Guardian 4721, Руководство по ремонту, Страница: 46 / 115

TRANSFER RELAY
Transfer relay operation is controlled by a control circuit
board mounted on the standby generator set. The
standby system installer must interconnect suitable
wiring to terminals 23 and 194 of a transfer switch ter-
minal block. He must interconnect that wiring with iden-
tically numbered terminals in the generators control
board. See Section 1.2, Figure 4.
Figure 5 on this page shows the transfer relay pictori-
ally and schematically. Relay operation may be briefly
described as follows:
1. Generator set battery voltage (12 volts DC) is available to
the transfer relay coil from the generator’s control board,
via terminal 194 and relay terminal A.
a. The 12 volt DC circuit is completed through the
transfer relay coil and back to the generator’s con-
trol board, via transfer switch terminal 23, customer
installed wiring, and control board terminal 23.
b. Control board action normally holds the Wire
No. 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 con-
tacts 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 mechanis-
m’s standby closing circuit.
2. During automatic system operation, when the generator’s
control board “senses” that utility source voltage has
dropped out, the circuit board will initiate engine cranking
and startup.
3. When the control 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, control
board action completes the Wire No. 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, stand-
by source power is delivered to the standby
closing coil and transfer to “Standby” occurs.
5. When the generator’s control board “senses” that utility
source voltage has been restored above a preset level,
the board will open the Wire No. 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.
Figure 5. Transfer Relay Schematic
NEUTRAL LUG
See Figure 1. The standby generator is equipped with
an UNGROUNDED neutral. The neutral lug in the
transfer switch is isolated from the switch enclosure,
since its base is of plastic. Load, Utility and Standby
neutral lines all should be attached to the neutral lug’s
3/8 inch stud and securely retained with the 3/8”-16
hex nut.
MANUAL TRANSFER HANDLE
The manual transfer handle (Figure 1) 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 7-point terminal block
must be properly interconnected with an identically
labeled terminal block in the generator’s control mod-
ule assembly.
1
6 9
7
A
B
23
194
N1A 126
205 E1
PART 3
Page 42
“V-TYPE” PREPACKAGED
TRANSFER SWITCHES
SECTION 3.1
DESCRIPTION & COMPONENTS