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Ask whether their kit is Kraken compatible for when Octopus take over the universe. I personally paid for a propane heat pump on the basis it is more efficient in cold weather than a standard R32 or R400 series refrigerant. We are still getting a CoP of about 6 even with temperatures dropping to near zero overnight.
A couple of bits dud annoy me about our install though. The first being that we had to replace a perfectly fine 250litre Worcester Bosch hot water tank as they wouldn't guarantee the system without replacement. The existing tank had as good insulation and basically the same coil area as the new one. Grr.
Second point was that they ended up having to run large bore (mebbes 30mm) pipes to and from the heat pump up into our loft to the balance tank they also installed. I know that the heat pump circulates hot water at a quicker rate than a gas boiler, but why don't they just stick in a more powerful pump so it copes with the increased pressure drop? It means we have two ugly lagged pipes running up the entire side of our house, instead of them just popping through the wall to the conveniently placed supply and return pipes from the old boiler. Also Grr.
edit - others more relevant
Thanks all. Appreciated. We’ll see what they have to say. ?
Second point was that they ended up having to run large bore (mebbes 30mm) pipes to and from the heat pump up into our loft to the balance tank they also installed. I know that the heat pump circulates hot water at a quicker rate than a gas boiler, but why don’t they just stick in a more powerful pump so it copes with the increased pressure drop?
It’ll be 28mm probably, or, 35mm pipes. They need to be that size to be able the transfer the heat at an efficient level. Gas boilers probably run the water at a similar speed, it is the difference between the flow and return temperatures that determine the pipe size. Gas boiler have at least 10 degrees difference between flow and return, and usually 20 degrees. Heat pumps want a 5 degree difference.
Because of the small difference, it impacts on the heat given out by the radiators by both having a lower flow temperature, and the flow/return being a lot closer. Yes, pump speed can be increased, but that causes more problems. The typical pump speed is 0.9 metres per second for a well deisgned system. It can be a bit either way, but 0.9mps is a good compromise. If its slower, the flow/return temps will have a larger spread, as the water is out at the rads for longer, but less heat is put out, as the water speed cannot transfer all of the heat from the heat source. Doubling the pump speed increases the internal pipe friction by 4 times,the pump consumes 8x more power, it can get noisy, and will wear out quicker.
So, keeping 22mm piping (at more than 6kW output power) will limit the output at the Heat Pumps most efficient range, and is pretty much a Manufacturers requirement, as all of the ones I’ve dealt with require a minimum of 28mm primary piping. Sticking it on 22mm piping will invalidate any warranty if it ever goes wrong.
Coming up to a week after signup now (tomorrow). I've had an 'Introducing' email for the installer from HG but radio silence from the installer themselves.