Guardian Technologies 4758, 4456 TEST 25- TEST LIMIT SWITCH XB1, Section, Diagnostic Tests, Part

SECTION 3.4

DIAGNOSTIC TESTS

PART 3

V-TYPE PREPACKAGED TRANSFER SWITCHES

DISCUSSION:

In automatic operating mode, when utility source voltage drops below a preset level, the engine should crank and start. On engine startup, an "engine warm-up timer" on the generator circuit board should start timing. When that timer has timed out (about 15 seconds), the transfer relay should energize to deliver utility source power to the standby closing coil terminals. If normal utility source voltage is available to the standby closing coil terminals, but transfer to STANDBY does not occur, the cause of the failure may be (a) a failed standby closing coil and/or bridge rectifier, or (b) a seized or sticking actuating coil or load contact. This test will help you evaluate whether any sticking or binding is present in the transfer mechanism.

PROCEDURE:

1.With the generator shut down, set the generator AUTO- OFF-MANUAL switch to OFF.

2.Set the generator main circuit breaker to OFF or "Open".

3.Turn off the utility power supply to the transfer switch, using whatever means provided (such as a utility source main line breaker).

DANGER: DO NOT ATTEMPT MANUAL TRANSFER SWITCH OPERATION UNTIL ALL POWER VOLTAGE SUPPLIES TO THE SWITCH HAVE BEEN POSITIVELY TURNED OFF. FAILURE TO TURN OFF ALL POWER VOLTAGE SUPPLIES MAY RESULT IN EXTREMELY HAZARDOUS AND POSSIBLY LETHAL ELECTRICAL SHOCK.

4.In the transfer switch enclosure, locate the manual transfer handle. Handle is retained in the enclosure with a wing nut. Remove the wing nut and handle.

5.See Figure 3. Insert the un-insulated end of the handle over the transfer switch operating lever.

a.Move the transfer switch operating lever up to actuate the load contacts to the UTILITY position, i.e., load connected to the utility source.

b.Actuate the operating lever down to move the load contacts against the standby contacts, i.e., load connected to the STANDBY source.

6.Repeat Step 5 several times. As the transfer switch operating lever is moved slight force should be needed until the lever reaches its center position. As the lever moves past its center position, an over-center spring should snap the moveable load contacts against the stationary STANDBY or UTILITY contacts.

7.Finally, actuate the main contacts to their UTILITY power source side, i.e., load contacts against the UTILITY contacts (upward movement of the operating lever).

RESULTS:

1.If there is no evidence of binding, sticking, excessive force required, replace the appropriate closing coil.

2.If evidence of sticking, binding, excessive force required to move main contacts, find cause of binding or sticking and repair or replace damaged part(s).

TEST 25- TEST LIMIT SWITCH XB1

DISCUSSION:

Standby power source voltage must be available to the standby closing coil in order for a TRANSFER TO STANDBY action to occur. To deliver that source voltage to the coil, limit switch XB1 must be closed to the "Standby" power source side. If the limit switch did not get actuated or has failed open, the source voltage will not be available to the closing coil and transfer to "Standby" will not occur.

PROCEDURE:

With the generator shut down, the generator main circuit breaker turned OFF, and with the utility power supply to the transfer switch turned OFF, test limit switch XB1 as follows:

1.To prevent interaction, disconnect Wire 205 and Wire B from the limit switch terminals.

2.Set a VOM to its "R x 1" scale and zero the meter.

3.See Figure 1. Connect the VOM test probes across the two outer 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 position. 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, repair or replace Wire B between limit switch and Standby Coil (C2).

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