Carrier 42C Series Product Data page 33

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, Model 42S stack units and Model
42V (except 42VC and VE).
These heaters consist of coils of the highest grade resis-
tance wire, insulated by ceramic insulators on plated steel
brackets. High limit thermal cutouts protect the unit in the
event of airflow loss.
All heaters except those used in 42S stack units are posi-
tioned on the incoming (preheat) side of the unit coil. On
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 42VC and 42VE
vertical units. There heaters consist of the highest grade
resistance wire, centered in a
plated steel sheath. The wire is insulated from the sheath
by magnesium oxide powder packed around it. To increase
the heater surface exposed to air, a 1
per plated steel is wound around the sheath in a spiral that
makes 5 turns per linear inch. Sheath and fin are perma-
nently bounded together by copper brazing. The heaters
are positioned on the leaving (rehead) 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 except for
42SM, which offers 2-stage electric heaters.
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
1 / in. diameter copper
2
1
/ in. OD fin of cop-
4
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