Daikin McQuay AGZ-D 25, Operating And Maintenance Manual

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OMM 1087-1 AGZ 025D through 190D 25
T3 – Run to Off
Requires all of the following
•
Unit state is Off
•
LWT is higher than the Evap Freeze set point or LWT sensor fault is active
T4 – Start to Off
Requires all of the following
•
Unit state is Off
•
LWT is higher than the Evap Freeze set point or LWT sensor fault is active
T5 – Run to Start
This transition should occur per the requirements for pump staging and evaporator flow loss alarm.
Pump selection
The pump output used will be 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.
LWT Target
The LWT Target varies based on settings and inputs.
The base LWT Target is selected as follows:
Control Source
Set Point
Mode
Input
BAS
Request
Available Modes
Set Point
Base LWT Target
Local OFF COOL Cool Set Point 1
Local ON COOL Cool Set Point 2
Network COOL BAS Cool Set Point
Local OFF COOL w/Glycol Cool Set Point 1
Local ON COOL w/Glycol Cool Set Point 2
Network COOL w/Glycol BAS Cool Set Point