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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 mecha-
nism’s standby closing circuit.
1
69
7
A
B
23
194
N1A
E1
126
205
Figure 5. Transfer Relay Schematic
2. During automatic system operation, when the genera-
tor 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.
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.
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 3-point terminal block
must be properly interconnected with an identically
labeled terminal block in the generator control panel
assembly.
0 15B 23
Figure 6. Transfer Switch Terminal Block
Terminals used on the terminal block are identified as
0, 15B and 23.
UTILITY N1 AND N2:
Interconnect with identically labeled terminals in the
generator control panel assembly. This is the utility
voltage signal to the circuit board. The signal is deliv-
ered to a step-down transformer in the control module
assembly and the resultant reduced voltage is then
delivered to the circuit board. Utility 1 and 2 power is
used by the circuit board as follows:
• If utility source voltage should drop below a pre-
set level, circuit board action will initiate automatic
cranking and startup, followed by automatic transfer
to the standby source.
• Utility source voltage is used to operate a battery
trickle charge circuit which helps to maintain battery
state of charge during non-operating periods.
PART 3
Page 58
TRANSFER SWITCH
SECTION 3.1
DESCRIPTION & COMPONENTS