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Fig. 37 — 42S Unit Supply Air Installation (All Units)
Step 2 — Make Electrical Connections
Refer to unit nameplate for required supply voltage, fan and heater
amperage, and required circuit ampacity. Refer to unit wiring dia
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gram for unit and field wiring. Since each project is different and
each unit on a project may be different, the installer must be famil
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iar with the wiring diagram and nameplate on the unit before be
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ginning any wiring. Make sure all electrical connections are in ac
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cordance with unit wiring diagram and all applicable codes. The
type and sizing of all wiring and other electrical components such
as circuit breakers, disconnect switches, etc. should be determined
by the individual job requirements, and should not be based on the
size and/or type of connection provided on the equipment. All in
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stallations should be made in compliance with all governing codes
and ordinances. Compliance with all codes is the responsibility of
the installing contractor.
The fan motor(s) should never be controlled by any wiring or de
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vice other than the factory-supplied switch or thermostat/switch
combination unless prior factory authorization is obtained. Fan
motor(s) may be temporarily wired for use during construction
only with prior factory approval and only in strict accordance with
the instructions issued at that time.
The unit electrical supply is designed to enter through knockouts
provided in the top of the unit and pass down through matching
knockouts in the control section top. Where space allows, power
may be pulled directly through the side of the cabinet into the con
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trol section.
All components furnished for field installation by either the facto
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ry or the controls contractor should be located and checked for
proper function and compatibility. All internal components should
be checked for shipping damage, and any loose connections
should be tightened to minimize problems during start-up.
Any devices such as fan switches or thermostats that have been
furnished from the factory for field installation must be wired in
strict accordance with the wiring diagram that appears on the unit.
Failure to do so could result in personal injury or damage to com
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ponents, and will void all manufacturer's warranties.
The manufacturer assumes no responsibility for any damages and/
or injuries resulting from improper field installation and/or wiring.
FACTORY-INSTALLED OPTIONS
Condensate Overflow Switch
The condensate overflow switch is used to detect a clogged con
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densate drain pan. The condensate switch uses a normally closed
contact to allow the system control power to pass through the
switch energizing the water valves and fans allowing normal oper
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ation. When an overflow condition is detected by the switch, it
opens the NC contact and de-energizes the water valve and fans.
Aquastat
The aquastat must be able to sense whether the flowing water is
being chilled or heated and switches a contact closed to provide
automatic summer or winter changeover for the system. When a
two-pipe cooling/heating system with optional auxiliary electric
heat is desired, an additional aquastat is required.
If the valve package is field-supplied, the aquastat must be
installed in a location where it will sense the water temperature
regardless of control valve position. A bleed bypass should be pro
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vided for proper operation of aquastat. The bleed line allows a
small amount of water to flow from supply to return piping when
the control valve is closed for loop temperature sensing.
All field wiring must be in accordance with governing codes and
ordinances. Any modification of unit wiring without factory au
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thorization will invalidate all factory warranties and nullify any
agency listings. The manufacturer assumes no responsibility for
any damages and/or injuries resulting from improper field installa
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tion and/or wiring.
Units may be equipped with line voltage controls or 24 vac control
systems. The following descriptions are for typical control se
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quences only. For detailed control operating sequence, refer to
thermostat operating instructions.
STANDARD WIRING PACKAGES
Thermostatic Electric Valve Control, 2-Pipe
A thermostatically controlled 2-position valve provides superior
control to fan cycling. With this control, the fan runs continuously
unless it is manually switched to the OFF or AUTO position. The
fan must be on before the valve can be opened to supply water to
the coil.
This system can be used for normal 2-pipe changeover systems
and can also be furnished for cooling-only or heating-only appli
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cations by omitting the changeover and specifying which applica
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tion is intended. Wiring diagrams show typical applications. Refer
to wiring diagram on unit blower housing for unit specific wiring.
Thermostatic 2-Pipe Auxiliary Electric Heat with Valve
Control
This system, also called twilight or intermediate season electric
heat, goes a long way towards solving the spring and fall control
problems of 2-pipe systems.
Chilled water can be run late into the fall, turned on early in the
spring, and electric heat will still be available to all units whenever
required.
In winter, the system is switched over to hot water. Two change
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over devices are required for this. One device switches the action
of the thermostat and the other locks out the electric heat when hot
water is in the coil.
With this system, the fan runs continuously unless manually
switched to OFF or AUTO position. Fan must be on before ther
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mostat can send signal to open chilled water valve or turn on elec
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tric heater.
Two control methods are available:
1. Use the standard automatic changeover thermostat with a
dead band between heating and cooling.
2. Use a manual changeover thermostat. With this method only
one changeover is required.
Be sure to include a 2-way or 3-way electric valve with this sys
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tem.
NOTE: Wiring diagrams are for typical applications. If other volt
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ages for heaters or controls are specified, wiring may differ from
that shown. Refer to wiring diagram on unit blower housing for
unit specific wiring.
Duct Flange
90°
Unit Wall
Unit
Installation
IMPORTANT: Refer to unit wiring label for specific func
-
tions. Standard wiring diagram configurations are maintained
in separate Fan Coil Wiring Diagram literature. Refer to unit
wiring label for specific functions.