AERCO BMK 3.0 LN Nat. Gas Jan 2011 - Manual (Page 20)

INSTALLATION
2-8
mA OUT
RS-485
COMM.
+
-
+
-
ANALOG IN
SENSOR COMMON
OUTDOOR SENSOR IN
REMOTE INTL'K IN
B.M.S. (PWM) IN
SHIELD
+
-
+
-
(AIR) AUX SENSOR IN
NOT USED
EXHAUST SWITCH IN
DELAYED INTL'K IN
FAULT RELAY
120 VAC, 5A, RES
AUX RELAY
120 VAC, 5A, RES
G
RELAY CONTACTS:
120 VAC, 30 VDC
5 AMPS RESISTIVE
DANGER
120 VAC USED
IN THIS BOX
NOT USED NOT USED
NC
COM
NO
NC
COM
NO
NOT USED
0 – 10V
AGND
Figure 2-11. I/O Box Terminal Strip
2.9.1 Constant Setpoint Mode
The Constant Setpoint Mode is used when it is
desired t o ha ve a f ixed s etpoint t hat d oes not
deviate. No w iring connections, oth er than AC
electrical po wer c onnections, ar e r equired f or
this mode. Ho wever, if desired, fault monitoring
or enable/disable interlock wiring can be utilized
(see paragraphs 2.9.9.1 and 2.9.10).
2.9.2 Indoor/Outdoor Reset Mode
This mode of oper ation i ncreases s upply water
temperature as outdoor temperatures decrease.
An outside air temperature sensor (AERCO Part
No. 122790) is required. T he sensor MUST BE
wired to the I/O Box wiring terminals (see Figure
2-11). Ref er to par agraph 2.10.1 f or add itional
information on ou tside air tem perature s ensor
installation.
2.9.3 Boiler Management System Mode
NOTE
BMS Mo del 16 8 c an utilize eit her p ulse
width m odulation ( PWM) or R S485
Modbus s ignaling to t he Boiler. BMS II
Model 5R 5-384 c an u tilize onl y RS 485
signaling to the Boiler.
When us ing an AERCO Boi ler M anagement
System ( BMS), th e f ield wir ing is c onnected
between th e BM S P anel and e ach Bo iler’s I/O
Box ter minal s trip ( Figure 2- 11). T wisted
shielded pair wire f rom 18 to 22 A WG must be
utilized for the connections. The BMS Mode can
utilize e ither pu lse width modulation ( PWM)
signaling, or RS485 Modbus signaling. For PWM
signaling, c onnections a re m ade f rom the
AERCO B oiler M anagement System to th e
B.M.S. ( PWM) IN ter minals on t he I/O Box
terminal s trip. F or RS 485 Mo dus s ignaling,
connections ar e m ade f rom the BMS t o th e
RS485 COMM terminals on the I/O Box terminal
strip. Polarity must be maintained and the shield
must be c onnected o nly at th e AERCO BMS.
The boiler end of the shield must be left floating.
For ad ditional i nstructions, r efer to C hapter 5,
paragraph 5.6 in this manual. Also, refer to GF-
108M ( BMS Mod el 1 68) and G F-124 ( BMS I I
Model 5R5-384), BMS -Operations Guides.
2.9.4 Remote Setpoint and Direct Drive
Modes
The Benc hmark 3.0 Boi ler c an ac cept s everal
types of s ignal f ormats f rom an E nergy
Management S ystem ( EMS), Building
Automation S ystem ( BAS) or oth er s ource, to
control e ither the s etpoint ( Remote Setpo int
Mode) or f iring r ate ( Direct Dr ive Mo de) of the
Boiler. These formats are:
•
4 to 20 mA/1 to 5 VDC
• 0 to 20 mA/0 to 5 VDC
• PWM – ( Pulse Width Modulated signal. Se e
para. 2.10.4)
• Network (RS485 Modbus. See para. 2.10.8)