Ducted (Air-Source) Heat Pump
Ducted Heat Pump Systems extracts heat from the air and transfers heat to either the inside or outside of your home depending on the season.
Winter – Heat pumps move heat from the cool outdoors into your warm house.
Summer – Heat pumps move heat from your cool house into the warm outdoors.
Ductless Heat Pumps (Mini Splits)
- Currently heat with electric baseboard.
- Wish to supplement existing boiler system.
- Don’t have a central air handling system.
Air-source heat pumps can be add-on, all-electric or bivalent:
All-electric air-source heat pump – Comes equipped with their own supplementary heating system in the form of electric-resistance heaters.
Bivalent heat pump – A Special type of heat pump, developed in Canada. It uses a gas or propane fired burner to increase the temperature of the air entering the outdoor coil. This allows these units to operate at lower outdoor temperatures.
How a Heat Pump Works:
THE HEATING CYCLE:
- First, the liquid refrigerant passes through the expansion device, changing to a low-pressure liquid/vapour mixture. It then goes to the outdoor coil, which acts as the evaporator coil. The liquid refrigerant absorbs heat from the outdoor air and boils, becoming a low-temperature vapour.
- This vapour passes through the reversing valve to the accumulator, which collects any remaining liquid before the vapour enters the compressor. The vapour is then compressed, reducing its volume, causing it to heat up.
- Finally, the reversing valve sends the gas, which is now hot, to the indoor coil, which is the condenser. The heat from the hot gas is transferred to the indoor air, causing the refrigerant to condense into a liquid. This liquid returns to the expansion device and the cycle is repeated. The indoor coil is located in the ductwork, close to the furnace.
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, the ability of the heat pump to absorb heat also drops.
At the outdoor ambient balance point temperature, the heat pump’s heating capacity is equal to the heat loss of the house.
Below this outdoor ambient temperature, the heat pump can supply only part of the heat required.
In heating mode without any supplementary heat, the air leaving a heat pump is cooler than air heated by a normal furnace. Furnaces generally deliver air to the living space at between 55°C and 60°C. Heat pumps provide air in larger quantities at about 25°C to 45°C and tend to operate for longer periods.
THE COOLING CYCLE:
- As in the heating cycle, the liquid refrigerant passes through the expansion device, changing to a low-pressure liquid/vapour mixture. It then goes to the indoor coil, which acts as the evaporator. The liquid refrigerant absorbs heat from the indoor air and boils, which becomes a low-temperature vapour.
- This vapour passes through the reversing valve to the accumulator, which collects any remaining liquid, and then to the compressor. The Vapour is compressed as its volume is reduced, causing it to heat up.
- Finally, the gas, which is now hot, passes through the reversing valve to the outdoor coil, which acts as the condenser. Heat from the hot gas is transferred to the outdoor air, causing the refrigerant to condense into a liquid. This liquid returns to the expansion device, and the cycle is repeated.
During the cooling cycle, the heat pump also dehumidifies the indoor air. Moisture in air passing over the indoor coil condenses on the coil’s surface. Then collected in a pan at the bottom of the coil. A condensate drain connects this pan to the house drain.
THE DEFROST CYCLE:
This frost buildup decreases the efficiency of the coil by reducing its ability to transfer heat to the refrigerant. To remove frost the heat pump will switch into the defrost mode.
- First, the reversing valve switches the device to the cooling mode. This sends hot gas to the outdoor coil to melt the frost.
- While this is happening, the heat pump is cooling the air in the ductwork.
There are 2 methods of defrost mode. Demand-frost controls monitor airflow, refrigerant pressure, air or coil temperature and pressure differential across the outdoor coil to detect frost accumulation on the outdoor coil.
Time-temperature defrost is started and ended by a preset interval timer or a temperature sensor located on the outside coil. The cycle can be initiated every 30, 60 or 90 minutes, depending on the climate and the design of the system.
Unnecessary defrost cycles reduce the seasonal performance of the heat pump. The Demand-frost method is generally more efficient since it starts the defrost cycle only when it is required.
Heat Pump Advantages:
Savings – You may be able to reduce your heating costs by up to 50 % if you convert from an electric furnace to an all-electric air-source heat pump.
Dehumidify – High-efficiency heat pumps also dehumidify better than standard central air conditioners, resulting in less energy usage and more cooling comfort in summer months.
Comfort – Heat pump systems deliver constant, even temperatures, and are quiet inside and out.
Durability – With routine maintenance, heat pump systems are typically durable and highly reliable. A properly maintained and installed heat pump can deliver service for 20 years or more.
Heat Pump Energy efficiency ratings: SEER and HSPF
- SEER (Season Energy Efficient Ration) – is the cooling efficiency, and ranges from 13 to the 20s (it’s rising as technology advances).
