Carrier 50HCQ07 Installation Instructions Manual

21Auxiliary (Electric) Heat controlThe 50HCQ unit can be equipped with one or two auxiliaryelectric heaters, to provide a second stage of heating. The DFBwill energize this Heating System for a Stage 2 Heating Com-mand (heaters operate concurrently with compressor(s) in theStage 1 Heating cycle), for an Emergency Heating sequence(compressors are off and only the electric heaters are ener-gized) and also during the Defrost cycle (to eliminate a “coldblow” condition in the space).DefrostThe defrost control mode is a time/temperature sequence.There are two time components: The continuous run periodand the test/defrost cycle period. The temperature componentis provided by Defrost Thermostat 1 and 2 (DFT1 and DFT2)mounted on the outdoor coil.The continuous run period is a fixed time period between theend of the last defrost cycle (or start of the current Heating cy-cle) during which no defrost will be permitted. This period canbe set at 30, 60, 90 or 120 minutes by changing the positions ofDIP switches SW1 and SW2 (see Fig. 31 and Table 4). The de-fault run period is 30 minutes.Shorting the jumpers for a period of 5 to 20 seconds bypassesthe remaining continuous run period and places the unit in aForced Defrost mode. If the controlling DFT is closed whenthis mode is initiated, the unit will complete a normal defrostperiod that will terminate when the controlling DFT opens orthe 10 minute defrost cycle limit is reached. If the controllingDFT is open when this mode is initiated, the Defrost cycle willrun for 30 seconds. Both modes end at the end of the Defrostcycle.Fig. 31 — DIP Switch Settings - Defrost BoardELECTRIC HEATERS50HCQ units may be equipped with field-installed accessoryelectric heaters. The heaters are modular in design, with heaterframes holding open coil resistance wires strung through ce-ramic insulators, line-break limit switches and a control con-tactor. One or two heater modules may be used in a unit.Heater modules are installed in the compartment below the in-door (supply) fan outlet. Access is through the indoor accesspanel. Heater modules slide into the compartment on tracksalong the bottom of the heater opening. See Fig. 32-34.Not all available heater modules may be used in every unit.Use only those heater modules that are UL listed for use in aspecific size unit. Refer to the label on the unit cabinet for thelist of approved heaters.Unit heaters are marked with Heater Model Numbers, but heat-ers are ordered as and shipped in cartons marked with a corre-sponding heater Sales Package part number. See Table 5 forcorrelation between Heater Model Number and Sales Packagepart number.NOTE: The value in position 9 of the part number differs betweenthe sales package part number (value is 1) and a bare heater modelnumber (value is 0).Fig. 32 — Typical Access Panel LocationFig. 33 — Typical Component LocationFig. 34 — Typical Module InstallationDISCONNECT MOUNTINGLOCATIONUNIT BLOCK-OFFPANELOUTDOORACCESS PANELINDOORACCESSPANELDISCONNECTMOUNTINGLOCATIONEMT OR RIGID CONDUIT(FIELD-SUPPLIED) SINGLEPOINT BOX CENTERPOSTHEATERCOVERSHEATERMOUNTINGBRACKETHEATERMODULE(LOCATION 2)HEATERMODULE(LOCATION 1)SINGLE POINTBOXMOUNTINGSCREWBRACKET ANDCONDUITDRIP BOOTMAINCONTROLBOXCONTROL WIRE TERMINAL BLOCKMANUAL RESETLIMIT SWITCHTRACKFLANGE