ASHP - Weather Compensation AND Zoning?

[SBMS]

I was speaking to a potential installer today re ASHP and asked about his thoughts on zoning.  His view was to install individual room stats, but in such a way that the room stats were not able to call for heat from the heat pump, and were set 1-2 degrees higher than the ideal temperature to prevent overheating.  The heat pump would then operate solely in weather compensation mode.  He stated that this would stop short cycling on the heat pump, but also prevent individual rooms from potentially overheating.

 

I think I understood but wanted to double check... In this arrangement am I right in thinking that the heat pump continues to operate and circulate to all the UFH zones, no matter whether zones are calling for heat or not, but that an individual zone (room stat) has the ability to close its flow down in the event it gets to over temperature?  If my understanding is correct, what happens if all zones get up to temperature and the heat pump continues to operate, but there's no call for flow to any zones??  What is the heat pump...heating?

[JohnMo]

If a zone is controlled it will close the loop flow, so no flow.  If all zone are not calling for heat everything off.

 

Are you new build, well insulated and what depth of screed?

[SBMS]

36 minutes ago, JohnMo said:

If a zone is controlled it will close the loop flow, so no flow.  If all zone are not calling for heat everything off.

 

Are you new build, well insulated and what depth of screed?

So if a single zone is left on, the heat pump would just be running for that zone? Would that work?

 

New build, well insulated, 85mm screed.

[JohnMo]

So decent amount of screed, so it's really a huge buffer for heat. We have a 100mm, and zones just killed efficiency.

 

So some facts.

Water flow temperature doesn't equal floor temp, temperature as the heat is dispersed gets lower as energy is removed and absorbed into screed.

 

Floor surface temperature is pretty close to room temperature.

 

So,

If you have overheating in a room from solar gain, the UFH stops giving out heat. A 5 to 10 degree day your floor surface is about 1 Deg hotter than target room temperature. So if target is 21, floor is say 22 - room increases to 22 the floor heat output goes zero - a zone thermostat does nothing for you. You may as well just buffer heat for later.

 

19 minutes ago, SBMS said:

if a single zone is left on, the heat pump would just be running for that zone? Would that work

Only with a buffer and you don't want one for good efficiency.

 

Yesterday we put 40kWh of heat into floor, at the hottest time of the day - because it was free from excess PV. It was 2 degs overnight, no heat needed at night. House was fine, cool down is slightly slower, but fine.

 

You may as well just have a single thermostat is a good location (so wireless), that switches off the heat pump - but your controller may already have this!

[ReedRichards]

20 hours ago, SBMS said:

So if a single zone is left on, the heat pump would just be running for that zone? Would that work?

 

Yes, it would work but the heat pump is more likely to cycle if it is only heating part of your house.  

[JohnMo]

On 04/04/2025 at 17:18, ReedRichards said:

 

Yes, it would work but the heat pump is more likely to cycle if it is only heating part of your house.  

Where is the water going, how does it maintain min flow requirements - without a buffer?

 

My max loop flow is around 2 L/min - lounge has two loops so around 4 L/min, my heat pump needs about 16 L/min so it doesn't trip on low flow.

[ReedRichards]

On 04/04/2025 at 18:43, JohnMo said:

without a buffer?

That's your suggestion, I think, not something the OP said.  How about a volumiser if you don't like buffers?

[JohnMo]

13 minutes ago, ReedRichards said:

How about a volumiser

That doesn't help flow, it just adds system volume. One zone open equals one zones flow rate. You could add a bypass and big volumiser, so you can run one zone, but why?

[DamonHD]

I am running WC, volumiser and bypass, with each (micro)zone able to call for heat, and no zones permanently on.  Works efficiently and pleasantly for us, and typical cycles are an hour or (much) more.

 

https://www.earth.org.uk/heat-pump-16WW-control.html

Edited Sunday at 07:45 by DamonHD

[JoeBano]

I run 2 zones upstairs and downstairs. Gone back to a 4 port buffer and now got a balancing valve on the return heat pump side. Seen the short cycle reduced in this mild temperatures. Probably not the way for a new build but I live in 1930s solid brick house and with one room can be 21c and the next room 19c, completely different scenario to a new build. I use my stats as a temperature limiter, weather compensation set up for a max room temperature 21c @ -3 room stats set for 21.5c. The other reason is cooling in summer it’s needs very little cooling downstairs but upstairs is very warm for sleeping.