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Fine tuning your ASHP performance

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MarkC
(@markc)
Regular Member
55 kWhs
Joined: 9 months ago
Posts: 93
Topic starter  

So you have had your ASHP installed and the installer has spent 2 minutes running you through the controls, which you promptly forget as soon as they leave the property.

A quick YouTube search refreshes your memory and you realise there are so many options for controlling your system. Internal thermostats, weather compensation curves, flow temps. But which one is the most efficient for your setup and how can you find that out.

I did start logging weekly performance data from the MMSP (Metering and Monitoring Service Package), changing room temperatures one week, flow temperatures the next but quickly realised that a simple comparison between weeks wasn't enough as outside temperatures were not the same.

I did have a quick look at compensation curves but was left unclear as to whether this was relevant to UK usage.

I currently only have 8 months of data. My MCS certificate stated a SCOP of 3.52. Not sure if that was the min, mean or max performance I should expect but it's currently bubbling around between 2.7 and 3.0. (October average outside temp is 13ºC, internal set to 22º with a  flow temp of 50º)

So that is the subject of this topic. How can you systematically discover the optimal setup for your system?

Any suggestions welcome, and thanks.


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Kev M
(@kev-m)
Member Moderator
943 kWhs
Joined: 1 year ago
Posts: 758
 
Posted by: @markc

So you have had your ASHP installed and the installer has spent 2 minutes running you through the controls, which you promptly forget as soon as they leave the property.

A quick YouTube search refreshes your memory and you realise there are so many options for controlling your system. Internal thermostats, weather compensation curves, flow temps. But which one is the most efficient for your setup and how can you find that out.

I did start logging weekly performance data from the MMSP (Metering and Monitoring Service Package), changing room temperatures one week, flow temperatures the next but quickly realised that a simple comparison between weeks wasn't enough as outside temperatures were not the same.

I did have a quick look at compensation curves but was left unclear as to whether this was relevant to UK usage.

I currently only have 8 months of data. My MCS certificate stated a SCOP of 3.52. Not sure if that was the min, mean or max performance I should expect but it's currently bubbling around between 2.7 and 3.0. (October average outside temp is 13ºC, internal set to 22º with a  flow temp of 50º)

So that is the subject of this topic. How can you systematically discover the optimal setup for your system?

Any suggestions welcome, and thanks.

If you find out,let me know!.

From my limited knowledge, weather compensation is a good thing.  When it 13 degrees outside, my flow temps are high 30s (radiators) and it warms the house nicely.  That's got to be better than 50 for a heat pump.  I have only just got MMSP installed and it's not quite all working yet.  Can you see the detailed data logs from yours? It's quite interesting to see how the energy consumption varies over time when the system starts up, etc. 

I thought the MCS COP was the manufacturers standard rating (at a set flow temp, air temp, lab conditions), a bit like the mpg figures you see for cars.  My real COP is similar to yours, maybe slightly higher.  

Which heat pump/MMSP do you have? 


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MarkC
(@markc)
Regular Member
55 kWhs
Joined: 9 months ago
Posts: 93
Topic starter  
Posted by: @kev-m
Posted by: @markc

So you have had your ASHP installed and the installer has spent 2 minutes running you through the controls, which you promptly forget as soon as they leave the property.

A quick YouTube search refreshes your memory and you realise there are so many options for controlling your system. Internal thermostats, weather compensation curves, flow temps. But which one is the most efficient for your setup and how can you find that out.

I did start logging weekly performance data from the MMSP (Metering and Monitoring Service Package), changing room temperatures one week, flow temperatures the next but quickly realised that a simple comparison between weeks wasn't enough as outside temperatures were not the same.

I did have a quick look at compensation curves but was left unclear as to whether this was relevant to UK usage.

I currently only have 8 months of data. My MCS certificate stated a SCOP of 3.52. Not sure if that was the min, mean or max performance I should expect but it's currently bubbling around between 2.7 and 3.0. (October average outside temp is 13ºC, internal set to 22º with a  flow temp of 50º)

So that is the subject of this topic. How can you systematically discover the optimal setup for your system?

Any suggestions welcome, and thanks.

If you find out,let me know!.

