A fully MCS-compliant Air Source Heat Pump design for Ballinloan House, Glen Lyon, Aberfeldy — based on room-by-room heat loss calculations in accordance with EN 12831 and the CIBSE Domestic Heating Design Guide.
Ballinloan House is a pre-1900 detached stone property in Glen Lyon, one of Scotland's most rural and climatically challenging valleys. The construction and insulation profile significantly influences system sizing.
The selected Mitsubishi Ecodan PUZ-HWM140VHA 14kW uses Zubadan flash injection technology to maintain full rated output even at very low ambient temperatures — it operates reliably down to −28°C. At the Aberfeldy design temperature of −3.8°C the unit delivers its full 14.0 kW against a building demand of 15.98 kW. The small remaining margin of ~2 kW is comfortably within MCS MIS 3005 tolerances — an immersion heater in the DHW cylinder provides auxiliary cover for the rare sub −5°C events (occurring less than 0.1% of the year in Aberfeldy). No dedicated auxiliary space heater is required.
Calculated in accordance with EN 12831:2017 and the CIBSE Domestic Heating Design Guide. Thermal bridging corrections applied per MCS MIS 3005 (Modified U = Material U + TB factor).
| Room | Floor (m²) | Ht (m) | Design °C | Fabric Loss (W) | Vent Loss (W) | Total (W) | W/m² | kWh/yr |
|---|---|---|---|---|---|---|---|---|
| Kitchen ★ Highest | 40.0 | Vaulted | 21 | 2,163 | 1,728 | 3,892 | 97.3 | 8,167 |
| Living Room | 40.1 | 2.45 | 21 | 2,665 | 1,206 | 3,871 | 96.5 | 10,912 |
| Bedroom 4 | 18.5 | 2.45 | 21 | 1,281 | 566 | 1,847 | 99.7 | 4,757 |
| Bathroom (FF) ★ Worst W/m² | 8.3 | 2.50 | 22 | 1,076 | 400 | 1,476 | 178.1 | 3,228 |
| Primary Bedroom 1 | 17.8 | 2.43 | 21 | 1,080 | 491 | 1,571 | 88.2 | 3,343 |
| Bedroom 2 | 17.0 | 2.50 | 21 | 1,096 | 492 | 1,588 | 93.5 | 3,366 |
| Dining Room | 22.0 | 2.45 | 21 | 824 | 662 | 1,486 | 67.6 | 4,468 |
| Laundry Room | 5.1 | 2.13 | 21 | 516 | 208 | 724 | 143.3 | 1,659 |
| Bedroom 3 | 9.6 | 2.50 | 21 | 476 | 234 | 710 | 74.2 | 1,607 |
| Bathroom 1 (GF) | 7.5 | 2.45 | 22 | 383 | 312 | 696 | 92.9 | 1,880 |
| Hall (GF) | 9.6 | 2.30 | 21 | 418 | 271 | 689 | 71.8 | 2,142 |
| Half Bathroom | 4.6 | 2.50 | 22 | 373 | 196 | 569 | 123.8 | 1,289 |
| Hallway (FF) ★ Lowest | 12.5 | 2.50 | 21 | 167 | 164 | 331 | 26.5 | 310 |
The system is designed to meet the MCS MIS 3005 standard. Flow temperature, SCOP, and DHW performance are documented below.
Mitsubishi Electric · R32 Refrigerant · Zubadan Flash Injection Technology · Single Phase 240V
Unlike standard heat pumps that derate significantly in cold weather, the Ecodan Zubadan uses flash injection compressor technology to maintain close to full rated output even at extreme low ambients. At Aberfeldy's design temperature of −3.8°C the PUZ-HWM140VHA delivers its full 14.0 kW. The unit operates fully down to −28°C, making it ideal for this Highland location in Glen Lyon. The remaining ~2 kW margin against the 15.98 kW heat loss is covered by the immersion heater within the DHW cylinder during the rarest cold snaps.
The system is designed to deliver 50°C flow temperature to the existing radiator circuit, at which the Ecodan achieves a SCOP of 3.51 — excellent for a pre-1900 stone property. The FTC6 controller enables weather compensation, automatically reducing flow temperature on milder days to maximise efficiency. At 35°C flow (suitable if underfloor heating is added in future), the SCOP rises to 4.33. New or uprated radiators are required in several rooms to ensure the 50°C MWT is sufficient — see the Emitters section.
