heat pumps designs
Ductless heat pumps have a split design (they are two piece systems, with an outdoor and an indoor unit). Most central heat pumps have also the same split design, but there are also models with a single outdoor unit. As to the designs of ground and water heat pumps, they mostly differ on their underground loop.
See: New Heat Pumps: Basics and Types
Central air-source heat pumps designs
Types of heat Pumps
Most heat pumps are 1) Ductless; 2) Central Air Source Heat Pumps (the commonest type); 3) Ground and Water source Heat Pumps. Ground or geothermal heat pumps interacts with the ground via a series of pipes (loop). The other types interacts with the outside air.
Most central heat pumps have split designs, that is, they are two piece units: one indoors and one outdoors.
The outdoor unit looks like an air conditioner in size and appearance, and comprises the outdoor coil, a compressor, a reversing valve and a fan.
The indoor unit looks like a gas furnace and contains a large blower and a filter, also like conventional air conditioners.
These heat pumps have supply and return ducts connected to the central blower (located indoors).
But there are also systems with a package design, that is, with both coils and the central fan outdoors. In this case heated and cooled air is delivered to the home from ductwork.
Left: New heat pump from York (air-source hybrid split design)
Ductless heat pumps designs
Like central air-source heat pumps, the ductless design has two main components: an outdoor unit involving the compressor and the condenser; and an indoor air-handling unit (blower and filter). These two parts are linked by a conduit, housing the power cable, the suction and refrigerant tubing, and the condensate drain.
Some models have as many as four indoor blowers, all of them connected to the same outdoor unit. The term "mini" associated to these pumps describes these small indoor units, typically located in different rooms or parts of the house.
The number of indoor units depends on the size and layout of the building and on how much heating and cooling is required (each indoor unit has its own thermostat, to respond to different needs of different rooms and parts of the house, allowing to save energy).
Ductless heat pumps offer extensive flexibility in their designs, like their ductless air conditioners cousins. The indoor components can be floor standing models, or can be positioned high or low in a wall, or suspended from a ceiling...
Ground-source heat pumps designs
The designs of ground-source heat pumps depend on the available land area, economical considerations and also on the type of soil, water or rock where the pump is going to be installed. The design may also differ in terms of configuration and extension of the underground pipes, or on the way the loops are installed in the ground: vertically, horizontally or in a pond or lake.
In a first and simple approach, ground-source heat pumps involve two big designs: the closed ground loop and the open ground loop design (loops, in this case, refers to a series of pipes buried in the ground).
Ground source heat pumps are based on the same principles as air source heat pumps. The difference is that they interact with the ground, instead of with outside air...
Close loop heat pump design
In the closed loop design the loop carries a fluid (water or antifreeze solution).
During cold weather the fluid collects heat from the ground (or well, or lake or other body of water) and carries it through the pipes and system into the house.
During hot weather conditions the process is reversed: the system collects heat from the house and carries and places it in the ground.
Closed loop heat systems are by far the commonest type of heat pump design.
Open loop heat pump designs
Open loop heat pump designs do not use an antifreeze fluid in their pipes. They use underground water as the heat exchange medium. In other words: the water of the lake or well where the loop is buried circulates directly through the system.
Open loop heat pumps are very uncommon in residential applications. They require an adequate supply of clean ground water which isn't easy to achieve, and the use of that water and its discharge (after used by the system) has to comply with local codes and regulations.
Vertical and horizontal pipes
The most common ground and water heat pump design involves two pipes buried horizontally in a trench of two-foot wide or so: one of the pipes is buried at about six feet and the other at about four feet; alternatively they can be placed side-by-side at around five feet. But there are other horizontal designs (see image on left, from Danfoss).
Vertical loops can also be used, to reduce the disturbance of the surrounding landscape, or when there isn't enough land or where trenching is difficult.
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