I’m seeing lots of comments regarding weather compensation is how you should be setting up the ASHP.
Currently my heating is all controlled by zoned thermostats.
What is weather compensation, and how do I know if my ashp is capable of it?
Hi Dan,
Weather compensation is a capability that most modern ASHP's appear to have. If you provide the manufacturer and model details I will check for you.
When set to operate, weather compensation measures the outside air temperature and automatically adjusts the water flow temperature from your ASHP. When optimised it will try to maintain the desired indoor temperature as the heat loss varies due to the changing outdoor air temperature. As the outdoor air temperature falls, the system will gradually increase the water flow temperature to compensate. This helps to improve the overall system efficiency by running the heat pump at the lowest water flow temperature.
I am assuming by your comments that your system has not been set up for weather compensation. Whilst I have a read through the Ecodan manual, I think that you should try as you suggest and lower the water flow temperature to 35C.
Sorry, I sent you the Midea data for the 12kW rather than the 14kW unit. I have now attached the correct one.
Could you please provide details of your controller and any other control equipment, so that I can be certain that I giving you the correct information.
That is correct, it's on a flow temp setting and several thermostats control the calling for heat.
Our setup...
The pump is situated directly outside the DHW cylinder and heating controls, i.e. on the opposite side of the external wall so minimal distance. Spacing around the pump is adequate as is the front area to blow out.
The 250l DHW cylinder and controls are within our utility room. There are what looks like two expansion tanks (see photo).
Downstairs is heated fully with UFH installed at the same time as the pump, pipe centres spacing 150mm and 60mm screed on top of 150mm insulation. This is set up in 3 zones, controlled by separate thermostats connected to a Heatmiser control box which in turn controls the UFH actuators on the manifold (see photo). The temp we have set on all downstairs thermostats is 22º.
Upstairs there are 5 rads, controlled by 1 thermostat. Set to 19º. 3 rads have TRVs and 2 do not.
We also have a detached building which is heated by the same ASHP, water flowing underground through 150mm insulated pipework.
This detached building has 6 rads, all newly upgraded as part of the ASHP installation and controlled by 1 thermostat. Currently set to 14º as we don't use the building much.
The Ecodan control board has been set up with 2 heating zones, one for the UFH area and the other for the radiator heated areas.
Looking at the photo it looks like your controller is an FTC5, can you please confirm. Because your controller is located in your utility room, do you have a remote wired or wireless sensor in your living area. Is the temperature in the utility room representative of the rest of your home? The reason that I ask is that for weather compensation to operate correctly, either the FTC5 controller needs to be in the main living area, or a remote sensor needs to be added, this being located in the main living area.
How familiar are you with the controller and what information have you so far extracted from your system?
The Therma V does support weather compensation. How familiar are you with the operation of your controller and how is your system controlled at present?
We have a central control unit in a cupboard with the hot water tanks.
The hot water is heated at intervals during the day, 12-3pm, and 6-7pm.
The heating is on demand as and when it’s called for by the thermostats.
To be fair our bills this year have been much less than last year (Same tariff) with far less kWh used in like for like months, following the advice from you and others here and the tweaks we made.
Im vaguely familiar with the control panel but some features are locked behind engineer access.
I managed to find some data although not as granular as your charts. For the Mitsubishi Ecodan 14Kw R32 PUZ-HWM140VHA model it states that at 7º outside and 45º flow temp should achieve a SCOP of 3.5. Your 12Kw Midea model has 3.89 for the same settings. Approx 10% better.
For my current settings at 10º outside and 50º flow your Midea could achieve 3.46, whereas I'm currently getting 2.7.
All things being equal I should be at an SCOP of around 3.12.
Having read the previous posts it sounds like the 50º flow temp which was set by the installers (interestingly the MCS certificate states this and that is what the RHI has been calculated with) is too high causing the pump to have periods of inactivity.)
@derek-mWhat are your thoughts on this as a test? At 10º outside and 35º flow temp your Media is at a SCOP of 5.22.
If I set my flow temp to 35º and leave it for a week, assuming outside temp remains at 10º, all thermostats on something unobtainable like 30º and app TVRs fully opened I should see an SCOP around 4.7.
