Air Source Heat
Pump FAQ Technical Hub

Before installation, your home must have the correct electrical supply for both the outdoor unit and indoor equipment.

See pages 11 & 12 of site preparations document for more information.

A. Outdoor Unit (Heat Pump)

• Must have its own dedicated earthed circuit from the fuse board (no shared circuits).

• Correct fuse / breaker:
  
  • 6 kW → 16 A Type B
  • 10 kW → 20 A Type B
  • 14 kW (single phase) → 32 A Type B
  • 14 kW (3-phase) → 16 A Type B 3P+N

• Armoured supply cable:
  
  • 6 kW: 3-core (3×2.5 mm²)
  • 10 kW & 14 kW: 3-core (3×4 mm²)
  • 14 kW 3-phase: 5-core (5×2.5 mm²)

• An isolated rotary switch must be fitted on the outside wall near the heat pump.
• All work must comply with BS 7671 standards.

B. Indoor Equipment

• Cylinder + Thermostat: Dedicated 16 A Type B RCBO circuit.
• Buffer Tank Immersion: Separate 16 A Type B RCBO circuit.
• Armoured 3-core cable (3×2.5 mm²) for the indoor supplies.
• Connections use 20 A double-pole contactors and fuse spurs.

Important If your existing fuse board or meter cupboard does not meet these requirements, Adlår will pause installation until it is upgraded. We can carry out the electrical work for you if requested.

Contact us on 01252 268 669 for a pre-survey or advice.

Before your Adlår Castra heat pump can be installed, a pre-survey is carried out to make sure your site is fully prepared.

Key checks include:

• Location & Clearances Suitable outdoor space with good airflow and correct distances from walls, windows, and neighbours.
• Mounting & Base Solid, level base or bracket with proper condensate drainage.
• Plumbing & Ducting Pipework, cold feed, PRV, and external air intake/exhaust ducting ready.
• Electrical Supply Dedicated circuits from the fuse board for the outdoor unit and indoor equipment (correct fuse ratings, armoured cables, rotary isolator switch, and full BS 7671 compliance).

Important If any of these are not ready, installation will be paused until the work is completed. Adlår can carry out the electrical upgrades for you if requested.

Full checklist Download the complete Adlår Castra Pre-Survey Checks PDF here: 

Contact us on 01252 268 669 to book your pre-survey.

Before your Adlår Castra heat pump can be installed, the following site preparations must be completed:

Key requirements:

• Outdoor Unit Location & Clearances Place the unit outside with good airflow. Keep it more than 5 m from neighbours’ windows. Minimum clearances: 50 cm (one side), 30 cm (sides), 100 cm (top), 30 cm (front), 20 cm (base).
• Base & Mounting Install on a solid, level base (concrete slabs on soft ground or drainage tray on hard surfaces). Ensure good condensate drainage to prevent ice or slip hazards.
• Plumbing Pre-install flow/return pipework, hot/cold water connections for the cylinder, PRV pipework, and balancing valves.
• Air Ducting Prepare external air intake and exhaust ducting in advance (wall, loft, or roof venting). Ducts must be correctly sized and terminated outdoors.
• Electrical Supply Dedicated circuits from the fuse board for the outdoor unit and indoor equipment (correct fuse ratings and armoured cables for your model). An isolated rotary switch must be fitted outdoors.

Important If the site is not fully prepared, installation may be delayed or additional charges could apply. Adlår can carry out electrical upgrades if requested.

Full checklist Download the complete Adlår Castra Site Preparations PDF here