036-21371-001-B-0203
Unitary Products Group
11
ACCESSORIES (FIELD-INSTALLED)
Three-Phase Electric Heaters are available in several capaci-
ties to provide maximum flexibility. The heater can be
selected to precisely meet the supplemental heating require-
ment of the conditioned space.
These heaters are designed for easy field-installation over
the supply air opening of the indoor unit. They have been
tested by Underwriters’ Laboratories and will be shipped with
a UL label. Every heater will be fully protected against exces-
sive current and temperature by fuses and two high limit ther-
mostats.
Units with Electric Heat will require only one power supply for
both the heating elements and the supply air blower motor,
and the power wiring can be protected by either dual ele-
ment/time delay fuses or an inverse time circuit breaker.
Supply Air Plenums and Return Air Grilles (expanded metal)
are available for free-standing indoor units located in the con-
ditioned space. Both accessories are finished to match the
exterior of the basic unit, and both can be applied with either
vertical or horizontal units. The supply air plenums are fully
insulated and have double-deflection, adjustable grilles.
Base Sections are available to raise vertical indoor units
above the floor. Outdoor air may be introduced through these
bases by cutting an access opening for the outdoor air duct
connection. These bases are finished to match the exterior of
the basic unit. They may have to be insulated in the field for
certain applications.
Decorative Coil Guards can be field installed to enhance pro-
tection of the unit.
Thermostats with either manual or automatic changeover are
available for precise control of the temperature within the
conditioned space. The manual thermostat has a four-posi-
tion selector switch - COOL, OFF, HEAT, and EMERGENCY
HEAT, and three stages of control - one stage of cooling and
two stages of heating. The automatic thermostat has a three-
position selector switch - OFF, AUTOMATIC and EMER-
GENCY HEAT, and four stages of control - two stages of
cooling and two stages of heating.
Both thermostats have a two-position fan switch, AUTO and
ON to provide intermittent or continuous blower operation.
NOTE: The automatic changeover thermostat must be used
on units equipped with a field-supplied economizer.
The first cooling stage of the automatic thermostat
will only control the position of the reversing valve;
the system will still operate with only one stage of
cooling.
The EMERGENCY HEAT position on the selector
switch and the second stage of heating will only func-
tion on systems with an electric heat accessory.
TABLE 9: STATIC RESISTANCES FOR UNIT ACCESSORIES (IWG)
Unit Model
Accessory
CFM
2400
2700
3000
3300
3600
FA090
ELECTRIC HEAT
10 KW
0.01
0.01
0.01
0.02
0.02
16 KW
0.01
0.02
0.02
0.03
0.04
26 KW
0.03
0.04
0.05
0.06
0.07
36 KW
0.05
0.07
0.08
0.10
0.11
Supply Air Plenum
0.03
0.03
0.04
0.05
0.06
Return Air Grille
0.02
0.03
0.04
0.05
0.06