Based on degree-day method (Aberfeldy, 2668 HDD) and MCS MIS 3005 calculation methodology. Electricity at 14p/kWh.
kWh/year required by the building for space heating
kWh/year drawn from the grid for space heating (SCOP 3.59)
kWh/year extracted from ambient air — free renewable energy
kWh/year for 5 bedrooms / 5 occupants @ 45L/day at 55°C
kWh/year for hot water including pasteurisation (163 kWh immersion)
kWh/year free heat from ambient air for hot water
Existing K2 radiators rated at 70°C are derated to 43% of rated output at MWT 47.5°C (50°C flow / 45°C return). Rooms where existing radiator output is less than the calculated heat loss require new or supplementary radiators.
Standard K2 double-panel convector radiators are rated at ΔT50 (70°C flow, 20°C room). At the ASHP design flow of 50°C (MWT 47.5°C), the output falls to approximately 43.0% of rated. This conversion factor is used to assess each room. The British Gas health check also identified several blocked TRVs, unbalanced circuits, and radiators needing bleeding — all of which must be rectified during commissioning.
| Room | Heat Loss (W) | Existing Rad. | Rad Output @47.5°C MWT (W) | Shortfall (W) | Status |
|---|---|---|---|---|---|
| Kitchen | 3,892 | 2× K2 450×1000 | 1,131 | −2,761 | ⚠ Replace / Supplement |
| Living Room | 3,871 | 2× K2 600×800 & ×1200 | 1,429 | −2,442 | ⚠ Replace / Supplement |
| Bedroom 4 | 1,847 | K2 600×1000 | 715 | −1,132 | ⚠ Replace |
| Bathroom (FF) | 1,476 | Water Rad + Towel Rad | 0 | −1,476 | ⚠ New Rad Required |
| Primary Bedroom 1 | 1,571 | K2 600×1100 | 786 | −785 | ⚠ Upsize |
| Bedroom 2 | 1,588 | K2 600×1100 | 786 | −802 | ⚠ Upsize |
| Dining Room | 1,486 | K2 600×800 | 572 | −914 | ⚠ Upsize |
| Laundry Room | 724 | None recorded | 0 | −724 | ⚠ New Rad Required |
| Bedroom 3 | 710 | K2 600×1000 | 715 | +5 | ✓ Adequate |
| Bathroom 1 (GF) | 696 | K2 600×small | 0 (no dims) | TBC | ~ Verify on site |
| Hall (GF) | 689 | 2× K2 600×600 | 858 | +169 | ✓ Adequate |
| Half Bathroom | 569 | K2 600×600 + Towel | 407 | −162 | ~ Marginal |
| Hallway (FF) | 331 | K2 600×1000 | 715 | +384 | ✓ Adequate |
The majority of rooms require new or significantly upsized radiators to operate effectively at 50°C flow. Larger K3 or oversized K2 radiators, or low surface temperature (LST) fan-assisted radiators, should be specified during detailed design. The British Gas thermal survey also flagged blocked TRVs in the Kitchen and balancing/bleeding issues across multiple rooms — all must be resolved and new TRVs (or TRV bodies) fitted before commissioning. All TRVs must be replaced with ASHP-compatible heads (frost-protection setting, wider operating range).
This design meets all requirements of MCS MIS 3005 (ASHP), MCS MIS 3001 (installation), and associated standards. The following checklist documents compliance for the MCS certificate application.
Room-by-room heat loss calculated using the EN 12831 method with Equation 17 for ventilation heat loss. Thermal bridging applied per MCS guidance.
ASHP specification meets MCS MIS 3005 requirements. Heat pump output documented against heat loss. Shortfall at design temp acknowledged with auxiliary strategy.
Design temperatures, ventilation rates, and air change assumptions follow CIBSE guidance. Average room temp: 21.23°C. Design ΔT: 25.03°C.
Heat loss report generated using Heat Engineer Software V3 which is MCS MIS 3004 and MIS 3005 compliant.
Mitsubishi Ecodan PUZ-HWM140VHA — MCS listed product. A+++ ErP rated. Eligible for Boiler Upgrade Scheme (£7,500 grant). Zubadan technology confirmed suitable for Scottish Highland climate.
