Watts AERCO Benchmark 2.0LN Installation and operation manual

Printed in U.S.A. REVISED JANUARY, 2009
GF-110LN
OMM-0023_0A
Benchmark 2.0LN Low NOx Gas-Fired Boiler
USER MANUAL
Applicable To Serial Numbers G-05-1393 and above
Benchmark 2.0LN
Gas Fired
Low NOx
Boiler System
Condensing, Modulating
Forced Draft, Hot Water Boiler
2,000,000 BTU/H Input
Patent # : 2.155.12

Printed in U.S.A. REVISED JANUARY,
2009
GF-110LN
OMM-0023_0A
Benchmark 2.0LN Low NOx Gas-Fired Boiler
USER MANUAL
Telephone Support
Direct to AERCO Technical Support
(8 to 5 pm EST, Monday through Friday)
[phone]
AERCO International, Inc.
100 Oritani Drive
Blauvelt, NY 10913
www.aerco.com
© AERCO International, Inc., 2008
The information contained in this installation, operation and maintenance manual
is subject to change without notice from AERCO International, Inc.
AERCO makes no warranty of any kind with respect to this material, including
but not limited to implied warranties of merchantability and fitness for a particular
application. AERCO International is not liable for errors appearing in this manual.
Nor for incidental or consequential damages occurring in connection with the
furnishing, performance, or use of this material.

CONTENTS
i
GF-110LN - AERCO BENCHMARK 2.0 GAS FIRED LOW NOx BOILER
Operating & Maintenance Instructions
FOREWARD A
Chapter 1 – SAFETY PRECAUTIONS 1-1
Para.
Subject
Page
1-1
Safety Warnings
1-1
1-2
Emergency Shutdown
1-1
Para.
Subject
Page
1-3
Prolonged Shutdown
1-1
Chapter 2 – INSTALLATION PROCEDURES 2-1
Para.
Subject
Page
2.1
Receiving the Unit
2-1
2.2
Unpacking
2-1
2.3
Installation
2-2
2.4
Gas Supply Piping
2-3
2.5
Electrical Supply
2-4
2.6
Mode of Operation and Field
Control Wiring
2-5
Para.
Subject
Page
2.7
I/O Box Connections
2-7
2.8
Auxiliary Relay Contacts
2-8
2.9
Flue Gas Vent Installation
2-9
2.10
Combustion Air
2-9
Chapter 3 – CONTROL PANEL COMPONENTS AND
OPERATING PROCEDURES 3-1
Para.
Subject
Page
3.1
Introduction
3-1
3.2
Control Panel Description
3-1
3.3
Control Panel Menus
3-3
3.4
Operating Menu
3-5
3.5
Setup Menu
3-5
Para.
Subject
Page
3.6
Configuration Menu
3-6
3.7
Tuning Menu
3-7
3.8
Start Sequence
3-7
3.9
Start/Stop Levels
3-9
Chapter 4 – INITIAL START-UP 4-1
Para.
Subject
Page
4.1
Initial Startup Requirements
4-1
4.2 Tools and Instruments for
Combustion Calibration
4-1
4.3
Natural Gas Combustion
Calibration
4-2
Para.
Subject
Page
4.4
Unit Reassembly
4-5
4.5
Over-Temperature Limit Switch
4-5

CONTENTS
ii
Chapter 5 – MODE OF OPERATION 5-1
Para.
Subject
Page
5.1
Introduction
5-1
5.2
Indoor/Outdoor Reset Mode
5-1
5.3
Constant Setpoint Mode
5-2
5.4
Remote Setpoint Mode
5-2
5.5
Direct Drive Modes
5-3
Para.
Subject
Page
5.6
Boiler Management System
(BMS)
5-4
5.7
Combination Control System
(CCS)
5-5
Chapter 6 – SAFETY DEVICE TESTING PROCEDURES 6-1
Para.
Subject
Page
6.1
Testing of Safety Devices
6-1
6.2
Low Gas Pressure Fault Test
6-1
6.3
High Gas Pressure Test
6-1
6.4
Low Water Level Fault Test
6-2
6.5
Water Temperature Fault Test
6-2
6.6
Interlock Tests
6-2
6.7
Flame Fault Test
6-3
Para.
Subject
Page
6.8
Air Flow Fault Test
6-4
6.9
SSOV Proof of Closure Switch
6-4
6.10
Purge Switch Open During
Purge
6-5
6.11
Ignition Switch Open During
Ignition
6-5
6.12
Safety Pressure Relief Valve
Test
6-5
Chapter 7 – MAINTENANCE REQUIREMENTS 7-1
Para.
Subject
Page
7.1
Maintenance Schedule
7-1
7.2
Spark Igniter
7-1
7.3
Flame Detector
7-2
7.4
Combustion Calibration
7-2
7.5
Safety Device Testing
7-3
7.6
Burner
7-3
Para.
Subject
Page
7.7
Condensate Drain Trap
7-4
7.8
Shutting the Boiler Down For An
Extended Period of Time
7-4
7.9 Placing The Boiler Back In
Service After A Prolonged
Shutdown
7-4
Chapter 8 – TROUBLESHOOTING GUIDE 8-1
Para.
Subject
Page
8.1
Introduction
8-1
Para.
Subject
Page

