Ground source heat pumps
Ground-source heat pumps extract heat from the ground – and in cold climates this is more efficient than extracting it from the air like a conventional heat pump. But there are catches.
Heating & Energy
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The right information is essential when choosing a heat pump. Our guide takes you through finding the right type and size to considering reliability and installation. Then use our databases of models to find one with the right price, specifications and features for your needs.
Snapshot: The Carrier 42NQV025H-A /38NYV025H-A is a small wall-mounted heat pump that uses R410A refrigerant. But how efficient is it at heating your home?
Snapshot: The Carrier 42NQV035H-A /38NYV035H-A is a medium-sized wall-mounted heat pump that uses R410A refrigerant. But how efficient is it at heating your home?
Snapshot: The Carrier 42NQV045H-A /38NYV045H-A is a medium-sized wall-mounted heat pump that uses R410A refrigerant. But how efficient is it at heating your home?
Snapshot: The Carrier 42NQV050M-A /38NYV050M-A is a medium-sized wall-mounted heat pump that uses R410A refrigerant. But how efficient is it at heating your home?
Snapshot: The Carrier 42NQV060M-A /38NYV060M-A is a large wall-mounted heat pump that uses R410A refrigerant. But how efficient is it at heating your home?
Snapshot: The Fujitsu ABTG18LVT is a medium-sized floor-mounted heat pump that uses R410A refrigerant. But how efficient is it at heating your home?
Snapshot: The Fujitsu ABTG24LVT is a large floor-mounted heat pump that uses R410A refrigerant. But how efficient is it at heating your home?
Snapshot: The Fujitsu AGTV09LAC is a small floor-mounted heat pump that uses R32 refrigerant. But how efficient is it at heating your home?
Snapshot: The Fujitsu AGTV14LAC is a medium-sized floor-mounted heat pump that uses R410A refrigerant. But how efficient is it at heating your home?
Snapshot: The Fujitsu ASTG09KMCA is a small wall-mounted heat pump that uses R32 refrigerant. But how efficient is it at heating your home?
Snapshot: The Fujitsu ASTG09LVC is a small wall-mounted heat pump that uses R410A refrigerant. But how efficient is it at heating your home?
Snapshot: The Fujitsu ASTG12KMCA is a small wall-mounted heat pump that uses R32 refrigerant. But how efficient is it at heating your home?
Snapshot: The Fujitsu ASTG12LVC is a medium-sized wall-mounted heat pump that uses R410A refrigerant. But how efficient is it at heating your home?
Snapshot: The Fujitsu ASTG14LUC is a medium-sized wall-mounted heat pump that uses R410A refrigerant. But how efficient is it at heating your home?
Snapshot: The Fujitsu ASTG18KMCA is a medium-sized wall-mounted heat pump that uses R32 refrigerant. But how efficient is it at heating your home?
The smaller versions are designed for a single room; the larger, for a whole house. It takes 10 to 30 minutes to bring a room up to temperature, after which the level will be maintained within 1 or 2 degrees.
A heat pump works by extracting heat from the air outside your house and bringing it indoors. It's like a refrigerator in reverse. By trying to cool the world it can extract heat, or vice versa.
Use an old-style bicycle pump for a while and it will get hot. That's because gas (air) is being compressed. Spray an aerosol can and the valve area will become cold. That's because the compressed gas in the aerosol can is expanding.
Heat pumps (like refrigerators) have a system of pipes containing gas (refrigerant) that is continuously expanding in one part of the system and compressing in another. When the gas is being compressed, it gets hot. A heat pump's exterior unit compresses the gas, then pumps it to the interior unit where the gas runs over a series of finned coils, giving off its heat.
The gas is then returned to the outside unit, where it expands and runs through another set of finned coils, which become cold. The cold gas is then recompressed and the cycle continues. For summer cooling, the refrigerant flow is reversed, so the interior unit becomes cool, while the exterior cold.
Heat pumps shift more heat than the electrical energy consumed in compressing the refrigerant and running the fans, making them highly-efficient methods of heating – up to 3 times as much in the right conditions.
This has a major influence on heat-pump performance and as most manufacturers use the same one (R-410A, which itself is a mixture of another 2 refrigerants R-125 and R-32), there are limits to the performance gains they can achieve. It also means there are relatively small performance differences across different models with a similar heat output.
