WattMaster Water Source Heat Pump, Installation & Operation Manual

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Section 1
WattMaster WHP
1-8
Design Guide
HVAC Operation w/ Reversing Relay
If the user has configured the WHP to control a Reversing Valve and a Compressor, the
following sequence of operation occurs during a heating or cooling demand.
Note:
If you configure the WHP to look for a proof of flow Enable signal from the
Loop Controller then the following sequence assumes a request was made by
the WHP during a demand condition and that the Loop Controller gave
permission for the WHP to start its compressor. Otherwise, the WHP will
ignore the Enable signal and operate anytime there is a heating or cooling
demand.
a. If the last mode was the opposite of the current demand mode, make sure
the Changeover Delay has been satisfied.
b. If the unit is configured to control an Isolation Valve, the valve relay is
activated ( Relay #5 ). The Minimum Off Timer is reset to ZERO and
must be satisfied before any further operations are allowed.
c. If the current mode requires the Reversing Valve to be activated, its relay
contact is closed and a 10 second delay is started.
d. Ten seconds after the Reversing Valve is activated, the Compressor relay
is activated.
e. If the Space Temperature continues to exceed the affected setpoint by the
full amount of Deadband and you have configured for 2 stages in the
current mode of operation, relay #5 will activate for the second stage of
heating and/or cooling. A second stage of either implies that no Isolation
Valve exists!
f. Once the Space Temperature has crossed back over the affected setpoint,
stage 2 will be turned off if the unit has a stage 2.
g. As the Space Temperature continues to cross back over the affected
setpoint by half the Deadband value, the compressor will then be allowed
to turn off if the Minimum Run Time has been satisfied.