Heat Pumps

At moderate temperatures of heating days, heat pump handle heating needs. If the outside temperature reaches the equilibrium point of the house, that when the heat loss is equal to the heat pump heat power, in two stages, indoor thermostat activates furnace (secondary source of heat, in most cases, the electric heating elements). Once the oven is on, thermal relay deenergizes the heat pump. When the second stage (oven) need met the Plenum and cooled to a temperature below 90 to 100F (32 to 38C), the heat pump, switch turns the heat pump back and control the conditioned space, until the second stage of the operation is necessary. Fig. 2-12 shows the heat pump. Additional electric thermal unit shown in Fig. 2-13 added in geographic locations where it is needed. This particular device can provide on 23 000 56 000 BTU/h and to 112,700 BTU/h with the addition of electric heat.

If the outdoor temperature drops below the level established for refrigeration compressors monitoring, control is deactivated heat pump fully and furnace processes all heating needs.

During the defrost cycle, the heat pump switches from heating to cooling. For ingress of cold air from the spread in the house, when the heating is necessary to control automatically switches to the furnace to compensate for the heat pump defrost cycle (see Fig. 2-14). When the supply air temperature rises above 110 120F (43 to 49C)limitations of defrost control off one oven, and keeps the air in the room becomes too warm.

If after defrost cycle, the air downstream of the coil receives more than 115F (65C)last paragraph heat pump relay, compressor stops until the heat exchanger cooled up to 90 to 100F (32 to 38C), as it does during normal Cycling operation between the furnace and heat pumps.

Summer cooling, heat pump works like a normal split-system, with the help of fan oven as the primary air the engine (see Fig. 2-15).

In direct heat pump/additional electric heater application, at least one outer thermostat is required to cycle heaters, as the outdoor temperature drops. In the system, as shown here, indoor thermostat controls an additional heat source (oven). Outdoor thermostat is not required.

With oven, serving as a secondary source of heat, the system requires house amendments, usually associated with an additional electric strip heating.