From my limited knowledge, weather compensation is a good thing.  When it 13 degrees outside, my flow temps are high 30s (radiators) and it warms the house nicely.  That's got to be better than 50 for a heat pump.  I have only just got MMSP installed and it's not quite all working yet.  Can you see the detailed data logs from yours? It's quite interesting to see how the energy consumption varies over time when the system starts up, etc. 

I thought the MCS COP was the manufacturers standard rating (at a set flow temp, air temp, lab conditions), a bit like the mpg figures you see for cars.  My real COP is similar to yours, maybe slightly higher.  

Which heat pump/MMSP do you have? 

Mitsubishi Ecodan 14Kw R32 with the MelCloud MMSP. I had 4 months of incorrect metering as they had been wired up incorrectly, registering energy output only, not consumption. So my first 4 months show a SCOP of 6500 🙂 


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Kev M
(@kev-m)
Member Moderator
943 kWhs
Joined: 1 year ago
Posts: 758
 
Posted by: @markc
Posted by: @kev-m
Posted by: @markc

So you have had your ASHP installed and the installer has spent 2 minutes running you through the controls, which you promptly forget as soon as they leave the property.

A quick YouTube search refreshes your memory and you realise there are so many options for controlling your system. Internal thermostats, weather compensation curves, flow temps. But which one is the most efficient for your setup and how can you find that out.

I did start logging weekly performance data from the MMSP (Metering and Monitoring Service Package), changing room temperatures one week, flow temperatures the next but quickly realised that a simple comparison between weeks wasn't enough as outside temperatures were not the same.

I did have a quick look at compensation curves but was left unclear as to whether this was relevant to UK usage.

I currently only have 8 months of data. My MCS certificate stated a SCOP of 3.52. Not sure if that was the min, mean or max performance I should expect but it's currently bubbling around between 2.7 and 3.0. (October average outside temp is 13ºC, internal set to 22º with a  flow temp of 50º)

So that is the subject of this topic. How can you systematically discover the optimal setup for your system?

Any suggestions welcome, and thanks.

If you find out,let me know!.

From my limited knowledge, weather compensation is a good thing.  When it 13 degrees outside, my flow temps are high 30s (radiators) and it warms the house nicely.  That's got to be better than 50 for a heat pump.  I have only just got MMSP installed and it's not quite all working yet.  Can you see the detailed data logs from yours? It's quite interesting to see how the energy consumption varies over time when the system starts up, etc. 

I thought the MCS COP was the manufacturers standard rating (at a set flow temp, air temp, lab conditions), a bit like the mpg figures you see for cars.  My real COP is similar to yours, maybe slightly higher.  

Which heat pump/MMSP do you have? 

Mitsubishi Ecodan 14Kw R32 with the MelCloud MMSP. I had 4 months of incorrect metering as they had been wired up incorrectly, registering energy output only, not consumption. So my first 4 months show a SCOP of 6500 🙂 

That's interesting; same ASHP and MMSP but mine isn't registering energy output, only consumption.  I'm trying to get the supplier back to fix it.  Does yours monitor energy consumed from the ASHP and the Immersion/ancillaries separately?  Mine doesn't and I think it should. 


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MarkC
(@markc)
Regular Member
55 kWhs
Joined: 9 months ago
Posts: 93
Topic starter  
Posted by: @kev-m
Posted by: @markc
Posted by: @kev-m
Posted by: @markc

So you have had your ASHP installed and the installer has spent 2 minutes running you through the controls, which you promptly forget as soon as they leave the property.

A quick YouTube search refreshes your memory and you realise there are so many options for controlling your system. Internal thermostats, weather compensation curves, flow temps. But which one is the most efficient for your setup and how can you find that out.

I did start logging weekly performance data from the MMSP (Metering and Monitoring Service Package), changing room temperatures one week, flow temperatures the next but quickly realised that a simple comparison between weeks wasn't enough as outside temperatures were not the same.

I did have a quick look at compensation curves but was left unclear as to whether this was relevant to UK usage.

I currently only have 8 months of data. My MCS certificate stated a SCOP of 3.52. Not sure if that was the min, mean or max performance I should expect but it's currently bubbling around between 2.7 and 3.0. (October average outside temp is 13ºC, internal set to 22º with a  flow temp of 50º)

So that is the subject of this topic. How can you systematically discover the optimal setup for your system?

Any suggestions welcome, and thanks.

If you find out,let me know!.