- HSPF (Heating System Performance Factor) – is the heating efficiency and ranges from 7.7-10.
For Canadians a higher HSPF rating will have a larger impact on yearly energy bills and cost of operation than what SEER ratings will.
FILTER AND COILS:
Inspect filters monthly, and clean or replace as required by the manufacturer’s instructions. Vacuum or brush clean the coil at regular intervals as indicated in the manufacturer’s instruction booklet. Hose down the outdoor unit with a garden hose. While cleaning filters and coils, look for symptoms of other potential problems.
Check the fan speed at the same time. Incorrect pulley settings, loose fan belts, or incorrect motor speeds in the case of direct drive fans can all contribute to poor performance.
Do not restrict airflow. Ensure vents and registers are clear of furniture, carpets or other items. Extended periods of inadequate airflow can lead to compressor damage.
You will need to hire a competent service contractor to do more difficult maintenance such as checking the refrigerant level and making electrical or mechanical adjustments.
Heat Pumps – Frequently Asked Questions
What temperature is a heat pump not effective?
Do you really save money with a heat pump?
With the added benefit of being able to cool your home in the summer months. Heat Pumps not only helps you save, but contribute to year round comfort.
How does my heat pump work with my other heat source?
During cold winter months (February & January) a power bill should be expected to rise as the system has less ideal temperature to run. The entire season’s results will show savings. Relative to outdoor temperature and where the heat from a system will travel, it may also be necessary to run heat sources (ex. Electric baseboard) in other parts of the home. Don’t worry, as these sources will only be supplementing at a fraction of their regular use. To some measure, heat from the ductless system will reach these areas, and less heat is produced by the alternative (such as electric baseboard) in order to reach a comfortable temperature.
We recommend all systems be shut off at -15°C (with the exception of our cold climate heat pumps), this will assist the lifespan of the unit as it works hardest during colder temperatures. This will also maintain efficiency of the unit, as at this temperature the cost of operation is the same as electric baseboards.
Why is my heat pump making a temporary rushing water/ crackling sound/ vibrating noise?
It is cold outside; why is my heat pump not working?
It may also make an unusual sound when this mode is activated. In this mode your heat pump may not appear to be pumping out hot air. If this is the case, it is best to leave the unit alone until it has gone through this cycle. If you know it is going to be cold and frosty overnight, you can be sure your system will go through at least one of these cycles. The colder the temperatures that a heat pump operates at, the more often defrost cycles must occur. The unit is removing frost and ice buildup, in order to run as efficiently as possible.
Should I turn my Heat Pump off at night?
Heat pumps are most efficient when they slowly maintain the temperature of the room. When a large difference in temperature is required (more than 1°C), compressors ramp up, and a heat pump will activate alternate/backup modes of heating in order to quickly achieve temperature.
It is possible to turn a heat pump down overnight. Program the system to drop 1°C every hour, and rise 1°C every hour to when you wake up.
Generally it is recommended to have the home stay a consistent temperature.
How often do I need to clean my heat pump?
E.T. Mechanical recommends becoming a club member to guarantee an annual visit by our technicians. This will help your unit to continue to run as specified and to its full capabilities.
For more information on how to best keep your filters clean see our user guide.
How high can I increase the temperature on my Heat Pump?
Why does my heat pump blow cold air when it starts/or runs?
Heat Pumps are designed to gradually rise to a desired temperature over a long period of Time with a small heat output and a large amount of air flow. A comfortable temperature could be considered 22°C, yet our body temperature is 37°C; because the Heat Pump is producing air potentially colder than our body temperature the outputted air could seem lukewarm or
even slightly cold to the touch. Don’t worry; this is part of its normal operation of being efficient and producing proper comfort.
What is that smell coming from my new heat pump?
After cooling season aux heating elements that have been unused for an entire season have been coated with dust, once auxiliary heat is initiated this dust burns off and has a temporary but distinct odor.
Do I need to clear the snow from around my heat pump?
What’s the whooshing sound coming from my ductwork?
operation. This is performed in the summer by closing registers in the cooler rooms downstairs, allowing cold air to reach the upper levels of a home. In the winter, closing registers in warmer rooms upstairs, allowing warm air to reach the lower levels of the home.
Why is my indoor fan running but my heat pump is off?
This energy saving feature is enabled when the fan is set to “Auto” mode. In addition, the fan can be set to run continuously in the “On” mode creating perpetual airflow through the ductwork, and to better mix air in the home providing more consistent temperatures.
Why is my Heat Pump steaming large plumes?
Why is my Heat Pump thermostat displaying aux/auxiliary heat?
Schedule a FREE Heating or Cooling Estimate
For E.T. phone 506-444-HOME (4663)