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Advice needed on inefficient Samsung ASHP installation

mjw321 · 2024-09-13T20:41:56Z

Hi All, I bought this property a few years ago and previous owner had installed an ASHP about a year prior. She opted for this based on advice of her sister who lived in Germany (I don't believe she knew much/anything about them compared to conventional boiler-powered systems. TBF neither did I at that point. Alarmingly high bills led me to do some research, which has supported my suspicions that this is a poorly installed and very inefficient system. I'm hoping some of the SME's on this forum may be able to offer their thoughts so that I can prioritise and carry out a list of remediations and help inform us with respect to our further plans for home improvement. I've attached several photos of the system as well as a floor plan of the house. I'll also share a list of what I'm wondering are the main culprits (based on alot of reading on this forum...) Current Config Central heating: Downstairs: UFH in reception room and hallway(suspected as main culprit - see below), electric heater in kitchen (temporary solution) Upstairs: Rads with Thermostatic Valves (we've replaced and oversized these as we've redecorated) the 2 floors are regulated by separate thermostats and both have pumps (see attached pics) Hot water: Tank is an unvented system which we want to replace for mains hot water. Currently we use a basic Triton power shower which is also very greedy. Hot water consumption from tank is low/moderate at best Outdoor unit: Samsung unit (pics attached) - model number I believe is RC090MHXEAThis unit sustained some damage to the side from a power washer (My daughter - she intended well) - also shown in pics General (not visible in pics): I'm told that one length of the pipe - from outdoor unit to the indoor cupboard, does not meet recommended minimum width for required flow - approx length is 3.5M My concerns UFH - seems very expensive and I wonder about the width of the pipe (I had a specialist firm booked to install, they let me down and as it was just before xmas I made what I believe was a very bad decision to trust the plumber working with the decorators - is this UFH system fundamentally unsuitable for ASHP or is optimisation possible? Main controller in airing cupboard and use of remote stats which impose on/off behaviour - should I aim for control solely by main unit (repositioned)? Main controller seems very basic compared to what I've read from others on here - suggestions welcome here Subsidiary pumps for both up- and downstairs systems - removed these? (incl flow control on UFH system) traditional valves (visible in pics of indoor install)- replace with valves optimised for flow? restricted flow rate due to narrow gauge pipe as described above - would like to understand priority of doing this damage to outdoor unit from pressure washer - how much inefficiency is this causing and can I replace damaged parts? Lastly (I think) - I live in a very hard water area in SE England and suspect lack of maintenance of pipework throughout property (built ~1960) - should I consider a water softening solution at source of the property and a descaling procedure?Any advice from the many helpful experts here would be greatly appreciated - a good friend is a plumber and would be keen to be involved in any suggested remediations. Thanks in advance all, Mark

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Air Source Heat Pumps (ASHPs)

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HughF

(@hughf)

Noble Member Member

Joined: 3 years ago

Posts: 489

18/09/2024 6:24 am

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.

👍

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JamesPa

(@jamespa)

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Joined: 3 years ago

Posts: 3120

18/09/2024 7:06 am

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?

This post was modified 1 year ago by Mars

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.

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HughF

(@hughf)

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Joined: 3 years ago

Posts: 489

18/09/2024 8:12 am

@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.

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JamesPa

(@jamespa)

Illustrious Member Moderator

Joined: 3 years ago

Posts: 3120

18/09/2024 8:20 am

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.

This post was modified 1 year ago by JamesPa

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.

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HughF

(@hughf)

Noble Member Member

Joined: 3 years ago

Posts: 489

18/09/2024 9:01 am

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.

This post was modified 1 year ago by HughF

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.

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Anonymous 5011

(@Anonymous 5011)

Joined: 3 years ago

Posts: 563

18/09/2024 9:03 am

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

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

Screenshot 2024 09 18 08 46 41 61 40deb401b9ffe8e1df2f1cc5ba480b12

Screenshot 2024 09 18 08 46 17 59 40deb401b9ffe8e1df2f1cc5ba480b12

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.