Secondary circulation pump settings
I have a secondary circulation pump on the other side of my Low Loss Header from my heat pump. I realise there is a lot to discuss about the problems around an LLH but for now I am interested in the setting of the pumps and therefore how they might be interacting.
The pump in question is a Grundfos UPM3 AUTO 25-70 130 zzz, I've included a picture below which shows the setting of the pump. It is not speed controlled by the heat pump and appears to be on all the time except when the heat pump is doing DHW.
Given the pump inside the heat pump is variable speed I can't see how having a fixed speed pump on a high setting will do anything other than cause a lot of mixing in the LLH and so might help partially explain the low COP values I get (currently 1.8 - 2.4).
The heat pump is a 16kW Midea monobloc. From the manuals for similar pumps there seem to be setting options for Proportional Pressure, Constant Pressure, and Constant Curve but I don't know which of these would work best in my setup (diagram below).
Any thoughts greatly appreciated.
16kW Midea Monobloc R32 Heat Pump (Heating & DHW)
4kW Solar PV (No battery storage yet)
CPC 12 INOX Solar Thermal (DHW)
Posted by: @alan-mGiven the pump inside the heat pump is variable speed I can't see how having a fixed speed pump on a high setting will do anything other than cause a lot of mixing in the LLH and so might help partially explain the low COP values I get (currently 1.8 - 2.4).
Your concern about mixing flow and return temperatures within the LLH is an issue for efficiency. And this is very likely to be more extreme if flow rates are in any way different either side of the low loss header. The mixing of the hotter LWT with the RWT means that the HP is having to work harder to produce the correct deltaT only for it to be mixed and cooled again before the water gets to the emitters.
if you have some means of measuring pipe temps entering and leaving the LLH you will know straight away if you have a significant heat mixing/loss problem.
However if you have a heat pump that has an internal circulation pump built in then this may be more complicated to do anything about it especially if it is a variable speed pump and you’re secondary pump is manually controlled and especially if operating at a fixed full speed setting.
Our situation is different to yours in that our Ecodan has an external Primary circulation pump which is now set to a constant pressure on the slowest speed which gives us a flow rate of 13 litres per minute. (Well within manufacturers minimum required flow rate) the hp then modulates to produce the deltaT of about 5 to 7c. Again this might be different to how your Midea HP regulates it’s heat output.
We have then adjusted our secondary pump to the same pump speed and checked flow rates again to try and match the flows through both circuits. This has meant that the temperature loss through the header has been measured to be only 1c. Not ideal but it’s much better than it was.
Im not sure how you might do something similar if you have a variable pump speed from an internal pump.... unless you can get a second output cable from controller to try to match the pump speeds but then you would need a compatible pump.
The other option, as I think you were hinting at, would be to explore the possibility of removing the low loss header but only if your system can operate as a single circuit.
i hope this helps clarify what can be done and perhaps someone who knows Midia might have an easier fix solution.
Our COP figures were significantly improved from 1.59 to a promising 3.3 to 3.7 depending on outside ambients. We still have the LLH fitted at the moment.
- 26 Forums
- 2,221 Topics
- 49.3 K Posts
- 127 Online
- 5,881 Members
Join Us!
Podcast Picks
Latest Posts
-
RE: Isolating the system for a planned power cut
Insurance helps and when adding high powered devices li...
By Batpred , 2 minutes ago
-
RE: New Fogstar 15.5kWh upright solution
I'm finding it difficult to follow your descriptions. ...
By Transparent , 29 minutes ago
-
RE: Grant 13kW Aerona3 - issues getting zones to temp
R290 has an explicit installer setting for 'no buffer'....
By JamesPa , 1 hour ago
-
RE: Odd noise in our Ideal Logic ASHP
These are well respected pumps so far as I know. Onl...
By JamesPa , 2 hours ago
-
RE: Should Our Water Circulation Pump Be Configured to Run All The Time?
Noted The Vaillant doesn't either, other than with a ...
By JamesPa , 4 hours ago
-
RE: What crazy nonsense are inverter limits and why are they imposed?
Is there a lookup facility to see your limit, or is it ...
By DREI , 6 hours ago
-
RE: Electricity price predictions
Without getting too much into politics, given that the ...
By Batpred , 6 hours ago
-
UK Consumer Law Reality Check (for anyone dealing with ...
By DREI , 6 hours ago
-
@dgclimatecontrol Thanks... this was resolved back in M...
By Sandman1600 , 7 hours ago
-
RE: Help me keep the faith with my air source heat pump installation
That's the problem with the UK, in comparison with Amer...
By DREI , 7 hours ago
-
Electrical is the only way forward.. But until we get...
By Batpred , 7 hours ago
-
RE: Air source heat pump roll call – what heat pump brand and model do you have?
Manufacturer: Panasonic Model: WH-WXG12ME8 Type: AS...
By Andy-e , 7 hours ago
-
In our installation, we actually have an LLH but any di...
By Toodles , 8 hours ago
-
RE: Large heat pump options for church building
This church project has more in common with a commercia...
By GrahamF , 8 hours ago
-
RE: How good is the app support for your heat pump?
It looks quite interesting and, like you, I'd only want...
By Sheriff Fatman , 8 hours ago
-
RE: External wall insulation - your experience
So our house is in SE England. We mainly had mixed w...
By Batpred , 18 hours ago
-
RE: 5 Star Service from Havenwise
@majordennisbloodnok and @benson Good suggestion! We'll...
By HCas , 19 hours ago
-
This is an important and relevant topic of discussion i...
By wully , 20 hours ago
-
RE: Midea ASHP – how to set weather compensation
@pash44pump - pull the data from the data loggers and s...
By cathodeRay , 22 hours ago
-
RE: Pump and Esbe mixing valve for UFH
So my next question is about calculating pressure loss ...
By AndyCoo , 24 hours ago