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Radiator Valves

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

Last Post by Toodles 2 years ago

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Mullions100

(@mullions100)

New Member Member

Joined: 2 years ago

Posts: 1

Topic starter 18/11/2024 11:24 am [#1869]

I am upgrading some of my radiators to meet the specifications of my heat loss survey

Working on the basis that Heat Pumps work more efficiently with a steady but high flow rate what is the advice on which type of radiator valves I should fit with the lowest flow losses?

Regular Lockshield valves seem to have very small internal chambers so I think they a very flow restrictive.

Are there ASHP system specific high flow rate radiator valves available as I can't see this mentioned in any of the tech specs on sellers websites?

Are TRVs at all necessary if house temp is set by a thermostat and Heat Pump modulation?

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Toodles

(@toodles)

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Joined: 4 years ago

Posts: 2985

18/11/2024 4:46 pm

Hello, the high flow rate is not necessarily what you require; a relatively slow flow through the emitters allow the energy in the water to transfer to the area which it comes into contact with. The water enters the radiator at say 40 degrees and if running quickly, might emerge at the other end of the radiator at 38 degrees but... if running more slowly, it has more ‘dwelling time’ to dissipate that energy and emerge at perhaps 35 degrees. The general guideline for low temperature ASHP’s is a Delta T of 5 degrees. So the speed of flow ideally allows (with the right sized radiator) for a drop of 5 degrees across the radiator.

My system has a pump within the Daikin ASHP cabinet which works at variable speed and does its’ utmost to send the leaving water at one temperature and see a return of 5 degrees lower. This water enters a low loss header which has a secondary pump thus allowing a certain independence to set the flow rate to the emitters. I have spent some time adjusting this pump (Wilo Pico) for least losses (LLH’s are low-loss but not no-loss!) and as near as I can get to 5 degrees Delta T. Nothing is perfect, including my set up but I does me best! 😊 Regards, Toodles.

Toodles, heats his home with cold draughts and cooks food with magnets.

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Toodles

(@toodles)

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Joined: 4 years ago

Posts: 2985

18/11/2024 4:54 pm

As a follow up on your question about lockshield valves etc. I think Heat Geeks did a YouTube presentation on the subject as there are now some (more expensive!) valve bodies available that have a more ‘swept path’ in the casting to improve flow and reduce turbulence. Regards, Toodles.

Toodles, heats his home with cold draughts and cooks food with magnets.

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Toodles

(@toodles)

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Joined: 4 years ago

Posts: 2985