Base Unit Operation
COOLING, UNITS WITHOUT ECONOMIZER — When
thermostat calls for cooling, terminals G and Y1 are ener-
gized. The indoor (evaporator) fan contactor (IFC), and com-
pressor contactor no. 1 (C1) are energized and evaporator-
fan motor, compressor no. 1 and condenser fans start. The
condenser-fan motors run continuously while unit is cool-
ing. If the thermostat calls for a second stage of cooling by
energizing Y2, compressor contactor no. 2 (C2) is energized
and compressor no. 2 starts.
HEATING, UNITS WITHOUT ECONOMIZER (If Acces-
sory or Optional Heater is Installed) — Upon a call for heat-
ing through terminal W1, IFC and heater contactor no. 1 (HC1)
are energized. On units equipped for 2 stages of heat, when
additional heat is needed, HC2 is energized through W2.
COOLING, UNITS WITH ECONOMIZER — Upon a call
for cooling, when outdoor ambient temperature is above the
outdoor-air temperature control setting, the evaporator and
condenser fans and compressor energize. The economizer
damper moves to VENT position.
Upon a first-stage call for cooling, when outdoor ambient
temperature is below the temperature control setting, the evapo-
rator fan starts and economizer damper modulates to main-
tain mixed-air temperature. The compressor(s) remains off.
Upon a second-stage call for cooling, compressor no. 1 is
energized and mechanical cooling is integrated with econo-
mizer cooling. Compressor no. 2 is locked out. If the outdoor-
air temperature is below 50 F, a cooling lockout switch pre-
vents the compressor(s) from running.
When supply-air temperature drops below a fixed set point,
the economizer damper modulates to maintain the tempera-
ture at the fixed set point.
FREEZE PROTECTION THERMOSTAT(S) — A freeze pro-
tection thermostat (FPT) is located on the top and bottom of
the evaporator coil. It detects frost build-up and turns off the
compressor, allowing the coil to clear. Once frost has melted,
the compressor can be reenergized by resetting the compres-
sor lockout.
HEATING, UNITS WITH ECONOMIZER (If Accessory
or Optional Heater is Installed) — The outdoor air damper
stays at VENT position while the evaporator fan is operat-
ing. Upon a call for heating through terminal W1, the indoor
(evaporator) fan contactor (IFC) and heater contactor no. 1
(HC1) are energized. On units equipped for 2 stages of heat,
when additional heat is needed, HC2 is energized through
W2.
SERVICE
Before performing service or maintenance operations on
unit, turn off main power switch to unit. Turn off ac-
cessory heater power switch if applicable. Electrical shock
could cause personal injury.
Cleaning — Inspect unit interior at beginning of each heat-
ing and cooling season and as operating conditions require.
Remove unit top panel and/or side panels for access to unit
interior.
EVAPORATOR COIL — Clean as required with a commer-
cial coil cleaner.
NOTE: The 50TJ028 unit has a mist eliminator screen at-
tached to the evaporator coil to prevent condensate runoff at
high wet-bulb conditions. Check periodically and clean as
necessary.
CONDENSER COIL — Clean condenser coil annually and
as required by location and outdoor-air conditions. Inspect
coil monthly — clean as required.
CONDENSATE DRAIN — Check and clean each year at
start of cooling season.
FILTERS — Clean or replace at start of each heating and
cooling season, or more often if operating conditions re-
quire. Refer to Table 1 for type and size.
NOTE: The 50TJ028 unit requires industrial grade throw-
away filters capable of withstanding face velocities up to
625 fpm. Ensure that replacement filters for the 50TJ028 units
are rated for 625 fpm.
OUTDOOR-AIR INLET SCREENS — Clean screens with
steam or hot water and a mild detergent. Do not use throw-
away filters in place of screens.
Lubrication
COMPRESSORS — Each compressor is charged with the
correct amount of oil at the factory. Conventional white oil
(Sontext 200LT) is used. White oil is compatible with 3GS
oil, and 3GS oil may be used if the addition of oil is re-
quired. See compressor nameplate for original oil charge. A
complete recharge should be four ounces less than the origi-
nal oil charge. When a compressor is exchanged in the field
it is possible that a major portion of the oil from the replaced
compressor may still be in the system. While this will not
affect the reliability of the replacement compressor, the ex-
tra oil will add rotor drag and increase power usage. To re-
move this excess oil, an access valve may be added to the
lower portion of the suction line at the inlet of the compres-
sor. The compressor should then be run for 10 minutes, shut
down, and the access valve opened until no oil flows. This
should be repeated twice to make sure the proper oil level
has been achieved.
FAN SHAFT BEARINGS — For size 016 units, bearings
are permanently lubricated. No field lubrication is required.
For size 020-028 units, the bearings are of the pillow block
type and have grease fittings. The bearing opposite the mo-
tor end has an extended tube line so it can be lubricated from
the motor side. Lubricate the bearings twice annually.
Typical lubricants are given below:
MANUFACTURER LUBRICANT
Texaco Regal AFB-2*
Mobil Mobilplex EP No. 1
Sunoco Prestige 42
Texaco Multifak 2
*Preferred lubricant because it contains rust and oxidation inhibitors.
CONDENSERAND EVAPORATOR-FAN MOTOR BEAR-
INGS — The condenser and evaporator-fan motors have
permanently-sealed bearings, so no field lubrication is
necessary.
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