Heat Pumps Installation

What are Heat Pumps & How Do They Work?

Heating & Cooling using Heat Pumps

When exploring the heating and cooling options for a new house, or looking for ways to lower energy expenditures, on an older house, you may be considering a heat pump. Properly installed heat pumps can provide year-round climate control for your house by delivering warmth in the winter and cooler air in the heat of summer.

Overall, using only a heat pump for all heating needs may be uneconomical. However, when utilised with an wood, gas or electric fireplace, a heat pump can provide good heating / cooling in winter / summer respectively. If you already have an existing solid fuel heating system, installing a heat pump might be a cost-effective way to reduce your energy bills.

It is important to evaluate the costs & benefits before purchase. Heat pumps have lower energy costs than conventional heating and cooling systems, but they are more expensive to purchase. Weigh your anticipated fuel savings against the initial costs. It is also important to realize that heat pumps will be most economical when used year-round. Investing in a heat pump makes more sense if you are interested in both summer cooling and winter heating applications.

In addition to looking at cost, you should consider:

  • space requirements
  • power interruption regularity
  • are changes to your ducting system? needed
  • how much servicing will the system need

Becoming fully informed about all aspects of home heating and cooling before making your final decision is the key to making the right choice. The guys at Aeon Energy are happy to discuss heat pump installation and explain the types of heat pumps, and the factors involved in choosing, installing, operating, and maintaining your new heat pump.

Home Energy Management

Heat pumps are very efficient heating and cooling systems and can significantly reduce your energy costs. However, there is little point in investing in an efficient heating system if your home is losing heat through poorly insulated walls, ceilings, windows and doors, and by air leakage through cracks and holes.

In many cases, it makes good sense to reduce air leakage and upgrade thermal insulation levels before buying or upgrading your heating system.

Summer Cooling Adds to Energy Costs

Heat pumps supply heat to the house in the winter and cool the house in the summer. They require electricity to operate. If you add a heat pump to your heating system or convert from another fuel to a heat pump, and your old system was not equipped with central air conditioning, you may find that your electricity bills will be higher than before.

Heating / Cooling using a Heat Pump

A heat pump is an electrical device that extracts heat from one place and transfers it to another. The heat pump is not a new technology; it has been used around the world for decades. Refrigerators and air conditioners are both common examples of this technology.

Heat pumps transfer heat by circulating a substance called a refrigerant through a cycle of evaporation and condensation. A compressor pumps the refrigerant between two heat exchanger coils. In one coil, the refrigerant is evaporated at low pressure and absorbs heat from its surroundings. The refrigerant is then compressed en route to the other coil, where it condenses at high pressure. At this point, it releases the heat it absorbed earlier in the cycle.

Refrigerators and air conditioners are both examples of heat pumps operating only in the cooling mode. A refrigerator is essentially an insulated box with a heat pump system connected to it. The evaporator coil is located inside the box, usually in the freezer compartment. Heat is absorbed from this location and transferred outside, usually behind or underneath the unit where the condenser coil is located. Similarly, an air conditioner transfers heat from inside a house to the outdoors.

The heat pump cycle is fully reversible, and heat pumps can provide year-round climate control for your home – heating in winter and cooling and dehumidifying in summer. Since the ground and air outside always contain some heat, a heat pump can supply heat to a house even on cold winter days. In fact, air at –18°C contains about 85 percent of the heat it contained at 21°C.

An air-source heat pump absorbs heat from the outdoor air in winter and rejects heat into outdoor air in summer. It is the most common type of heat pump found in Canadian homes at this time. However, ground-source (also called earth-energy, geothermal, geoexchange) heat pumps, which draw heat from the ground or ground water, are becoming more widely used, particularly in British Columbia, the Prairies and Central Canada.

Here are some common terms you’ll come across while investigating heat pumps.

Heat Pump Elements

The refrigerant is the liquid/gaseous substance that circulates through the heat pump, alternately absorbing, transporting and releasing heat.

The reversing valve controls the direction of flow of the refrigerant in the heat pump and changes the heat pump from heating to cooling mode or vice versa.

coil is a loop, or loops, of tubing where heat transfer takes place. The tubing may have fins to increase the surface area available for heat exchange.

The evaporator is a coil in which the refrigerant absorbs heat from its surroundings and boils to become a low-temperature vapour. As the refrigerant passes from the reversing valve to the compressor, the accumulator collects any excess liquid that didn’t vaporize into a gas. Not all heat pumps, however, have an accumulator.

The compressor squeezes the molecules of the refrigerant gas together, increasing the temperature of the refrigerant.

The condenser is a coil in which the refrigerant gives off heat to its surroundings and becomes a liquid.

The expansion device lowers the pressure created by the compressor. This causes the temperature to drop, and the refrigerant becomes a low-temperature vapour/liquid mixture.

The plenum is an air compartment that forms part of the system for distributing heated or cooled air through the house. It is generally a large compartment immediately above or around the heat exchanger.

Other Terms

Btu/h, or British thermal unit per hour, is a unit used to measure the heat output of a heating system. One Btu is the amount of heat energy given off by a typical birthday candle. If this heat energy were released over the course of one hour, it would be the equivalent of one Btu/h.

Heating degree-days are a measure of the severity of the weather. One degree-day is counted for every degree that the average daily temperature is below the base temperature of 18°C. For example, if the average temperature on a particular day was 12°C, six degree-days would be credited to that day. The annual total is calculated by simply adding the daily totals.

kW, or kilowatt, is equal to 1000 watts. This is the amount of power required by ten 100-watt light bulbs.

ton is a measure of heat pump capacity. It is equivalent to 3.5 kW or 12 000 Btu/h.

The coefficient of performance (COP) is a measure of a heat pump’s efficiency. It is determined by dividing the energy output of the heat pump by the electrical energy needed to run the heat pump, at a specific temperature. The higher the COP, the more efficient the heat pump. This number is comparable to the steady-state efficiency of oil- and gas-fired furnaces.

The heating seasonal performance factor (HSPF) is a measure of the total heat output in Btu of a heat pump over the entire heating season divided by the total energy in watt hours it uses during that time. This number is similar to the seasonal efficiency of a fuel-fired heating system and includes energy for supplementary heating. Weather data characteristic of long-term climatic conditions are used to represent the heating season in calculating the HSPF.

The energy efficiency ratio (EER) measures the steady-state cooling efficiency of a heat pump. It is determined by dividing the cooling capacity of the heat pump in Btu/h by the electrical energy input in watts at a specific temperature. The higher the EER, the more efficient the unit.

The seasonal energy efficiency ratio (SEER) measures the cooling efficiency of the heat pump over the entire cooling season. It is determined by dividing the total cooling provided over the cooling season in Btu by the total energy used by the heat pump during that time in watt hours. The SEER is based on a climate with an average summer temperature of 28°C.

The thermal balance point is the temperature at which the amount of heating provided by the heat pump equals the amount of heat lost from the house. At this point, the heat pump capacity matches the full heating needs of the house. Below this temperature, supplementary heat is required from another source.

The economic balance point is the temperature at which the cost of heat energy supplied by the heat pump equals the cost of heat supplied by a supplementary heating system. Below this point, it is not economical to run the heat pump.

Efficiency Terminology

The efficiency ratings for different types of heat pumps use different terminology. For example, air-source heat pumps have seasonal heating and cooling ratings. The heating rating is the HSPF; the cooling rating is the SEER. In the manufacturers’ catalogues you may still see COP or EER ratings. These are steady-state ratings obtained at one set of temperature conditions and are not the same as the HSPF or SEER ratings.

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