help with zone control on a underfloor heated Mitsubishi pre-plumbed cylinder and ASHP

[Markey]

Hi, I am having some troubles keeping my house and rooms right temp.

I have pre-plumbed cylinder, Mitsubishi ASHP and controller running a two zone underfloor heating setup.
https://heating.mitsubishielectric.co.uk/ForInstallers/Documents/FTC4 Cylinder Install Manual.pdf

I have obtained a copy of the original design from nu-heat and set all the flow rates appropriately now on the manifold. The Mitsubishi controller only seems to want to heat one zone, zone 1 (upstairs) or zone 2 (downstairs) at a time. Every time I check it it seems to spend most of its time heating upstairs and downstairs is not hitting temperature. I leave it on 24x7 and while it is not cold (by my standards, wife disagrees) I think it should be delivering more.

Is there anything else I can do ? Can I get it to spend more time on Zone 2 or even on both ?

The only other things I can seemingly control is a setting I don't understand to do with the zone mode which are Heating Flow Temp, Heating Room temp or Weather compensation.

Every room has an individual stat controlling the actuator on the manifolds which are wired to two UH3 8 zone wiring centres.

 

[Roger928]

Full output on these only occurs when the outside ambient temperature is 7c.
Below that their efficiency drops off. And at the moment its well below 7c.
Which unit do you have?

The controller may have decided the heating load is not within the set parameters.
In other words it could be undersized.

 

[snb]

The setup should allow it to heat both zones at the same time, but best option is to contact the installer. It may need a small adjustment in the parameters.

As long as you are running it for heating 24/7 on both zones with the room stats set at the same temp 24/7. The system should be fine. If you try to vary the stat Temps or use timing then you will have trouble. These units and the design is for them to maintain a temperature 24/7. It is much more important as the outside temp starts to drop as the units output starts to decrease and defrosting will occur more often.