Guardian Technologies 4390 Transfer Relay, Neutral LUG, Manual Transfer Handle, Terminal Block

SECTION 3.1

DESCRIPTION & COMPONENTS

PART 3

V-TYPE PREPACKAGED TRANSFER SWITCHES

TRANSFER RELAY

Transfer relay operation is controlled by a circuit board. That circuit board is a part of a control panel assembly, mounted on the standby generator set.

Figure 5 shows the transfer relay pictorially and schematically. Relay operation may be briefly described as follows:

1.Generator battery voltage (12 volts DC) is available to the transfer relay coil from the generator circuit board, via Wire 194 and relay terminal A.

a.The 12 volts DC circuit is completed through the transfer relay coil and back to the generator circuit board, via Wire 23.

b.Circuit board action normally holds the Wire 23 circuit open to ground and the relay is de- energized.

c.When de-energized, the relay’s normally open contacts are open and its normally-closed contacts are closed.

d.The normally-closed relay contacts will deliver utility source power to the utility closing circuit of the transfer mechanism.

e.The normally open relay contacts will deliver standby source power to the transfer mechanism’s standby closing circuit.

4.When the "engine warm-up timer" has timed out, circuit board action completes the Wire 23 circuit to ground.

a.The transfer relay then energizes.

b.The relay’s normally-closed contacts open and its normally open contacts close.

c.When the normally open contacts close, standby source power is delivered to the standby closing coil and transfer to "Standby" occurs.

5.When the generator circuit board "senses" that utility source voltage has been restored above a preset level, the board will open the Wire 23 circuit to ground.

a.The transfer relay will de-energize, its normally- closed contacts will close and its normally open contacts will open.

b.When the normally-closed relay contacts close, utility source voltage is delivered to the utility closing coil to energize that coil.

c.Retransfer back to UTILITY occurs.

NEUTRAL LUG

The standby generator is equipped with an UNGROUNDED neutral. The neutral lug in the transfer switch is isolated from the switch enclosure.

Figure 5. Transfer Relay Schematic

2.During automatic system operation, when the generator circuit board "senses" that utility source voltage has dropped out, the circuit board will initiate engine cranking and startup.

3.When the circuit board "senses" that the engine has started, an "engine warm-up timer" on the circuit board starts timing.

MANUAL TRANSFER HANDLE

The manual transfer handle is retained in the transfer switch enclosure by means of a wing stud. Use the handle to manually actuate the transfer mechanism load contacts to either the UTILITY or STANDBY source side.

Instructions on use of the manual transfer handle may be found in Part 5, "Operational Tests and Adjustments".

TERMINAL BLOCK

During system installation, this 5-point terminal block must be properly interconnected with an identically labeled terminal block in the generator control panel assembly.

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