Multiple zone UFH thermostats and MVHR

[Babak]

Hi 

 

Sorry if this has already been responded to as it must be an obvious question and indeed I have read a few discussion which are somehow related.

 

Self build house, two floors, both will have UFH. House is well insulated and will have MVHR therefore I am guessing most of the house will be roughly the same temperature.

 

Question is, to manage pressure drop, max pipe lengths, etc, I will have multiple ufh zones on each floor and one manifold per floor, and hence as many actuators, which I guess will connect to the room thermostats. Is there a way I can control multiple zones/rooms with just one thermostat? I am assuming this must be possible? Next level of complication is that upstairs I will have wood floor and so will definitely have floor sensors. So the question now is, can the wiring centre handle having a “master” thermostat which governs the air temperature, but also take a queue from the individual floor sensors and shut off the actuators if the water gets too warm for any reason.

 

My thoughts are (and not sure it will work) that I will have basic manual thermostats in each room to protect against overheating air and floor, but will have a completely independent whole house thermostat to do clever stuff like heating demand curve, etc, which I will somehow have to connect directly to the heat pump or somehow manage to use as a master for the wiring circuit.

 

Has anyone done this? Is it possible at all? I just think this must be such an obvious ask, or am I crazy here?!

 

 

 

 

Edited June 26, 2022 by Babak

[Conor]

You don't need any of that. Just setup each manifold as a zone. E.g. one per floor with a single stat for each. Let the ASHP control the water temp and the room stats to simply call on/off. There really is no advantage to anything more complicated like this in a modern, well insualted house. Don't need the actuators, sensors or individual stats at all.

 

You can set the "heat" in each zone by setting the flow rates. Your UFH design will tell you roughly what flow rates you need for each zone.

 

We have this setup with a 60l buffer. Works well for the rare times it's needed.

 

Edited June 27, 2022 by Conor

[JohnMo]

As above, but think you meant to say is you have multiple loops on each floor and you want to operate each floor as a single zone.

 

On the manifold, each loop will have a flow meter and isolation valve.  You don't really need to have an actuator.  The thermostat will call for heat and start the UFH manifold pump.  The mixer valve will limit flow temperature.  

 

You need to then balance the system so each room is at the correct temperature, so to increase temperature you give more flow, to decrease temperature less flow.

 

No need for floor sensors or that much complication.

[Adsibob]

8 hours ago, Babak said:

House is well insulated and will have MVHR therefore I am guessing most of the house will be roughly the same temperature.

I think that’s not a safe assumption. My house is not a new build but I covered the solid brick walls at the side and back with 50mm EWI and the rear is almost all brand new as we did a two storey extension, so it’s all double wall with cavity insulation. Loft has tonnes of insulation too. The second floor is considerably warmer than the rest of the house. The first floor is always 1 to 1.5C Warner than the ground floor, and there is also quite a bit of variation between the rooms with windows at the front elevation (East facing) and the rooms at the rear elevation (west facing). I’m sure our MVHR is doing something but don’t imagine it will equilibriate everything everywhere. I would suggest you have more thermostats. I have 12!

Edited June 27, 2022 by Adsibob

[ProDave]

8 hours ago, Babak said:

Is there a way I can control multiple zones/rooms with just one thermostat? I am assuming this must be possible? Next level of complication is that upstairs I will have wood floor and so will definitely have floor sensors. So the question now is, can the wiring centre handle having a “master” thermostat which governs the air temperature, but also take a queue from the individual floor sensors and shut off the actuators if the water gets too warm for any reason.

Multiple zones per thermostat is a standard function of a typical manifold control box.

 

Don't over complicate it, floor sensors not needed, just use room thermostats.

[Adsibob]

10 minutes ago, ProDave said:

Multiple zones per thermostat is a standard function of a typical manifold control box.

 

Don't over complicate it, floor sensors not needed, just use room thermostats.

Surely if you have multiple zones running off the same thermostat, it effectively just becomes one zone, right? In that case, what is the point of zoning?

[joth]

As others, we ran ours with a single thermostat and no actuators and no underfloor sensors and that's fine. Obviously set the flow temperature low enough not to cause any issues with the food flooring.

 

Couple more comments:

- size the system so it can run okay with only downstairs zone active, if you're like us upstairs will be a few degrees warmer than down even with no heating on.

- MVHR does not move heat around the house, at least not to any useful amount. We only have heating emitters downstairs (UFH) and they have to run a few hours per day in winter to keep living room above 20° but upstairs can easiy hit 23-24

I probably need to build a server room downstairs somewhere to get some of the electrical baseload and excess heat generated moved, lol.

 

[PeterW]

 Floor sensors aren’t good to stop extreme temperatures - you need to isolate that issue at source and put proper blending valves on the manifolds. 
 

When running multiple rooms in a zone I prefer to use the Salus auto balancing actuators as they will regulate flow and temperature - you then just need a simple (programmable) thermostat per zone and wire it to all the actuators in that zone. 
 

as others have said - upstairs will be 1-1.5°C warmer than downstairs and MVHR will not move that much heat around. 

[Babak]

8 hours ago, Adsibob said:

Surely if you have multiple zones running off the same thermostat, it effectively just becomes one zone, right? In that case, what is the point of zoning?

Zoning only to the extent that there are maximum pipe lengths so have to divide the floor space into manageable areas.  But if one thermostat manages all the actuators on the manifold, I guess that is what I need!

 

edit- to correct my phraseology, multiple loops, but only a single, and now maybe two zones based on comments above.

Edited June 27, 2022 by Babak

[Babak]

Thank you for all the comments.

 

my takeaways are:

 

- loops not zones!

- maybe two zones upstairs and downstairs - marginal extra cost of 1 thermostat

- take the risk of wood floor damage through managing ASHP output (aiming for 35 degrees)

-  MVHR not a big player and rooms can still have diff temps - manage this through flow rate adjustments

- yes, i have also thought of getting autobalancing actuators.

 

Thanks again. 🙂

[Temp]

We have UFH on both floors. Rooms on the west side get a bit more solar gain than others, and we normally turn on/off the bathroom at different times of the day/year to bedrooms. Some rooms only used when kids are home or we have guests.  Some family members like their room a lot colder than others at night. So we are glad each room has its own loop and programmable stat particularly the bathrooms.

 

If you have a large room a long way from the manifold it might need two loops on one stat as a loop is normally limited to 100m I think.

 

For the bathrooms we used a Stat with a remote sensor. The sensor is inside the bathroom, the stat is outside the bathroom door.

 

The only annoyance is that the stats don't automatically correct for British Summer time automatically.

 

We have engineered oak flooring in several rooms. Have run the UFH as hot as 55C with no issues. However we do see some movement. The wood shrinks in winter when the air is dry and expands in summer when it's more humid. This results in some T&G opening and closing slightly.

[Adsibob]

6 hours ago, Babak said:

edit- to correct my phraseology, multiple loops, but only a single, and now maybe two zones based on comments above.

I would suggest investing in more zone valves and more thermostats. Unless you live in a very small property that is. I know i went overkill with 12 zones and thermostats for a 5 bed house, but I honestly don't think i could have done it with less than 9. It's good to only heat what you use when you use it, and the more zones and thermostats you have the more precise you can be with that endeavour.