AERCO KC1000 Boiler July 2011 - Manual (Page 19)

INSTALLATION
2-9
2.7.3 ANALOG IN
The ANALOG IN + and – terminals are used
when an external signal is used to drive the
valve position (Direct Drive Mode) or change the
setpoint (Remote Setpoint Mode) of the Boiler.
Either a 4 to 20 mA / 1 to 5 VDC or a 0 to 20 mA
/ 0 to 5 VDC signal may be used to vary the
setpoint or valve position. The factory default
setting is 4 to 20 mA / 1 to 5 VDC, however this
may be changed to 0 to 20 mA / 0 to 5 VDC
using the Configuration Menu described in
Section 3. If voltage rather than current is
selected as the drive signal, a DIP switch must
be set on the PMC Board located inside the
Control Box. Contact the AERCO factory for
information on setting DIP switches.
All supplied signals must be floating
(ungrounded) signals. Connections between the
source and the Boiler’s I/O Box must be made
using twisted shielded pair of 18 –22 AWG wire
such as Belden 9841(see Figure 2.11). Polarity
must be maintained and the shield must be
connected only at the source end and must be
left floating (not connected) at the Boiler’s I/O
Box.
Whether using voltage or current for the drive
signal, they are linearly mapped to a 40°F to
240°F setpoint or a 0% to 100% valve position.
No scaling for these signals is provided.
2.7.4 B.M.S. (PWM) IN
NOTE
Only BMS Model 168 can utilize Pulse
Width Modulation (PWM), not the BMS II
(Model 5R5-384).
These terminals are used to connect the
AERCO Boiler Management System (BMS)
Model 168 to the unit. The BMS Model 168
utilizes a 12 millisecond, ON/OFF duty cycle.
This duty cycle is Pulse Width Modulated (PWM)
to control valve position. A 0% valve position =
a 5% ON pulse and a 100% valve position = a
95% ON pulse.
2.7.5 SHIELD
The SHIELD terminals are used to terminate any
shields used on sensor wires connected to the
unit. Shields must only be connected to these
terminals.
2.7.6 mA OUT
These terminals provide a 4 to 20 mA output
that can be used to monitor setpoint ( 40°F to
220°F), outlet temperature (30°F to 245°F), or
valve position (0% to 100%). This function is
enabled in the Configuration Menu (Section 3,
Table 3-4).
2.7.7 RS-485 COMM
These terminals are used for RS-485 MODBUS
serial communication between the unit and an
external “Master”, such as a Boiler Management
System or other suitable device.
2.7.8 EXHAUST SWITCH IN
These terminals permit an external exhaust
switch to be connected to the exhaust manifold
of the boiler. The exhaust sensor should be a
normally open type switch (such as AERCO Part
No. 123463) that closes (trips) at 500 o F.
2.7.9 INTERLOCKS
The unit offers two interlock circuits for
interfacing with Energy Management Systems
and auxiliary equipment such as pumps or
louvers. These interlocks are called the Remote
Interlock and Delayed Interlock (Figure 2.11).
The wiring terminals for these interlocks are
located inside the I/O Box on the left side of the
unit. The I/O Box cover contains a wiring
diagram which shows the terminal strip locations
for these interlocks which are labeled REMOTE
INTL’K IN and DELAYED INTL’K IN. Both
interlocks, described in the following
paragraphs, are factory wired in the closed
position.
NOTE:
Both the Delayed Interlock and Remote
Interlock must be in the closed position to
allow the unit to fire.
2.7.9.1 REMOTE INTERLOCK IN
The remote interlock circuit (REMOTE INTL’K
IN) is provided to remotely start (enable) and
stop (disable) the Boiler if desired. The circuit is
24 VAC and comes factory pre-wired closed
(jumpered).