Transfer Mechanism; Transfer Relay - Guardian 5240 Diagnostic Repair Manual

"V-TYPE" PREPACKAGED
TRANSFER SWITCHES

TRANSFER MECHANISM

The 2-pole transfer mechanism consists of a pair
of moveable LOAD contacts, a pair of stationary
UTILITY contacts, and a pair of stationary STANDBY
contacts. The load contacts can be connected to the
utility contacts by a utility closing coil; or to the stand-
by contacts by a standby closing coil. In addition, the
load contacts can be actuated to either the UTILITY
or STANDBY side by means of a manual transfer
handle. See Figures 2 and 3.
STANDBY
LOAD
Figure 2. Load Connected to Utility Power Source
STANDBY
LOAD
Figure 3. Load Connected to Standby Power Source
UTILITY CLOSING COIL C1:
See Figure 4. This coil is energized by rectified util-
ity source power, to actuate the load contacts to the
UTILITY power source side. When energized, the coil
will move the main contacts to an "overcenter" posi-
tion. A limit switch will then be actuated to open the
circuit and spring force will complete the retransfer to
STANDBY. A bridge rectifier, which changes the utility
source alternating current (AC) to direct current (DC),
is sealed in the coil wrappings. If coil or bridge recti-
fier replacement becomes necessary, the entire coil
and bridge assembly should be replaced.
STANDBY CLOSING COIL C2:
Coil C2 is energized by rectified standby source
power, to actuate the load contacts to their "Standby"
PART 3
UTILITY
UTILITY
DESCRIPTION & COMPONENTS
source side. Energizing the coil moves the load con-
tacts to an overcenter position; limit switch action then
opens the circuit and spring force will complete the
transfer action to "Standby". This coil's bridge rectifier
is also sealed in the coil wrappings. Replace the coil
and bridge rectifier as a unit.
LIMIT SWITCHES XA1 AND XB1:
Switches are mechanically actuated by load contacts
movement. When the load contacts are connected to
the utility contacts, limit switch XA1 opens the utility
circuit to utility closing coil C1 and limit switch XB1
closes the standby circuit to standby closing coil C2.
The limit switches "arm" the system for retransfer back
to UTILITY when the load contacts are connected to
the STANDBY side. Conversely, when the load con-
tacts are connected to the UTILITY side, the switches
"arm" the system for transfer to STANDBY. An open
condition in limit switch XA1 will prevent retransfer to
"Utility". An open switch XB1 will prevent transfer to
STANDBY.
N2A A
BRIDGE
RECTIFIER
UTILITY
CLOSING
COIL (C1)
LIMIT
SWITCH
(XA1)
MANUAL
TRANSFER
LEVER
LIMIT
SWITCH
(XB1)
STANDBY
CLOSING
COIL (C2)
BRIDGE
E2
RECTIFIER
Figure 4. The "V-Type" Transfer Mechanism

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 sche-
matically. 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 cir-
cuit board, via Wire 23.
b. Circuit board action normally holds the Wire
23 circuit open to ground and the relay is de-
energized.
SECTION 3.1
N1
N2
E1
E2
T2
B
T1
Page 51
A
126
205
B