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Auxiliary (Electric) Heat control
The 50HCQ unit can be equipped with one or two auxiliary
electric heaters, to provide a second stage of heating. The DFB
will energize this Heating System for a Stage 2 Heating Com-
mand (heaters operate concurrently with compressor(s) in the
Stage 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 "cold
blow" condition in the space).
Defrost
The defrost control mode is a time/temperature sequence.
There are two time components: The continuous run period
and the test/defrost cycle period. The temperature component
is 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 the
end of the last defrost cycle (or start of the current Heating cy-
cle) during which no defrost will be permitted. This period can
be set at 30, 60, 90 or 120 minutes by changing the positions of
DIP 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 bypasses
the remaining continuous run period and places the unit in a
Forced Defrost mode. If the controlling DFT is closed when
this mode is initiated, the unit will complete a normal defrost
period that will terminate when the controlling DFT opens or
the 10 minute defrost cycle limit is reached. If the controlling
DFT is open when this mode is initiated, the Defrost cycle will
run for 30 seconds. Both modes end at the end of the Defrost
cycle.
Fig. 31 — DIP Switch Settings - Defrost Board
ELECTRIC HEATERS
50HCQ units may be equipped with field-installed accessory
electric heaters. The heaters are modular in design, with heater
frames 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 access
panel. Heater modules slide into the compartment on tracks
along 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 a
specific size unit. Refer to the label on the unit cabinet for the
list 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 for
correlation between Heater Model Number and Sales Package
part number.
NOTE: The value in position 9 of the part number differs between
the sales package part number (value is 1) and a bare heater model
number (value is 0).
DISCONNECT MOUNTING
LOCATION
UNIT BLOCK-OFF
PANEL
Fig. 32 — Typical Access Panel Location
DISCONNECT
EMT OR RIGID CONDUIT
MOUNTING
(FIELD-SUPPLIED)
LOCATION
SINGLE POINT
MAIN
BRACKET AND
BOX
CONTROL
CONDUIT
MOUNTING
BOX
DRIP BOOT
SCREW
CONTROL WIRE TERMINAL BLOCK
Fig. 33 — Typical Component Location
Fig. 34 — Typical Module Installation
21
INDOOR
OUTDOOR
ACCESS
ACCESS PANEL
PANEL
SINGLE
CENTER
MANUAL RESET
POINT BOX
POST
LIMIT SWITCH
HEATER
COVERS
HEATER
HEATER
HEATER
MODULE
MODULE
MOUNTING
(LOCATION 1)
(LOCATION 2)
BRACKET
TRACK
FLANGE
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