Section 1 | WattMaster WHP |
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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.
Design Guide |
