Heat pump efficiency for air conditioning

Press, 30 April 1981, Page 25

Heat pump efficiency for air conditioning

Air to air heat pumps have now advanced to the stage of btdng highly - competitive with the longer established heating methods. They are easily installed and, above all, are superefficient. This, means they ’'cost much less to run for a given heat output. The principle they work on is that used in a refrigerator, only in reverse. Using electrical energy to drive pump and fan, they draw heat from the atmosphere and transfer it indoors. Or they can be switched over to have the opposite effect in summer, when they are extremely effective, as cooling units. As a heater, the heat pump takes advantage of the fact that even cold outdoor air contains Treat that can be . recovered. Liquid refrigerant Is supplied to the outdoor moil where Tt evaporates, returns to the comand is discharged to the indoor coil. : Thewapour then condenses in the indoor coil, gives > dp its ■ heat to the indoor air stream and returns to the outdoor coil.

Since it recovers heat, instead of producing it, the heat pump can release into the conditioned space far more energy than it uses. In fact, it can usually release two to four units of heat energy for every unit of electrical energy it consumes.

"Carrier” systems can be 120 per cent efficient even when the outdoor air temperature is down to minus 28 degrees. At minus 8 degrees they use 6.4 kilowatts of electricity and produce 15.6 kilowatts of heat.

The exact savings made with a heat pump depend on such variables as climate, heating requirements and energy costs, but the average heat pump is 280 per cent efficient which must provide considerable savings on running costs. At the same time, the heat pump is absolutely messfree.- there is no fuel storage involved and the unit itself is a neat package that takes up little space, even in split system form. The space saying advantage is spectacular when a

comparison is made between a . ducted heat pump system and a fully ducted oil or gasfired heating system. In addition, the heat pump also provides cooling in the summer. .

Another big advantage is that since the energy used for .a given heat output is relatively small, the heat pump can be a way of getting round having to upgrade electric mains where a premises has been extended. Particularly helpful for an office is the fact that a heat pump air conditioner keeps the air temperature and humidity at a comfortable level, avoiding the need for open windows. This means there are no draughts to scatter papers and outside noise is shut out. The unit itself operates with a gentle purr of air movement.

. The ducted heat pump system for total air-conditioning is a split system —- one part indoors (maybe in the ceiling) and one outside — but usually the pump chosen to serve just one or two rooms is a self-contained unit set on a walk or in a window. The only piping required with it is a condensation drain.

In the home, a further heat

pump advantage is that the equipment runs at a temperature safe to touch. There is no fire risk or danger to children.

As an additional "bonus,” the heat pump can serve as a super-booster for water heating — another saving against the electricity bill.