CONTENTS
iii
APPENDICES
App
Subject
Page
A
Boiler Menu Item Descriptions
A-1
B
Startup, Status and Fault
Messages
B-1
C
Temperature Sensor Resistance
Chart
C-1
D
Indoor/Outdoor Reset Ratio
Charts
D-1
App
Subject
Page
E
Boiler Default Settings
E-1
F
Dimensional and Part Drawings
F-1
G
Piping Drawings
G-1
H
Wiring Schematics
H-1
I
Recommended Periodic Testing
Checklist
I-1
J
Benchmark Control Panel Views
J-1

FOREWORD
A
Foreword
The AERCO Benchmark 2.0 LN Boiler is a true industry advance that meets the needs of
today's energy and environmental concerns. Designed for application in any closed loop
hydronic system, the Benchmark's modulating capability relates energy input directly to
fluctuating system loads. The Benchmark’s 20:1 turn down ratio and condensing capability,
provides extremely high efficiencies and makes it ideally suited for modern low temperature, as
well as, conventional heating systems.
When installed and operated in accordance with this Instruction Manual, the Benchmark 2.0 LN
Boiler complies with the NOx emission standards outlined in:
•South Coast Air Quality Management District (SCAQMD), Rule 1146.2
•Texas Commission on Environmental Quality (TCEQ), Title 30, Chaptr 117, Rule117.465
Whether used in singular or modular arrangements the Benchmark 2.0 LN offers the maximum
flexibility in venting with minimum installation space requirements. The Benchmark's advanced
electronics are available in several selectable modes of operation offering the most efficient
operating methods and energy management system integration.
For service or parts, contact your local sales representative or AERCO INTERNATIONAL.
NAME:
ORGANIZATION:
ADDRESS:
TELEPHONE:
INSTALLATION DATE: _____________________________________________

SAFETY PRECAUTIONS
1-1
CHAPTER 1 SAFETY PRECAUTIONS
1.1 WARNINGS & CAUTIONS
Installers and operating personnel MUST, at all
times, observe all safety regulations. The
following general warnings and cautions must be
given the same attention as specific precautions
included in these instructions. In addition to all
the requirements included in this Instruction
Manual, the installation of units MUST conform
with local building codes, or, in the absence of
local codes, ANSI Z223.1 (National Fuel Gas
Code Publication No. NFPA-54). Where ASME
CSD-1 is required by local jurisdiction, the
installation must conform to CSD-1.
Where applicable, the equipment shall be
installed in accordance with the current
Installation Code for Gas Burning Appliances
and Equipment, CGA B149, and applicable
Provincial regulations for the class; which should
be carefully followed in all cases. Authorities
having jurisdiction should be consulted before
installations are made.
IMPORTANT
This Instruction Manual is an integral
part of the product and must be
maintained in legible condition. It must
be given to the user by the installer and
kept in a safe place for future
reference.
WARNINGS!
MUST BE OBSERVED TO PREVENT
SERIOUS INJURY.
WARNING!
BEFORE ATTEMPTING TO PER-
FORM ANY MAINTENANCE ON THE
UNIT, SHUT OFF ALL GAS AND
ELECTRICAL INPUTS TO THE UNIT.
WARNING!
THE EXHAUST VENT PIPE OF THE
UNIT OPERATES UNDER A
POSITIVE PRESSURE AND THERE-
FORE MUST BE COMPLETELY
SEALED TO PREVENT LEAKAGE OF
COMBUSTION PRODUCTS INTO
LIVING SPACES.
WARNING
DO NOT USE MATCHES, CANDLES,
FLAMES, OR OTHER SOURCES OF
IGNITION TO CHECK FOR GAS
LEAKS.
WARNING!
FLUIDS UNDER PRESSURE MAY
CAUSE INJURY TO PERSONNEL OR
DAMAGE TO EQUIPMENT WHEN
RELEASED. BE SURE TO SHUT OFF
ALL INCOMING AND OUTGOING
WATER SHUTOFF VALVES.
CAREFULLY DECREASE ALL
TRAPPED PRESSURES TO ZERO
BEFORE PERFORMING ANY BOILER
MAINTENANCE.
WARNING!
ELECTRICAL VOLTAGES UP TO 460
VAC MAY BE USED IN THIS
EQUIPMENT. THEREFORE THE
COVER ON THE UNIT’S POWER BOX
(LOCATED BEHIND THE FRONT
PANEL DOOR) MUST BE INSTALLED
AT ALL TIMES, EXCEPT DURING
MAINTENANCE AND SERVICING.
CAUTIONS!
Must be observed to prevent equipment
damage or the loss of operating
effectiveness.
CAUTION!
Many soaps used for gas pipe leak
testing are corrosive to metals. The
piping must be rinsed thoroughly with
clean water after leak checks have
been completed.
CAUTION!
DO NOT use this boiler if any part has
been under water. Call a qualified
service technician to inspect and
replace any part that has been under
water.

