Field Installed Electric Heat Accessories; Options/Accessories; Economizer Sequences; Dry Bulb Changeover - York XP SERIES W/SIMPLICITY Installation Manual

Field Installed Electric Heat Accessories

These field-installed heater accessories can be wired for single
point power supply.
These CSA approved heater accessories shall be located
within the central compartment of the unit with the heater
elements extending into the supply air chamber.
Fuses are supplied, where required. Some kW sizes require
fuses and others do not. Refer to Table 8 for minimum CFM
limitations and to Table 6 for electrical data.
Table 8: Electric Heat Minimum Supply Air
Size
Voltage
(Tons)
208/230-3-60
180
460-3-60
(15)
600-3-60
208/230-3-60
240
460-3-60
(20)
600-3-60

Options/Accessories

Electric Heat
Electric heaters are available as a field-installed accessory.
These heaters mount in the heat compartment with the
heating elements extending into the supply air chamber. All
electric heaters are fused and intended for use with single
point power supply.
Economizer/Motorized Outdoor Damper Rain Hood
The instruction for the optional economizer/motorized damper
rain hood can be found in the rain hood kit. Use these
instructions when field assembling an economizer rain hood
onto a unit. The outdoor and return air dampers, the damper
actuator, the damper linkage, the outdoor and return air divider
baffles, and all the control sensors are factory mounted as part
of the "Factory installed" economizer option.
Power Exhaust/Barometric Relief Damper and Rain Hood
The instructions for the power exhaust/barometric relief damper
and rain hood can be found in the rain hood kit. The exhaust
fan, all supporting brackets, angles, and the wiring are factory
installed as part of the power exhaust option.

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
Johnson Controls Unitary Products
Minimum Supply Air (CFM)
Heater kW
18 36 54
4500 4500 5000
4500 4500 5000
4500 4500 4500
6000 6000 6000
6000 6000 6000
6000 6000 6000
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
72
rises above either the Economizer OAT Enable setpoint or the
5000
return air temperature.
5000
4500

Single Enthalpy Changeover

6000
6000
For single enthalpy economizer operation, the outside air is
6000
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
• Return and outside air dry bulb and outside air humidity =
single enthalpy
• Return and outside air dry bulb and return and outside air
humidity = dual enthalpy
• If either the return or outside air dry bulb sensors are
unreliable, free cooling is not available

Free Cooling Operation

When the control determines that the outside air is suitable, the
first stage of cooling will always be free cooling.
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