Carrier 42 SERIES Application Data

ELECTRIC HEATApplication — Electric heaters are available forin-stallation on Carrier fan coil units in the followingapplications.TOTAL ELECTRIC HEAT — This system provides com-plete heating during the heating season; no boiler is re-quired. Heating and cooling are now available on an indi-vidual basis throughout the year with a 2-pipe system.Chilled water is used for cooling and the electric heater isused for heating. Room controls can be supplied foreither manual or automatic changeover.AUXILIARY ELECTRIC HEAT — This system is used forheating between seasons or during the cooling season whenchilled water is being circulated. Individual room controlsare supplied to provide electric heat only when chilled wateris being circulated through the system. Water flow throughthe unit is shut off when the heater is turned on.During the winter heating season, heating is providedby hot water circulated through the system. A changeoverdevice locks out the electric heat when the hot water iscirculated.Heater ConstructionSTRIP HEATERS — Used with Model 42C ceiling units,Model 42D ducted units and Model 42S stack units.These heaters consist of coils of the highest graderesistance wire, insulated by ceramic insulators in alumi-nized brackets.All heaters except those used in 42S stack units are po-sitioned on the incoming (preheat) side of the unit coil. On42S stack units, the strip heater is located in the fan dis-charge on the leaving side of the coil.SHEATH HEATERS — Used with Model 42V vertical units.These heaters consist of the highest grade resistance wire,centered in a 1⁄2-in. diameter copper-plated steel sheath. Thewire is insulated from the sheath by magnesium oxide pow-der packed around it. To increase the heater surface exposedto air, a 11⁄4-in. OD fin of copper-plated steel is wound aroundthe sheath in a continuous spiral that makes 5 turns per lin-eal inch. Sheath and fin are permanently bonded together bycopper brazing.The heaters are positioned on the leaving (reheat) side ofthe unit coil. On special units with high efficiency motors, astrip heater will be installed in the fan discharge on the in-coming (preheat) side of the unit coil.Heater Electrical Data1. Load voltage may be 120, 208, 240 or 277 volts. For unitsize and kW limitations, refer to the specific unitcatalogs.2. All heaters are single stage and single phase.3. Unless a single power-source option is selected, the elec-tric heat units require 2 separate power sources. With thesingle power-source option, only one line circuit need bebrought into the unit. Fuse protection is added to the motor/control circuit to protect these components. This is sepa-rate from the field-furnished total unit overcurrent protection.MODEL 42V VERTICAL UNITWITH ELECTRIC SHEATH HEATERMODEL 42C CEILING UNITWITH ELECTRIC STRIP HEATER9