Hot Gas Bypass Ð An optional hot gas bypass system may be factory installed on circuit no. 1. This system will introduce discharge vapor from the compressor discharge line into the distributors and evaporator coil circuits on circuit no. 1 when suction pressures drop to damaging levels. No ®eld adjustments of the hot gas bypass valve should be required.
Condenser Fans Ð Each fan is supported by a formed wire mount bolted to fan deck and covered with a wire guard. The exposed end of the fan motor shaft is protected from weather by grease. If fan motor must be removed for service or replacement, be sure to regrease fan shaft and reinstall fan guard. For proper performance, fan should be 7¤8 in. (22 mm) below top of venturi on the fan deck to top of the fan hub. (See Fig. 64.) Tighten set screws to 15 ± 1
NOTE: Fan rotation is clockwise when viewed from top of unit.
Fig. 64 Ð Condenser Fan Adjustment
IMPORTANT: Check for proper fan rotation (clock- wise viewed from above). If necessary to reverse, switch leads.
Compressor Removal Ð Access to the pump end of the compressor is from the compressor side of the unit. Access to the motor end of the compressor is from the inside of the unit. All compressors can be removed from the com- pressor side of the unit.
IMPORTANT: All compressor mounting hardware and support brackets removed during servicing must be re- installed prior to
1.Disconnect power to unit; lockout power to compressor.
2.Close suction and discharge service valves.
3.Relieve refrigerant pressure into a refrigerant recovery system.
4.Remove:
a.
b.
c.
5.Disconnect power wires at terminal box and disconnect conduit.
6.Disconnect wires from crankcase heater.
7.Disconnect service valves from compressor.
NOTE: On units with 2 compressors per circuit, discon- nect both oil equalizer lines located on the motor barrel and on the oil pump sump.
8.Units 48/50MP62L:
a.Remove 4 large screws securing compressor mount- ing pan to unit base rail.
b.Slide compressor (on mounting pan) to outside of unit frame; support and/or lower to ground.
c.Unbolt compressor from mounting pan and remove.
9.Units 48/50MP70M,82N,90P,10R:
a.Remove 4 large screws securing compressor to the com- pressor rails.
b.Lift compressor off mounting bolts and remove.
Compressor Replacement Ð Perform the following:
1.Reverse procedure in Compressor Removal section to end of Step 4.
2.Reinstall service valves and safety switches, and tighten to torques as listed:
TORQUE | COMPRESSOR(S) |
Tighten discharge valves to Ð |
|
Tighten suction valves to Ð |
|
80- 90 | |
Tighten the following ®ttings as speci®ed Ð | |
120 | |
120 | |
3.
4.Recharge system per
5.Energize crankcase heater for 24 hours prior to restart of system.
TROUBLESHOOTING
The 48/50MP units provide extensive troubleshooting in- formation to service personnel through the use of status codes and alarm and alert codes from the control system, which are displayed on the unit HSIO or through the use of Service Tool or CCN Building Supervisor. For more information on diagnostics, codes, and possible causes, refer to the Controls and Troubleshooting manual.
Use the Quick Test function to check control inputs and outputs (including economizer actuators). Refer to Controls and Troubleshooting Guide.
If there are indications of hunting (rapid oscillations) of control functions (such as duct static pressure or supply air temperature), or if the response rate is too slow, check the gain values. Refer to the Control Loop Checkout section on page 40 for more information.
If the unit is equipped with an optional VFD and the sup- ply or exhaust fan is not running when required, refer to the troubleshooting section of the separate VFD technical manual provided with the unit.
For troubleshooting information on mechanical systems, refer to the troubleshooting and diagnostics table on the next page.
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