Are you like many of the new home owners that have bought a new house without any form of Air conditioning and then suffered over the heat wave we had during early February? Thankfully that extreme heat has settled down ( and before you know it the colder days will be upon us!) You may be planning ahead so you don’t sit freezing this winter and of course not repeating the uncomfortable feeling when we get the next hot spell?
Heat Pumps
New Zealand has seen a rise in the installation of heat pumps as a source of heating (and cooling) in recent years, and with so many different makes and models it can be a bit daunting choosing which will better suit your needs. so lets break it down into sections:
Firstly – What exactly does a heat pump heat your home?
If you think of a Heat pump as your refrigerator working backwards, it takes the warmth from the outside air and transfers it into your indoor space. And of course it works in the opposite direction when you wish to cool your room in the summer.
What Size do I need for my house?
Well this depends on the size of the space and also the environment you live in. The environmental factors and the size of the space are one of the most crucial factors in ensuring that you heat pump works efficiently. If you buy a heat pump that is too small for the room size it will struggle to keep the room at the desired temperature and will use more energy trying to do so.
If you buy a unit that is too large for the space, then it will turn on and off to keep the room at the set temperature, again this will not be energy efficient.
For help in deciding what size is best for your home,
contact us for a free home assessment.
Energy Efficiency
New Zealand is a land of many seasons, but if you take some time to research the options you can heat your home more efficiently.
Efficiency of a heat pump system is not constant – it varies along with the temperature differential between indoor and outdoor air. A heat pump’s rated efficiency is for an outdoor temperature of 7°C, so when designing a system, it is important to understand how it will perform at lower temperatures. Whether a heat pump is in heating or cooling mode, as the difference between outdoor temperature and desired indoor temperature increases, the efficiency of a heat pump system decreases. Figure 3.4, shows the efficiency of a heat pump in heating mode reducing as the outdoor temperature decreases. Different heat pumps will perform very differently at sub-zero temperatures – some may keep performing down to -20˚C while others will struggle at temperatures below freezing.
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Heat pumps can be the most energy efficient type of heating/cooling using electricity as long as you choose the right system for the space it will be heating. The most energy efficient qualify for Energy Star Qualification. If you want to thoroughly check the options available, you can use this link to compare your choices and see which brand/model will be best for your home.
Defrost Cycle
Another temperature-related factor that can impact on efficiency is the extra energy that may be required for defrosting at low temperatures. Ice build-up occurs at around at 0-4˚C (especially in high humidity), when any water vapour in the air will start to condense and freeze onto the evaporator (outdoor heat exchanger) coils. To remove ice build-up on the coils, most heat pumps have a defrost cycle where the system switches into cooling mode (taking some heat from inside), which could effectively cool the room.
The defrost frequency and performance are critical to heat pump efficiency. Undersized heat pumps will need to defrost frequently in low ambient temperatures, reducing the system’s ability to reach and maintain set point. If the defrost cycle operates too frequently or if it does not operate often enough, it will provide insufficient heating, and heat pump operation will be compromised. The defrost cycle control is either: • a time-temperature defrost starting and stopping at preset times (30-, 60- or 90-minute intervals); or • on-demand defrost, which is usually more efficient because it operates only when it detects frost build-up on the outdoor coil by monitoring air and coil temperature, outdoor airflow, pressure differential across the coil and refrigerant pressure. Systems that include a dry-coil defrost cycle briefly run the outdoor fan at maximum speed before the system starts to heat again, to remove any water that may still be on the coil fins and would immediately refreeze. The defrost frequency and performance are critical to heat pump efficiency.
Environment, Climate and Efficiency
The Climate and environmental factors also matter.
Undersized heat pumps will need to defrost frequently in low ambient temperatures, reducing the system’s ability to reach and maintain set point. If the defrost cycle operates too frequently or if it does not operate often enough, it will not provide sufficient heating, and heat pump operation will be compromised. Environment is also a factor, in geothermal (such as Rotorua) or coastal areas (salty atmosphere ), the outside unit will need have suitable protection against corrosion.
You can also run the unit more efficiently by setting the unit at a constant temperature that is not too hot or too cold, the unit will use less energy this way. Also letting the unit build up to the desired temperature also helps reducing the energy use, a heat pump soon heats up a room, but if you want a warm cosy home when you walk in the door after work, you can always use the timer settings which every brand, make and model have to set it to automatically turn on at a specific time each day.
Installation
The correct location and installation of both outdoor and indoor units is crucial for the most efficient performance. Consider noise and air flow. Locating the unit close to where you sit can mean the constant airflow may become irritating to you when sat watching TV. There are a number of different styles of indoor units, the most popular is the Split Hi Wall units (you can also get outdoor units that can run multiple indoor units). But if you want a heat pump in a bedroom with limited height such as a loft room, or you want your wall space for Artwork or shelving, then you may want to look at a floor mounted indoor unit. Do you want no unites on the walls? Then look at a ducted system.
Finally how much does a Heat Pump cost?
When it comes to buying anything, we always want the best price possible, and there are a lot of different prices ranges from the various manufacturers of Heat Pumps.
Not all heat pumps are created equal, this is where spending some time researching and comparing systems will benefit you.
Prices will range from size and also the features you can get, so remember that if a more energy efficient model is slightly more than the budget range, it will save you money in the long run. Use the tool here to compare models & sizes, because its not the initial outlay that you only have to think about, its your power bills at the end of each month that are more important. Or you don’t have time to do all of the above contact us today and find out how we can help.
Hitachi Guide for room size and location