Heat Pumps

Will a heat pump suit me?


Before you begin choosing a size, style or model of heat pump, you need to consider their pros, cons and cost-effectiveness.

Positives


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 subscribers 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 $30 per month) all year round, for a heating appliance you use for less than a whole year.

Cooling

A reverse-cycle heat pump is the only type of home heating system that can both heat and cool a room.

Dehumidifying

Do heat pumps dehumidify?

  • Yes … in cooling mode, the cooled air can’t hold as much water so the water condenses out of the air inside the heat pump and is drained away.
  • Yes … in dehumidifying (“dry”) mode, the heat pump alternates between cooling and heating modes to keep the room at an approximately constant temperature. Water is extracted during the cooling part of this cycle.
  • No … in heating mode, the heat pump doesn’t remove water from the air. However, because warm air can hold more water than cool air, the “relative humidity” decreases as the heat pump raises the air temperature. So the warmer air feels drier.

Air filtering

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.

House value

A heat pump installation may also add to your home’s resale value.

Negatives


Noise

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 neighbors 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.

Draughts

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 favorite armchair.

How much can you save on heating costs?


The answer isn’t as simple as you might think. Modern inverter-style heat pumps can adjust their power output to suit the heating requirements of the moment and are most efficient when working at part load.

Just where this efficiency “sweet spot” is to be found is difficult for us to test. Our testing procedure pushes the units on reverse-cycle heating mode towards their maximum output, where they are less efficient.

So if your installer makes sure the unit is large enough (or even a little too large) for your needs, you should get more heat per dollar of electricity than our test results suggest.

What is a heat pump?


Heat pumps are basically space heaters. They provide convenient, efficient, thermostatically-controlled heating that can be set to come on and off automatically at different times of the day.

The smaller versions are designed for a single room; the larger, for a whole house. It takes 20 to 40 minutes to bring a room up to temperature, after which the level will be maintained within 1 or 2 degrees.

How heat pumps work

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.

whatisaheatpump..

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, and 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.

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.Topic 2: Heat Pumps:

A heat pump is a machine or device that moves heat from one location (the ‘source’) to another location (the ‘sink’ or ‘heat sink’) using mechanical work. Most heat pump technology moves heat from a low temperature heat source to a higher temperature heat sink.[1] Common examples are food refrigerators and freezers, air conditioners, and reversible-cycle heat pumps for providing thermal comfort.

Heat pumps can be thought of as a heat engine which is operating in reverse. One common type of heat pump works by exploiting the physical properties of an evaporating and condensing fluid known as a

refrigerant. In heating, ventilation, and air conditioning (HVAC) applications, a heat pump normally refers to a vapour-compression refrigeration device that includes a reversing valve and optimized heat exchangers so that the direction of heat flow may be reversed. Most commonly, heat pumps draw heat from the air or from the ground. Some air-source heat pumps do not work as well when temperatures fall below around ?5°C(23°F).

Types of heat pumps

The two main types of heat pumps are compression heat pumps and absorption heat pumps. Compression heat pumps always operate on mechanical energy (through electricity), while absorption heat pumps may also run on heat as an energy source (through electricity or burnable fuels).

A number of sources have been used for the heat source for heating private and communal buildings.

air source heat pump (extracts heat from outside air)

air–air heat pump (transfers heat to inside air)

air–water heat pump (transfers heat to a tank of water)

geothermal heat pump (extracts heat from the ground or similar sources)

geothermal–air heat pump (transfers heat to inside air)

ground–air heat pump (ground as a source of heat)

rock–air heat pump (rock as a source of heat)

water–air heat pump (body of water as a source of heat)

geothermal–water heat pump (transfers heat to a tank of water)

ground–water heat pump (ground as a source of heat)

rock–water heat pump (rock as a source of heat)

water–water heat pump (body of water as a source of heat)

What are Heat pumps/Air Conditioners?

Heat Pumps cum Air Conditioners create a comfortable living and working environment for your Homes, Offices, Shops and Businesses.

Heat pumps work as heaters in cold weather and automatically adjust as air conditioners when the space is hot.

Heat pumps are among the most efficient heating option on the market – Consumes Institute

A 6 star heat pump will use 1 KW of electricity to produce about 5 KW of heat – EECA

Modern air conditioners/ Heat pumps come with a variety of features and high tech sensors and filtration systems. Leading brands such as Panasonic, Mitsubishi, Daikin, Fujitsu, Toshiba etc. have some specific features developed by them. Specific features of leading brands of heat pumps:

Intelligent Eye detects your presence in room and if you leave the room for more than 20 minutes, the Heat pump/Air conditioner will go into econo mode of operation to save you the power.

Iron Freshener – Negative iron generator – creates feeling of freshness

High coefficient of performance – saving you power costs and most efficient operation

Inverter system – variable speed compressor to match the heating/cooling load and energy saving – constant temperature comfort

Positives

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 subscribers 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 $30 per month) all year round, for a heating appliance you use for a few months.

Cooling

A reverse-cycle heat pump is the only type of home heating system that can both heat and cool a room.

Dehumidifying

If you switch a heat pump into cooling mode, it will also dehumidify the air in your house. In heating mode, heat pumps warm the air but don’t dehumidify. Some units have a special dehumidifying mode, but this is designed for humid tropical climates and is not suitable for New Zealand winter conditions.

Air filtering

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.

House value

A heat pump installation may also add to your home’s resale value.

If you’re thinking about buying a heat pump, you need to consider the climate you live in and the features you require.

Climate

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.

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. Where it’s available, we include it in our database of specifications.

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.

Features

Think about the features you particularly want in your heat pump. These may include:

        Automatic de-icing is vital if you live in a cold area – otherwise, in winter, the pump will stop providing heat because of frost build-up on the outdoor heat-exchanger coils. This is a standard feature on newer inverter models.

        A timer lets you switch the heat pump on and/or off automatically at certain times. However, there are big differences. A clock-based timer allows you to programme an actual “on” and “off” time, and the times you set remain active until they’re cancelled. A 7 (or more) day timer usually allows multiple on and off times.

        Sleep mode adjusts the temperature in several steps (up when cooling, down when heating) so that the system works less hard and more quietly when you’re sleeping. You can programme how long you want the sleep mode to operate.

        Airflow-control settings provide reduced airflow for quiet operation and/or extra-high airflow (may be called fast or jet operation). Ideally, you want your heat-pump/air-conditioner to have a big range of airflow settings. A high airflow will help distribute the air in a room more quickly – but the higher the airflow, the noisier and draughtier it is. So you want a low fan-setting that circulates the air but does so quietly, especially if you’re using the inside unit in your bedroom.

        Oscillating louvers allow the air to be distributed more evenly.

        Adjustable louvers can be pointed up for cool air and down for warm. Left and right adjustability helps direct air where it’s needed.

        Fan-only mode blows air without heating, cooling, or drying. This can provide adequate cooling at some times of the year, without the cost of running the heat pump.

        Restart delay is a protective feature that prevents the heat pump from starting up again too soon after being switched off.