Thermo King 914 724, Руководство пользователя

Страница: 53 / 111

Electrical Maintenance (Rev. 1/99)
43
ELECTRIC STANDBY CIRCUITS (Model 20
Only)
Make sure the unit is connected to the proper power source.
The current draw through the compressor motor should not
exceed the full load current listed in the Specifications.
The DC current draw through the 2B wire should not
exceed 35 amps in 12 volt systems and 22 amps in 24 volt
systems.
If the DC current is excessive, check the current draw
through each fan motor. The current draw through an indi-
vidual fan motor should not exceed the full load current
listed in the Specifications.
If the fan motor currents are satisfactory, check the control
relays and switches for shorts.
When the unit is inoperative, follow a systematic checking
sequence. This will save time and eliminate guesswork.
Check the power cable receptacle for power. If power is
present, check for power at the unit terminal board.
Check for control circuit power at the circuit breaker.
If the contactor is pulled down but the compressor motor
fails to start, the trouble is probably in the compressor motor
assembly.
12 Volt System, Three Phase Electric Standby
The DC voltage should be 12 to 15 volts and the current
through the 2B wire should be less than 35 amps. If the cur-
rent is less than 35 amps and the voltage is less than 12
volts:
1. Check the AC line voltage and the transformer fuses.
The line voltage must be at least 90% of the voltage
specified for the unit. If the AC line voltage is accept-
able and the transformer fuses are intact, go to step 2.
2. Measure the transformer output voltage (AC) at the ter-
minal board. Measure the voltage between wires A and
B, between wires B and C, and between wires A and C.
The voltage reading at each pair of wires should be
equal to (within 10%) the voltage readings at the other
pairs of wires. If not the transformer is defective. If the
transformer output voltage is acceptable, go to step 3.
3. Check the rectifier output voltage (DC) on the 2R wires
at CB1. If this voltage is less than 12 Vdc and the load
is not excessive (less than 35 amps) the rectifier is
defective.
24 Volt System, Three Phase Electric Standby
The DC voltage should be 24 to 30 volts and the current
through the 2B wire should be less than 22 amps. If the cur-
rent is less than 22 amps and the voltage is less than 24
volts:
1. Check the AC line voltage and the transformer fuses.
The line voltage must be at least 90% of the voltage
specified for the unit. If the AC line voltage is accept-
able and the transformer fuses are intact, go to step 2.
2. Measure the transformer output voltage (AC) at the ter-
minal board. Measure the voltage between wires A and
B, between wires B and C, and between wires A and C.
The voltage reading at each pair of wires should be
equal to (within 10%) the voltage readings at the other
pairs of wires. If not, the transformer is defective. If the
transformer output voltage is acceptable, go to step 3.
3. Check the rectifier output voltage (DC) on the 2R wires
at CB1. If this voltage is less than 24 Vdc and the load
is not excessive (less than 22 amps), the rectifier is
defective.