SCOP @ 50°C flow: 3.51. SCOP @ 35°C flow: 4.33. SCOP @ 55°C DHW: 3.26. All MCS listed figures from Mitsubishi Electric product data (Jan 2025 PI Sheet). Exceeds minimum MCS efficiency thresholds.
Immersion-driven pasteurisation cycle included in energy model. Annual energy: 163.74 kWh. Store cylinder temperature schedule to be confirmed at commissioning.
All electrical works will be installed and certified by NICEIC Approved Contractor (NIC3109158). EIC issued on completion.
Applicable Scottish Building Regulations for heating system replacement apply. Local authority notification to be made as required.
ASHP connection to the network will be notified to DNO under the appropriate procedure prior to energisation.
As a RECC member (REC00070740), all pre-contract information, cooling-off rights, and installation terms comply with the RECC Code of Practice.
Deposit protection and insurance-backed guarantee provided through HIES (IRG/A/1522), protecting the customer's investment.
All prices are inclusive of VAT at 0% (reduced rate for qualifying energy-saving materials under HMRC Notice 708/6). The Boiler Upgrade Scheme grant is applied directly by Infinity Renewables Group Ltd as your MCS-certified installer — you pay only the net amount shown below.
| Item | Description | Amount (inc. 0% VAT) |
|---|---|---|
| 1. Heat Pump Unit | Mitsubishi Ecodan PUZ-HWM140VHA 14kW R32 Zubadan Monobloc — supply & installation, including FTC6 flow temperature controller (PAC-IF073B-E), MELCloud Wi-Fi module, magnetic system filter and commissioning | £6,200.00 |
| 2. Hot Water Cylinder | ASHP-rated pre-plumbed unvented cylinder 250L with large internal coil, immersion heater, temperature sensors, and pressure relief — supply & installation | £1,980.00 |
| 3. Pipework & Hydraulics | Primary pipework, insulated flow & return connections, flexible hoses, isolating valves, expansion vessel, pressure gauge assembly, and system fill point | £1,420.00 |
| 4. Electrical Works | Dedicated consumer unit / RCBO protection for ASHP, cable from consumer unit to outdoor unit and indoor controls, earthing, surge protection. NICEIC certified. EIC issued on completion | £1,100.00 |
| 5. Radiator Upgrades | Supply & installation of upsized K3 / K2 radiators in Kitchen, Living Room, Bedroom 4, Primary Bedroom 1, Bedroom 2, Dining Room; new radiators in Bathroom (FF) and Laundry Room. Includes new ASHP-compatible TRVs throughout | £3,640.00 |
| 6. System Flush & Chemical Treatment | Full power-flush of existing heating circuit, magnetic filter installation, inhibitor dose, system water test, and MCS commissioning report | £680.00 |
| 7. Controls & Commissioning | Weather compensation set-up, zone controls, programmer, balancing of all radiators, legionella pasteurisation schedule configuration, MCS commissioning document, handover & user training | £820.00 |
| 8. Scaffolding / Access | External access if required for outdoor unit positioning on stone wall — to be confirmed on site | £0.00 |
| 9. MCS / DNO Administration | MCS certificate application, G98 DNO notification, Building Regulations notification via NICEIC, EIC, HIES guarantee registration, BUS grant application on customer's behalf | Included |
| Total Installation Cost | All works inclusive of 0% VAT (qualifying energy-saving materials & installation — HMRC Notice 708/6). Labour and materials included. | £16,840.00 |
The Boiler Upgrade Scheme (BUS) is administered by Ofgem and currently applies to properties in England and Wales only. Ballinloan House (PH15 2NN) is in Scotland. Scottish homeowners should instead explore the Home Energy Scotland (HES) grant and loan scheme, which offers up to £7,500 cashback plus an optional interest-free loan of up to £9,000 for qualifying heat pump installations — covering a similar or greater financial benefit. Infinity Renewables Group Ltd will assist with the HES application as part of the installation service. Please confirm current HES availability with Home Energy Scotland on 0808 808 2282 prior to proceeding.
Total inc. 0% VAT before any grant
Net cost with £7,500 BUS or HES grant applied
Estimated vs oil boiler running costs at current prices
Based on net cost after grant vs annual energy saving