Posted by: @peter

I finished building my house this year and moved in back in June.  I’ve been using my air source heat pump for heating and water and not really thought anything about it until I noticed my electricity bills.  I’m spending about £13 a day on electricity and decided I need to learn how to most efficiently run my airsource and heating schedule. 

 

There really isn’t much information online about this.  So I’m really hope someone here will be able to help me please. 

 

Thank you

 

My set up is as follows:

 

Mitsubishi Electric Ecodan PUHZ-HW140VHA2 14kW air-source heat pump

Mitsubishi Electric EHPT25X-UKHCW 250 litre water tank

Mitsubishi Electric FTC5 Ecodan Controller PAC-IF062B-E

Heatmiser Streamline thermostat/controllers in each room

 

House:

 

New build house.  Largely open plan downstairs.  Does have some large window walls in the entrance hall which we would lose a bit of heat through.

Floor coverings: upstairs is carpet and low tog underlay.  Carpet is thick, but we kept the total tog below the recommended amount (my memory is hazy, possibly 2.5 tog?)  Downstairs we have 12mm thick laminate.

 

Underfloor heating upstairs and down

 

Current schedules:

 

Ecodan controller currently set to run at 18degrees continuously. 

3 main living rooms (open plan kitchen, dining and lounge) set to 21 degrees between 5am-8.30am and then 16 degrees, then on again at 4pm for a couple of hours at 21, then back to 16

All other rooms in the house:  Heatmiser contollers set to Frost protection mode (set to between 10degrees and 15 degrees)

Hot water is heated from 6-7am and then half an hour in the afternoon 3-3:30pm.  Hot water seems to heat to 41degrees now – although it used to be higher (could it be the compensation curve?  Not sure if that changes DHW temp)

 

I think my hot water only heats when scheduled to heat on the Ecodan controller – I though it might be using the immersion heater.  From what I can work out, i don’t think the underfloor heating results in the water heating at all unless the immersion heater turns on.

 

Hot water use/costs:

October    158 kWh    £34.74
November    228 kWh    £50.13
December (<19th)    164 kWh    £36.06
 

Heating use/costs:

October    164 kWh    £36.06
November    621 kWh    £136.54
December (<19th)    491 kWh    £107.96
 

Temperatures

 

The room temp on the thermometers seems to average around between 15 and 17 degrees.  Which feels freezing.  We do have a wood burning stove which we have been using to heat the downstairs rooms to a more reasonable temp (gets up to 21-23 when this is running)

 

COP values

 

According to my MSC certificate we should get 3.48 COP.    I reckon we’re getting the following:

December 2021 <19th    2.348
November 2021    2.377
October to December 19th    2.179
 

If anyone can help with any advice that would be very much appreciated.  Thank you very much

Hi Peter,

Are you controlling your system on weather compensation, or thermostats, or a combination of both?

What are your water flow and return temperatures?

What is the floor area?

How are you calculating your COP?

Thanks @derek-m 

The system is being controlled using thermostats but the weather compensation is also turned on.

I'm not sure what the water temperatures are - where can I find these please?

Floor area is approx 300sqm total

The ecodan controller gives me figures for Consumed Electrical Energy and Delivered Energy - I used these to calculate the COP figure.

Hi @peter 

Do you know how to adjust the weather compensation curve, and if so what are the present settings?

Do you have any heat loss calculations?

Since your home is a new build, I am assuming a high level of insulation, though probably a low thermal mass, which would indicate that varying the temperature settings throughout the day may not be the most efficient.

What indoor temperatures would you like to achieve in the various areas?

@derek-m 

I've attached a pictures of the weather compensation curve

I have some heat loss calcs from my SAP EPC - I don't understand them, but does that help?

I'd like to get 20 or 21 degrees in the 3 main rooms living rooms (downstairs, open plan) of the house.  And then would be happy with 17/18 for the rest of the house.

@peter,

From your numbers it doesn't look like your ASHP is using £13 per day.  Your 1-19 Dec usage is 491kW.  That doesn't sound bad for a 300m2 house but of course not if your house is only 15-17C!! 

I have the same ASHP as you and although my house is smaller, its heat loss is in the same ballpark.  At 4.2C outside, your house heat loss looks to be 6.2kW and mine is about 5.6kW.  To keep my whole house at 20-21C (with radiators, not ufh) from 1-19 December has taken 440kWh.

