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.

Being without gas in my village, and currently using storage heaters, I have been tempted to replace my heating system for a while. After trying 3 installers (one can’t be bothered to show, the other wants me to install Solar, then an electric boiler and rads!) I finally get a quote but for a high temperature system.

Air Source heat pumps extract between 2.5 and 5 units of heat whilst using one unit of electricity, but they get less efficient when it is cold, and when the output temperature is high. Typically, they generate water at 35 celcius and this is too low for radiators to be very effective. It is also not really very good for hot water.

The Daikin Altherma HT has a two stage heat pump, and runs at up to 80 celcius. A seasonally averaged COP of 3 (for an output temp of 60C) doesn’t seem too bad, but I need to compare this like for like against a cheaper, simpler low temperature system.

So far, the installer and Daikin have both failed to come up with any data. They are pretty stupid if they think this ought to be secret/proprietary because I am fairly sure even I can make a stab at estimating it with access to an installed unit.

I’ve owned this car since 1998, and it was the 2nd Rx7 I bought – initially only as a short term thing since i kept the 1st gen I had. Some background is on my other website, which was one of the first UK based rotary websites.

Price £700
Tax 11/11
MOT 09/11
174,000 miles, but the engine was replaced at about 130,000 miles with a brand-new one.

Gearbox, turbo, roof and various other parts have been swapped from a donor car which had done about 70k miles (and the car has done maybe 10k since then)

Bluetooth Hands free/USB MP3 playing stereo (Blaupunkt Hamburg MP57)

Exhaust is new-ish all stainless.

Paint on the boot has peeled off, been resprayed, and not stuck too well. Also some paint peeling off the driver’s door. Doors are a little rusty although this is mainly just showing as marks on the sills.

Location Cambridge/Royston. Selling since I have bought a new CRZ, and I don’t need two fun cars, plus I no longer have time to maintain the RX7.

The passenger wing mirror is a replacement (painted red). The original is available, and just needs new glass. It hit the garage door on the way to it’s last MOT.

Click on the photos to see more from an album at picassa.