Dynamic Heating Balancing

[DIYWell]

Spotted Danfoss' RAS-B2 dynamic TRVs recently. Set the value according to rad size etc and replace across the house to automatically balance the heating system.

Anyone any experience of using these? Are there alternatives from other manufacturers?

 

[muggles]

I use the IMI Eclipse valves which do the same thing. Very accurate temperature control as well as balancing

 

[Mister Banks]

Drayton have an auto balancing TRV valve.

 

[ianmcd]

I have a heating balancing small adjustable spanner and f&R thermostat

 

[DIYWell]

I have a heating balancing small adjustable spanner and f&R thermostat

Don't we all though some of us have more free time than others

 

[DIYWell]

I use the IMI Eclipse valves which do the same thing. Very accurate temperature control as well as balancing

Are these your go to TRVs when doing a full install?

 

[muggles]

Yes, dependent on required flow rates of course as they'll do a max of 150l/hour. They do do a 300l/hour version as well for those times when more is needed, but it does cost a lot more

 

[Johntheo5]

What I don't really get is how these really control the flow when the TRV starts throttling down, OK, when fully open one can adjust the dP to give whatever max flow required but when the TRV starts closing down won't the dynamic part try and counteract this by moving the valve seat away from the valve?, the TRV must then throttle in further, the dynamic side then counteracts this??, do they tend to just give on/off control I wonder.

Edit: looking at the video there seems to be a separate valve/seat on the bottom so should be OK.

 

[DIYWell]

Edit: looking at the video there seems to be a separate valve/seat on the bottom so should be OK.

You got a link to the video?

 

[Johntheo5]

Try this one.

 

[DIYWell]

Yes, dependent on required flow rates of course as they'll do a max of 150l/hour. They do do a 300l/hour version as well for those times when more is needed, but it does cost a lot more

That's interesting. The Danfoss details I looked at didn't mention a max flow rate. Perhaps that's implied by being 15mm.

Checking my (non-condensing) boiler specs, it says it has a min pump of 28.5l/min, and dividing by the number of rads, I'd reckon some would be under and some over 150l/hr ... or I'm multiplying apples and oranges which is highly likely.

 

[Johntheo5]

Most 15mm TRVs or LSVs have a Kv of 0.75 to 1.0, this means a flowrate of 0.75m3/hr/12.5LPM to 1.0m3/hr/16.67LPM at 1 bar diff head. At a 1M head this is 3.95 to 5.27LPM, the flow through a TRV+Rad+LSV is probably ~ 3.3 to 4.2LPM, this doesnt mean that 10 rads will flow 30 to 40LPM. I have 10rads, all with TRVs, no balancing and a pump head of 3.6M give a "average" rad dT of around 10/12C. and my A rated pump power of 22W = a flowrate of 12/15 LPM.
If you aim for a 15C rad dT then you should try and get a flowrate of 1.0LPM/rad.kw (actually 0.96LPM).

My standard EPH TRVs show a Kv of 1.0 on the spec sheet.

 

[Mister Banks]

I thought balancing radiators was essential but if I have TRV’s on nearly all my radiators do I still need to balance them to even out the flow rates.

 

[Johntheo5]

Yes, the rads really should be balanced, I have two zones with 5 rads/zone but one zone only normally on, so after the heating has been on for around 1.5 hrs in the morning the TRvs take over for the remaining 13/14 hours that my heating is enabled.

Balancing Heating Systems: Ensure Even Radiator Heat

The Ultimate Guide to balancing heating systems. Balancing a heating system is simply making sure all the radiators or emitters heat up evenly.

www.heatgeek.com

 

[Harry Bloomfield]

I have a nine radiator system, with TRV's on all but the hall rad, where the wireless thermostat is located. I have never, ever balanced them, they have always everyone one, got hot enough, even before I added TRV's. Now with TRV's fitted, I think I have even less reason to bother balancing them, because even if they were balanced, the balancing would only limit the maximum flow, whilst the TRV was wide open. Once the TRV begins to be satisfied, begins to close, the balancing makes little or no difference, in my view.