Check Wiring And Wiring Connections; Check Voltage At Terminal Lugs N1, N2; Check Voltage At Utility 1 And Utility 2 Terminals - Guardian 4721 Repair Manual

"V-TYPE" PREPACKAGED
TRANSFER SWITCHES
PROCEDURE:
With the generator shut down and with the "Utility"
power supply to the transfer switch turned OFF, test
limit switch XB1 as follows:
1. To prevent interaction, disconnect Wire No. 205 and Wire
"B" from the limit switch terminals.
2. Set a VOM to its "Rx1" scale and zero the meter.
3. See Figure 1. Connect the VOM test probes across the
two terminals from which the wires were disconnected.
4. Manually actuate the main contacts to their "Standby"
position. The meter should read INFINITY.
5. Manually actuate the main contacts to their "Utility" posi-
tion. The meter should read CONTINUITY.
6. Repeat Steps 4 and 5 several times and verify the VOM
reading at each switch position.
RESULTS:
1. If limit switch XB1 fails the test, remove and replace the
switch or adjust switch until it is actuated properly.
2. If limit switch is good, go on to Test 6.
TEST 6- CHECK WIRING AND WIRING
CONNECTIONS
DISCUSSION:
An open circuit in transfer switch wiring can prevent a
transfer action from occurring.
PROCEDURE:
See Figure 1. Inspect transfer switch wiring carefully.
Make sure all wires are property and securely
attached to the correct terminals. Test wiring for an
open or shorted condition.
RESULTS:
Repair, reconnect or replace any damaged, discon-
nected, incorrectly connected, open or shorted
wire(s).
TEST 7- CHECK VOLTAGE AT TERMINAL
LUGS N1, N2
DISCUSSION:
If retransfer to the "Utility" power source side is to
occur, utility source voltage must be available to
Terminal Lugs N1 and N2 of the transfer mechanism.
In addition, if that source voltage is not available to
N1/N2 terminals, automatic startup and transfer to
"Standby" will occur when the generator's AUTO-
OFF-MANUAL switch is set to AUTO. This test will
prove that "Utility" voltage is available to those termi-
PART 3
nals, or is not available. It is the first test in a series of
tests that should be accomplished when (a) retransfer
back to "Utility" does not occur, or (b) startup and
transfer occurs unnecessarily.
DANGER: PROCEED WITH CAUTION! HIGH
!
AND DANGEROUS VOLTAGES ARE PRE-
SENT AT TERMINAL LUGS N1/N2. CONTACT
WITH HIGH VOLTAGE TERMINALS WILL
RESULT IN DANGEROUS AND POSSIBLY
LETHAL ELECTRICAL SHOCK. DO NOT
ATTEMPT THIS TEST WHILE STANDING ON
WET OR DAMP GROUND, WHILE BAREFOOT,
OR WHILE HANDS OR FEET ARE WET.
PROCEDURE:
1. Make sure that all main line circuit breakers in the utility
line to the transfer switch are ON or "Closed."
2. Test for utility source line-to-line voltage across Terminal
Lugs N1 and N2 (see Figure 1). Normal utility source volt-
age should be indicated.
RESULTS:
1. If low or no voltage is indicated, find the cause of the
problem and correct.
2. If normal utility source voltage is indicated, go on to Test 8.
TEST 8 - CHECK VOLTAGE AT UTILITY 1 AND
UTILITY 2 TERMINALS
N1 N2 T1
Figure 4. Transfer Switch Terminal Block
During installation the installer should have connect-
ed the "Utility 1" and "Utility 2" terminals in the trans-
fer switch with identically labeled terminals on a termi-
nal block on the generators control board. These ter-
minals deliver utility voltage "sensing" to a control
SECTION 3.4
DIAGNOSTIC TESTS
T2 23 194
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