Advice needed on inefficient Samsung ASHP installation
Interesting you mention that you’re surprised most installers don’t set up their curve like this, any heat pump supplied from freedom over the years that GH was in charge, would have been setup with a pretty reasonable curve of 37@15, 50@0 and with external thermostat control.
I always thought that was a bit of a cop out from a design perspective, but having looked at most heat pump controllers on the market I’ve come to the same conclusion as GH did, they’re awful things to use as a thermostat 🤣.
Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.
My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.
It is a cop out and as I say upthread will incur a penalty of 3-6% or more if it's more than a a couple of degrees out. However installers don't wast to return to site and setting up the perfect wc curve is iterative, so if running cost isn't critical it's an approach that has attractions. I'm not advocating it, just recognising it.
Why 37 at 15 incidentally, that's almost obviously too high in most cases, leading to a further penalty. Is this so that radiators always feel warm to avoid callouts?
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
@jamespa yes… it’s what I run at too. Keeps the wife happy.
Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.
My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.
I just ran the numbers through my WC simulator. This calculates, based on Ecodan R32 data, the efficiency gain from various WC curves relative to fixed temperature operation, based on an OAT pattern representative of southern England. If we take your 50;0, 37;15 case and assume that this is 5C higher above the ideal' WC curve until it reaches the floor at 37C, then the curve gives a 10% improvement on fixed temperature operation, as opposed to 20% if the WC curve is set up properly. So you can either look at that as a 12.5% penalty relative to optimum, or as a halving of the benefit of WC.
Most of the penalty is due to the curve being above the optimum value not the ('lizzie ') floor. So one good approach would be to set it up initially this way and (during the coldest season) gradually reduce the cold end until it didn't quite heat the house, then turn it up by a degree.
As I say I'm not advocating this method, only recognising it.
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
I should have added more flesh to my post but I was on my phone - We actually set the top end of the curve to the design flow temp, 45 degrees in my case (so 47.5 flow). The bottom end of the curve was also chosen as we have fan coils in some rooms/areas (kitchen, hallway, bathroom), and no-one wants to stand under cold air...
I also figured that lifting from 15 degrees ambient to 37.5 is hardly much work that I wasn't going to sweat the details. Also handy to have the rads deliver some heat on the odd occasion that it's 18 degrees outside and raining and the wife wants the heat on. Handy to be able to deliver some heat into the property in that case. I almost thought about switching to a fixed flow temp of 45 during the summer for this precise reason, but haven't needed to yet.
Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.
My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.
I did a couple of days testing running weather comp and a fixed flow temperature with thermostat control on similar average temperature days, one being 8.7 and the other 9.0. Very little difference in target flow temp.
Fixed flow temp (to simulate a slightly elevated flow temperature), compressor cutoff was 30.8, WC obviously varied between 29.1 and 29.2. But the starting temp was the biggest variable. WC never started the compressor until return temp had dropped to 21.6 degs, while the fixed with thermostat could be as high as 25 degs.
Fixed and thermostat
Space heating CoP 4.8
kWh used over 24hrs 6.8kWh
WC
Space heat CoP 5.4
kWh used over 24 hrs 4.6
You will see from the image the difference in run duration and frequency of starts. The one with plenty of starts is the thermostat.
CoP is generally made up of two components at a fixed outside temperature. Flow temperature and dT, the wider the dT the better the CoP.
The rest was not definitive as the temp varied over the day. But a 30% reduced kWh used was quite a suprise, when comparing WC to using the thermostat. Think that must be down to the the increased shorter duration cycling and less higher quality heat being delivered
The image below is the day I implemented the change in strategy to the left straight WC to the right thermostat control. The off period is some solar gain switching off the heat pump.
-
Bosch CS5800i 5kW - Experience So Far
6 days ago
-
Yes, the "zoning with ASHP" topic again...
5 months ago
-
My Octopus Cosy 6 Heat Pump Journey: From Quote to Completion
9 months ago
-
My British Gas – Heat Force ASHP Installation: A Frustrating Experience
1 year ago
-
Low shower pressure after ASHP retrofit
1 year ago
- 26 Forums
- 2,220 Topics
- 49.2 K Posts
- 150 Online
- 5,880 Members
Join Us!
Podcast Picks
Latest Posts
-
RE: Aira Heat Pump: Stylish Scandinavian Heating
Having joined the Aira owners group on Facebook (for so...
By Pirate Rich , 2 hours ago
-
RE: Should Our Water Circulation Pump Be Configured to Run All The Time?
Interesting. So if you set blocade it can't know the c...
By JamesPa , 3 hours ago
-
RE: Widespread failure of insulation installation
@jeff Along with a phone-in on BBC Radio Four today, mu...
By Toodles , 3 hours ago
-
RE: What is the Heat Geek Guarantee?
@editor Thanks Mars, it is encouraging that Heat Geek a...
By colinc , 4 hours ago
-
RE: 5 Star Service from Havenwise
Ok…a bit tumbleweed. From our own experience we were ...
By benson , 4 hours ago
-
RE: Renewables & Heat Pumps in the News
Love the thought of it! simplification and sometimes me...
By Batpred , 4 hours ago
-
RE: New Fogstar 15.5kWh upright solution
That's good news for the moment anyway. Can we try to...
By Transparent , 4 hours ago
-
RE: Havenwise App Help & Forum Support – Get the Most from Your Heat Pump
Hi, I've always found Henri to be super helpful. From ...
By davidnolan22 , 5 hours ago
-
RE: Help me keep the faith with my air source heat pump installation
@adamk Will not even get started... The power of the ...
By Batpred , 5 hours ago
-
Sounds like you got it working for monitoring! With wel...
By Batpred , 6 hours ago
-
RE: Are We Sleepwalking Into Another Race to the Bottom?
Thank you Aadil. We appreciate you taking the time to r...
By Mars , 7 hours ago
-
RE: Say hello and introduce yourself
@chris12 Let us hope that next year will be a bumper so...
By Toodles , 10 hours ago
-
RE: Isolating the system for a planned power cut
@batpred - that Solis installation page is too vague. ...
By Transparent , 10 hours ago
-
RE: Heating Turned Off but Radiators Still Warm
I love Necromancy... but to follow James, heat pumps WI...
By DREI , 10 hours ago
-
RE: Air source heat pump roll call – what heat pump brand and model do you have?
12kW Gen 6 AE120BXYDEG (currently NOT performing well a...
By DREI , 10 hours ago
-
RE: Heat loss calculations and how they work in conjunction with heat pump sizing
Buffer tanks can best be thought of as part of a 'produ...
By JamesPa , 12 hours ago
-
Very Much Awake – Renewing the Heating Industry One Step at a Time
Like any industry that touches so many lives, and is so...
By Aadil Qureshi , 13 hours ago
-
Ah.... I'd like to make a couple of observations: &nb...
By Transparent , 13 hours ago
-
RE: Battery storage to run Heat Pump.
Hats off to the ones that persist, @Transparent ! ...
By Batpred , 14 hours ago