A booboo may have been made

[ectoplasmosis]

What is the 'room stat'? Do you mean the Vaillant Sensocomfort controller? If yes, which weather-comp 'mode' is it set to (Active/Inactive/Expanded)?

 

What type (K2, K3 etc) of rads do you have upstairs, and how big are they in relation to room sizes? You should have had a 'radiator schedule' document with these details as part of the install/commissioning process.

 

You should not have to fit a TMV or auxiliary pump to your UFH circuit, providing the radiators have been properly specified. My house has UFH downstairs and rads on the upper 2x floors, no mixing valve, single flow temperature. Works perfectly, whole house stays at a constant 21.5C.

Edited Wednesday at 10:59 by ectoplasmosis

[Post and beam]

1 hour ago, ectoplasmosis said:

What is the 'room stat'? Do you mean the Vaillant Sensocomfort controller? If yes, which weather-comp 'mode' is it set to (Active/Inactive/Expanded)?

Yes its the 720/3 senso comfort and its on 'active' if i remember correctly.

Rads are K2 at the sizes specified. I dont believe these are the issue. Not an expert and happy to be proved wrong but they have no option to be controlled seperately and that is what i asked for and is in my unqualified opinion the issue.

[ectoplasmosis]

10 minutes ago, Post and beam said:

Yes its the 720/3 senso comfort and its on 'active' if i remember correctly.

Rads are K2 at the sizes specified. I dont believe these are the issue. Not an expert and happy to be proved wrong but they have no option to be controlled seperately and that is what i asked for and is in my unqualified opinion the issue.

 

Why do you want them to be controlled separately? All this would do is decrease efficiency, and increase the risk of defrosting problems in winter due to lack of water volume. 

 

Your current setup, with open-loop and no TMV or secondary pump on the UFH, is best-practice for achieving best comfort and efficiency... providing that the emitters have been sized/specified correctly!

 

From everything you've said, it sounds like the system is probably designed and installed well enough, but the radiator circuit has likely not been balanced/commissioned fully, causing the rooms with radiators to undershoot the target temps. I'd advise getting the installer to balance the whole system, then tweak the heat curve setting to achieve suitable flow temps which keep all rooms at their intended temps. I really wouldn't recommend installing any kind of zoning control, or thermostatic mixer on the UFH, this would only increase running costs.

Edited Wednesday at 12:16 by ectoplasmosis

[HughF]

26 minutes ago, ectoplasmosis said:

 

Why do you want them to be controlled separately? All this would do is decrease efficiency, and increase the risk of defrosting problems in winter due to lack of water volume. 

 

Your current setup, with open-loop and no TMV or secondary pump on the UFH, is best-practice for achieving best comfort and efficiency... providing that the emitters have been sized/specified correctly!

 

From everything you've said, it sounds like the system is probably designed and installed well enough, but the radiator circuit has likely not been balanced/commissioned fully, causing the rooms with radiators to undershoot the target temps. I'd advise getting the installer to balance the whole system, then tweak the heat curve setting to achieve suitable flow temps which keep all rooms at their intended temps. I really wouldn't recommend installing any kind of zoning control, or thermostatic mixer on the UFH, this would only increase running costs.

This is exactly what I'd be doing... I know it's not what you asked for, but it's the right way to run the system for maximum efficiency.

[SimonD]

49 minutes ago, ectoplasmosis said:

 Your current setup, with open-loop and no TMV or secondary pump on the UFH, is best-practice for achieving best comfort and efficiency... providing that the emitters have been sized/specified correctly!

 

From everything you've said, it sounds like the system is probably designed and installed well enough, but the radiator circuit has likely not been balanced/commissioned fully, causing the rooms with radiators to undershoot the target temps. I'd advise getting the installer to balance the whole system, then tweak the heat curve setting to achieve suitable flow temps which keep all rooms at their intended temps. 

 

 

I did ask... 

 

 

23 hours ago, SimonD said:

Have you not received a design from the installer? You probably have got the weather comp curve set too high and should have been told by your installer that it takes a while to set the system up properly. Has the installer arranged follow up visits to balance the system when it gets colder?

 

What we really need to know is what mean water to air temperature difference the radiators have been specified to. That way we can tell if there needs to be a flow temperature differential between the radiators and ufh.

 

In 2025, a 2 zone system with rads and ufh needs to have an electronic mixer to properly deal with weather and load compensation within the heatpump and both the zones.

 

 

[SimonD]

58 minutes ago, ectoplasmosis said:

Your current setup, with open-loop and no TMV or secondary pump on the UFH, is best-practice for achieving best comfort and efficiency... providing that the emitters have been sized/specified correctly!

 

Not necessarily. The heat outputs curves of radiators versus ufh are different - rads are calculated to the power of 1.3 and ufh to either 1 or 1.1 so it depends on multiple design factors and the thermal properties of the building, including the balance of area between rads and ufh.

 

Because this differential may often result in different flow rates, especially at higher mean water to air temperature differences, a mixer is used to offset this by adjusting flow temperatures to each zone.

[Post and beam]

So if i installed a mixer and ran the radiators at a slightly higher temperature. How would the UFH behave? bearing in mind the gentle .4 WC curve remains (perhaps not)

#A: down mix temperature to some value and run for as long as ... well how long actually?

#B: Run at the same temperature as the radiators but for a short period.

 

Currently the Delta T is 3 degrees so the down mix would be minimal would it not.

[JohnMo]

1 hour ago, Post and beam said:

Currently the Delta T is 3 degrees

But think about this logically - if inside of house is 21, and you are flowing 25, 25 less 3 is 22. If your floor temp is 1 Deg above room temperature your dT cannot be any different. Your return temp cannot be lower than the floor temperature ever.

 

But as asked previously are your room temps accepted and at target temperature upstairs now you are living in the house. Is this a  question you seem to avoid for any reason or have you just missed the previous questions?

[Post and beam]

3 minutes ago, JohnMo said:

 

But as asked previously are your room temps accepted and at target temperature upstairs now you are living in the house.

No. Apologies, appear to have missed responding to that.

 

 

[JohnMo]

And?

[Post and beam]

I only really mentioned the Delta T figure because the discussion usually mentions a 7 degree Delta T when the topic comes up.

[Post and beam]

No they are not at the target temperature.

 

And because i dont have seperate temperature control upstairs i wonder how it could be otherwise. Not withstanding that the radiators are the sizes specified by installer.  

[JohnMo]

Simple way is to flow higher temperature in weather compensation, but reduce floor output by reducing the flow through floor loops. On a day where you normally flow 25, increase flow to 26+ but increase dT across each loop (reduce flow) to 4+. Play with settings to get outputs of radiators where you need them while maintaining UFH output stable so as not to overheat downstairs.

[HughF]

1 hour ago, Post and beam said:

No they are not at the target temperature.

 

And because i dont have seperate temperature control upstairs i wonder how it could be otherwise. Not withstanding that the radiators are the sizes specified by installer.  

Take the TRV heads off, turn the room stat right up. Leave it for a day.

[sharpener]

 

[ectoplasmosis]

13 hours ago, Post and beam said:

No they are not at the target temperature.

 

And because i dont have seperate temperature control upstairs i wonder how it could be otherwise. Not withstanding that the radiators are the sizes specified by installer.  

As several have tried to suggest already: your best bet is to get the installer back to balance your system. It’s not that difficult to achieve. 
 

You don’t need to add or change anything right now. The system needs to be balanced and commissioned properly. Begin with this goal, and see how you go. 

 

Edited 3 hours ago by ectoplasmosis