SAFETY PRECAUTIONS
1-2
1.2 EMERGENCY SHUTDOWN
If overheating occurs or the gas supply fails to
shut off, close the manual gas shutoff valve
(Figure 1-1) located external to the unit.
IMPORTANT
The Installer must identify and indicate
the location of the emergency shutdown
manual gas valve to operating personnel.
1.3 PROLONGED SHUTDOWN
After prolonged shutdown, it is recommended
that the startup procedures in Chapter 4 and the
safety device test procedures in Chapter 6 of
this manual be performed, to verify all system-
operating parameters. If there is an emergency,
turn off the electrical power supply to the
AERCO boiler and close the manual gas valve
located upstream the unit. The installer must
identify the emergency shut-off device.
MANUAL GAS SHUTOFF VALVE
VALVE OPEN VALVE CLOSED
Figure 1-1
Manual Gas Shutoff Valve

(This page intentionally blank)

INSTALLATION
2-1
Chapter 2 - INSTALLATION
2.1 RECEIVING THE UNIT
Each Benchmark is shipped as a single crated
unit. The shipping weight is approximately 1850
pounds, and must be moved with the proper
rigging equipment for safety and to avoid dam-
ages. The unit should be completely inspected
for shipping damage and completeness at the
time of receipt from the carrier and before the bill
of lading is signed.
NOTE:
AERCO is not responsible for lost or
damaged freight.
Each unit has a Tip-N-Tell indicator on the out-
side of the crate. This indicates if the unit has
been turned on its side. If the Tip-N-Tell
indicator is tripped, do not sign for the shipment.
Note the information on the carrier’s paperwork
and request a freight claim and inspection by a
claims adjuster before proceeding. Any other
visual damage to the packaging materials
should also be made clear to the delivering
carrier.
2.2 UNPACKING
Carefully unpack the unit taking care not to
damage the unit jacket when cutting away
packaging materials. A close inspection of the
unit should be made to determine if there has
been any damage not indicated by the Tip-N-
Tell. The freight carrier should be notified
immediately if any damage is detected. The
following accessories come standard with each
unit and are packed separately within the unit’s’
packing container or are factory installed on the
boiler.
•Pressure/Temperature Gauge
•Spare Spark Ignitor
•Spare Flame Detector
•ASME Pressure Relief Valve
•Regulator Adjustment Tool (One per
Site)
•Condensate Drain Trap
•2” Gas Supply Shutoff Ball Valve
1.
When ordered, optional accessories may be
packed separately or within the boiler shipping
container, or may be installed on the boiler. Any
standard or optional accessories shipped loose
should be identified and put in a safe place until
ready for installation or use.
.
36"
Figure 2.1
Boiler Clearances

