AERCO Control System (ACS) - Manual (Page 24)

MC2: 04/23/13 Page 24 of 144
GF-131
AERCO Control System (ACS)
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, New York 10913 • Phone: 800-526-0288
Installation, Operation, and Maintenance Manual
OMM-0081_0D
NOTE
With Method A, the last C-More on the daisy chain must remain powered
for the bus to be stable.
The advantage of using Method B is that the bias and termination of the
RS485 loop do not require any changes to be made to the DIP switches on
the PMC board in the last C-More Control Box. The bus is independent of
any C-More control box.
Method B: For Method B, bias is controlled at the ACS by setting the two bias switches (Figure
2-6) to the active (down) position. Termination at the boiler end of RS485 loop is accomplished
by activating the “MODBUS R6-ON” switch in the I/O Box in the last boiler on the daisy-chain. If
this is an older box, install a 120 ohm, 1/2 Watt termination resistor in the I/O Box of the last
boiler on the daisy-chain. Refer to sheet 2 of Figure 2-7 (Benchmark), or Figure 2-8 (KC1000)
and proceed as shown below:
BIAS/Loop Term: METHOD A
1. Using a daisy-chain wiring configuration, connect the RS485 positive lead to the RS485 +
terminal in the I/O Box for each boiler.
2. Connect the RS485 negative lead to the RS485 - terminal in the I/O Box for each boiler.
3. DO NOT terminate the shields to the Ground ( GND) terminal at the boiler end of the RS485
loop. Connect the shields of the incoming and outgoing leads together. The RS485 loop shield
should only be terminated at terminal 3 of the ACS.
4. At the last boiler in the daisy-chain, activate the BIAS1, BIAS2 and TERM switches on the PMC
board in the C-More Control Box. Refer to GF-114, paragraph 4.3.2 for detailed instructions on
accessing the PMC board.
If an Oxygen Sensor is used, ensure that R1 DIP Switch is set to OFF (Disabled). Set it to ON
(Enabled) if there is no Oxygen Sensor used.
5. DO NOT activate the bias switches on the ACS. These switches must be in the up position
towards the operator when using Method 1.
BIAS/Loop Term: METHOD B
1. Using a daisy-chain wiring configuration, connect the RS485 positive lead to the RS485 +
terminal in the I/O Box for each boiler.
2. Connect the RS485 negative lead to the RS485 - terminal in the I/O Box for each boiler.
3. DO NOT terminate the shields to the Ground ( GND) terminal at the boiler end of the RS485
loop. Connect the shields of the incoming and outgoing leads together. The RS485 loop shield
should only be terminated at terminal 3 of the ACS.
4. At the last boiler in the daisy-chain, activate the “MODBUS R6-ON” dipswitch, or install a 120
ohm, 1/2 Watt termination resistor across the RS485 + and - terminals in the boiler’s I/O Box.
5. When using Method 2, activate the two bias switches in the ACS (Figure 2-6) by placing them
in the down or toward the wall position toward the wall.