I created a spreadsheet for myself a few months. I’ve just shared it on reddit so though I’d share here for helpfulness & scrutiny.
It isn’t formatted very well, as I only ever intended to use it for myself, but feel free to make a copy of it, reformat it and send a copy back if you wish.
The purpose was to calculate the required dt and flow rate at each radiator while keeping the overall dt as close to your target overall dt (cell N18) as possible. You can play around with the flow temperature (A1) and the target room temperatures to get this right.
I suggest saving a copy to work on. Let me know what you think.
Also - if anyone would like to join the UK heat pumps specific subreddit that I set up last year, you’re all welcome. I wanted to create a space seperate to the general heat pumps subreddit, which has a lot of members from America, and the advice being given wasn’t generally cross compatible with UK systems. We have over 1200 members at the moment and generally get at least a couple of posts a day.
@glyn.hudson Hi Glyn, I see you now stock the FRVs from Firepower on OEM shop. It might be useful to provide a tool like this one for installers to be able to quickly calculate what to set the FRVs to. I’ve been speaking with Sune Nightingale, who has validated the calculations and is going to publish his own simplified, single room and radiator, version of this on the Firepower site, in time.
I know you have them too, so you might also find some use in it
Sure, we could include a link. However, with a heat pump that varies the flow rate (most apart from Vaillant) I think a simpler method is to work out what percentage of heat loss each room is and then check to see what percentage of the primary flow rate is going to the radiator in that room.
e.g if the total house heat loss is 5kW and the living room has 1kW heat loss then the rad in the living room needs 20% of the primary flow rate at any given time e.g of the primary flow is 14lpm then the living room rad needs 2.8lpm, but at low modulation when the primary flow is 6lpm, the living room rad now should have 1.2lpm.
True. I hadn’t considered it that way and it is alot simpler.
The issue with variable systems is that it throws out the balancing as it doesn’t reduce the flow rate to all radiators evenly. That doesn’t change the fact that most heat pumps run this way though.
What makes you think they don’t reduce the flow rate evenly? I’ve got FRVs on all my rads and whatever the primary flow rate, the sum of the FRVs always adds up to the primary flow. In my experience, once adjusted, the % distribution will stay the same. The FRVs are just lockshields valves with a flow gauge.
The FRVs are fantastic I was sceptical until I fitted them myself. It’s game changing being able to see exactly how much flow each rad is getting, it makes balancing a very precise process. FRVs would also highly any issues with suboptimal flow rates due to blockages or suboptimal pipework size or layout etc.
I agree with this sentiment entirely. It was something I’d theorised would make a be a huge benefit. I’d played around with the idea of running all of my radiator pipework from an UFH manifold to be able to accomplish this, but then saw these. I fit mine a couple of months ago and the biggest benefits are a much more even temperature throughout the house, balancing now only takes minutes instead of days, and they’re alot quieter than my previous lockshields.
My main issue was the mismatched radiator sizes throughout my house which require vastly different dTs (hence the complicated spreadhseet that deals with this) so balancing the system without knowing the flowrates was neigh on impossible.
Sune sent me some 0-2.5L litre inserts (current ones are 0-5L) to try out last week but as I’ve just cleaned, refilled and inhibited my system recently, I won’t get round to fitting them this heating season.
In my mind, it won’t because the speed of the water affects the pressure drop non-linearly, so circuits will be affected differently. The longer, more resistive circuits will drop at a higher rate when the pump speed is reduced.
The only way I can think to describe this is with traffic. When it’s busy (high pump speed), the shortest, main routes get blocked up as it can only carry so much traffic so some vehicles will try to go down side roads to get around. Even going a longer distance could get you to your destination in the same time. But when it’s quiet (low pump speed), everyone will go down the main routes as there are no hold ups and the shortest route will be the quickest.
This is slightly backed up with some anecdotal experience with the FRVs, but I’ll do some testing to put some numbers to it.
I was sceptical until I fitted them myself. It’s game changing being able to see exactly how much flow each rad is getting, it makes balancing a very precise process. FRVs would also highly any issues with suboptimal flow rates due to blockages or suboptimal pipework size or layout etc.