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 18 hours ago 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 17 hours ago 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.