Air Source Heat Pumps

Chrislincs wrote: »

Hi again,
Just back from the Build and renovate show at NEC armed with many brochures, I've had many questions answered but now have new ones. Above E7 usage is mentioned, and was brought up by a salesman of pumps (Trianco, I think) but he waffled rather than clarified how and what for. He used the word storage of heat produced but didn't elucidate the point.

I didnt' go for the Trianco system because IIRC it doesn't operate below -5degC and thus, whilst ok for 99% of the year, I just felt that I didn't want it operating at near it's minimum range during winter when the temperature hovers around freezing. The Mitsubishi system I got operates down to -20degC.

Other displays stated that pumps could be sited in the loft - why is this not generally considered when it would elminate the problems of distance from the tank, and the air always warmer?

I was also told this when I bought my system, but it doesn't work. We had to temporairly install ours in our conservatory for a few weeks for various reasons and the reason it won't work in a conservatory or loft is this:

A heat pump draws warm air in the back, extracts the warmth out (and directs it into your house) and blows cold air out the front. It is assumed that you have access to an unlimited supply of warm air, which you only get outside as the fan in the heat pump blows the cold air away from the HP so new warm air can be drawn in. If you install it in your loft, you are effectively putting you HP in a big box. Whilst it is initially warmer in your loft, your HP will rather quickly remove all that warm air and replace it with cold air. As a loft doesn't have many drafts, that cold air then stays in your loft and just gets recirculated through your HP, whilst the tempeature in your loft will get lower and lower...

We found that our single glazed conservatory is normally around a few degrees warmer than outside, after about an hour of HP operation, it droped to many degrees colder than outside, thus making it less efficient, caused water pipes to freeze, massive amounts of condensation and created a higher temperature differential between inside the house and the conservatory.

So when a salesman tells you that it is warmer in a loft and thus the HP will work better, that is only true for about the first hour of operation. (Unless you have a highly ventilated loft).

Imagine what would happen if you put a fridge in a box, the box would get warmer and warmer, and the fridge would have to work harder and harder to keep the inside of the fridge cold, thus causing the box to get even warmer, thus causing the fridge to work even harder etc...