5
2.5 OVERLOAD PREVENTION CONTROL
BOARD (OPCB)
The OPCB can control an air conditioner (24 VAC) directly or a sepa-
rate contactor PPM (24 VAC or 120 VAC operating coil) which can
control any load connected to it. See Figure 2.1.
The Power Management Module (PMM) is not supplied with the trans-
fer switch. It can be purchased separately from the manufacturer for
use with the Overload Prevention Control Board (OPCB) mounted in
the transfer switch. The OPCB is designed and connected to power
the PMM contactor operating coil. The OPCB is supplied by a 24 VAC
supply, class 2 power supply transformer, connected to the LOAD
supply in the RTS. (Each output is limited to 1 amp) The PMM contac-
tor coil connections are made at the OPCB terminal strip.
Connect the PMM contactor coil to OPCB contactor terminals (1, 2,
3 or 4). The selection of contactor terminal used will depend on the
priority of the load being controlled. This is a 24 VAC circuit and wiring
methods for class 2 should be used. Use ¼” quick connect terminals
to make the contactor coil connections on the PMM. See Figure 2.1.
A grommet is provided to route Class 2 wiring through. The grommet
can be used in any knockout for NEMA 1 installations. The grommet
can only be used in the bottom knockouts for NEMA 3R installations.
Control of Air Conditioner Load
1. Route the thermostat cable (from the furnace/thermostat to the
outdoor air conditioner unit) to the transfer switch.
2. Connect the wire to the terminal strip terminals (Air 1) on the
OPCB as shown in Figure 2.1. These are normally closed con-
tacts which open upon load shed conditions. Route thermostat
wire away from High voltage wires.
3. If required, connect the second air conditioner to the terminal
strip terminals (Air 2).
Contact Ratings
Air 1 & 2
24 VAC, 5.0 Amps Max
Installation
Y w
ir
e
Y wire
0 Ground
194 +12V
23 Transfer
T1
NEUTRAL
A/C 1
24V
A/C 2
24V
LOAD 1
LOAD 2
LOAD 3
LOAD
4
A/C 1 & LOAD 1
PMM #1
Load #1
Supply
Coil wires
PMM #2
Load #2
Supply
PMM #4
Load #4
Supply
PMM #3
Load #3
Supply
LOAD
SUPPLY
LOAD
SUPPLY
1
2
1
2
2
2
2
1
1
1
1A MAX
1A MAX
1A MAX
1A MAX
A/C 2 & LOAD 2
LOAD 3
LOAD 4
Figure 2.1 — Overload Prevention Control
