AERCO KC1000 Heater 2002 - Manual (Page 15)

INSTALLATION
2-7
connected only at the source end. It must be left
floating (not connected) at the Heater’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
2.6.4 B.M.S. (PWM) IN
Not applicable to Water Heaters.
2.6.5 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.
2.6.6 mA OUT
These terminals provide a 4 to 20 mA output that
can be used to monitor setpoint ( to 220°F),
outlet temperature (
to 245°F), or fire rate (0% to
100%). This function is enabled in the
Configuration Menu (Section 3, Table 3.4).
2.6.7 RS-485 COMM
These terminals are used for RS-485 MODBUS
serial communication between the unit and an
external “Master”, such as an Energy Manage-
ment System.
2.6.8 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 P/N
123463) that closes (trips) at 500°F.
2.6.9 INTERLOCKS
The unit offers two interlock circuits for
interfacing with Energy Management Systems
and auxiliary equipment such as pumps or
louvers or other accessories. These interlocks
are called the Remote Interlock and Delayed
Interlock (Fig. 2.10). 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
labeled REMOTE INTL’K IN and DELAYED
INTL’K IN. Both interlocks, described below, 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.
2.6.9.1 REMOTE INTERLOCK IN
The remote interlock circuit (REMOTE INTL’K
IN) is provided to remotely start (enable) and
stop (disable) the unit if desired. The circuit is
24 VAC and comes factory pre-wired closed
(jumped).
2.6.9.2 DELAYED INTERLOCK
The delayed interlock circuit (DELAYED INTL’K
IN) is typically used in conjunction with the
auxiliary relay described in paragraph 2.6.11.
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
unit’s auxiliary relay. The delayed interlock must
be closed for the heater 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
unit long enough for a proving switch to make
(close) can be programmed. Should the proving
switch not prove within the programmed time
frame, the unit 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).
2.6.10 FAULT RELAY
The fault relay is a single pole double throw
(SPDT) relay having a normally open and
normally closed set of relay contacts that are
rated for 5 amps at 120 VAC and 5 amps at 30
VDC. The relay energizes when any fault condi-
tion occurs and remains energized until the fault
is cleared and the
CLEAR button is depressed.
The fault relay connections are shown in Figure
2.10.
2.6.11 AUXILIARY RELAY CONTACTS
Each unit is equipped with a single pole double
throw (SPDT) relay that is energized when there
is a demand for heat and de-energized after the
demand for heat is satisfied. The relay is pro-
vided for the control of auxiliary equipment, such
as pumps and louvers, or can be used as a unit
status indictor (firing or not firing). Its contacts
are rated for 120 VAC @ 5 amps. Refer to
Figure 2.10 to locate the AUX RELAY terminals
for wiring connections.