You might but whether it would heat your house adequately or not is a different matter. It might though. I have the same ASHP as you but a much simpler set up (2 zones, all radiators). It's currently set on weather compensation on 2 zones/thermostats and works OK. I was thinking of trying the same (thermostats right up, on 24/7) but run on weather compensation; albeit set lower than it is now. Currently at 10 C flow temps are about 40 and that heats the house well. I do like an experiment, I just have to convince Mrs M...
We have a central control unit in a cupboard with the hot water tanks.
The hot water is heated at intervals during the day, 12-3pm, and 6-7pm.
The heating is on demand as and when it’s called for by the thermostats.
To be fair our bills this year have been much less than last year (Same tariff) with far less kWh used in like for like months, following the advice from you and others here and the tweaks we made.
Im vaguely familiar with the control panel but some features are locked behind engineer access.
Hi Dan,
From what I have read in the operator's manual, it would appear that you cannot use the weather compensation facility if you have a thermostat connected. It is unclear in the operators manual exactly how to set the system if the thermostat is removed, but since your controller is in the cupboard then it probably would not work correctly.
As a test you could try pressing the 'View Temp' button. Repeatedly pressing this button will cycle through the various system temperatures as detailed on page 10 of the operator's manual. I would be interested to see what values you are getting.
If you really wish to go down the route of weather compensation you may have to ask your installer about how it can be accomplished. I will see if I can find an installer's manual tomorrow which may give further details.
In the meantime you could try varying the water flow temperature setting to see how it effects system efficiency.
Looking at the photo it looks like your controller is an FTC5, can you please confirm. Because your controller is located in your utility room, do you have a remote wired or wireless sensor in your living area. Is the temperature in the utility room representative of the rest of your home? The reason that I ask is that for weather compensation to operate correctly, either the FTC5 controller needs to be in the main living area, or a remote sensor needs to be added, this being located in the main living area.
How familiar are you with the controller and what information have you so far extracted from your system?
It's possibly an FTC6 looking at the product number and date of manufacture (see sticker).
No there is no wired or wireless sensor attached.
No the temperature in the utility is higher, according to MelCloud it is a constant 29º.
I can navigate a user manual and know that basic settings. I have 8 months of usage data to look at if that is what you are referring to.
The system was set up to have DHW at 50º, set to heat on demand 24/7 with a 5º temp drop reheat setting and heating flow temp at 50º.
Since I lowered the flow temp to 35º ( at 12 noon on 01/11/21 ) the DHW heating has none wappy.
I've also noticed on 31/10/21 the DHW was being heated at several points in the day but there was no-one at home the entire weekend so I think this is looking like the DHW isolator valve isn't operating correctly.
I have set the DHW heating to OFF but the valve is still seemingly open (the metal handle is loose not stiff) and when I turned the DHW heating off the cylinder temp was 50º, 10 minutes later it was 39º. I also had all 3 UFH zones calling for heat but the heating was paused (see controller pic).
@markc That valve you have there is a low flow high-temperature valve, you are throttling your system, effectively it cannot breathe. You need to change it to a full bore 3 port valve for it to work properly.
Professional heat pump installer: Technical Director Ultimate Renewables Director at Heacol Ltd
@derek-m You are correct for old fixed compressor units. Most manufacturers recommend 10 litres per KW from flowing volume for a heat pump. Most new inverter units modulate down to about 2 Kw, therefore you only need an open zone volume of 20 litres. Buffer tanks drop the flow temperature by 5-10 Deg C, therefore resulting in a significant loss of performance, hence very few people here can fun their systems in the upper 20 Deg C where they should be at this time of year, they have to fun at 35-40 to get a flow temperature in the high 20's. In addition, you have to run a second pump which adds about £100.00 directly to your electricity bill every year without any benefit.
Heat pumps are very sensitive to flow, if the flow rate drops they will switch off. Companies like Freedom Heat Pumps insist on buffer tanks as, with one, a heat pump is very unlikely to suffer due to poor system design.
A correctly designed heat pump system does not require a buffer tank. It is impossible to get a high performing system with a buffer tank.
Professional heat pump installer: Technical Director Ultimate Renewables Director at Heacol Ltd
