UTILITY VOLTAGE CHECKS
1. Turn ON the UTILITY power supply to the transfer switch with whatever means provided (such as the UTILITY main
line circuit breaker).
2. With an accurate AC voltmeter, check for correct voltage.
Measure across ATS terminal lugs N1 to N2, N2 to N3, and N1 to N3.
Measure across ATS terminal lugs N1 to NEUTRAL, N2 to NEUTRAL, and N3 to NEUTRAL.
3. Locate the 3 phase power monitor relay. Verify the following:
208 Vac system - LED green and ON
480 Vac system - LED - NORM indicator (green ON)
The factory setting is 80% of nominal voltage (208 Vac systems = 166 Vac dropout)
(480 Vac systems = 384 Vac dropout)
4. If the LED indicator is not ON, then it will be necessary to adjust the power monitor relay setting. Rotate the
adjustment potentiometer in a counter-clockwise direction until the LED turns ON. At this point the 3 phase power
monitor relay is the most sensitive to irregular power line conditions.
5. When certain that UTILITY supply voltage is cor-rect and compatible with transfer switch ratings, turn OFF the
UTILITY supply to the transfer switch.
GENERATOR VOLTAGE CHECKS
1.
On the generator panel, set the AUTO/OFF/MANUAL switch to MANUAL position. The gen-erator should crank and
start.
2.
Let the generator stabilize and warm up at no-load for at least five minutes.
3.
Set the generator's main circuit breaker (CB1) to its ON or CLOSED position.
4.
With an accurate AC voltmeter and frequency meter, check the no-load, voltage and frequency. Measure across ATS
terminal lugs E1 to E2, E2 to E3 and E1 to E3.
Measure across ATS terminal lugs E1 to NEUTRAL, E2 to NEUTRAL and E3 to NEUTRAL.
a. Frequency ....................................... 60-62 Hz
b. Terminals E1-E2, E2-E3, E1-E3 ..... 208-212VAC or 470-485
c. Terminals E1-N, E2-N, E3-N ........... 120-122VAC or 272-282
d. It will also be necessary to verify that the phase rotation of the utility matches the phase rotation of the
generator. This can be done by using a phase rotation indicator
PDU-ATS-100A-208Y.120-3PH
Larson Electronics, LLC
Phone: (800) 369-6671
Fax: (903) 498-3364
www.larsonelectronics.com
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CLOSE TO
EMERGENCY SOURCE SIDE
Before proceeding, verify the position of the switch by observing the "STANDBY" window. If the "STANDBY" window reads
“ON”, the contacts are closed in the EMERGENCY (STANDBY) position. No further action is required. If it reads “OFF”,
proceed with Step 1.
Step 1: With the handle attached to the actuating shaft, move the handle in the direction of the arrow on the switch cover
until it stops - DO NOT FORCE. Release handle slowly to allow the spring in the switch box to relax. “OFF” now appears in
the "UTILITY" window and “ON” appears in the "STANDBY" window.
5.
When certain that UTILITY supply voltage is cor-rect and compatible with transfer switch ratings, turn OFF the
UTILITY supply to the transfer switch.
6.
Set the generator’s main circuit breaker (CB1) to its OFF or OPEN position.
7.
Set the AUTO/OFF/MANUAL switch to the OFF position to shut down the generator.
