Trane RTWA 70-125 TON - Manual (Page 39)

RLC-SVD03A-EN 39
Compressor Capacity
pressure, then the Slide Valve is bound.
5. If cylinder cavity pressure does not decrease or is at suction pressure
before the Unload toggle switch was closed, the problem lies with either
the solenoid coil or valve.
6. Check coil
7. If coil checks out, change the valve.
NOTE: Refer to the Flow Chart in Figure 6 .
Checkout Procedure for MCSP Step Load Output
The MCSP controls the step load solenoid valve on the respective
compressor with a 115 VAC dry contact output relay. This differs from the
Load/Unload solenoid output, which is from a triac (solid state relay). Refer to
the Chiller Control Wiring diagrams and the Component Layout Drawings for
the following procedure.
Unload:
10. Manually unload compressor in short increments.
11. Does RLA Decrease? Check UCM Stop
Replace
12. Does Cavity Press
decrease to a level
close to suct pressure?
Slide valve mechanism bound
13. Does Magnetic Field on
Solenoid Coil exist?
Solenoid valve mechanism bound
14. Is wiring to valve OK? Check for open solenoid coil
15. Repair and reverify.
Figure 6 Manual Slide Valve Diagnostic Flow Chart
No
Yes
Bad
Good
Yes
No
Yes
No
Yes
No