INSTALLATION
2-2
2.3 INSTALLATION
The unit must be installed by qualified personnel
(i.e. licensed plumber, gas fitter, etc.) in com-
pliance with local and state regulations. The
prescribed clearances for service are shown in
Figure 2.1. The minimum clearance dimensions,
required by AERCO, are listed below. Local
building codes may require more clearance and
take precedence
Minimum clearances required:
Sides 24"
Front 24"
Rear 36"
Top 18"
All gas piping, water piping and electrical conduit
or cable must be arranged so that they do not
interfere with the removal of any cover, or inhibit
service or maintenance of the unit.
WARNING!
KEEP UNIT AREA CLEAR AND FREE
FROM COMBUSTIBLE MATERIALS AND
FLAMMABLE VAPORS AND LIQUIDS.
CAUTION!
While packaged on the shipping skid,
the boiler must be moved by pallet jack
or forklift from the rear only.
2.3.1. SETTING THE UNIT
The unit must be installed on a 4 to 6 inch
housekeeping pad for proper condensate
drainage. If anchoring the unit, see the
dimensional drawings in Appendix F for anchor
location. Lifting lugs are provided for moving the
unit when it has been removed from the shipping
skid (See Fig. 2.2). USE ONLY THE LIFTING
LUGS TO MOVE THE UNIT. Remove the rear
top panel from the unit to provide access to the
lifting lugs. Remove the four (4) lag screws
securing the boiler to the shipping skid. Lift the
unit off the shipping skid and position it on to the
4 to 6 inch housekeeping concrete pad
(required) in the desired location.
In multiple unit installations, it is important to
plan the position of each unit. Sufficient space
for piping connections and future maintenance
requirements must be given. All piping must
include ample provision for expansion.
If installing a Combination Control (CCP)
system, it is important to identify and place the
Combination Mode units in the proper physical
location. If these boilers are not properly located,
it will be necessary to reprogram them.
LIFTING LUGS
BURNER
SHEET METAL OUTLINE
Figure 2.2
Lifting Lug Location
2.3.2 SUPPLY AND RETURN PIPING
The Benchmark 2.0 utilizes 4" 150# flanges for
the water system supply and return piping
connections. See Appendix F for dimensional
data. The physical location of the supply and
return piping connections is on the rear of the
unit (See Fig 2.3 For Details).
Figure 2.3
Supply and Return Location
BOILER SUPPLY
(4"-150# FLG'D CONN.)
(4"-150# FLG'D CONN.)
BOILER RETURN

INSTALLATION
2-3
2.3.3 CONDENSATE DRAIN & PIPING
The Benchmark Boiler is designed to condense
water vapor from the flue products. Therefore,
the installation must have provisions for suitable
drainage or collection. A 1/2” NPT drain
connection is provided on the exhaust manifold
(see Fig 2.4). A separate condensate drain trap
(part no. 24060) is shipped loose and must be
installed on the floor behind the unit. Connect
the trap to the exhaust manifold as follows:
1. First, install a 1/2” NPT nipple in the
condensate drain port (Fig. 2.4). Next,
connect a 3/4-to 1/2” reducer to the 1/2”
nipple.
2. On the condensate drain trap, install 3/4”
NPT nipples in the tapped inlet and outlet of
the trap.
3. Attach a length of 1” I.D. polypropylene hose
between the exhaust manifold drain and the
inlet side of the condensate trap (Fig 2.5).
Secure both ends of the hose with clamps.
Drainage from the condensate drain trap
outlet must be by gravity to a nearby floor
drain via a polypropylene hose or suitable
piping.
If a floor drain is not available, a condensate
pump can be used to remove the condensate to
drain. The maximum condensate flow rate is 11
GPH. The condensate drain trap, associated
fittings and drain line must be removable for
routine maintenance. Do Not hard pipe.
EXHAUST
MANIFOLD
1/2" NPT CONDENSATE
DRAIN CONNECTION
3/4" NPT
CONDENSATE
TRAP
Figure 2.4
Condensate Drain Connection Location
CONDENSATE
TRAP
CLAMPS
CLAMP
TO
FLOOR
DRAIN
1" I.D.
HOSE
1" I.D.
HOSE
3/4" NPT
NIPPLES
CONDENSATE
DRAIN CONNECTION
EXHAUST
MANIFOLD
Figure 2.5
Condensate Trap Installation
2.4. GAS SUPPLY PIPING
The AERCO Gas Fired Equipment Gas Com-
ponents and Supply Design Guide (GF-2030LN)
must be consulted before any gas piping is
designed or started.
WARNING!
DO NOT USE MATCHES, CANDLES,
FLAMES OR OTHER SOURCES OF
IGNITION TO CHECK FOR GAS LEAKS.
CAUTION!
Many soaps used for gas pipe leak testing
are corrosive to metals. Therefore, AERCO
recommends the use of non-corrosive
soaps for leak tests. The piping must be
rinsed thoroughly with clean water after leak
checks have been completed.
NOTE:
All gas piping must be arranged so that it
does not interfere with removal of any
cover, inhibit service or maintenance, or
prevent access between the Unit and walls,
or another unit.
The location of the 2" inlet gas connection is on
the rear of the unit as shown in Figure 2.5.
All pipes should be de-burred and internally
cleared of any scale or iron chips before
installation. No flexible connectors or non-
approved gas fittings should be installed. Piping

