CVHE-SB-32A 20
3 Item 1 reference the mechanical limitation of the stepper motor while the software limitation is
a pulldown rate of 5°F/minute of the leaving water temperature. This maximum cannot be
overridden.
Problem 47: Memory Error
Corrective action
1 Replace the Chiller module.
Problem 48: Momentary Power Loss (MPL)
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.
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.
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.
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 X-13650450 -04 or newer.
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