AERCO BMK 1.5 LN Dual Fuel Feb 2013 - Manual (Page 24)

CHAPTER 2: INSTALLATION
Page 24 of 162 PR2: 05/09/12
Benchmark 1.5LN Dual-Fuel Low NOx Boiler
Operation and Maintenance Manual
OMM-0041_0C
GF-121
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913 • Ph: 800-526-0288
IMPORTANT
DO NOT USE the mA OUT output to remotely monitor Setpoint,
Outlet Temp or Fire Rate Out.
mA Out (6) 2.10.6
These terminals provide a 4 to 20 mA output to the VFD (if so equipped) to control the rotational
speed of the blower. This function is enabled in the Configuration Menu (Chapter 3, Table 3-4).
RS-485 Comm (7) 2.10.7
These terminals are used for RS-485 MODBUS serial communication between the unit and an
external “Master” such as a Boiler Management System (BMS or ACS), Energy Management
System (EMS), Building Automation System (BAS) or other suitable device.
TxD, RxD (8) 2.10.8
These terminals provide a parallel connection to the connector on the C-More Controller front
panel, for connecting a computer or laptop.
VFD/Blower (9) 2.10.9
These terminals provide a 0 to 10 volt output to control the rotational speed of the blower. This
function is enabled in the Configuration Menu (Chapter 3, Table 3-4).
Exhaust Switch In (11) 2.10.10
These terminals permit an external exhaust switch to be connected to the exhaust manifold of
the boiler. The exhaust switch should be a normally open type switch (such as AERCO Part No.
123463) that closes (trips) at 500°F.
Interlocks (10, 12) 2.10.11
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 2-10). The wiring terminals for these interlocks are located inside
the I/O Box on the unit front panel. The I/O Box cover contains a wiring diagram which shows
the terminal strip locations for these interlocks (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.
Remote Interlock In (10) 2.10.11.1
The remote interlock circuit is provided to remotely start (enable) and stop (disable) the Boiler, if
desired. The circuit is labeled REMOTE INTL’K IN and is located inside the I/O Box on the front
panel. The circuit is 24 VAC and is factory pre-wired in the closed (jumpered) position.
Delayed Interlock In (12) 2.10.11.2
The delayed interlock is typically used in conjunction with the auxiliary relay described in
paragraph 2.11. 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 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 a
proving switch to make can be programmed. Should the proving switch not prove within the