SERVICING
S-1 CHECKING VOLTAGE
1.Remove doors, control panel cover, etc. from unit being tested.
With power ON:
LINE VOLTAGE NOW PRESENT.
2.Using a voltmeter, measure the voltage across terminals L1 and L2 of the contactor for single phase units, and L3, for 3 phase units.
3.No reading - indicates open wiring, open fuse(s) no power or etc. from unit to fused disconnect service. Repair as needed.
4.With ample voltage at line voltage connectors, energize the unit.
5.Measure the voltage with the unit starting and operating, and determine the unit Locked Rotor Voltage.
Locked Rotor Voltage is the actual voltage available at the compressor during starting, locked rotor, or a stalled condition. Measured voltage should be above minimum listed in chart below.
To measure Locked Rotor Voltage attach a voltmeter to the run "R" and common "C" terminals of the compres- sor, or to the T1 and T2 terminals of the contactor. Start the unit and allow the compressor to run for several sec- onds, then shut down the unit. Immediately attempt to restart the unit while measuring the Locked Rotor Volt- age.
6.Should read within the voltage tabulation as shown. If the voltage falls below the minimum voltage, check the line wire size. Long runs of undersized wire can cause low voltage. If wire size is adequate, notify the local power company in regards to either low or high voltage.
Unit Supply Voltage
Voltage Min. Max.
460 437 506
208/230 198 253
Three phase units require a balanced 3 phase power supply to operate. If the percentage of voltage imbalance exceeds 3% the unit must not be operated until the voltage condition is corrected.
% Voltage = | Max. Voltage Deviation |
From Average Voltage X 100 | |
Imbalance | Average Voltage |
To find the percentage of imbalance, measure the incoming | ||
power supply. |
|
|
L1 - L2 = 240V |
| |
L1 - L3 = 232V | Avg. V = 710 = 236.7 | |
L2 - L3 = 238V | 3 | |
Total | 710V |
|
To find Max. deviation: | 240 - 236.7 = +3.3 | |
|
| 232 - 236.7 = |
|
| 238 - 236.7 = +1.3 |
Max deviation was 4.7V
% Voltage Imbalance = 4.7 = 1.99% 236.7
If the percentage of imbalance had exceeded 3%, it must be determined if the imbalance is in the incoming power supply or the equipment. To do this rotate the legs of the incoming power and retest voltage as shown below.
L1 - L2 = 240V
L1 - L3 = 227V
L2 - L3 = 238V
L1 | L2 | L3 | Rotate all 3 incoming | |
legs as shown. | ||||
|
|
|
L1 - L2 = 227V
L1 - L3 = 238V
L2 - L3 = 240V
L1 L2 L3
By the voltage readings we see that the imbalance rotated or traveled with the switching of the incoming legs. Therefore the power lies within the incoming power supply.
If the imbalance had not changed then the problem would lie within the equipment. Check for current leakage, shorted mo- tors, etc.
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