41
START-UP
Compressor crankcase heaters must be on for 24 hours be-
fore start-up. To energize the crankcase heaters, close the field
disconnect and turn on the fan circuit breakers. Leave the com-
pressor circuit breakers off/open. The crankcase heaters are
now energized.
Preliminary Charge — Refer to GTAC II (General
Training Air Conditioning), Module 5, Charging, Recovery,
Recycling, and Reclamation for charging procedures. Using
the liquid charging method and charging by weight procedure,
charge each circuit with the amount of Puron
®
refrigerant
(R-410A) listed in Table 11. This table is based on 25 ft (7.6 m)
of liquid line and does not include the indoor coil refrigerant
charge which must be added to the preliminary charge amount.
For liquid lines longer than 25 ft (7.6 m), additional charge is
required and can be found in the notes section of the table.
Adjust Refrigerant Charge
Table 11 — Preliminary Puron Refrigerant (R-410A)
Charge, lb (kg)
NOTES:
1. Preliminary charge is based on 25 ft (7.6 m) of interconnecting liquid line
piping between indoor and outdoor units.
2. For liquid line piping longer than 25 ft (7.6 m), use the following
information:
1
/
2
in. (12.7 mm) liquid line — 0.6 lb per 10 linear ft (0.27 kg per 3 m)
5
/
8
in. (15.9 mm) liquid line — 1.0 lb per 10 linear ft (0.45 kg per 3 m)
7
/
8
in. (22.2 mm) liquid line — 2.0 lb per 10 linear ft (0.91 kg per 3 m)
1
1
/
8
in. (28.6 mm) liquid line — 3.5 lb per 10 linear ft (1.59 kg per 3 m)
1
3
/
8
in. (34.9 mm) liquid line — 5.1 lb per 10 linear ft (2.32 kg per 3 m)
Due to the compact design of microchannel heat exchang-
ers, refrigerant charge is reduced significantly. As a result,
charging procedures for MCHX units require very accurate
measurement techniques. Charge should be added in small
increments. Using cooling charging charts provided, add or
remove refrigerant until conditions of the chart are met. As
conditions get close to the point on the chart, add or remove
charge in
1
/
4
lb. (0.11 kg) increments until complete. Ensure
that all fans are on and all compressors are running when using
charging charts. If the unit is equipped with a digital compres-
sor, disable the digital operation while charging the machine to
maintain stable operation. To disable the digital compressor
operation, set Configuration
UNIT
A1.TY (Compressor
A1 Digital?) to NO. Be sure to re-enable the digital operation
after charging operation is complete. If charging at low out-
door ambient, the condenser coil can be partially blocked in
order to increase head pressure.
NOTE: Do not use recycled refrigerant as it may contain
contaminants.
IMPORTANT: Before beginning Pre-Start-Up or Start-Up,
review Start-Up Checklist at the back of this publication.
The checklist assures proper start-up of a unit and provides a
record of unit condition, application requirements, system
information, and operation at initial start-up.
CAUTION
Crankcase heaters on all units are wired into the control cir-
cuit, so they are always operable as long as the main power
supply disconnect is on (closed), even if any safety device
is open. Compressor heaters must be on for 24 hours prior
to the start-up of any compressor. Equipment damage
could result if heaters are not energized for at least 24 hours
prior to compressor start-up.
CAUTION
Never charge liquid into the low pressure side of system.
Do not overcharge. During charging or removal of refriger-
ant, be sure indoor fan system is operating. Failure to com-
ply could result in personal injury or equipment damage.
CAUTION
Charging procedures for MCHX (microchannel heat
exchanger) units require very accurate measurement tech-
niques. Charge should be added in small increments. Using
cooling charging charts provided, add or remove refriger-
ant until conditions of the chart are met. As conditions get
close to the point on the chart, add or remove charge in
1
/
4
lb (0.11 kg) increments until complete. Ensure that all
fans are on and all compressors are running when using
charging charts (Fig. 50-76). Failure to comply may result
in equipment damage.
38AP UNIT SIZE CIRCUIT A CIRCUIT B
38APS025 24 (10.9) —
38APD025 12 (5.6) 12 (5.6)
38APS027 26 (11.6) —
38APD027 13 (6.0) 13 (6.0)
38APS030 29 (12.9) —
38APD030 14 (6.5) 14 (6.5)
38APS040 39 (17.7) —
38APD040 21 (9.5) 17 (7.8)
38APS050 48 (21.5) —
38APD050 22 (9.9) 26 (11.6)
38APD060 27 (12.1) 29 (12.9)
38APS065 — 55 (25.0)
38APD070 29 (12.9) 33 (15.1)
38APD080 29 (12.9) 46 (20.7)
38APD090 39 (17.7) 46 (20.7)
38APD100 46 (20.7) 46 (20.7)
38APD115 46 (20.7) 55 (25.0)
38APD130 46 (20.7) 71 (32.3)
IMPORTANT: For proper charging, units equipped
with a digital compressor must have the digital com-
pressor operation disabled to maintain stable operation.
To disable digital compressor operation, set Configura-
tion
UNIT
A1.TY (Compressor A1 Digital?) to
NO. Be sure to re-enable the digital operation after
charging operation is complete.
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