Daikin Altherma Duel system space heating control - not right

[jrp13149]

Good morning,

Apologies for the vague description in the title. I've been in this house for 8 months during the summer and haven't noticed this issue until the cold weather in the last week.

I have the comfort temperature set to 20C, and eco set to 16C. I have a schedule programmed which targets comfort from 0600 to 1100, then eco from 1100-1600, comfort again from 1600-2000, and then eco for the rest of the day.

During the summer, the temp when I got up at 0630 was at or above 20C. This past week it's been 17-18C. The control panel quite happily tells me that it's targetting 20, and the actual temp is 17.5, but there is no flame or leaf on the control panel, so it looks like it's neither using gas nor the air pump. Why is this?

If I manually bump the target up to 22, then within a few minutes the boiler has fired, and the radiators are getting warm. Drop it back to 20, and they stay on, until the house has warmed up, then behave themselves properly for the rest of the day.

Is this a fault? Anyone else experienced this?

Thanks!

[Brian_UK]

Perhaps adjust your set point upwards a degree or two.

Also allowing for the lower ambients now expecting the temperature to be at set point within 30 minutes might be a bit hopeful.

[jrp13149]

I'll give that a go Brian. However, 22 is too warm.

If it the system was coming on but taking it's time to warm up, I would just adjust the start time. I'm just converned that it doesn't seem to come on without a little encouragement.

[Brian_UK]

It perhaps depends n the actual space temperature compared with the setpoint.

E.g. Some systems need the temperature to drop between one or two degrees below setpoint to switch on or even switch over from cooling to heating modes.

I'm not saying your system does as I don't know the workings of the Altherma but if your set point is 20⁰ and your space is 18.5⁰ then you may just be on the cusp of switching on ( hope that makes sense).

[Brian_UK]

Just been having a quick look at Daikin manual, ( don't know your model no.) and there seem to be quite a few settings to be checked regarding the heating operation.

Have you checked that all of the parameters have been correctly set?

[frank]

There could be a chance that the system is set for DHW priority (which is the norm) and is bringing the cylinder upto temp before changing over to heating mode?

Although I know the old Altherma's quite well (low & high temp), I don't have any experience with the new stuff

[jrp13149]

There are loads of parameters! As far as I can tell they all look fairly sensible for a working family. The only changes I've made are to the comfort and eco temperatures - I lowered them both by a few degrees.

I didn't see any settings for the sensitivity of the space temp vs target temp. I suppose it would make sense for there to be some logic in there both around how close the space temp needs to be to the target to activate heating, to avoid the system chattering.

I'll look out the model today. Thanks for looking into it.

[jrp13149]

Last night I brought the water heating timing forward a couple of hours to stop it interfering with the space heating. This morning it looks like the heating did come on as scheduled. It was off when I got up, but the space temp was 19.4C and there was some heat in the radiators.

Feels like the system is working. I just need to understand how to get it to do what I want.

[Brian_UK]

Good news JP, as with all of these things small steps is the way to go.

Change one thing and allow a few days to settle before the next adjustment.