Wet underfloor heating - Honeywell CM907 problem?

[Johnfwells]

New church hall. Builder gone into liquidation. Just finishing off all outstanding bits. We have three Honeywell thermostats for three areas. Two are CM907 and the other is the wireless version of the same. Wet underfloor heating with a long heat up and cool down time.
First problem: With varied usage day by day what is best control regime?
Second problem: I have been running a consumption test with the two CM907 stats set MANUAL at 18 degrees. But one of the two stats seems unaccountably to reset the target temp to 12 degrees occasionally. I haven't touched the set up since the builders walked away leaving the display showing MAN. Am I missing something?

 

[D_Hailsham]

Wet underfloor heating with a long heat up and cool down time.

First problem: With varied usage day by day what is best control regime?

Email Honeywell and ask for their advice.

Second problem: I have been running a consumption test with the two CM907 stats set MANUAL at 18 degrees. But one of the two stats seems unaccountably to reset the target temp to 12 degrees occasionally. I haven't touched the set up since the builders walked away leaving the display showing MAN. Am I missing something?

Probably someone fiddling with the stat.

Make sure as few people as possible know how to adjust the times and temperature - preferably only one.

Do NOT leave the instruction manual lying around

Set the Upper temperature limit to 21C (minimum allowed) and Lower limit to 17C, so no one can change the temperature by more than +4C/-1C from 18C.

Use the Auto feature so you can set the times/temperatures for a week at a time.

Turn Optimization ON. The stat will then automatically adjust the ON times so the hall is up to temperature when the event starts. It may take a week or so for the stat to learn the heating/cooling characteristics of the hall.

Use a thermometer to check the actual temperature around the room and compare to the stat reading. You may find that there is a difference due to the location of the stat, ie. the room is at 18 when the stat is reading 17, or vice versa. Change the Temperature Offset so the stat reads the same as the thermometer.