Air Conditioning
Air conditioning units must not be operated when the exterior temperature is less than about 16 degrees Celsius or 61 degrees Fahrenheit or terminal damage may be caused to the compressor.
Fault conditions cannot always be determined or recreated by running the unit for a few minutes. You may for instance have to run the unit for several hours before the fault condition occurs. Unless the unit is running at the time of the inspection, a typical home inspection test may only be for ten minutes or so (to let the unit come up to operating temperature).
Be sure to read and comply with the manufacturer’s instructions before each summer start up, or serious damage may occur.
We recommend that all air conditioning units are serviced regularly and that you take advantage of one of the many service contracts that are available.
Winter conditions prevent the testing of air conditioning units or the cooling feature of heat pump systems. You must arrange to have a service engineer test and examine the units before use during the next cooling season.
The plastic or vinyl covers often supplied with air conditioning units are not recommended for use in colder climates.
During the winter months, moisture tends to rise inside the covers where it has no means of escape. This can cause rust to the cabinet and other metal parts inside.
We recommend that you cover the top of the unit with a piece of plywood, weighted down with some bricks or rocks. This allows air circulation while still preventing snow from building up inside or on the fan blades.
When a house is equipped with individual through wall units, be sure that your contract specifies whether these air conditioning units are to be included, or not.
Air Conditioning
Air conditioning units are either water cooled or air cooled.
They work by dehumidifying the air inside the house and discharging the moisture into the stone under the building or into a drain. In the course of drying the air, the temperature is reduced and the combination of drying and a lower temperature creates the air conditioning effect.
Service all air conditioning and heat pump systems annually. Service agreements are recommended for all units.
Its important that all units are level. The speed of the fan rotation on tilted units can cause premature wear to the bearings.
Many air conditioning or air source heat pump systems have the insulation missing from the supply pipes between the exterior unit and the house wall. This lowers the efficiency, as does any significant fin damage to the exterior coils.
Exterior temperatures below about 16 degrees Celsius (61 degrees Fahrenheit) prevent use or testing, because of the possibility of damage to the compressor. If the temperature is below this point – do not start up the air conditioner. The compressor is the most important and most costly to replace.
Heat Pumps
Consider this:
A refrigerator cools the inside (to keep the food cold) and dumps the heat out the back into the coils. Feel the back of your fridge and it will be warm.
Similarly – an air conditioning unit cools a unit called an A coil, in the ducts just above the furnace and dumps the heat outside.
Now suppose you could reverse the process – making the outside cold and dumping the heat inside. You could heat your home that way.
And that’s how a heat pump works – it takes heat from the air, the ground or from well water and dumps it into the house ducts. Remembering back to your Physics 101 you will (hopefully) recall that you can remove heat from things right down to absolute zero.
So even though water might be at 48 degrees Fahrenheit or air at minus five, we can still extract some heat from it and move it into the house.
Then in the summer – a special reversing valve allows us to move heat from the house – outside – which is of course -air conditioning.
Heat pumps are expensive to buy but they have low running costs. You need to be careful about buying one in replacement for a more typical furnace or for a new home, as it may take you many years to recover the capital cost by way of heat cost savings.
Ensure all heat pumps are serviced annually. Take advantage of one of the service contracts available.
Most heat pump systems have an electric back up installed into the furnace ducts. Typically its called a plenum heater and acts like a small electric furnace.
The plenum heater kicks in whenever the heat pump cant keep up with the heat demand (when you suddenly crank up the thermostat by ten degrees for instance) or when the heat pump is in defrost mode.
Because a heat pump uses low grade heat – it needs to run a lot of the time and for that reason, you cant use it with a programmable thermostat.
