Sean Houlihane

As of today, I have an air-source heat pump replacing my old storage heater system. The old system needed replacing anyway since it was not at all flexible to use. The property is 81sqm bungalow, 1970′s construction with 270mm loft insulation.

The new system consists of:

• 7.1 kW nominal output heat pump
• Unvented solar+heap pump cylinder
• 8 radiators
• Weather Compensation controller from Hitachi

Total installed cost £8500 plus vat (minus £800 RHI payment).

After some comissioning problems (air in the pipes, blocked strainer) there were still some teething problems due to overheating.

Step 1) Put the pump into local, then test mode, Sw 1-3 on, PU displayed. Hold both push buttons for 3 sec. Pump comes on, helps to clear out airlocks.

Step 2) With pump in normal mode, check th (without a dot). This is the target set point, and was 60 degrees, same as the shur-off temperature.

I had issues with the set point commanded by the controller, and had to reduce DHW offset and compensation factor to reduce the set point on the heat pump to below 55C. Oddly, the SSUP parameter on the controller was always lower.

See sidebar link for full installation details