Honeywell 927

[Johnytuono]

Hi
First time poster so please be gentle with me.
Have just bought a 927 p/thermostat and am waiting for the receiver to be wired up to the boiler.
In the meantime i ve put the batteries in the thermostat so i can edit/set my auto on times so its all ready. Also ive been trying the stat in various rooms to see what the display shows as the room temperature ( i know its not going to control my boiler or anything just yet so please dont think thats what i'm expecting it to do). Anyway the problem seems to be in the room temperature reaction time showing on the set ie when i place it in a different (colder or hotter room..ambient-wise). It seems to me that no way will it show a..say.. 2 C difference in less than an hour..meaning if the sets showing 10c at 0600 and i wanted it to get up to 18c it will (according to theory) come on but if i changed the temp so it will go off at 10c at 0730 it wont cos the reading will still be too high on the set. If i ve got it all wrong please let me know. I bought this because of all the recommendations ive heard. How quickly (or not) do other peoples 927's react? No factory settings (apart from the daily/temp on off times/temps have been altered.
Thanks in advance
JohnyT

 

[snb]

put in the fridge and go back 20 mins later. bet the temp has reacted

 

[Johnytuono]

Hi
Thanks for that although really i was questioning the reaction time.
JohnyT

 

[D_Hailsham]

The spec says:

Temperature control accuracy: ±0.5K (nominal) @ 20°C, 50% load, 3KΔ/hour.

Not sure what they mean by a 50% load; but I take the rest to mean that the thermostat will maintain a temperature of 20°±0.5C, provided the rate of temperature change, due to heat loss, is no greater than 3°C per hour.

I have found that it reacts very quickly to temperature changes, so I can't see you having any problem; though I'm not sure what you are trying to achieve as this is rather confusing:

If the set is showing 10c at 0600 and I wanted it to get up to 18c, it will (according to theory) come on; but if I changed the temp, so it will go off at 10c at 0730, it won't cos the reading will still be too high on the set.

Are you saying that, if you set the temperature to be 18C at 0600 and 10C at 0730, you think it won't go off because the temperature will be too high?

The programmer's optimizing feature only works for the first on period, i.e the 18C at 0600. The programmer will turn the boiler on earlier that 0600 to ensure the temperature is up to 18C by 0600; how much earlier depends on the overnight temperature drop. If you then set a change of temperature to 10C at 0730, the boiler will maintain the 18C temperature until 0730. From 0730 the boiler will stay off until the temperature has dropped to 10C; it will then maintain the temperature at 10C.

 

[Johnytuono]

Hi
Thanks for the informed reply.
After re-reading my quote that you highlighted it seems I got a little confused. I'm used to a on/off time clock so its a little different using temperatures to turn the boiler on/off.
Thanks again
JohnyT

 

[D_Hailsham]

I'm used to a on/off time clock so its a little different using temperatures to turn the boiler on/off.

You are not really using temperatures to turn the boiler on and off. All you are doing is telling it what temperature you want the programmer to maintain between two times. The CM927 does not have an OFF switch, like a timer. So, if you do not want the boiler to come on, say overnight, you set the overnight temperature, usually time period 6, to a low temperature, 5-10C. You can disable unwanted times if necessary or set them all to the same temperature. For example:

1. 0600 - 21C
2. 0900 - 20C
3. Disabled
4. Disabled
5. 1800 - 21C
6. 2300 - 5C

The temperature will be maintained from 0900 to 1800 at 20C. Times 3 and 4 have been disabled as they are not required. The temperature cannot fall below 5C from 2300 to 0600. The boiler will, of course, come on before 0600 to bring the house up to 21C by 0600.

 

[Johnytuono]

Hi
Thanks again for the reply. When I said turning it off I meant by setting the temperature low it will effectively not come on (unless it drops below that temperature). Got it now (hopefully)
JohnyT