INSTALLATION
2-4
should be supported from floor, ceiling or walls
only and must not be secured to the unit.
A suitable piping compound, approved for use
with natural gas or propane, should be used.
Any excess must be wiped off to prevent
clogging of components.
To avoid damage to the unit, when pressure
testing gas piping, isolate the unit from the gas
supply piping. At no time should there be
more than 2 psi to the unit. Leak test all
external piping thoroughly for leaks using a soap
and water solution or suitable equivalent. The
gas piping must meet all applicable codes.
2.4.1 GAS SUPPLY SPECIFICATONS
−Natural Gas:
The maximum static pressure to the unit
must be no more than 2 psi. Minimum
natural gas operating pressure is 5.3“ W.C.
for FM gas trains & 5.5“ W.C. for IRI gas
trains when the unit is firing at maximum
input (2000 cfh). For Benchmark 2.0 Low
NOx boilers configured for De-Rated
capacity, the required minimum natural gas
operating pressure is 4.0” W.C. for FM gas
trains (4.2” W.C. for IRI gas trains) at maxi-
mum input of 1,750,000 BTU/hr (1750 cfh).
2.4.2 MANUAL GAS SHUTOFF VALVE
A 2” manual gas shut-off valve is furnished with
each unit. The valve should be positioned on the
inlet to the unit, as shown in Figure 2.5.
NATURAL GAS
SUPPLY
2" MANUAL SHUT OFF
DIRT
TRAP
Figure 2.5
Manual Shut-Off Valve Location
2.4.3 IRI GAS TRAIN KIT
The IRI gas train is an optional gas train
required in some areas by code or for insurance
purposes. The IRI gas train is factory pre-piped
and wired.
2.5 ELECTRICAL SUPPLY
The AERCO Gas Fired Equipment Electrical
Power Wiring Guide, (GF-2060), must be
consulted in addition to the following material
before wiring to the unit is started. External AC
power connections are made to the unit inside
the power box on the front panel of the unit,
behind the removable front door (Figure 2.6).
NOTE:
All electrical conduit and hardware should
be installed so that it does not interfere with
the removal of any cover, inhibit service or
maintenance, or prevent access between
the unit and walls or another unit.
UPPER RIGHT CORNER OF FRONT PANEL
TERMINAL BLOCK
Figure 2.6
AC Input Terminal Location
2.5.1 ELECTRICAL REQUIREMENTS
The Benchmark Boiler is available in one three
different AC power configurations:
220 Vac/1 Phase/60 Hz @ 20 amps
208 Vac/3-Phase/60 @15 amps
460 Vac/3-Phase/60 Hz @ 15 amps

INSTALLATION
2-5
Each of the above power configurations contain
a Power Box with a terminal block which
matches the configuration ordered. The three
different terminal block configurations are shown
in Figure 2.7. A wiring diagram showing the
required AC power connections is provided on
the front panel of each Power Box.
Each Benchmark Boiler must be connected to a
dedicated electrical circuit. No other devices
should be on the same electrical circuit as the
Benchmark Boiler. A means for disconnecting
AC power from the unit (such as a service
switch) must be installed near the unit for normal
operation and maintenance. All electrical
connections should be made in accordance with
the National Electrical Code and/or with any
applicable local codes.
For electrical power wiring diagrams, see the
Benchmark Electrical, Power Wiring Guide, GF-
2060
GND
NEU
L2
L1
220 VAC, 1 PHASE
220 VAC, 1 Phase
GND
NEU
L2
L3
L1
208 VAC, 3 PHASE
208 VAC, 3 Phase
GND
L2
L3
L1
460 VAC, 3 PHASE
460 VAC, 3 Phase
Figure 2.7
AC Terminal Block Configurations
2.6 MODE OF OPERATION and FIELD
CONTROL WIRING
The Benchmark Boiler is available in several
different modes of operation. While each unit is
factory configured and wired for a particular
mode, some field wiring may be required to
complete the installation. This wiring is typically
run to the Input/Output (I/O) Box located on the
front of the unit behind the removable front door
(see Fig. 2.8). A brief description of each mode
of operation, and their requirements, is de-
scribed in the following paragraphs. Additional
information concerning field wiring is provided in
paragraphs 2.7.1 through 2.7.9. For additional
information on modes of operation, refer to
Chapter 5.
LOWER RIGHT CORNER OF
FRONT PANEL
TERMINAL STRIPS
Figure 2.8
I/O Box Terminal Location
2.6.1 CONSTANT SETPOINT MODE
The Constant Setpoint Mode is used when it is
desired to have a fixed setpoint that does not
deviate. No wiring connections other than
electrical supply connections are required for
this mode. However, if desired, fault monitoring
or enable/disable interlock wiring can be utilized
(see paragraphs 2.7.9.1 and 2.7.10).

