Going from Coal to Air Heat Source Pump and PV's using ECO4 grant scheme

Pec123

Thank-you.

Images to follow of amended Documents. Please see the attached documents (next post) where this mistake has been amended and as you have put above the heating SCOP is 4.14.

Quoted SCOP for hot water is so low because this value of 1.75 is a fixed value they are unable to change this as this is the MCS standard.

Based on a 170 litre hot water cylinder with a start temperature of 50⁰C and get the cylinder up to 65⁰C it will require a energy input of 2.97kw so the figure generated by the heat loss software would appear to be accurate.

They have reviewed the hot water pdf and there seems to have been a error in the software they have had to delete it out the software and start again please see revised pdf.

From Mitsubishi they have been informed it is normal for their Ecodan heat pumps consume around 0.7kw/hr per day in standby.

Reed_Richards

Pec123 said:

Thank-you.

Images to follow of amended Documents. Please see the attached documents (next post) where this mistake has been amended and as you have put above the heating SCOP is 4.14.

Great

Pec123 said:

Quoted SCOP for hot water is so low because this value of 1.75 is a fixed value they are unable to change this as this is the MCS standard.

This wasn't a fixed value when I had my heat pump installed by an MCS installer in December 2020. So if that is true now then something has changed.  My SCOP for hot water was 2.89 (assuming I heated the cylinder to 50 C using a flow temperature of 55 C).

Pec123 said:

From Mitsubishi they have been informed it is normal for their Ecodan heat pumps consume around 0.7kw/hr per day in standby.

Mine consumes about 0.25 kWh per day in standby.  So from my perspective 0.7 kWhr per day seems a bit high but not drastically so.  That's something like 20p per day just to keep the thing ticking over.
  

Pec123

The Forum is having trouble uploading my latest data images.

I wonder if there are any AHSP's that have weather compensation curves for the temperature flow as UFH does?

I wonder if Octopus Energy do ECO4 grants I will have to contact them on Monday as the company we have chosen so far has a Trustpilot score of 3.2 and Octopus Energy Trustpilot score of 4.8. I can see why our company 2, score is low just due to the calculations they made as demonstrated in this thread. I wonder how many companies to go through during this process with? I feel things have to be correct before, during and after the install starts.

Reed_Richards

Almost all ASHPs have Weather Compensation and this applies equally to radiators as it does to UFH.  When the heat loss from your various rooms was calculated then it was assumed that there was a particular outside temperature, typically a few degrees below zero.  If it's milder than that outside then the heat loss will not be so great so you don't need your radiators to be so hot as the 45 C (input flow), or whatever you end up with.  For your heat pump to be operated most economically it's important that you use Weather Compensation.

Edit:  The outside air temperature is assumed to be -2.18 C so that's the air temperature when the input flow to the radiators needs to be 45 C.  If it's colder out you'll need the flow to be hotter, and you have some headroom.  If it's warmer out you don't need the flow to be as hot.

One of the figures in the chart says you are heating your hot water cylinder with water at 45 C (under "Primary and Auxiliary Heat Sources").  Your heat pump will be capable of 55 C or more.  Ask them to change the 45 C to 55 C and I bet that makes your SCOP for hot water go up.  It looks like your installers don't have a good understanding of the software they are using so if there's a wrong number somewhere they don't spot it.   

Pec123

Here’s a comprehensive summary of everything I’ve shared about your Air Source Heat Pump (ASHP) and Solar PV system under the ECO4 scheme:

Property Overview

• Location: Tring, England
• Type: 1952 semi-detached, 3-bedroom house
• Size: 116 m²
• Upgrades under ECO4:

• Mitsubishi Ecodan ASHP (PUZ-WM85VAAMCS)
• 200L unvented hot water cylinder
• 8 radiators (various types and sizes)
• Solar PV system (4.0 kWp)
• Room-in-roof and loft insulation
• Thermostatic radiator valves
• FTC6 controller with room thermostat
• Pipework above floorboards (deal breaker consideration)
• Ventilation as required under PAS2035

•  Solar PV System Details

  • Panels: 10 × Longi HiMo5 400W All Black Mono
  • Inverter: SolaX X1-3.6T (WiFi included)
  • Estimated Annual Generation: 3,399 kWh
  • Self-consumption: 36% of generation
  • Independence: 31% of household electricity covered by solar
  • Export: ~51,212 kWh over 25 years
  • Savings: ~£18,444 over 25 years
  • Export Income: ~£9,889 over 25 years
  • Net Present Value: £17,216.56
  • Payback: Immediate (system cost covered by ECO4)

  • ASHP System Details

    • Model: Mitsubishi Ecodan PUZ-WM85VAAMCS
    • Design Output: 8.5 kW (range up to 14 kW)
    • Design Flow Temperature: 45°C (requested for efficiency)
    • SCOP for Heating: Corrected to 4.14
    • SCOP for Hot Water: Fixed at 1.75 (MCS default)
    • Hot Water Heating:
    • Weekly Legionella cycle to 60°C via immersion heater
    • Estimated immersion use: ~155 kWh/year (corrected from 1514 kWh error)
    • Standby Load: ~0.7 kWh/day (Mitsubishi confirmed

    • Radiator Configuration

      • Total Output at 55°C: ~7.5 kW
      • Concerns:
      • Kitchen and lounge may be under-radiated for lower flow temps
      • Bedroom 3 radiator appears oversized
      • Radiator types include K-Rad and CenterRad, mix of K1, K2, and P+
      • Suggested Improvements:
      • Larger radiators or dual units in key rooms
      • Consider plinth heater in kitchen (with modified thermal switch)
      • Weather compensation curve setup via FTC6 controller

      • Technical & Installer Notes

        • Heat loss calculations:
        • Whole-house average: 8.5 kW
        • Room-by-room total: ~4.77 kW (excluding conservatory)
        • Weather Compensation: Supported by Mitsubishi Ecodan
        • Documentation Errors:
        • SCOP for 45°C initially misquoted (now corrected)
        • Hot water heating flow temp listed as 45°C (should be 55°C)
        • Customer Service Concerns:
        • Installer Trustpilot score: 3.2
        • Considering Octopus Energy (Trustpilot 4.8) as alternative

Pec123

This is actually what we achieved:

• SCOP for Heating:  3 last year and 2.5 this year less than we were quoted.
• SCOP for Hot Water: Fixed at 1.75 (MCS default)

• Weather compensation curve setup via FTC6 controller 45 degrees to minus 3 degrees

Hot water heating flow temp now 46 degrees

What tinkering would you do?

QrizB

Pec123 said:

This is actually what we achieved:

• SCOP for Heating:  3 last year and 2.5 this year less than we were quoted.
• SCOP for Hot Water: Fixed at 1.75 (MCS default)

How did you calculate your COPs?

At a 45C flow temperature your heat pump should be achieving a COP of 4-ish.

Pec123

FTC6 controller gave us the figure so something is not right

QrizB

Pinging @matt_drummer who knows more about measuring COPs than most of the other regulars.