5703827-XIM-A-0319
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Johnson Controls Ducted Systems
Operation
Compressor operation
Compressor operation details include:
a. Compressors are controlled by the Y1 through Y2 thermostat inputs. If the Lead/Lag function is turned OFF, a Y1 input
energizes the C1 output when the compressor number 1 anti-short cycle delay is at 0 and all refrigerant safety devices are
closed (default 5 minutes).
b. The FAN output for indoor fan operation energizes with any cooling output after the Indoor Fan Cool On Delay expires.
c. When the thermostat cooling inputs are lost
and
the minimum runtime expires, the compressor outputs stage off (default 3
minutes).
d. A 30-second interstage delay occurs when multiple stages are requested.
NOTE:
A Y2 input without a Y1 input energizes a C1 first and then C2 30 seconds later.
Intelli
Speed
™ supply fan control
1.
Setpoints and related data
• Fan Control Type Fixed Variable
• Occupied, No Heat Or Cool % Command 0-100%
• Occupied, One Stage of Cool % Command 0-100%
• Occupied, Two Stage of Cool % Command 0-100%
• Occupied, One Stage of Heat % Command 0-100%
• Occupied, Two Stage of Heat % Command 0-100%
• Economizer Minimum Position 0-100%
• Economizer Minimum Position for Low Speed Fan 0-100%
2.
Outputs
• 24 VAC from FAN on the unit control board (UCB) to enable VFD.
• 2-10 vdc from the VFD terminal on the UCB for controlling the speed of the VFD drive.
3.
VFD operation
• 2-10vdc output from the VFD terminal on the UCB operates the supply fan VFD proportional to the minimum and maximum
frequency settings of the VFD drive (defaults 25hz - 60hz)
4.
Supply fan only operation
• When there is no demand for heating or cooling, the supply fan to run operate at the percent output that relates to the "No Heat
Or Cool % Command" setpoint.
5.
Cooling supply fan operation
• With a demand for cooling stage 1 only, the VFD operates at the frequency relating to the setpoint "Occupied, One Stage of
Cool % Command"
• With a demand for two cooling stages, the VFD operates at the frequency relating to the setpoint "Occupied, One Stage of
Cool % Command"
Economizer sequences
Several functions can drive the economizer, including: minimum position, free cooling, economizer loading, and minimum outdoor air
supply.
Economizer minimum position
The economizer minimum position is set during occupied mode when outside air is not suitable for free cooling. The position of the
damper is set proportionally between the economizer minimum position and the economizer minimum position low speed fan
setpoints, in relationship to the VFD output percentage. On a constant volume single speed supply fan system, both setpoints should
be set to the same value.
Free cooling
Four types of free cooling options are available: dry bulb changeover, single enthalpy, dual enthalpy changeover, and auto.
