902 868-1324
mannmechanical@gmail.com
Air-source Heat Pumps
Air-source heat pumps draw heat from the outside air during the heating season and dump heat outside during the summer cooling season.
The most common type of air-source heat pump is the air-to-air heat pump. It extracts heat from the air and then transfers it to either inside or outside your home depending on the season.
Benefits of installing an air-source heat pump:
Typical savings on yearly heating cost - 40 % or more
Savings on home insurance
Better for the environment
No oil smells or spills
Efficiency
Year round comfort- provides cooling in the summer and heating in the winter
Less space required than geothermal unit
Less disturbance for your home and grounds than a geothermal unit
Quiet
How Does an Air-source Heat Pump Work?
The Heating Cycle
During the heating cycle, heat is extracted from outdoor air and pumped indoors.
The ability of the heat pump to transfer heat from the outside air to the house depends on the outdoor temperature. As this temperature drops, so does the ability of the heat pump to absorb heat (the unit's capacity).
The Cooling Cycle
The heating cycle is reversed to cool the house during the summer. The unit takes heat out of the indoor air and transfers it outside.
During the cooling cycle, the heat pump also dehumidifies the indoor air. Moisture in the air passing over the indoor coil condenses on the coil's surface and is collected in a pan at the bottom of the coil. A condensate drain connects this pan to the house drain.
The Defrost Cycle
If the outdoor temperature falls to near or below freezing when the heat pump is operating in the heating mode, moisture in the air passing over the outside coil will condense and freeze on it. The amount of frost build-up depends on the outdoor temperature and the amount of moisture in the air.
This frost build-up decreases the efficiency of the coil by reducing its ability to transfer heat to the refrigerant. At some point, the frost must be removed. To do this, the heat pump will switch into the defrost mode.
Life Expectancy and Warranties
Air-source heat pumps have a service life of between 20 and 25 years. The compressor is the critical component of the system.
HRV - Heat Recovery Ventilators*
Although
your HRV should have been balanced during installation, it is a good
idea to have the system checked by a qualified contractor once a year
Components of an HRV System
An HRV system generally consists of the following equipment:
* Insulated ducts for incoming (fresh) and outgoing (stale) air, along with exterior hoods;
*Ductwork to distribute fresh air throughout the home and to return stale air to the HRV;
*Fans to circulate air throughout the home and to exhaust stale air to the outdoors;
*A heat-exchange core, where heat is transferred from one air stream to the other;
*Filters to keep dirt out of the heat-exchange core;
*A
defrost mechanism (some units use a preheater) to prevent freezing and
blocking of the heat-exchange core when the temperature of the incoming
air is cold;
*A drain to remove any condensation from inside the HRV (may not be required with all models);
*Operating controls to regulate the HRV according to ventilation needs.
During
the heating season, an HRV recovers heat from the outgoing, stale
household air and uses it to preheat incoming, fresh outdoor air. The
HRV then distributes the incoming air throughout the house.
Air Distribution
There
are two standard ways to distribute fresh air throughout the home –
through ductwork installed specifically for the HRV (direct ductwork) or
through the ductwork of a forced-air furnace system.
The Need for a Balanced System
HRVs
are designed to operate in a balanced state – the same amount of air
should be drawn into the home as is being exhausted. An unbalanced
system results in poor airflow and poor heat recovery and can lead to
other problems, including an undesirable, continuous air-pressure
difference between the inside and outside of your home.
Withdrawing
more air from the house than comes in creates excessive negative
pressure. This can cause spillage of carbon monoxide and other
combustion by-products from fuel-burning appliances (e.g., a furnace,
water heater or fireplace). Instead of leaving the house via the
chimney, these combustion by-products can be pulled back into the house
where they may be inhaled by occupants. Negative pressure can also
increase the rate of entry of undesirable gases and moisture from the
soil surrounding the basement. Either scenario can threaten the health
of the occupants.
Pulling
more air into the home than is exhausted, or excessive positive
pressure, can cause moist air from the home to be pushed into the walls
and roof of the house, where it can condense and lead to deterioration
of the building materials. This hidden problem often goes undetected
until severe damage has been done. As well, moisture escaping through
exterior door locks can freeze the lock mechanism, making it difficult
to enter or leave the house. An imbalanced airflow can also cause the
HRV core to develop frost or freeze, restricting or completely blocking
further airflow.
*Information from Natural Resources Canada www.nrcan.gc.c