A major manufacturer of TEVs provided several valves it was felt would meet the needs of the VSGSHP based on the detailed data obtained during the first-stage testing. Although the ultimate goal is to locate a single bi-directional valve, two TEVs and two check valves were used at this stage. Unfortunately, none of the valves tested operated acceptably. Better regulation has been achieved, but cooling capacity has been compromised compared to the values reported during the first phase. A bi-flow valve was also tested and performed in a similar manner. However, the manufacturer has used the liquid refrigerant line between the two TEVs as the inverter heat sink. This created a problem since this line does not exist when a bi-flow TEV is used.

The cost of adding a variable-speed fan motor to the unit is significant. It is desirable to eliminate similar added costs for the loop pump and hot water pump. Therefore, lower cost alternatives have been explored.

The most suitable option is a modification of a device used to reduce outdoor fan speed of DX aircooling units when ambient temperatures are low enough to cause liquid slugging. This type of speed control incorporates a silicon-controlled rectifier (SCR) that "clips" a portion of each AC cycle. The momentary reduction in current causes the motor to slip (difference between synchronous speed and actual speed) more than normal. Initial tests using a fan motor indicated the controller was marginally effective in reducing energy consumption when speed was reduced,...