What type of heat pump and position will suit your house best?
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Reverse cycle heat pumps can heat the room or cool it at the touch of a button. There are several types of heat distribution to choose from.
A split system has an exterior compressor unit connected to an interior ceiling or wall unit by copper pipes (for the refrigerant) and wiring.
The interior unit is made up of electrical/electronic controls and a fan which circulates air over finned tubing for either cooling or heating, depending on the setting of the unit.
Much of the installation cost of split systems comes from running the pipes and wires from the exterior to the interior locations.
Split systems work well in a large lounge or the main living area of an open-plan home.
In a multi-split system the exterior unit connects to more than one interior unit. Often, one interior unit is located in the living space and another in the bedroom area.
The interior units can have separate controllers – but it is not possible to have one interior unit cooling while the other is heating.
Multi-split systems can be cheaper than having separate external units for different parts of the house, but there may be extra installation costs from longer piping runs and some extra control complexity.
These have a single, large capacity interior unit mounted in the ceiling space, or under the floor. The heated (or cooled) air is pumped through insulated ducts to ceiling or floor outlets in many or all of the rooms in the house.
Ducted systems have the least visual impact of any heat pump system – just small flush vents in each room.
Because there is some heat loss from ducts themselves, they are slightly less efficient than other systems. They are also expensive to install – costs can be as much as $15,000 or more for a 150m² home, depending on ceiling height.
The options are high wall, ceiling, low wall or floor.
High wall units are the most common heat pumps in New Zealand. They're usually long and thin, are mounted close to the ceiling and circulate enough air to heat a room evenly.
They should be located so the airflow can reach as much of the room as possible, but not close to where you'd normally sit (so you don't have to put up with fan noise in your ear while you're watching TV).
High wall units can cause the surrounding wall and ceiling area to become covered in dirt and grime, and the high location makes filter cleaning difficult, particularly for the elderly and disabled. Some makers offer self-cleaning filter models to solve this problem.
These either hang off the ceiling or are fitted into the ceiling. One advantage of ceiling units is they can be installed where wall space is at a premium. They have the same dirt and filter changing drawbacks as high wall units.
These sit on the floor, alongside a wall. They must be sited so furniture does not obstruct the airflow, and should be located where they can distribute the warm air to as much of the house as possible. Filter cleaning is a breeze.
Some suppliers suggest that for the best heating effectiveness, the internal unit should be floor mounted. This could be particularly important if you have high ceilings. Hot air rises and, if your unit is up on the wall, all your lovely heat could end up keeping the roof warm. But floor-mounting may not be possible. Also, we're not saying a wall-mounted unit won't work. You should carefully discuss your options with the supplier before you sign up.
For best cooling effectiveness, a unit mounted high on the wall or on the ceiling is best. This is because cold air falls.
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.
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.