@crimson remind your builder this is 22mm plastic, which is almost equivalent to 15mm copper in bore size. if you ask him "would you have done it in 15 copper" he'll say no of course not. would he have done it in 22 copper - "yes of course" - and that would have been fine. But this is really important: plastic pipe has a much fatter wall than copper pipe so for the same outer size, the inner bore is a lot less. you go up a size if you need to use plastic.
the fact you are closing the lockshields almost to zero in one floor, and fully open in the other, and you still can't balance it, says there is something else restricting flow in the floor thats fully open.
maths: 5 radiators at 1kw each (my assumption) requires 14l/min, 22mm plastic pipe means flow velocity of 1m/sec (too fast, should be below 0.9) and 20 m of such pipe will have a head loss of 1.6m. I don't know what your head loss for the rest of the system is, but burning 1.6m of head just on the pipe is quite a lot. Thats like the pipe itself is a part closed lockshield.
of course given all the issues you've had there could be something else lurking causing this, but really this long run of 22mm plastic is not acceptable, regardless.
for reference, I have two rads in my house on the end of 10m (each way, so 20m total) of 22mm plastic, its a legacy of many previous changes. they are always the worst to warm up. I have only just about been able to balance against them. I will be upping it to 28mm in the summer. and thats just for 2 rads.
Thanks @iancalderbank , we’re obviously past point of upping the pipes, am very frustrated they made such an error.
however the upstairs uses same and I’d expect ones at end of the run furthest to suffer so like you say must be something else here, or simply the calcs downstairs are so off the rads just indersized
Was surprised by them saying it was 22mm, this photo was the one that made me think the size differential between the main and branch to rads looked bigger than that. Tweetop Pert on the box on the floor but never know if that was for underfloor in the kitchen diner.
Today will be my final attempt on lockshields for upstairs. No matter how much I dial back rooms easily hit 20.5-21C. Barely get lower than 19.8C with windows open over night. The irony of trying to pull down rooms temps while fighting to have others higher…
@crimson It really is looking more likely that the downstairs rads need a serious uprating now. Your heat pump has the capacity, your pipework will probably cope and when the rads are replaced with greater capacity, you should be able to lower the LWT and do some serious rad balancing! Regards, Toodles.
Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!
From the recent photo's it would appear that both the upstairs radiators and downstairs radiators are fed from similar main pipework consisting of probably in the main 22mm plastic. The pipework supplying individual radiators being a mixture of plastic and copper with an assumed diameter of 15mm, the main difference being longer pipework runs to the downstairs.
I would suggest that you calculate the actual volume of heated space for both the downstairs and upstairs areas and compare this with the heating capacity of the radiators in each area. Is the relevant capacity approximately the same?
A further thing to remember is that thermal energy will feed from downstairs to upstairs, and if the pipework in the ceiling voids and walls is not adequately insulated, this will also add to the upstairs heat supply.
One further thing to check is the pipework after the LLH via the zone valves. I would suggest looking under the insulation for any pipe fittings that may impede the water flow, also check the size of the zone valves and that they open fully.
Longer runs to downstairs from trunk line - yes however - upstairs will have longer main tund total as the rear of downstairs is underfloor, with rads on first floor above that.
As a snapshot example for areas I’ve done Living 2 v Bed 2. He living rooms are slightly bigger than bedrooms above due to a small sloping roof above them extending out slightly (those were replaced and re insulated also).
Bed 2
19.8 (floor area) x 2.44 (ceiling height) = 48sqm
2x 1000x500
746 per rad
0.301 (using Stelrad D20 as that’s how it was called when though D16.5 would have been more appropriate)
(Usually I’d take room watt requirement and divide that by correction factor to get the larger watt requirement at the delta rating but to simplify just multiplied the rad total watts by the factor)
449W
Living 2
28 x 2.59 = 72sqm (50% larger)
1x 963x200 = 880W
1x 1694x200 = 1540W
0.41 (using Eskimo D20 correction factor)
992W - (120% larger)
Pipe insulation. I saw one site photo from later on that showed lagging was added to pipes so I believe that was done. Plus insulation in ceilings, this was a requirement I believe as constantly insulation and thermal upgrade was a big part of the project, hence the 75-100mm wall insulation internally.
“I would suggest looking under the insulation for any pipe fittings that may impede the water flow” - could you provide examples, sorry again new to all this.
Zone valves. Now that is a point as for whatever reason the downstairs on differs to the 2 identical underfloor and upstairs valves.
Note tonight I’ve actually turned off upstairs at the heatmiser as we’re just too hot upstairs. In morning going to double check lockshields and start it again but probably resort to TRVs again. Note this however is with the max LWT pulled up by 1.5C to see if effects downstairs but didn’t do that much, so that can go back to 40C tomorrow too.
Note tonight I’ve actually turned off upstairs at the heatmiser as we’re just too hot upstairs. In morning going to double check lockshields and start it again but probably resort to TRVs again. Note this however is with the max LWT pulled up by 1.5C to see if effects downstairs but didn’t do that much, so that can go back to 40C tomorrow too.
Can you provide some better photo's of all the labels on the Honeywell valve, preferably the correct way up for ease of reading. I wonder if the plumbers have mixed up the valves for the radiator circuits and the UFH? Do you have a copy of the design specification?
Safe to say I don’t think upstairs is undersized rads. Hearing off over night and a number of windows open. Most rooms sitting at 18.5-19C. Landing 19.5C. I think in terms of lockshields to keep the ASHP running longer I’d probably need to just completely just off 1/2 rads in each room. Downstairs seems to be sliding due to the cycling happening more often
@crimson so the downstairs is a honeywell V4043H1056 which has a KVS of 6.9 . the other two are EPH controls V222P with a KVS of 4.6. KVS is the expected flow rate at 1 bar (10 m of head) pressure loss. higher is better. So the fact that one is different doesn't help as a pointer to the problem because the problem zones has the (in theory according to spec sheet) slightly better valve.
that said , none of these valves are really suitable for a high flow rate ASHP system. they are boiler system valves for boiler flow rates. That is not helping the problem. The solution to that is to replace all 4 of those valves (including the HW one above) with a single large bore 3 way valve diverting between CH and DHW. There is no need to switch flow to the heating zones on and off independently if the zones are properly balanced (and in fact doing so leads to cycling as you have seen, so should not be done).
