Defrost; Electric Heaters - Carrier 50FCQ 04-07 Series Service And Maintenance Instructions

Defrost

The defrost control mode is a time/temperature sequence. There
are 2 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 cycle)
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. 35 and Table 8). The default 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 de-
frost 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. 35 — DIP Switch Settings — Defrost Board

ELECTRIC HEATERS

The 50FCQ units can be equipped with field-installed accessory
electric heaters. The heaters are modular in design, with heater
frames holding open coil resistance wires strung through ceramic
insulators and control contactor(s), using a combination of 24-v
control side break/auto-reset or line-break/auto-reset limit switch-
es and a pilot-circuit/manual reset limit switch to protect the unit
against over-temperature situations. All 50FCQ Model electric
heaters are one module containing either one or 2 banks of electric
heat coils.
Heater modules are installed in the compartment below the indoor
(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. 36-38.
1 2
1 •
0 •
30 minutes
(factory default)
Table 8 — DIP Switch Positions
1 2
1 •
0 •
60 minutes
Fig. 36 — Typical Access Panel Location
Not all available heater modules can 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 regarding approved
heaters.
Optional
Factory-Installed
Disconnect
Fig. 37 — Typical Component Location
Fig. 38 — Typical Module Installation
1 2
1 1
0 • • 0
90 minutes
24
Control Box
Access Panel
Vane Axial
Main
Single
Center Indoor Fan
Control
Point
Post System
Box
Box
Heater
Control Wire
Heater
Mounting
Terminal Block Cover
Bracket
1 2
• • 1
0
120 minutes
Indoor
Access
Panel
Manual
Reset Limit
Switch
Heater
Module
3
• On
Off
Fan Delay