YORK INTERNATIONAL
62
FIG. 22
LOCATION OF THE MICROPROCESSOR BOARD
26001A
26000A
MICROPROCESSOR
BOARD
SYSTEM SWITCHES 1 - 4
ON MICROPROCESSOR BOARD
FIG. 22
ALARM CONTACT
CONNECTION LOCATION
LD01645
A new lead/lag assignment is made whenever both
compressors shut down. The micro will assign the lead
to the compressor with the shortest anti-recycle time.
This will tend to balance run time between the two com-
pressors.
AUTO Lead/Lag will cause the lag compressor to auto-
matically become the lead, anytime the compressor cur-
rently in the lead shuts down due to a safety threshold
being exceeded. This is done to maintain water tem-
perature as close to setpoint as possible. Additionally,
the lag system will automatically become the lead any-
time the system switch on the Microprocessor Board
of the compressor currently in the lead is placed in the
OFF position. This is also done to maintain water tem-
perature as close to setpoint as possible.
If MANUAL Lead/Lag is selected, an external dry con-
tact (switch) must be wired into the chiller. This contact
is supplied by others. When the contact is closed, SYS
2 will be the lead system. With the contact open, SYS
1 is the lead.
Manual Lead/Lag selection can be automatically over-
ridden by the micro to allow the lag compressor to au-
tomatically become the lead, anytime the selected lead
compressor shuts down due to a safety threshold be-
ing exceeded. This is done to try to maintain water
temperature as close to setpoint as possible. No lead/
lag switchover will take place if the system switch