Carrier 50EQ - Manual (Page 6)

10. Reset thermostat at a setting above room tem­
perature. Compressor(s) will shut off.
TO SHUT OFF UNIT — Set system selector switch
at OFF position or reset thermostat at a setting
above room temperature.
Do not shut off unit circuit breakers except when
unit is to be serviced. Crankcase heaters are ener­
gized only when unit power is on.
Units are equipped with Signal-LOC™ compres­
sor protective device. Unit shuts down on trip of any
safety device and indicator light on thermostat
comes on. Check reason for safety device trip. Com­
pressor restart is accomplished by manual reset at
room thermostat by moving selector switch to OFF
and then ON.
Heating — To start unit, turn on main power
supply. Refer to Crankcase Heaters.
Set thermostat at HEAT, fan at AUTO, and a
setting above room temperature.
First stage of the heating thermostat energizes
compressor no. 1; the second stage energizes com­
pressor no. 2. The electric heater elements are not
energized until the field adjustable outdoor air ther­
mostat closes. When this occurs, the first stage of the
thermostat energizes compressor no. 1 and no. 2;
the second stage energizes the electric heater
elements.
Fig. 7 — Enthalpy Control Assembly
Wiring Connections
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Fig. 8 — Field Power Wiring Connections
REMOVABLE JUMPER
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Fig. 9 — Field Control Thermostat Wiring
Check heating effect at duct supply outlets.
Check unit operation. Referto heating operation
chart in service section.
TO SHUT OFF UNIT — Set system selector switch
at OFF or set heating selector lever below room
temperature.
Safety Relief — A fusible plug in the accumulator
provides pressure relief under abnormal tempera­
ture and pressure conditions.
Defrost Cycle — As frost builds up on the outdoor
coil, the defrost thermostat closes and the unit
operates in a defrost cycle (controlled by the defrost
timer and thermostat). During this cycle the outdoor
air fan shuts off and the unit operates on cooling
cycle for a maximum of 10 minutes. During defrost,
bottom of outdoor coil defrosts first to ensure
proper drainage.
If only compresor no. 1 is operating at beginning
of a deUost cycle, compressor no. 2 is started to
maintain warm air supply to conditioned space.
If both compressors are operating, one is pre­
vented from defrosting as the other compressor con­
tinues thru the defrost cycle. The electric heaters are
not automatically energized during a defrost cycle.
Automatic Changeover (with Automatic
Changeover Thermostat only) — The unit will
automatically switch from heating mode to cooling
mode when the system selector switch is set at
AUTO, and the temperature of the conditioned
space rises to cooling selector lever setting. When
the temperature of the conditioned space falls to the
heating selector lever setting, the unit will auto­
matically change from cooling mode to heating
mode.
The thermostat and unit are so connected that
the cooling and heating systems will not operate
simultaneously.
Economizer Operation — If unit is equipped with
a modulating outdoor air control (economizer), it
should operate as follows:
THERMOSTAT SETTINGS — Set enthalpy con­
trol to the desired temperature and relative humidity
which provides cooling with outside air only (no
compressor operation). To determine appropriate
setting of enthalpy control:
1. Determine the maximum combination of relative
humidity and temperature of the supply air con­
sidered acceptable for the installation.
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