Product Manual

4. Troubleshooting 8-2018

4.2.2 Generator-to-Utility Sequence of Events

The following steps describe what normally happens when the transfer switch is connected to the

generator, utility power returns, and the switch moves from the Generator position to the Utility position.

1. The utility returns.

2. The generator control receives a ground (B-) signal from the TB4-2 utility sense relay.

3. The generator control de-energizes the relay coil (K1), which closes K1-1/K1-9 and K1-2/K1-10 and

opens K1-7/K1-11 and K1-8/K1-12 to move the transfer switch from the Generator position to the

Utility position.

4. The S1 auxiliary switch within the transfer switch mechanism breaks the signal to the ATS operator

coil (C).

5. The BSW limit switch removes the ground (B-) signal (TB4-6), signaling the transfer switch has

disconnected from the generator.

6. The ASW limit switch provides a ground (B-) signal to TB4-5, signaling that the transfer switch has

connected to the utility.

7. The load is retransferred to the utility.

8. After a delay to let the engine cool down, the generator stops.

4.2.3 Troubleshooting with Symptoms

Use the troubleshooting guide to help diagnose transfer switch problems. It is divided into sections based

on the symptom. Common problems are listed with their possible causes. Refer to the corrective action

column for the appropriate test or adjustment procedure. The section in the right column lists the location

of the test or adjustment procedure in the manual.

Always refer to the schematic and wiring diagram package that was shipped with the transfer switch for

specific information about its configuration.

Make a thorough inspection of the transfer switch wiring to make sure that good wire harness and ground

connections are made. Correct wiring problems before performing any test or replacing any components.

4.2.4 Important Troubleshooting Reminders

When troubleshooting the transfer switch, it is important to remember the following:

• The generator control may use limit switches (ASW and BSW) on either side of the transfer switch to

determine if the switch has opened or closed. If either the ASW or BSW limit switches are bad, the

generator control may display a transfer switch signal failure.

• This is a two-position transfer switch. It can be connected only to either one source. There is no

neutral position.

• The generator control energizes relay coil K1 by supplying B+ (C13N6H, C17N6H, C20N6H, and

C20N6HC) or a B- (all other models).

• The terminal Block Jumper (A034N106) provided with the generator set is installed between TB4-3

and TB-4 on Air Cooled Generator Sets (C13N6H, C17N6H, C20N6H, and C20N6HC).

The transfer switch design is intended to signal when the utility voltage is not present and when it returns.

The utility sense relay coil will energize or stay energized at voltages other than nominal. Therefore, the

unit should not be expected to signal a failed utility to the generator set during utility undervoltage or

overvoltage conditions.