Johnson Controls ZZ Series, Installation Manual

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5834853-YIM-B-0320
Johnson Controls Ducted Systems 53
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.
IntelliSpeed 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 Unit Control Board (UCB) to enable
VFD.
• 2-10 VDC from VFD terminal on UCB for controlling speed
of the VFD drive.
3. VFD Operation
• 2-10vdc output from VFD terminal on UCB will operate
supply fan VFD proportional to the min and max
frequency settings of 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, VFD will operate
at the frequency relating to setpoint "Occupied, One
Stage of Cool % Command"
• With a demand for Two Cooling Stages, VFD will operate
at the frequency relating to 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" set points, in relationship to the VFD output
percentage. On a constant volume single speed supply fan
system both set-points 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.
Dry Bulb Changeover
For dry bulb economizer operation, the outside air is suitable for
free cooling if the outside air temperature is 1°F below the
Economizer OAT Enable Setpoint
and 1°F below the Return Air
Temperature.
Free cooling is no longer available if the outside air temperature
rises above
either the Economizer OAT Enable setpoint or the
return air temperature.
Single Enthalpy Changeover
For single enthalpy economizer operation, the outside air is
suitable for free cooling if the outside air enthalpy is at least 1
BTU/lb below the Economizer Outside Air Enthalpy Setpoint
and the outside air temperature is no greater than the RAT plus
9°F.
If the outside air temperature rises above the RAT plus 10°F,
free cooling is no longer available. The outside air temperature
must drop to no greater than RAT plus 9°F to enter free cooling
again.
Free cooling is no longer available if the outside air enthalpy
rises above the Economizer Outside Air Enthalpy Setpoint.
Dual Enthalpy Changeover
For dual enthalpy economizer operation, the outside air
enthalpy must be lower than the return air enthalpy by 1 btu/lb
AND the outside air temperature is no greater than the RAT
plus 9°F.
Auto
The control determines the type of free cooling changeover
based on which sensors are present and reliable. Conditions
include:
• Return and outside air dry bulb = dry bulb changeover