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Balancing UFH flow rates, pump speeds etc

Thermostats, Volumisers, Buffer Tanks, TRVs, Pumps, Piping, Valves, Radiators & Controls

Last Post by Tim441 10 months ago

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Tim441

(@tim441)

Honorable Member Contributor

Joined: 4 years ago

Posts: 463

Topic starter 05/01/2026 4:19 pm [#2710]

I have an old building with modern extension & ashp. I am trying to get best efficiency by setting flow rates, pump speeds etc. But am unsure of what I'm doing! Setup:

Old part building. 50sq m UFH (3 zones, 3 loops) & 50sq m upstairs rads (undersized)
New extension in 2015. 100sq m UFH (3 zones, 5 loops) separate manifold
Original design for oil boiler with 150mm centres
16kw ashp since 2020. Believe correctly sized. UFH at 150mm centres.
Using weather compensation with reasonable outcomes. Living areas at 21deg. Bedrooms cooler - as expected.

I'm not sure if the setup is right for best efficiency as room and floor temperatures vary. I tweak reasonably successfully with use of the room thermostats but feel i would ideally leave it alone!⁸

I'm thinking i should try and balance - in part by varying flow rates to individual loops and/or changing manifold pump speeds.

Both manifolds have older 3 speed pumps.

Is there any simple way to approach this? Or any checks or more information?

Circulating water is clean but the flow gauges on the manifold are difficult to rrad due to dirt (i think rust from old boiler).

Circulating LWT from ashp is currently 42deg. One manifold shows temp as 40deg and the other as 37deg

I should mention the extension has a lot of glazing and benefits from solar gain on sunny days. So an element of tweaking or adjustment is likely to be needed even if system is well balanced

This topic was modified 10 months ago 2 times by Tim441

Listed Grade 2 building with large modern extension.
LG Therma V 16kw ASHP
Underfloor heating + Rads
8.7kw pv solar
3 x 8.2kw GivEnergy batteries
1 x GivEnergy Gen1 hybrid 5.0kw inverter
Manual changeover EPS
MG4 EV

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