7.8.1 Pump Selection
The pump output used is determined by the Evap Pump Control set point. This setting allows the following configurations:
• #1 only – Pump 1 will always be used
• #2 only – Pump 2 will always be used
• Auto – The primary pump is the one with the least run hours, the other is used as a backup
• #1 Primary – Pump 1 is used normally, with pump 2 as a backup
• #2 Primary – Pump 2 is used normally, with pump 1 as a backup
Primary/Standby Pump Staging
The pump designated as primary will start first. If the evaporator state is start for a time greater than the recirculate timeout
set point and there is no flow, then the primary pump will shut off and the standby pump will start. When the evaporator is
in the run state, if flow is lost for more than half of the flow proof set point value, the primary pump will shut off and the
standby pump will start. Once the standby pump is started, the flow loss alarm logic will apply if flow cannot be established
in the evaporator start state, or if flow is lost in the evaporator run state.
Auto Control
If auto pump control is selected, the primary/standby logic above is still used. When the evaporator is not in the run state,
the run hours of the pumps will be compared. The pump with the least hours will be designated as the primary at this time.
7.9 Condenser Pump Control
There are three condenser pump control states for control of the condenser pump:
• Off
• Start – Pump is on, water loop is being recirculated
• Run – Pump is on, water loop has been recirculated
The control state is Off when any of the following are true:
• Unit state is Off
• LWT is higher of Evap Freeze set point or LWT sensor fault is active
• EWT is higher of Evap Freeze set point or EWT sensor fault is active
The control state is Start when any of the following are true:
• The unit state is auto
• LWT is lower than (Evap Freeze set point - 0.6 °C) and LWT sensor fault is not active or EWT is lower than
(Evap Freeze set point – 0.6 °C) and EWT sensor fault is not active.
The control state is Run when the flow switch input has been closed for a time greater than the loop Recirculate set point.
7.10 Condensation Control
Three condensation control modes are available:
• Cond In – the condensation control measure is the condenser entering water temperature
• Cond Out - the condensation control measure is the condenser leaving water temperature
• Pressure - the condensation control measure is the gas pressure referred to condenser saturated temperature
The Condenser control mode is determined by the Condensation Control Value set point.
Within these control modes, the application manages the outputs for the control of condensation devices:
• n.4 on/off signals, always available
• n.1 modulating 0-10V signal, whose availability is determined by the Condensation Analog Output type set
point.
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