Grundfos Default setting

[DaleAlan]

Hi everyone. Bit of a daft question but I’ve just had the pump replaced by the housing group where I live.
They’ve fitted a Grundfos UPS3 15-50/65 and the fitter has left it on the default constant curve 3 which is a bit noisy and seems overpowered for the property, they’ve also snapped the gland on the installer plug as they didn’t rotate it and when they’ve shut the cover it’s cracked the thing against the pcb cover so I’ll try and get that sorted if a Grundfos sell them separately just for safety grrrr. Failing that I can always get them back out but didn’t want to be a bother if I can fix it myself.
I’ve turned it down to constant curve 1 and the radiators seem to be working fine and all get up to temp and the noise is much more manageable.
It‘s a small house with 6 radiators ( 3 up and 3 down with trv’s on 5 of them and the one in the same room as the thermostat without and are all balanced)
The combi is a Baxi Potterton Promax He Plus and no ABV as far as I can tell so I was wondering if I should use the constant curve as it’s working fine or the Proportional Pressure setting as recommended in the instructions as I don’t want to blow anything up.
Any help would be fantastic and sorry for the long essay.

 

[John.g]

The UPS 3 has a high output for a 6.4M pump but its PP curves (like most grundos pumps) are far too low for most domestic heating demands but just may do the job for your modest installation.
Assuming a total rad output of 12kw with a required rad dT of 15C, the required flowrate is 12LPM or 0.72m3/hr. CC1 is providing this at a 4.1M head, PP2 may just be OK at a 2.3M head but CP1 should be perfect IMO at a 3M head.
Try it on PP2 first, if not powerful enough then suggest CP1 you mightpost back your final setting.

 

[DaleAlan]

The UPS 3 has a high output for a 6.4M pump but its PP curves (like most grundos pumps) are far too low for most domestic heating demands but just may do the job for your modest installation.
Assuming a total rad output of 12kw with a required rad dT of 15C, the required flowrate is 12LPM or 0.72m3/hr. CC1 is providing this at a 4.1M head, PP2 may just be OK at a 2.3M head but CP1 should be perfect IMO at a 3M head.
Try it on PP2 first, if not powerful enough then suggest CP1 you mightpost back your final setting.

View attachment 78555

Thank you so much for the reply. I’ve tried it on both PP settings but unfortunately as you’ve said they both seemed too low and the radiators upstairs remained cold so I went back to CC. I’m trying CP1 as we speak and so far it seems to be working well and all the radiators are hot. I’ll let it run for a bit but so far so good as my house is quite small and the radiators aren’t very large apart from the one in the front bedroom which is ridiculously long. I’m off to see if I can replace this broken terminal cover fingers crossed and thank you once again it’s hugely appreciated and your reply was above and beyond.

 

[DaleAlan]

All still working fine @John.g . It was the only setting I was scared to try as the manual said the CP setting was for underfloor heating and didn’t mention radiators with TRVs like it did with CC and PP so I didn’t try it as I thought if the TRVs shut it would self destruct is it recommended to rebalance with the new CP setting or leave as is? It’s all working spot on but it’s no bother to rebalance if recommended. Thanks again my good chap.

 

[John.g]

No, leave everything as is, while the CP setting is (rightly recommended) for UFH, it works quite well with rads as well and the power required will decrease with the TRVs closing in. I have a Wilo yonos Pico where the CP and PP settings can be incrementally changed in 0.1M steps to give almost any desired pump head, I have 12 rads, ~ 20kw, I have the pump set to 4.6M (PP mode) which results in a head of ~ 3.4M with all TRVs open and falls to about 2.7M when they throttle down, power from 22W to ~ 16W. As a minimum, all A rated pumps should display the power, you can then read off the head/flowrate from the pump curves.
Some like the DAB Evosta 3, display the power in watts, W, the pump head in meters,M and the flowrate in M3/hr.

 

[DaleAlan]

No, leave everything as is, while the CP setting is (rightly recommended) for UFH, it works quite well with rads as well and the power required will decrease with the TRVs closing in. I have a Wilo yonos Pico where the CP and PP settings can be incrementally changed in 0.1M steps to give almost any desired pump head, I have 12 rads, ~ 20kw, I have the pump set to 4.6M (PP mode) which results in a head of ~ 3.4M with all TRVs open and falls to about 2.7M when they throttle down, power from 22W to ~ 16W. As a minimum, all A rated pumps should display the power, you can then read off the head/flowrate from the pump curves.
Some like the DAB Evosta 3, display the power in watts, W, the pump head in meters,M and the flowrate in M3/hr.

Brilliant. Saves me getting the thermometers out. Think the housing group just went for the Grundfos as they have always used them but they just fit and forget and don’t bother setting them up so they leave at factory defaults CC3 which is much too much. Grundfos seems well off the mark for their PP settings as they seems so low and the PP2 wasn’t even reaching the upstairs rads Which is shocking in a house as small as mine with 6 rads. The lad up the street swears by the DABs as he said the newer Grundfos pumps are trading on their past reputation. That Wilo sounds amazing but I’d never stop fiddling with it. Huge thanks for the response again John I can now relax.
Edit: just had a Google of both the Wilo and the DAB. They both look so much better specced for configurability.