Honeywell CM67 strange behaviour!.

Mine is doing something similar, turning on during the day when set back to 15 deg well in advance of the later target of 20.5. For the moment, I simply use the separate controller to disable daytime use, but it rather misses the point.

Chris

It sounds like you got the optimising turned on. I started off with this and on occasions found the heating switching on several hours early with the temp being just a couple of degrees below the target. I've now turned it off and just set the times a bit early to give a warming up period.

Interesting, does anyone understand the algorithm which the optimisation is based on? I'd guess it should be fairly simple - it would measure the rate at which the system is usually able to raise the temperature, look at the gap between the prevailing temperature and the target and work out how early everything needs to come on. But for it to go this wrong it must be be trying to do something too clever for its own good? I've recently got the CM927, is this prone to the same problems?

Does optimising also increase the target temperature as Tony S reports? I don't think so. Tony S, have you tried mailing Honeywell? How old is the thermostat?

Thanks for this, I need to check what my CM907 does; trouble is I am either away or asleep when optimisation normally kicks in. Need to set up an experiment :-)

Kostas

It is presumably an adaptive process - hence it may take a number of iterations to arrive at appropriate settings.

Could it be using the (low) setting of 10 degrees as part of its optimisation - even though the house will never get so cold - it may be planning to heat it from that temperature and therefore turns on early.

I suggest changing from 10 degrees to something more practical - such as 17 degrees and see what happens.

Usually for temperature control, the method used is PID.

Ah!, its intended with 21, not what it is doing..

Haven't mailed Honeywell yet thought peeps here would have err.. more experience;)

In article , John scribeth thus

Good thinking .. I'll try that and see..

Thanks..

Imagine the guy programming the logic of the device "Let's see, we need to raise the temp from the low setting to the next setting. We will use this difference to calculate the start time" Flawed logic maybe as it should perhaps be using the ACTUAL low temp rather than the low target temp, but perhaps there is a good reason.

Let us know the outcome. I have my thermostat set at 17 during the night and it rarely comes on (if it does then I am grateful!)

I just gave up on it. Truth be said, for me I may regard 21C as the comfortable temperature, I don't really worry if it's 18C when I come in if the temperature is rising.

In article , John scribeth thus

Well seemed to be fine last nite with the new revised settings but then again it wasn't quite so cold as it has been!..

We'll keep it under review for the time being.. Mind you the new wireless one would make the positioning of it better;!...