Carrier 30GA - Manual (Page 8)

CRANKCASE HEATER prevents absorption of
liquid refrigerant by oil in crankcase during brief or
extended shutdown periods. Source of 115-volt
power is the auxiliary control power, independent
of the main unit power. This assures compressor
protection even when main unit power disconnect
switch is off.
BiPORTANT; Never open any switch or discon­
nect that de-energizes fee craxrkcase heater unless
unit is being serviced ox is to be shut down for a
prolonged period. After a pr<^osged slrutdown
or a service job. energiae fee crankcase heater
for 24 hours before starting the compiessor.
Cooler Freeze-Up Protection
HEATER CABLE — A lead-sheathed 200-watt cable
is helically wound around the entire length of the
cooler. A thermostat energizes the cable whenever
the ambient temperature is 35 F or lower. The cable
is between the cooler and the 2-in. thick insulation
blanket around the cooler. The heater cable and
the insulation protect the cooler down to —20 F
ambient.
Since the 115-volt auxiliary power source for the
heater cable is separate from main unit power
source, power to heater is assured even though the
main unit power may be off. From the same source,
a 115-1-60 convenience outlet is provided for field-
supplied heating elements for chilled water piping.
CAUnON; Do noi disconrteci iieafer cable
power vfeen sexvicfeg compressor jf mbient
hafoperamre is below 40 F. ifpowertofee beater
is cat off, or if ami is to be down for a pro-
kaiged period^ drain fee cooler.
SAFETY THERMOSTAT (Freezestat or Low Water
Temperature Cutout) is a noncycling, manual reset
type, to protect against freeze-up due to operating
malfunction. The sensing bulb is installed in top of
the cooler shell at leaving chilled water end. Freeze­
stat is set to break the control circuit at 36 ± 2 F,
locking out the unit. The thermostat must be reset
before the unit can restart under Time Guard®
control. The chilled water circulating pump con­
tinues to operate during the lockout period.
When cooling below 33 F (glycols or brines), use
thermostat no. HH22PB030, with well no. 30HH
406102. Install well in connection provided in
leaving chilled waterline elbow at exit from cooler.
Check thermostat at installation and at least
once each season thereafter. (See Fig. 7.)
To Check — Insert screwdriver into adjusting slot
and turn dial assembly until desired cutoff temper­
ature is directly under fixed indicator. Place bulb
in vacuum bottle filled with mixture of water and
crushed ice. Stir mixture with thermometer. As ice
melts, temperature of mixture goes down. Note
TEMPERATURE
SENSING-~____|;
BULB
STOP LUG
dial screws
RESET BUTTON
capillary
Fig. 7 — Safety Thermostat
temperature where thermostat cuts out. This
should be within one or 2 degrees of dial setting.
Recalibrate if variation is greater.
To Recalibrate — Break painted seal at dial screw.
With a screwdriver in the adjusting slot, hold the
angular position of the dial assembly while com­
pleting the following steps:
1. Loosen the 2 dial screws.
2. Rotate dial only until the number under the
fixed indicator is the observed temperature of
the mixture.
3. Re tighten dial screws.
Turn dial assembly until desired compressor cut­
off temperature is directly under fixed indicator.
Recalibration is now complete.
WINTER SHUTDOWN — At the end of the cooling
season, drain the water from the cooler (see drain
location in Fig. 1). Replace the drain plug and put
2 gallons of ethylene glycol in the cooler to prevent
any residual water in the cooler from freezing. At
the beginning of the next cooling season, refill the
cooler and add the recommended inhibitor.
High-Pressure Switch has fixed, nonadjustable
settings.
TO CHECK — Open the condenser fan circuit
breaker. Head pressure will build up until the com­
pressor shuts down. This should be at the cutout