Air source heat pumps can provide a more energy-efficient alternative to conventional heating systems in households and have been proven to be a reliable way of heating a home.
Air source heat pump heating systems work slightly differently to traditional heating systems in that they extract and release heat more slowly, and at lower temperatures.
This means that heat pump heating systems may need to run for longer periods of time to get the same desired heating effect, and air to water heat pumps should be paired with large surface area devices such as underfloor heating and larger, modern, radiators to efficiently release this heat around a whole home.
An air source heat pump can heat a whole house if the outdoor unit is appropriately sized and there’s a sufficient heating system installed indoors. The size of heat pump required to heat a home can be determined by several factors, including how big the property is.
Our air source heat pump provides both heating and hot water to the whole of our house.
It was installed when the house was built and so both the external heat pump unit shown above, and the internal apparatus was sized appropriately for the size of house.
In this article we discuss more about how our air source heat pump can heat our whole house, detail how air source heat pumps work, the importance of choosing the right size heat pump and the factors that can determine their size.
It can be possible to have an air source heat pump system that serves a whole house.
Air source heat pump installations typically provide the required heating, cooling and/or hot water for a whole household and can entirely replace any existing systems.
In general, the size of a home determines the size of the air source heat pump required to heat it.
The larger the house, the bigger the air source pump that will need to be installed. However, it’s also import that a heat pump system remains energy efficient by ensuring it’s not oversized, as well as not being undersized.
There are several rules and guidelines that can help to determine the ideal and most energy-efficient pump. For example, if a 100-square meter (1,076.4-square foot) house can require a 6kW air source heat pump, a 200-square meter (2,153-square foot) house can need as much as a 12kW heat pump to heat the whole house.
The size and power of heat pump can determine if it will be able to heat a whole house.
If an air source heat pump is sized too small, it can struggle to keep up with demand for heating (and also potentially hot water) and be less energy-efficient because it’s working overtime.
Repair and maintenance costs can also increase because of the increased operating times.
On the other hand, if a heat pump is sized too big, it can be more expensive and energy-consuming, also reducing its efficiency.
For these reasons, it’s always best to install the correct size heat pump for the size of home.
An installer will be able to design a system for your home and particular requirements where the whole house can be heated, and the right size of outdoor heat pump unit is used.
Our air source heat pump (ASHP) is sized correctly for our 5-bedroom home.
It can therefore keep up with our demand for heating and domestic hot water when required and is more energy efficient when demand is lower.
There are two popular methods professionals use to size heat pumps in the HVAC industry.
These two methods are Manual J and square footage.
Manual J is the standard and most popular method of heat pump sizing, developed by the Air Conditioning Contractors of America. It uses eight parameters to determine the ideal heat pump size for a home.
These parameters are:
- Your local climate and the number of days you need heating and cooling throughout the year. You’ll likely need a higher heating output if you live in a colder climate.
- The general layout of your home, including the shape and square footage.
- The number of windows and where they’re installed.
- Your home’s air filtration direction and effect.
- The quality of insulation in your home.
- The number of people living in your home.
- The temperature preferences of the occupants of your home.
- The number of heat-generating appliances in your home, including washing machines, ovens, etc.
These eight factors are more complex than they appear, so it’s always best to work with an installer to determine the ideal size of your heat pump, whether that’s through the Manual J method or not.
This method can be less complicated than the Manual J and is more useful for non-experts. As the name suggests, it uses the square feet of your home to help you choose the correct size heat pump.
The following is a summary of the guidelines behind the Square Footage Method:
- 500 square feet (46.45 square meters) of your home requires a 1-ton capacity (12,000 BTU).
- 1000 square feet (93 square meters) will require 2 tons (24,000 BTU).
- 1500 square feet (139.35 square meters) requires 3 tons (36,000 BTU).
- 2000 square feet (185.8 square meters) requires 4 tons (48,000 BTU).
- 2500 square feet (232.3 square meters) requires 5 tons (60,000 BTU).
- 3000 square feet requires (278.7 square meters) 6 tons (72,000 BTU).
Once you know the square feet of your home, you can look for an air source heat pump with the corresponding capacity. However, you may still want to consult an expert to avoid choosing the wrong heat pump.
Our air source heat pump is a 11.2kW (38,000 BTU) maximum rated heating capacity appliance, correctly sized to provide both heating and hot water for our whole home.
The capacity output and size of our heat pump was based on factors such as the climate we live in (mild UK climate), the floor space, number of occupants, and more.
When looking to size the right air source heat pump to heat a whole house, it’s important to understand how they work.
An air source heat pump absorbs heat from a colder environment and transfers it into your house, raising the temperature. They function similarly to refrigerators but in reverse.
This heat absorbed from outside air may then be used for heating radiators and underfloor heating systems. You can also use them to provide hot water or air convectors in your home.
An air source heat pump system typically consists of a compressor and heating coils.
The refrigerant flowing through a heat pump absorbs the heat energy of the outside air and the low boiling point means that it can be converted to a gas. A compressor further increases pressure and therefore temperature; allowing a heat pump to get the most amount of heat from the air.
Heat is expelled indoor for use as either water heating, air heating or for domestic hot water. The refrigerant returns to a liquid as pressure and temperature decreases as it loses heat and goes through an expansion valve, before the cycle is repeated.
There are a few more things to consider when purchasing a new heat pump once you’ve determined the ideal size. Here are some other things to keep an eye out for:
- Energy Efficiency Ratings: Some of the most important things to check for are the SEER and HSPF. You should aim for a higher rating for better efficiency.
The efficient of our heat pump is stated by the Coefficient of Performance (COP). A higher COP, or any other rating, can mean more heat is generated from the electricity consumed.
An air source heat pump that’s sized correctly for heating the size of house can be running more efficiently at the upper end of these efficiency ratings.
- Blower Motor Type: There are different blower motor types, including fixed speed, multi-speed, variable speed. The type of blower can also affect the efficiency of the heat pump.
An air source heat pump can heat a whole house. However, it will have to be sized correctly based on the size of the house, climate, and demand, among other factors.
Larger properties will typically require larger sized air source heat pumps with greater heating capacities.
In many cases, it’s best to seek the help of an installer to choose the correct size and type (air to air or air to water) of heat pump that can heat your whole house. However, you can start a preliminary search on your own to get a sense for what you might need and how much it’ll cost.