19
START-UP
Use the following information and Start-Up Checklist on
page CL-1 to check out unit PRIOR to start-up.
Unit Preparation —
Check that unit has been installed in
accordance with these installation instructions and all applica-
ble codes.
Compressor Mounting —
Compressors are internally
spring mounted. Do not loosen or remove compressor hold-
down bolts.
Refrigerant Service Ports —
Each refrigerant sys-
tem has a total of 3 Schrader-type service gage ports. One port
is located on the suction line, one on the compressor discharge
line, and one on the liquid line. In addition Schrader-type
valves are located underneath the low-pressure switches. Be
sure that caps on the ports are tight.
Compressor Rotation —
It is important to be certain
the compressors are rotating in the proper direction. To deter-
mine whether or not compressors are rotating in the proper
direction:
1. Connect service gages to suction and discharge pres-
sure fittings.
2. Energize the compressor.
3. The suction pressure should drop and the discharge pres-
sure should rise, as is normal on any start-up.
If the suction pressure does not drop and the discharge pres-
sure does not rise to normal levels:
1. Note that the evaporator fan is probably also rotating
in the wrong direction.
2. Turn off power to the unit.
3. Reverse any two of the incoming power leads.
4. Turn on power to the compressor.
The suction and discharge pressure levels should now move
to their normal start-up levels.
NOTE: When compressors are rotating in the wrong direction,
the unit will have increased noise levels and will not provide
heating and cooling.
After a few minutes of reverse operation, the scroll
compressor internal overload protection will open, which will
activate the unit’s lockout and requires a manual reset. Reset is
accomplished by turning the thermostat on and off.
Internal Wiring —
Check all electrical connections in
unit control boxes; tighten as required.
Crankcase Heater (Size 028 and Units with
MoistureMiser) —
Heater is energized as long as there is
power to unit and compressor is not operating.
Evaporator Fan —
Fan belt and variable pulleys are
factory installed. Remove tape from the fan pulley. See Table 8
for air quantity limits. See Tables 9-14 for fan performance
data. Be sure that fans rotate in the proper direction.
See Tables 15A-17B for static pressure information for
factory-installed options and field-installed accessories. See
Tables 18A and 18B for fan revolutions at various motor pulley
settings. See Fig. 30 for fan performance using horizontal
adapter. Refer to Table 19 for evaporator-fan motor perfor-
mance. To alter fan performance, see Evaporator-Fan Perfor-
mance Adjustment section on page 27.
Condenser Fans and Motors —
Fans and motors
are factory set. Refer to Condenser-Fan Adjustment section on
page 28 as required.
Return-Air Filters —
Check that correct filters are in-
stalled in filter tracks. See Tables 1A and 1B. Do not operate
unit without return-air filters.
Outdoor-Air Inlet Screens —
Outdoor-air inlet
screens must be in place before operating unit.
Accessory EconoMi$er Adjustment —
Remove
filter access panel. Check that the outdoor-air damper is closed
and return-air damper is open.
EconoMi$er operation and adjustment is described in Base
Unit Operation section below and EconoMi$er Adjustment
section on page 28.
Base Unit Operation
COOLING, UNITS WITHOUT ECONOMI$ER — When
thermostat calls for cooling, terminals G and Y1 are energized.
The indoor (evaporator) fan contactor (IFC), and compressor
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 cooling. If the thermostat
calls for a second stage of cooling by energizing Y2, compres-
sor contactor no. 2 (C2) is energized and compressor no. 2
starts.
HEATING, UNITS WITHOUT ECONOMI$ER (If Acces-
sory or Optional Heater is Installed) — Upon a call for heat-
ing through terminal W1, IFC and heater contactor no. 1 (HC1)
are energized. On units equipped for 2 stages of heat, when ad-
ditional heat is needed, HC2 is energized through W2.
Table 8 — Air Quantity Limits
COOLING UNITS WITH ECONOMI$ER — When the
OAT is above the ECON SP set point and the room thermostat
calls for Stage 1 cooling (R to G + Y1), the indoor-fan motors
(IFM) is energized and the EconoMi$er damper modulates to
minimum position. The compressor contactor and outdoor-fan
contactor (OFC) are energized to start the compressor and
outdoor-fan motor (OFM). After the thermostat is satisfied, the
damper modulates to the fully closed position when the IFM is
deenergized.
When the OAT is below the ECON SP setting and the room
thermostat calls for Stage 1 cooling (R to G + Y1), the
EconoMi$er modulates to the minimum position when the
IFM is energized. The EconoMi$er provides Stage 1 of cooling
by modulating the return and outdoor air dampers to maintain a
30 C (55 F) supply air set point. If the supply-air temperature
(SAT) is greater than 32 C (57 F), the EconoMi$er modulates
open, allowing a greater amount of outdoor air to enter the unit.
If the SAT drops below 29 C (53 F), the outdoor air damper
modulates closed to reduce the amount of outdoor air. When
the SAT is between 29 C (53 F) and 32 C (57 F), the
EconoMi$er maintains its position.
If outdoor air alone cannot satisfy the cooling requirements
of the conditioned space, and the OAT is above the MECH
CLG LOCKOUT set point, the EconoMi$er integrates free
cooling with mechanical cooling. This is accomplished by the
strategies below.
NOTE: Compressors have a two-minute Minimum On and
Minimum Off, which are accomplished by the strategies
below.
1. If Y1 is energized, and the room thermostat calls for Y2
(2-stage thermostat), the compressor and OFC are ener-
gized. The position of the EconoMi$er damper is main-
tained at its current value.
IMPORTANT: Unit power must be on for 24 hours prior to
start-up. Otherwise, damage to the compressor may result.
UNIT
50TJ
MINIMUM
MAXIMUM
L/s
Cfm
L/s
Cfm
016
2125
4500
3525
7,500
024
2800
6000
4800
10,000
028
3300
7000
5300
11,250
