UCP2 Momentary Power Loss (MPL)

Issue:

UCP2 Momentary Power Loss (MPL)

Resolution:

Momentary power losses are temporary interruptions in the power being delivered to the motor. The UCP2 monitors MPL by measuring currents from phase A and C and by monitoring the 24 VAC input power to the Starter module (terminals J2 1,2). Since the UCP2 is looking at actual power flow into the motor, it needs the relationship of voltage and current. MPL is active anytime the compressor is running, but not on startup.

Corrective Action:
1. MPL is active for the Run mode, not in the Start mode.
2. CT wiring on J5 of the Starter module must be wired White-Black per print and Phase A must be on Terminals 1 and 2, Phase B on 3 and 4 and Phase C on 5 and 6. CT polarity must be correct.
3. Wrong CTs installed (ratio).
4. Check phasing of the supply voltage. The ?A? phase must be delivered to J2-2 of the Starter module. 24 volt AC polarity must be correct. (Try swapping the 24 vac module power supply wires)
5. Look at the voltage on J2 for noise. J2 should be a smooth 24 VAC sine wave. If we get electrical noise from things such as inverters or high frequency generators, you will see noise blips off the sine wave.
6. Verify the polarity of the CT circuit is correct. For single CT circuits the White wire must be connected to J5-5 with the dot on the CT facing the line. For dual CTs. The ?HI? polarity dot on the line CT must be facing the line, the Brown wire from the X-13650266 transformer primary connected to Xl and the White wire from X-13650266 secondary connected to J5-5.
7. Verify that there is voltage delivered to the J6 terminal, if not check the HPC circuit, circuit breaker or Starter Interlock.
8. Check for loose wires.
9. Check the wiring from J8 to 2K1 Coil and Auxiliary.
10. Two wiring errors will allow you to start and go out on Momentary Power Loss when the unit loads up. The CTs and 24 VAC may be wired up improperly. As the loading is changed due to vane movement, then MPL may be called. If the unit starts and runs for a period of time before tripping on MPL (on a regular basis), you probably have one of two issues. Either 2 wiring errors (i.e., polarity on J2 and CT wiring error) or line noise on the incoming J2 24 VAC.
11. Defective HPC (high pressure control).
12. PFCCs installed incorrectly. Verify proper wiring through CT's per schematics.
13. If the unit trips on Momentary Power Loss, vanes stay where they were and then restart without going through a Vane Closure or BPI search, two modules need to be changed:

• Chiller module needs to be a X13650450-04 or newer
• Stepper module must be X13650455-04 or newer

14. Starter module X-13650453-13 and greater have a less sensitive MPL diagnostic trip point.

Notes:

RTHB:

• Swap the wiring on the 2T3 current transformer where it connects to the 2U1 module.
• Swap the H1 and H4 primary power side wiring on the 2T4 control power transformer.
• Check for loose wiring at J2-1 and J2-2 on the 2U1 starter module.
• A chattering High Pressure Cutout switch can also cause a Momentary Power Loss problem.
• It is NOT recommended to use Starter X13650453-13 through -15. Use -16 or newer.

Other Question/Problem/Cause Statements:

• MPL
• Momentary Power loss when starting up the chiller
• Momentary Power Loss
• UCP2 Momentary Power Loss (MPL)

Facts:

• CDHF, CDHG
• CVHE, CVHF, CVHG
• RTHC
• CenTraVac - Direct Drive Duplex (La Crosse) (CDHF, CDHG)
• CenTraVac - Direct Drive Simplex (CVHE, CVHF, CVHG)
• Swapping the 2U1 starter module with another chiller did not help
• Water-Cooled Chiller (Pueblo) (RTHB)
• Water-Cooled Chiller (Pueblo) (RTHC)