Carrier 42C Series Product Data page 24

Application data (cont)
Electric heat
Electric heaters are available for installation on Carrier fan
coil units in the following applications.
Total electric heat — This system provides complete
heating during the heating season; no boiler is required.
Heating and cooling are now available on an individual
basis throughout the year with a 2-pipe system.
Chilled water is used for cooling and the electric heater is
used for heating. Individual room controls can be supplied
for either manual or automatic changeover.
Auxiliary electric heat — This system is used for heat-
ing between seasons or during the cooling season when
chilled water is being circulated. Individual room controls
are supplied to provide electric heat only when chilled
water is being circulated through the system. Water flow
through the unit is shut off when the heater is turned on.
During the winter heating season, heating is provided by
hot water circulated through the system. A changeover
device locks out the electric heat when the hot water is
circulated.
Heater construction
Strip heaters are used with Model 42C ceiling units,
Model 42D ducted units and Model 42S stack units.
These heaters consist of coils of the highest grade resis-
tance wire, insulated by ceramic insulators in aluminized
brackets.
All heaters except those used in 42S stack units are posi-
tioned on the incoming (preheat) side of the unit coil. On
MODEL 42V VERTICAL UNIT
WITH ELECTRIC SHEATH HEATER
24
42S stack units, the strip heater is located in the fan dis-
charge on the leaving side of the coil.
Sheath heaters are used with Model 42V vertical units.
These heaters consist of the highest grade resistance wire,
1
centered in a / -in. diameter copper-plated steel sheath.
2
The wire is insulated from the sheath by magnesium oxide
powder packed around it. To increase the heater surface
exposed to air, a 1 1 / -in. OD fin of copper-plated steel is
4
wound around the sheath in a continuous spiral that makes
5 turns per lineal inch. Sheath and fin are permanently
bonded together by copper brazing.
The heaters are positioned on the leaving (reheat) side of
the unit coil. On special units with high efficiency motors, a
strip heater will be installed in the fan discharge on the
incoming (preheat) side of the unit coil.
Heater electrical data
1. Load voltage may be 120, 208, 240 or 277 volts. For
unit size and kW limitations, refer to the specific unit
catalogs.
2. All heaters are single stage and single phase.
3. Unless a single power-source option is selected, the
electric heat units require 2 separate power sources.
With the single power-source option, only one line cir-
cuit need be brought into the unit. Fuse protection is
added to the motor/control circuit to protect these
components. This is separate from the field-furnished
total unit overcurrent protection.
MODEL 42C CEILING UNIT
WITH ELECTRIC STRIP
HEATER