JOHNSON CONTROLS
134
FORM 150.72-ICOM7
ISSUE DATE: 10/22/2020
SECTION 7 – UNIT CONTROLS
Option 8 – Condenser Fan Control Mode
F A N C O N T R O L
D I S C H A R G E P R E S S U R E
Condenser fans are controlled by discharge pressure
only. This mode must be chosen.
or
F A N C O N T R O L
A M B I E N T & D S C H P R E S S
Do not select this option on R-410A chillers.
Option 9 – Manual Override Mode
M A N U A L O V E R R I D E M O D E
D I S A B L E D
This option allows overriding of the daily schedule
that is programmed. MANUAL OVERRIDE MODE –
DISABLED indicates that override mode has no effect.
or
M A N U A L O V E R R I D E M O D E
E N A B L E D
Manual Override Mode is enabled. This is a service
function and when enabled, will allow the unit to start
when shut down on the daily schedule. It will auto-
matically be disabled after 30 minutes.
Option 6 – Display Units
D I S P L A Y U N I T S
I M P E R I A L
This mode displays system operating values in Impe-
rial units of °F or psig.
or
D I S P L A Y U N I T S
S I
This mode displays system operating values in Scien-
tific International Units of °C or barg.
Option 7 – Lead/Lag Type (two system units
only)
L E A D / L A G C O N T R O L
M A N U A L S Y S 1 L E A D
SYS 1 selected as lead compressor. SYS 1 lead option
MUST be chosen if Hot Gas Bypass is installed.
or
L E A D / L A G C O N T R O L
M A N U A L S Y S 2 L E A D
SYS 2 selected as lead compressor.
or
L E A D / L A G C O N T R O L
A U T O M A T I C
Lead/lag between systems may be selected to help
equalize average run hours between systems on chillers
with 2 refrigerant systems. Auto lead/lag allows auto-
matic lead/lag of the two systems based on an average
run hours of the compressors in each system. A new
lead/lag assignment is made whenever all compressors
shut down. The microprocessor will then assign the
“lead” to the system with the shortest average run time.
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