AERCO KC1000 Boiler equipped with C-More 2002 - Manual (Page 19)

INSTALLATION
2-9
voltage rather than current is selected as the
drive signal, a DIP switch must be set on the
CPU 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 Fig. 211). 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% firing rate. 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 firing rate. A 0% firing rate = a 5% ON
pulse and a 100% firing rate = 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
fire rate (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 (Fig. 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).
2.7.9.2 DELAYED INTERLOCK IN
The delayed interlock circuit (DELAYED INTL’K
IN) is typically used in conjunction with the
auxiliary relay described in paragraph 2.8. This
interlock circuit is located in the purge section of
the start string. It can be connected to the
proving device (end switch, flow switch etc.) of
an auxiliary piece of equipment started by the
boiler’s auxiliary relay. The delayed interlock
must be closed for the boiler to fire. If the
delayed interlock is connected to a proving
device that requires time to close (make), a time
delay (Aux Start On Dly) that holds the start
sequence of the boiler long enough for for a
proving switch to make can be programmed.
Should the proving switch not prove within the
programmed time frame, the boiler will shut
down. The Aux Start On Dly can be
programmed from 0 to 120 seconds. This option
is locate in the Configuration Menu (Section 3).
2.7.10 FAULT RELAY
The fault relay is a single pole double throw
(SPDT) relay having a normally open and