From my limited knowledge, weather compensation is a good thing.  When it 13 degrees outside, my flow temps are high 30s (radiators) and it warms the house nicely.  That's got to be better than 50 for a heat pump.  I have only just got MMSP installed and it's not quite all working yet.  Can you see the detailed data logs from yours? It's quite interesting to see how the energy consumption varies over time when the system starts up, etc. 

I thought the MCS COP was the manufacturers standard rating (at a set flow temp, air temp, lab conditions), a bit like the mpg figures you see for cars.  My real COP is similar to yours, maybe slightly higher.  

Which heat pump/MMSP do you have? 

Mitsubishi Ecodan 14Kw R32 with the MelCloud MMSP. I had 4 months of incorrect metering as they had been wired up incorrectly, registering energy output only, not consumption. So my first 4 months show a SCOP of 6500 🙂 

That's interesting; same ASHP and MMSP but mine isn't registering energy output, only consumption.  I'm trying to get the supplier back to fix it.  Does yours monitor energy consumed from the ASHP and the Immersion/ancillaries separately?  Mine doesn't and I think it should. 

It will be a simple wire in the wrong place but you need someone who knows what they are doing to fix it. No, it just measures DHW and Heating as two  inputs/outputs.

We have the DHW set to be on 24/7 and maintain 50º with a 5º drop to trigger a reheat. From my understanding the only time the immersion would be used is if you drain the tank and need more hot water quickly, so manually turn the DHW heating on or when the legionella cycle runs.

I have a 250l tank and have never totally drained it of hot water.


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Brendon Uys
(@heacol)
Active Member
150 kWhs
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Joined: 11 months ago
Posts: 192
 
Posted by: @markc

So you have had your ASHP installed and the installer has spent 2 minutes running you through the controls, which you promptly forget as soon as they leave the property.

A quick YouTube search refreshes your memory and you realise there are so many options for controlling your system. Internal thermostats, weather compensation curves, flow temps. But which one is the most efficient for your setup and how can you find that out.

I did start logging weekly performance data from the MMSP (Metering and Monitoring Service Package), changing room temperatures one week, flow temperatures the next but quickly realised that a simple comparison between weeks wasn't enough as outside temperatures were not the same.

I did have a quick look at compensation curves but was left unclear as to whether this was relevant to UK usage.

I currently only have 8 months of data. My MCS certificate stated a SCOP of 3.52. Not sure if that was the min, mean or max performance I should expect but it's currently bubbling around between 2.7 and 3.0. (October average outside temp is 13ºC, internal set to 22º with a  flow temp of 50º)

So that is the subject of this topic. How can you systematically discover the optimal setup for your system?

Any suggestions welcome, and thanks.

Markc, I am sorry to say but with a flow temperature of 50 deg C at this time of year, I hope you have a very big pocket because your bill is going to be very high. It appears that your system has been very poorly designed and set up and certinly, with a predicted SCOP of 3.52, not designed for performance but for low installation cost. The flow temperature should be in the high 20's at this time of year.

SCOP is the anual average performance or total heat produced by the machine divided by the electricity used. At this time of year you should be runnig at above 5. Here is a picture from one of my installations.

IMG 20211029 WA0003

 

 


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Mars
 Mars
(@editor)
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@heacol, I had no idea the flow temperature should be so low (20C) in November. We're currently running at 35C (manually set) at it feels about right - COP at just over 3 for later September to today.

Caernarfon 18kW ASHP from Global Energy System – 6.16kW solar PV array
Follow our sustainability journey at My Home Farm
Our heat pump installation: https://youtu.be/c3V0k_GeFOo


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Brendon Uys
(@heacol)
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@editor Mars, your unit had a co of 3, My customers had a COP of 5. He has used nearly halve the electricity you have to do the same job, that will be the same for every month of the year. His house has no thermostats and the house is treated as a single zone with TRV's the bedroom radiators to reduce the temperatures there. The heat pimp controlls the temperature in the living areas, all living areas and batherooms are kept at the same temperatures. It is contrary to the normal thinking, but it works.


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Brendon Uys
(@heacol)
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Joined: 11 months ago
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@editor Low flow temperatures = low bills. It realy is that simple.


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Mars
 Mars
(@editor)
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@heacol, does you customer have very good/excellent insulation?