Fujitsu's new model range (“E” series) uses solely R-32. The company claims this refrigerant increases heat-pump performance over R-410A-filled models. R-32 requires new interconnecting-pipe-termination techniques and installers are required to undertake an industry training conversion course. We expect other manufacturers will also introduce R-32 models.
Is a heat pump the same as a ventilation system?
No. A heat pump uses refrigeration principles to shift relatively large amounts of heat in or out of your home to warm or cool it. A domestic ventilation system shifts drier air from the ceiling space into the living space, and is designed to reduce condensation.
Warm, dry and comfortable
Heat pumps can provide a level of all-round comfort not easily obtained by plug-in electric heaters. They can quickly bring a room up to temperature and then maintain it.
Lower heating costs
If you install a heat pump and keep your home about as warm as you do now, you could save a considerable amount in heating costs. But some of our members with heat pumps tell us they use their units to keep their homes warmer than before, so their heating bills haven't dropped by much.
No gas charge
If you install a gas heater, you'll have to pay a gas connection charge (often around $40 per month) all year round, for a heating appliance you use for less than a whole year.
A reverse-cycle heat pump is the only type of home heating system that can both heat and cool a room.
Do heat pumps dehumidify?
Many modern heat pumps incorporate a washable filter unit that removes dust and particles from the air. This could be an important feature for people with asthma and allergies. The filters need regular cleaning to keep the unit working at maximum efficiency. Some have a deodorising function as well.
A heat pump installation may also add to your home's resale value.
Whirring fans can be very annoying. Fans run in both the interior and exterior units all the time they are switched on. The fan in the inside unit of a heat pump should produce little more than a low hum in low-speed mode, but the compressor plus fan of the outside unit can be quite noisy. Check the manufacturer's specifications. Also, consider the impact on neighbours if the outdoor unit must be mounted near their sleeping areas.
Our 2009 member survey found noise was more likely to be an issue with older heat pumps – 15 percent of those bought before 2004 made enough noise to be "mildly disturbing". This fell to 7 percent for models less than 2 years old.
Not so good in low temperatures
Extracting heat from outdoor air gets more difficult as the temperature drops. Sometimes, especially on frosty nights, exterior heat pump units freeze up and have to stop working for several minutes while they defrost. If you live in a frosty area see "What are your needs" for more about this problem.
Nearly 1 in 5 owners in our 2012 reliability survey said their heat pump performed poorly in very cold weather.
Circulating air can cause draughts – which means you need to think about where to place the unit. You don't want one on the wall just above your favourite armchair.
In areas with hot humid summers, good cooling performance may be important. If you live in a colder area, you'll want a model that has good heating performance. Look for a model that claims to be able to operate at temperatures below the worst you'd expect.
When the outside unit of a heat pump detects ice, it will automatically de-ice and stop producing heat. This is most likely to occur as the air temperature approaches freezing (at below-zero temperatures all the water in the air will have frozen and formed frost or snow, so the unit should no longer ice up). This can happen to all heat pumps but some do a better job of cold-weather performance than others. Our Heat pump FAQs section has more about this.
H2 output capacity
This shows the heat output capacity of the heat pump when the air temperature is 2°C. The H2 output capacity really matters if you live in a colder area, especially where the night temperatures go below 5°C but don't often dip below zero. If this is your climate, insist on being told what the H2 output capacity is.
The bigger the H2 output capacity the better. It's optional to have H2 output capacity on energy labels, but we hope makers will adopt it. If the H2 information can't be supplied make sure your contract with the supplier says that you'll get adequate heating during cold nights.
A large heat pump may be enough for the whole of an open-plan house, although the back of the house won’t be as evenly warmed as the living area. You could install a smaller unit at the back. This is also a good solution for houses that aren’t open-plan. The second unit can be run at a lower set temperature just to keep the chill off the sleeping areas and reduce heating costs.
Because heat pumps warm the air, you need to keep interior doors open so the air can circulate. Inexpensive desk fans at floor level in bedrooms and aimed at the door can help air circulation by blowing cold air (at floor level) out of bedrooms – this cold air will be replaced by higher-level warmed air.
