How responsive is the CM927 to temp change?

[falkirkbairn11]

Can anyone tell me how responsive the CM927 is supposed to be.?
My one seems to be incredible sluggish in showing a change.
It seems to take an age to change even when I can feel it getting colder.
As an experiment, I placed it outside on a cold day and it took a long time to show any change.
It is a new unit, and there doesn't appear to be any packaging to be removed but perhaps there is an unseen transit protective membrane or similar to be removed. Anyone know?

 

[D_Hailsham]

Which make batteries are you using?

 

[falkirkbairn11]

Which make batteries are you using?

The batteries that were supplied with the unit
IE AA GP ALKALINE
I have since changed them to ENERGISER in the last few hours to see if there is any difference

 

[Agile]

It will not make any difference.

Part of the design is that it does not change too quickly otherwise it will be constantly changing due to draughts.

It aims to average out the temperature.

I think the is a differential adjustment so you can set it at either 1.0 C or 0.5 C. Obviously the latter would respond faster.

Tony

 

[achrn]

As an experiment, I placed it outside on a cold day and it took a long time to show any change.

I've got one sat here that's not controlling anything, so I just put it in the fridge for you. In 20 minutes it dropped from indicating 21C to 12C.

Having taken it out, it took 3 minutes to go back up 1C to 13C, but in the next 2 minutes (ie, now 5 minutes since coming out of the fridge) it has rocketed up another 2C to 15C.

I'm not sure that actually tells you anything, but you could compare it with the speed yours responded to being put outside.

 

[D_Hailsham]

I think there is a differential adjustment so you can set it at either 1.0 C or 0.5 C.

Some manufacturers provide this, but not on the Honeywell CM9XX stats.

The spec says: 'Temperature control accuracy: ±0.5 K (nominal) @ 20°C, 50% load, 3 K Δ/hour.'

The first part is obvious, but I don't understand what the bit in italics means.

 

[Agile]

Well the "K" is obviously the degrees ( Kelvin ) which is the same as centigrade in that application.

The 50% load probably means when the boiler is on for 50% of the time under the control of the stat.

The 3 K Δ /hour, I would guess means that the rate of increase or decrease of the room temperature is no more than 3 degrees per hour. That is of little importance in practice but means the stat will respond differently if the rate of change is faster ( than 0.5 C per 10 minutes ). Thats where the response time of the stat becomes involved.

Tony