Amada Miyachi Unitek STA-100A, Operation Manual, Page: 139 / 154

STA SERIES AC CONTROLS
990-351 K-
1
APPENDIX K
CIRCUIT MODIFICATION FOR
EXTERNAL TRANSFORMER THERMOSTAT
External Transformer Thermostat Connection
The following procedure will enable you to connect an external transformer thermostat to the Control
such that it will monitor that thermostat the same as the SCR thermostat.
WARNING:
Lethal voltages are present in the unit. Disconnect power before making this
modification.
Required Parts:

1 relay, 24VDC, 75mA maximum coil current, octal base (Recommended: Grainger 1A485)

1 octal relay socket (Recommended: Grainger 5X852)

Miscellaneous wire, tape, insulation, and mounting hardware, as needed
1 Determine a location in the Control cabinet for mounting the relay. This location should be
away from the high voltage terminals.
2 Mount the relay socket and perform the following wiring procedure:
a) On one of the SCR thermostats, locate the red wire tagged "
5
."
b) Cut the wire and splice on two extension wires long enough to reach the relay socket
Connect these wires to the socket terminals for the
NO
and
COM
terminals of the relay.
c) Connect a wire from one of the socket terminals for the relay coil to the
+24VDC
terminal
on connector
J14
of the
AC Timer Main Board, A1
. Do not remove the existing jumper
already on this terminal.
d) Connect the external transformer thermostat to the
COM
terminal on connector
J14
of the
AC Timer Main Board, A1
, and the socket terminal for the other side of the relay coil.
3 Carefully check all wiring and plug the relay into the relay socket.
To Normally-
Closed (NC)
Transformer
Thermostat
SCR
Driver Board
Thermostat
Existing SCR thermostat wires (2 red)
4 1
2
7
AC Timer Main Board, A1
+24V PULLUP COM
DO NOT REMOVE
JUMPER
Cut at tag "5"
SCR