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Manual 2100-517
Page 4 of 11
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.