Product Manual A

3. Description 11-2017

FIGURE 2. AUXILIARY CONTACTS

3.3 Available Transfer Modes

• Open Transition (OT) with Sync Check

• Programmed Transition (PT)

3.3.1 Open Transition with Sync Check

Open transition with sync check executes an open transition (OT) transfer when both sources of power

are within specified tolerances of frequency, voltage and relative phase difference. If both sources meet

the tolerances, a fast transfer occurs.

3.3.1.1 Transfer from Source 1 to Source 2 (OT)

This sequence begins with Source 1 supplying power to the load. The Source 1 Available and Source 1

Connected indicators are lit. The sequence ends with Source 2 (generator) assuming the load.

1. When Source 1 goes “out of spec," the control starts a Time Delay to Engine Start (TDES) timer and

the Source 1 Available indicator goes out.

2. If the TDES expires without a return to acceptable Source 1 power, the genset receives a remote

start signal. The engine starts and accelerates to rated speed.

3. When the alternator output reaches the “pickup" level, the Source 2 Available indicator is lit. The

control starts the Time Delay Normal to Emergency (TDNE) timer.

3.3.1.2 Transfer from Source 2 to Source 1 (OT)

This sequence begins with Source 2 supplying power to the load. The Source 2 Available and Source 2

Connected indicators are lit. The sequence ends with Source 1 (utility) assuming the load.

1. When Source 1 returns to “in spec," the Source 1 Available indicator is lit and the control starts the

Time Delay Emergency to Normal (TDEN) timer. When this time is complete, the controller starts

monitoring both live sources looking for when they are in sync

2. When both sources are in sync, the switch transfers the load to Source 1. However, if the two

sources fail to synchronize and the “Return PT Enabled" feature is active, the switch executes a

programmed transition by stopping in the Neutral position and transferring the load to Source 1. If

Source 2 goes offline while the controller is trying to synchronize the two sources, the controller

executes a Programmed Transition and transfers the load to Source 1.

3. A Time Delay Engine Cool-down (TDEC) for the genset is activated. When the engine cool-down

delay expires, the genset shuts down and the Source 2 Available indicator goes out.