Was on a bit of a rant other day, I'd just had enough this weekend.
not a problem. sounds like youve had a crap time of it.
I noticed a lot of discussion about heat zones further back. If possible try to get your system reconfigured so that all heat zones are always open - Ideally get rid of the zoning. The golden rule of heat pumps is as many emitters (radiators, UFH) as possible open and taking heat for as much time as possible.
Yeah, that's my current goal is to keep those going in sync really. As it was clear when only downstairs was on, finally getting heat through the LLH. Soon as upstairs decided to pipe up, it went cold, as likely zone just shut off for so long. My thinking is dial back the bedrooms with TRVs (as other's mentioned) but keep the zone demanding heat. Underfloor will be somewhat the harder one to get just right.
@crimson one little known fact , particularly by "ex gas fitter" plumbers, is that zone valves themselves slow the flow down. A "typical boiler style" zone valve with a ball that moves longitudinally in response to a lever moving, has a really thin aperture compared to its nominal fitting size (28mm). In boiler systems this doesn't matter. In heat pump systems, it does. which is why I say "get rid of the zones" as an ideal.
I'll mention that to plumber as well. Also the TRVs, if set to max all the time, what's the point in them? (End of the day they're cheap but cost money per radiator, all seems fruitless to me).
@crimson the only places for TRV's in an ASHP system are a) a room with large solar gain b) bedrooms, you may want them to run cooler than the rest of the house. the rest of the house should not have them.
Stelrad compact with horizontal line style K1 type. Those matched the heat loss calls performed by plumbers, think mostly 1000x500 in size. 2 per room upstairs, 1 on landing. Think they’re rated at approx 750 watts a piece at D50, highest demand room is 470W, so 470 / 0.301 for d20= 1561, about there (0.301 was Stelrad’s correction factor)
Downstairs:
Eskimo column radiators, largest demand room is 1050 watts, in there are 2x1451x200 rads rated at 1320w each. Eskimos correction factor for D20 is 0.41, so 1050 / 0.41 = 2560 which the 2640 covers.
I'm no expert but I think you are using the correction factors incorrectly, your rads can't output more heat at a lower DT, so even if you do have a dT of 20 (which is unlikely with a heat pump). The heat output of the rads upstairs is 750 x 0.301 = 225 x2 = 450 so is barely enough to heat the upstairs at DT 20.
If its more like DT10 then the output will be 0.15 of 750 = 112 x 2 = 225W so half what you need.
I suspect that you may be getting the DT's confused.
The standard thermal output of radiators is normally specified at DT50, which means the average water temperature would be 50C higher than the indoor room temperature.
I do believe that when @Crimson refers to DT20, this would mean that for a room temperature of 20C, this would require an average water temperature of 40C.
I have attached a Radiator Heat Output calculator that can be used to obtain the approximate thermal energy output for different radiators at different water temperatures. The cells highlighted in yellow can be adjusted.
Still awaiting word from Plumber and what Grant is saying. Spoke with builder earlier, he's frustrated as Grant did calcs and actually downsized the ASHP itself from the original calcs. So a lot in their court atm.
Soon as any updates will get back on how they approach things in case of use to anyone.
Plumber couldn't make it - but passed Grant tech support to me.
We've now set:
21 00 - from 0 to 1
21 02 - set at 50c
21 03 - now set to 40
21 04 - set to -3 (my original post was incorrect, it was changed from -4 to -3 by plumber)
21 05 - now set to 25
We also checked the holding return and seeing 00 00 at 37c and 00 09 was 50c, and he remarked the house is taking a chunk of the heat out.
Not quite sure why downstairs refuses to heat up though. I sent a photo to plumber showing the valves for the 3 main zones, upper and uf are midway, down is all way to right.
Hi Crimson.
Looking at the photo above, the downstairs valve would appear to be in the closed position. I would suggest that you raise and then lower the downstairs thermostat setting and check that this valve is actually opening and closing as should be indicated by the lever on the upper end.
If this is not the case then try moving the lever from right to left and latch it in the manual open position, then see if you get water flow to the downstairs radiators.
@derek-m Hi Derek - it definitely opens, have tried putting into manual and still zone doesn't hit temp.
@iancalderbank - I've set up those temp probes - albeit with no pipe insulation currently. Photos attached. This is when down and up are still demanding heat
I've set up those temp probes - albeit with no pipe insulation currently. Photos attached. This is when down and up are still demanding heat
obviously not the values that we're hoping for in terms of a working system but at least you have numbers you can quote to the installers now to prove that it isn't (a working system).
Yeah that's very useful, me commenting on touch heat hasn't helped, but it's clear heat not passing to top left properly. I'll have a look when a hot water run goes, at what the difference is.
Thanks for suggesting these, much more insightful to see what's going on
@crimson I've lost track a wee bit. Is there a slow flow rate issue on the primary side? as that is a possible explanation for the numbers you see.
If that is the case what you could have happening is this:
Hot comes in from HP top right but only slowly. Water goes out to house top left, at higher flow rate. There is not a fast enough "hot flow " coming from top right so therefore to satisfy the flow rate need of the house's circulation rate, it has to pull from bottom left. so its basically the same 34C water going round the house in a circle with a tiny trickle of 38C being added to it but making no noticeable difference.
Thinking about installing a heat pump but unsure where to start? Already have one but it’s not performing as expected? Or are you locked in a frustrating dispute with an installer or manufacturer? We’re here to help.
