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2 remote setpoint startup, 5 direct drive modes, 1 direct drive field wiring – AERCO BMK 1.5 LN July 2011 User Manual

Page 56: Benchmark 1.5ln low nox boiler, Gf-120

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CHAPTER 5: MODE OF OPERATION

Page

56 of 152 PR2: 05/09/12

Benchmark 1.5LN Low NOx Boiler

Operation and Maintenance Manual

OMM-0041_0D

GF-120

AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913 • Ph: 800-526-0288

multiple units, each unit’s wiring must conform to the above.

Remote Setpoint Startup

5.4.2

Since this mode of operation is factory preset and the setpoint is being externally controlled, no

startup instructions are necessary. In this mode, the

REMOTE LED will light when the external

signal is present.

To operate the unit in the Manual mode, press the

AUTO/MAN switch. The REMOTE LED will

go off and the

MANUAL LED will light.

To change back to the Remote Setpoint mode, simply press the

AUTO/MAN switch. The

REMOTE LED will again light and the MANUAL LED will go off.

5.5 DIRECT DRIVE MODES

The unit’s air/fuel valve position (% open) can be changed by a remote signal which is typically

sent from an Energy Management System (EMS) or from a Building Automation System (BAS).

The Direct Drive mode can be driven by a current or voltage signal within the following ranges:

4-20 mA/1-5 Vdc

0-20 mA/0-5 Vdc

The factory default setting for the Direct Drive mode is 4-20 mA/1-5 Vdc. With this setting, a 4

to 20 mA signal, sent by an EMS or BAS is used to change the unit’s valve position from 0% to

100%. A 4 mA/1V signal is equal to a 0% valve position, while a 20 mA /5V signal is equal to a

100% valve position. When a 0-20 mA/0-5 Vdc signal is used, zero is equal to a 0% valve

position.
In addition to the current and voltage signals described above, the Direct Drive mode can also

driven by a RS485 Modbus Network signal from an EMS or BAS.
When in a Direct Drive mode, the unit is a slave to the EMS or BAS and does not have a role in

temperature control. Direct Drive can be used to drive single, or multiple units.

NOTE

If a voltage, rather than current signal is used to control the

remote setpoint, a DIP switch adjustment must be made on the

CPU Board located in the Control Box Assembly. Contact your

local AERCO representative for details.

To enable the Direct Drive Mode, the following menu setting must be made in the Configuration

Menu:

MENU OPTION

SETTING

Boiler Mode

Direct Drive

Remote Signal

4-20mA/1-5V,
0-20mA/0-5V, or
Network

Refer to paragraph 3.3 for instructions on changing menu options.

If the Network setting is selected for RS485 Modbus operation, a valid Comm Address must be

entered in the Setup Menu. Refer to Modbus Communication Manual GF-114 for additional

information.

Direct Drive Field Wiring

5.5.1

The only wiring connections necessary for Direct Drive mode are connection of the remote