but TEM floor plus controllers, viessmans mixing valve and vaillant mixer module all offer possibilities...

recently I have installed systems with no controls and an out door sensor... the other day the flow temp was 24c...room 21c.

It can be retrofitted, when chaining a boiler...done that too..

 

[mikely]

You should be able to connect a ‘master thermostat’ in parallel with your programmer CH output so that when the temperature drops below the set-back level it will turn on all zones. This will operate at all times effectively like a frost thermostat so would also be useful for maintaining a background level when you are away.