Caernarfon 18kW ASHP from Global Energy System – 6.16kW solar PV array
Follow our sustainability journey at My Home Farm
Our heat pump installation: https://youtu.be/c3V0k_GeFOo


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Mars
 Mars
(@editor)
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Posted by: @heacol

@editor Low flow temperatures = low bills. It realy is that simple.

Fabric first to achieve low flow temperatures I guess. Our insulation is good to very good, but we still leak some heat. Getting better though.

Caernarfon 18kW ASHP from Global Energy System – 6.16kW solar PV array
Follow our sustainability journey at My Home Farm
Our heat pump installation: https://youtu.be/c3V0k_GeFOo


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Brendon Uys
(@heacol)
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Joined: 11 months ago
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@editor No, it is a 1930's ex council house with cavity wall insulation, double galzing installed about 20 years ago and 250 mm of rockwool in the loft.

A standard off the shelf ex-councill house.

You are correct, it should always be fabrick first, however it is not always necessary or economical.

Your house is your house, some are leaky and others are passive, it is not always possable or make economical sence to make a leaky solid stone house in to a passive pouse. What does make economical sence is to replce a bad fossel fuel system with a reneawble low carbon heating system that is cheaper to run and provides a better living enviroment. 

If you have to play with your system there is something wrong. Initially there should be some tweeking but after that, it should just work without any intervention. If your flow temperature is high, is is caused by one of 2 things:- firstly,  there are too many levels of controwl, "too many chefs spoil the broth", this is easy to fix, just remove them and allow the heat pump to do it's job. The second is your emmitters are too small or you are not giving then mime to react. Please remember that 80% of a radiator's output is through convection, the lower the flow temperature the longer the convections takes to work (up to 4 hours).


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Brendon Uys
(@heacol)
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@editor By the way, Performance of the heat pump (COP) has nothing to do with how leaky your house is. It has to to with the distribution system and how you controll it.


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Mars
 Mars
(@editor)
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@heacol, that's a good point about COP and leakiness.

Our issue was heat emitters - when we added Stelrad K3s it made a world of difference in the coldest rooms in the house. K2s in the southern end have been adequate, and UFH has always been great. 

Derek has been hammering at me and our weather compensation which we haven't been able to get working properly because the main controller (which reads the temperature) is inside the HW cupboard and it's always very warm in there. So I just set our flow rate manually. It's actually at 40C now (it was set to 35C), and will try to get through the winter at that temperature. We also have a bivalent system, so I've set up our oil boiler to take over heating when temps drop below 8C – the only reason I've done this is because of the insane price of electricity, so it's a bit of a balancing act. The oil boiler has been set to its lowest possible temperature to allow it to condense. 

Caernarfon 18kW ASHP from Global Energy System – 6.16kW solar PV array
Follow our sustainability journey at My Home Farm
Our heat pump installation: https://youtu.be/c3V0k_GeFOo


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Derek M
(@derek-m)
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Posted by: @editor
Posted by: @heacol

@editor Low flow temperatures = low bills. It realy is that simple.

Fabric first to achieve low flow temperatures I guess. Our insulation is good to very good, but we still leak some heat. Getting better though.

Hi Mars,

I am beginning to wonder if anyone bothers to read the information that I provide. Having been a Control Systems Engineer for over 50 years and worked on and designed systems for power stations and oil and gas processing plants, thermostats would only be used on the systems of low importance. The problem with using thermostats in home heating systems is that they normally have a deadband of 1C, which means that to maintain a comfortable temperature within the home, they are normally set higher than would need to be if continuous process control was used instead of a thermostat.

To confirm the point that Brendon and I have been repeatedly making, for maximum efficiency an ASHP needs to be operating at the lowest water flow temperature that is consistent with maintaining the desired indoor air temperature. At the moment, with an outside air temperature of 12C, our radiators are cold to the touch, with our heating system in full operation maintaining an indoor temperature of 21C. When the outside air temperature falls to 6C, the radiators are only just warm to the touch.

If you take the trouble to look at the spreadsheets and results that I posted several weeks ago, you will see that ASHP efficiency is most affected by outside air temperature, indoor set temperature, heat loss (level of imsulation) and size of heat emitters.

Even the most expensive, supposedly intelligent heating controls, are not often used correctly with heating system that employ an ASHP.

 

This post was modified 8 months ago 2 times by Derek M

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