Installation / Operation / Maintenance Manual
10/28/2019
21
II)
AUTOMATIC TRANSFER SWITCH WILL NOT TRANSFER TO NORMAL
1)
Improper Utility Voltage
Using an appropriately set voltmeter, check the utility voltage on terminals NL1 and NL2 and NL2 to
NL3 and NL3 to NL1. If each set of readings indicate the utility line to line voltage, continue to Step 2.
If the readings do not indicate proper line to line voltage, call the local utility.
2)
Blown Fuse on Normal Source
Using an appropriately set voltmeter, check the output voltage on terminals NA-1 to NB-1 and NB-1 to
NC-1 and NC-1 to NA-1. If each set of readings indicate utility line to line voltage, continue to step 3.
If the readings do not indicate line to line voltage, replace the defective fuse.
3)
Defective Normal Control Transformer NCT
Using an appropriately set voltmeter, check the voltage on terminals X1 to X2. If the voltage is 120
VAC nominal, check the NCT transformer and/or return to Step 2.
4)
Phase Failure Relay Not Functioning (PFR)
Using an appropriately set voltmeter, check the voltage on the phase failure relay terminal C to N.O. If
the voltage is 120 VAC nominal, the Phase Failure Relay Normal is defective and must be replaced. If
the voltage is zero, continue to step 5.
5)
Load Test
Verify that the Load Test Switch is in the “NORMAL” position.
6)
Defective T Timer
Using an appropriately set voltmeter, measure the voltage from terminals A to B of the “TNR” Timer.
If this voltage is 120 Volt Nominal, continue to step 7. If not, replace the defective “T” Timer.
7)
Defective TNR Timer
Using an appropriately set voltmeter, measure the voltage from wire 15 to wire 25 of the “TNR” Timer.
If this voltage is 120 Volt nominal, continue to step 8. If not, replace the defective “TNR” Timer.
8)
Normal Microswitch (MSN) Defective
a.
Using an appropriately set voltmeter, check the voltage at terminals 15 to 25. If the voltage is
120 VAC Nominal, continue to Step b; if voltage is not 120 VAC nominal, continue to Step b;
if voltage is not 120 VAC nominal, return to Step 7.
b.
Using an appropriately set voltmeter, check the voltage at terminals 16 to 25. If the voltage is
120 VAC nominal, continue to Step 9; if voltage is not 120 VAC nominal, microswitch MSN
and its actuator should be checked and replaced if necessary.
9)
Transfer Motor (TM) Defective
Using an appropriately set voltmeter, check the voltage at terminals 9 to 25. If the voltage is 120 VAC
nominal, replace the motor gear box assembly; if voltage is not 120 VAC nominal, return to Step 8.