York International XN SERIES Installation Manual Download Page 30

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5188238-YIM-D-0518

Johnson Controls Ducted Systems

Optional Electric Heat

The factory or field installed heaters are wired for single point
power supply. Power supply need only be brought into the
single point terminal block, and thermostat wiring to the low
voltage terminal strip located in the upper portion of the unit
control box.

These CSA approved heaters are located within the central
compartment of the unit with the heater elements extending in
to the supply air chamber.

Fuses are supplied, where required, by the factory. Some kW
sizes require fuses and others do not. refer to Table 9 for
minimum CFM limitations and to Table 7 for electrical data.

Options/Accessories

Economizer/Motorized Damper and Rain Hood

The instruction for the optional economizer/motorized damper
rain hood can be found in the accessory. 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/motorized damper options.

Power Exhaust/barometric Relief Damper and Rain Hood

The instructions for the power exhaust/barometric relief damper
and rain hood can be found in form 1200060.

All of the components, including the dampers, hardware, and
mounting instructions are shipped in a single package external
from the unit and must be field assembled and installed.

Power exhaust is only available as a field installed accessory.

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

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

Table 9: Electric Heat Minimum Supply Air

Size

(Tons)

Voltage

Minimum Supply Air (CFM)

Heater kW

036

(3.0)

208/230-1-60