Discover how gas heat pumps can help you achieve excellent efficiency and low running costs with your home heating and cooling needs. Check out the advantages and disadvantages of gas-fired heat pumps and how they compare to electric types.
Gas-fired air conditioning was widespread over fifty years ago, but it lost its popularity because of low efficiencies and the higher cost to buy and install systems. Electrically powered heat pumps became popular because they were more efficient and they consume less energy. They are also cheaper to buy, install, and run. However, in some cases, electric heat pumps are less well suited to larger homes, which often require zoned temperature control, so the latest natural gas-fired heat pumps are gaining popularity.
Advances in natural gas cooling technology have developed natural gas-fired heat pump systems, specifically for use in larger residential properties. This is a direct result of the growth in the size of new homes. The average home is now 2000 sq. ft., with more than 10% of new homes in the 4000 sq. ft. plus range, where standard heat pumps are often not ideal.
Absorption heat pumps are air-source units powered by natural gas, propane, solar, or geothermal heated water instead of electricity, but because natural gas is the most commonly used power source, they are usually known as gas-fired heat pumps.
They work in a different way to an electric heat pump, but they don't use ozone-damaging refrigerants under high pressure. Instead, they use ammonia as a natural refrigerant with water as an absorber.
A gas-fired absorption heat pump incorporates a generator, and an absorber, which combined is called a thermal compressor. This replaces the electric compressor, which is standard in air conditioning and heat pump systems. Using a pump rather than a compressor makes greater efficiency and lower running costs achievable.
An ammonia and water solution is heated by gas in the generator to raise the pressure. This results in the ammonia separating into a vapor, leaving a weak ammonia/water solution.
This solution passes into the absorber unit, and the ammonia vapor is pumped through the condenser, where it condenses as it passes through, releasing its heat into the room.
As the heat dissipates, the ammonia becomes liquid again but remains under high pressure. It then passes into the evaporator unit via an expansion valve, which lowers the pressure as it passes through. Reducing the pressure lowers the temperature at which the ammonia will boil. It passes into the evaporator, and returns to a vapor, evaporates, and quickly becomes very cold, pulling heat from the surrounding air, which drops in temperature as the solution gets warmer.
The warmed ammonia vapor passes back into the absorber unit, where it re-recombines with the weak ammonia/water solution. It returns to a liquid and discharges any remaining heat into the system.
The re-combined ammonia solution returns to the generator unit, where the cycle starts over.
An available addition to a natural gas-fired heat pump today is a heat exchanger system [GAX], which harvests the heat given off by the generator and absorber units when it heats the ammonia to separate it from the water. This increases the overall efficiency of the process.
Electric systems can struggle to deliver adequate levels of heating, especially in extremely cold weather. Weather conditions, which are outside of our direct control, influence air source heat pumps. Inevitably their efficiency will vary according to the prevailing conditions. In a moderate climate, they will work efficiently and provide cooling and heating to keep your home comfortable all year.
In more extreme conditions with freezing winters and hot, humid summers, electric heat pumps may struggle to cope. The benefits of a gas-fired unit will become evident when the temperature plummets and the amount of available warmer air lessens. An electric heat pump will have to work extra hard to operate efficiently, which in turn means higher power costs and wear to your equipment as it will be running flat out to cope.
A natural gas-fired heat pump is an excellent choice, especially if you have a larger home (4000sq ft +). It will deliver greater efficiency in heating and cooling over a larger area, with the benefits of zone control.
They will also deliver greater efficiency, especially in areas where temperatures are extreme. The cost to buy, install and run is higher, but the benefit of having a system that will deliver a comfortable living environment year-round, no matter what the weather does, may offset the higher initial higher costs.
For most of us living in average homes in moderate climates, the standard electric air source heat pump should fulfill your requirements perfectly and provide you with excellent efficiency and low running costs. However, if your requirements dictate you need something more powerful, then a natural gas-fired heat pump could be your ideal choice.
In every case, you should consult a professional HVAC technician from a reputable company to discuss your specific requirements in detail and offer guidance and advice. You know it makes sense.