12
Capacity Control — Unit 38AKS012 Only — A
suction pressure-actuated unloader controls 2 cylinders and
provides capacity control. Unloaders are factory set (see
Table 1A or 1B), but may be field adjusted as follows:
CONTROL SET POINT (cylinder load point) is adjustable
from 0 to 85 psig (586 kPa). To adjust, turn control set point
adjustment nut (Fig. 14) clockwise to its bottom stop. In this
position, set point is 85 psig (586 kPa). Then, turn adjustment
counterclockwise to desired control set point. Every full turn
counterclockwise decreases set point by 7.5 psig (51.7 kPa).
PRESSURE DIFFERENTIAL (difference between cylinder
load and unload points) is adjustable from 6 to 22 psig (41.4 to
152 kPa). To adjust, turn pressure differential adjustment screw
(Fig. 14) counterclockwise to its back stop position. In this
position, differential is 6 psig (41.4 kPa). Then, turn adjust-
ment clockwise to desired pressure differential. Every full turn
clockwise increases differential by 1.5 psig (10.3 kPa).
Compressor Removal — See Tables 1A and 1B for
compressor information. Follow safety codes and wear safety
glasses and work gloves.
1. Shut off power to unit and tag disconnect. Remove unit
access panel (front of unit).
2. Remove refrigerant from system using refrigerant remov-
al methods described in the Carrier GTAC-II, Module 5,
Charging, Recovery, Recycling, and Reclamation.
3. Disconnect compressor wiring at compressor terminal
box.
4. Remove bolts from suction flange and discharge service
valves (38AKS008,009,012 units only). Loosen sweat
connections (38AK007,008, and 012 units only).
5. Remove crankcase heater from compressor base
(38AKS008,009,012, 38AK008,012).
6. Remove compressor holddown bolts.
7. Remove compressor from unit.
8. Clean system. Add new liquid line filter drier.
9. Install new compressor in unit.
10. Connect suction and discharge lines to compressor, as
applicable. Ensure that compressor holddown bolts are in
place.
11. Connect wiring.
12. Install crankcase heater on 38AKS008,009,012 and
38AK008,012 units.
13. Evacuate and recharge unit.
14. Restore unit power.
Crankcase Heater (Except 38AK007) — The crank-
case heater on the 38AK008,012 condensing units prevents
refrigerant migration and compressor oil dilution during shut-
down when compressor is not operating.
Close both compressor service valves if applicable (on
38AKS008,009,012) when crankcase heater is deenergized for
more than 6 hours.
Excessive movement of copper lines at compressor
may cause higher levels of vibration when unit is restored
to service.
Fig. 14 — Compressor Capacity Control Unloader
NOTE: Fan height adjustments are as follows:
Fig. 13 — Condenser-Fan Adjustment
UNIT in. mm
38AK007 (60 Hz)
All 50-Hz Units 4.50 114
All 60-Hz Units
(Except 38AK007) 6.42 163