Bard GVDM-26 Operation of the Heat Recovery Unit, Start UP and Check OUT, Maintenance

OPERATION OF THE HEAT RECOVERY UNIT

The pump module is a very simple device containing basic controls and a circulating pump. Heat is transferred from the hot refrigerant (discharge gas) to the cool water.

The operation of the Desuperheater Pump Module is controlled first by the operation of the Geothermal Heat Pump and secondly by internal controls within the Pump Module. A low voltage signal from Thermostat “Y” is connected to the internal control board of the GVDM-26 and acts as the primary on/off switch for the circulating pump.

Also connected to this board is a temperature overlimit device which shuts down the GVDM-26 once inlet water has exceeded 125° so the water cannot create a scald condition.

There are also two (2) thermistor sensors connected to the control board. These thermistors are measuring and controlling to ensure there is a positive heat differential across the water being circulated. When operating in Part Load Condition, there are certain conditions (Ground Loop Temperatures versus Hot Water Temperatures) that potential exists where heat could transfer from the hot water into the refrigeration system instead of the refrigeration system into the hot water. Through the control board logic, these thermistors ensure there is at least 2° positive differential between entering/leaving water temperatures and will shut down the pump accordingly.

START UP AND CHECK OUT

Be sure all shut off valves are open and all power supplies are on. Open a hot water faucet to permit any air to bleed from the plumbing.

NOTE: The inherent design of this pump for maximum efficiency means this pump is not self-priming. It is imperative to check that the air has been adequately bled from the system. There is a bleed-port built into the pump module that can be utilized after the system water has been fully restored. See Figure 2 for this bleed port location.

Turn ON the air conditioning system and verify the circulating pump will operate. Feel the “Water to Unit” and “Water from Water Heater” tubes for noticeable difference in temperature. Turn OFF the system and verify that the circulating pump stops.

NOTE: When checking the refrigerant operating pressures of the ground source heat pump. The GVDM-26 must be turned off. With the GVDM-26 operating a wide variance in pressures can result, giving the service technician the indication there is a charge problem when the unit is operating correctly.

MAINTENANCE

CLEANING THE HEAT EXCHANGER – If scaling of the coil is strongly suspected, the coil can be cleaned with a solution of phosphoric acid (food grade acid). Follow the manufacturer’s directions for the proper mixing and use of cleaning agent.

Manual	2100-517
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