A system with more stars will give you more heating or cooling energy per unit of electricity than one with fewer stars.
These cooling and heating star ratings tell you how efficient a heat pump is. More-efficient models get more stars and are cheaper to run.
But because heat pumps are becoming more efficient, the rating system has run out of stars. So the ratings have been “dialled back” by about 2 stars.
Revised labels have also been phased in: instead of the old combined heating/cooling label, there’s one that shows cooling and heating side-by-side. (During the phase-in period the old rating can still be listed in a panel at the bottom of the revised label.) We list the new star ratings in our heat pump comparison database.
The Energy Star labelling system is the benchmark for efficient performance. Energy Star is an international energy-rating symbol used to identify the most energy-efficient products in the US, Canada, Europe, Australia, Asia and New Zealand.
To qualify for Energy Star since April 2011, manufacturers are required to supply laboratory test results for a heat pump’s performance at 2°C.
We list Energy Star models in our heat pump comparison database.
COP (Co-efficient of Performance)
The COP is a technical calculation of heating efficiency which is used in the formula for calculating star ratings. For heating, a good unit has a COP of 3 or more. The heating COP can be reduced by cold temperatures because de-icing takes extra energy.
Energy efficiency ratio (EER)
This is the calculated cooling efficiency, and is also used to calculate the star rating. The higher the rating, or the more stars, the better. An EER of 3 or more is good.
All heat-pump/air-conditioner units imported or manufactured after 16 June 2006 must meet a new Minimum Energy Performance Standard or MEPS. But these minimums are set quite low, particularly for larger units.
MEPS has little relevance to your buying decision – it's there to make sure manufacturers don't sell unacceptably inefficient heat pumps to unsuspecting consumers.
Some maintenance requires professional help – but much of it you can do yourself. That’s provided you don’t mind standing on steps to reach inside units mounted high on the wall. If steps are a problem, get professional help.
These collect the dust and dirt that’s removed from the air passing through the indoor unit. The most regular maintenance job is filter cleaning. If the unit’s been operating for a few months or more the filter’s likely to be quite dirty.
Removing the filter(s) is relatively simple – see your instruction manual. In most models you lift the front cover and slide out the filter.
Take the filter to the bath or shower (or outside) and spray it with a neutral “spray & wipe” type of cleaner, then rinse it thoroughly. Repeat if necessary. Don’t use solvents or other harsh cleaners.
You can get dedicated filter-cleaning sprays from refrigeration wholesalers. They’ll make the air delivered by the heat pump smell nice – but they won’t clean the dirt any better.
Other indoor cleaning
While you’re dealing with the indoor unit, inspect the cylindrical fan vanes – and also the heating/cooling fins – for dirt build-up. Use your vacuum cleaner’s upholstery brush to gently vacuum dirt away from the vanes and the fins. Finally give the outer casing a wipe with a soft cloth dampened with a squirt of neutral spray & wipe cleaner.
How often? If you have carpet and the heat pump runs for many hours a day all year round, the filters could need cleaning four times per year. Cleaning will be less frequent if you run the heat pump less or have hard floors. For a heat pump that runs for a few hours a day mainly for heating, then once a year in the autumn should be enough. If the heat pump is used regularly for cooling as well, then go for an autumn and spring clean.
The first job with the outdoor unit is to make sure air can get to and through the unit without obstruction. That means clearing away any vegetation that could reduce airflow. Next, make sure the air grilles each side of the unit are clear of debris such as leaves and twigs.
Inspect the fan blades, fins and the outer casing for signs of corrosion. Rust never sleeps, so deal with corrosion – or get it dealt with – as soon as possible. This will lengthen the life of the unit.
How often? A heat pump used mainly for heating only needs a maintenance check once a year in the autumn. If you use the heat pump regularly for cooling, then look at doing another check in spring.
Even if you do the basic cleaning yourself, getting a professional to check the heat pump every couple of years is worthwhile. Professionals can measure the delivered air temperature and check the unit is operating properly. Probably the best professional to use is the person who installed the unit.
Tip: Beware of cold-calling, high-pressure outfits that try to bulldoze their way on to your property. See our October 2014 news article for more on this.
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