I'm sure @Derek-m will be able to help you improve things.

Kev

Hi @peter 

So, it would appear that your weather compensation curve is set for a water flow temperature of 50C @ an outside air temperature of -15C and a water flow temperature of 25C @ an outside air temperature of +35C. I think that they are being a little optimistic with the later figure, but with global warming you never know. 😀 From the data at the bottom of the last sheet, the estimated heat loss at an outside air temperature of 4.2C is 6231 Watts.

The way your system is set up at the moment, the FTC controller and the thermostats are probably having a duel to decide who is in charge.

I would suggest that you change the setting parameters for the weather compensation to the following.

Leave the 50C @ -15C as is, or maybe change it to 50C @ -10C.

Change the 25C @ 35C to 25C @ 18C.

Set the upstairs thermostats to 18C.

Increase the downstairs thermostats to 22C and monitor the temperature. If the indoor air temperature increases to 22C, then set the temperature offset on the FTC controller to -1. Wait several hours, because UFH reacts very slowly, then if the indoor temperature has not reduced to 21C, set the offset to -2. Repeat this procedure until the indoor air temperature is maintained at 21C.

Monitor your system performance to see if your COP has improved and the system is operating more efficiently.

If your FTC controller is located in a position that is measuring the downstairs room temperatures, then you could consider setting it to operate in the auto adaptation mode.

Posted by: @derek-m

Hi @peter 

So, it would appear that your weather compensation curve is set for a water flow temperature of 50C @ an outside air temperature of -15C and a water flow temperature of 25C @ an outside air temperature of +35C. I think that they are being a little optimistic with the later figure, but with global warming you never know. 😀 From the data at the bottom of the last sheet, the estimated heat loss at an outside air temperature of 4.2C is 6231 Watts.

The way your system is set up at the moment, the FTC controller and the thermostats are probably having a duel to decide who is in charge.

I would suggest that you change the setting parameters for the weather compensation to the following.

Leave the 50C @ -15C as is, or maybe change it to 50C @ -10C.

Change the 25C @ 35C to 25C @ 18C.

Set the upstairs thermostats to 18C.

Increase the downstairs thermostats to 22C and monitor the temperature. If the indoor air temperature increases to 22C, then set the temperature offset on the FTC controller to -1. Wait several hours, because UFH reacts very slowly, then if the indoor temperature has not reduced to 21C, set the offset to -2. Repeat this procedure until the indoor air temperature is maintained at 21C.

Monitor your system performance to see if your COP has improved and the system is operating more efficiently.

If your FTC controller is located in a position that is measuring the downstairs room temperatures, then you could consider setting it to operate in the auto adaptation mode.

@Derek-m, @peter said "Ecodan controller currently set to run at 18degrees continuously."  

do you think it is maybe set to run in Ecodan's room temperature/auto adaptation mode already?  If it is, that would confuse it even more.

Hi @kev-m 

I have no idea, that is what I am trying to discover.

Thanks for all the replied - appreciate you taking the time.  I can understand you being confused about how I've got it set up because it makes no sense to me.

@Derek-m That's very helpful thank you - I'll try exactly what you said and see how it goes.  Thanks.  

@Kev-m Quite frankly I'm not sure, but now I'm wondering if I do have it on.  The temperature is being set on the FTC controller like so:  

But then its also got a remote controller (screenshot below) which I now see has a built-in temp sensor.  This has just been sitting by the tanks/FTC controller since install and I've never used it.  But I presume this could be problematic as well as the room tends to stay quite warm with the tanks etc being in there.

I guess I'll need to either try and turn of Auto Adaptation or move the remote control sensor into one of the downstairs roms

I appreciate it I am being very clueless - I feel a bit like the installers did their job installing and of they go and I have no idea what how the whole system works.  

Thanks for your patience

Hi @peter 

Do not forget to provide feedback, so that we are all not laying awake all night worrying about whether or not your system is working correctly. 🙄 

Hi @peter 

Try moving the remote controller into your living area and allowing its temperature to stabilise. Kev, could you explain to Peter how to monitor the water flow and return temperatures, and any further useful information.