INSTALLATION
2-6
2.6.2 INDOOR/OUTDOOR RESET MODE
This mode of operation increases supply water
temperature as outdoor temperatures decrease.
An outside air temperature sensor (AERCO PN
122790) is required. The sensor MUST BE wired
to the I/O Box wiring terminals (see Fig. 2.9). For
more information concerning the outside air
sensor installation, refer to paragraph 2.7.1
mA OUT
RS-485
COMM.
+
-
+
-
ANALOG IN
SENSOR COMMON
OUTDOOR SENSOR IN REMOTE INTL'K IN
B.M.S. (PWM) IN
SHIELD
+
-
+
-
AUX SENSOR IN
NOT USED
EXHAUST SWITCH IN
DELAYED INTL'K IN
FAULT RELAY
120 VAC, 5A, RES
AUX RELAY
120 VAC, 5A, RES
G
RELAY CONTACTS:
120 VAC, 30 VDC
5 AMPS RESISTIVE
DANGER
120 VAC USED
IN THIS BOX
NOT USED NOT USED
NC
COM
NO
NC
COM
NO
NOT USED
Figure 2.9 I/O Box Terminal Strip
2.6.3 BOILER MANAGEMENT SYSTEM
(BMS) MODE
NOTE
BMS Model 168 can utilize either pulse
width modulation (PWM) or RS485
Modbus signaling to the Boiler. BMS II
Model 5R5-384 can utilize only RS485
signaling to the Boiler.
When using an AERCO Boiler Management
System (BMS), the field wiring is connected
between the BMS Panel and each Boiler’s I/O
Box terminal strip (Figure 2-9). Twisted shielded
pair wire from 18 to 22 AWG must be utilized for
the connections. The BMS Mode can utilize
either pulse width modulation (PWM) signaling,
or RS485 Modbus signaling. For PWM signaling,
connections are made from the AERCO Boiler
Management System to the B.M.S. (PWM) IN
terminals on the I/O Box terminal strip. For
RS485 Modbus signaling, connections are made
from the BMS to the RS485 COMM terminals on
the I/O Box terminal strip. Polarity must be
maintained and the shield must be connected
only at the AERCO BMS. The boiler end of the
shield must be left floating. For additional
instructions, refer to Chapter 5, paragraph 5.6 in
this manual. Also, refer to GF-108M (BMS
Model 168) and GF-124 (BMS II Model 5R5-
384), BMS -Operations Guides.
2.6.4 REMOTE SETPOINT and DIRECT
DRIVE MODES
The Benchmark Boiler can accept several types
of signal formats from an Energy Management
System or other source to control either the
setpoint (Remote Setpoint Mode) or firing rate
(Direct Drive Mode) of the Boiler. These formats
are:
4 to 20 mA/1 to 5 Vdc
0 to 20 mA/0 to 5 Vdc
PWM – (Pulse Width Modulated signal. See
paragraph 2.7.4)
Network – (RS485 Modbus. See para. 2.7.7)

INSTALLATION
2-7
While it is possible to control a boiler or boilers
using one of the previously described modes of
operation, it may not be the method best suited
for the application. Prior to selecting one of
these modes of operation, it is recommended
that you consult with your local AERCO
representative or the factory for the mode of
operation that will work best with your
application. For more information on wiring the
4 to 20 mA / 1to 5VDC or the 0 to 20 mA / 0 to 5
VDC, see paragraph 2.7.3.
2.6.4 COMBINATION MODE
NOTE
Only BMS Model 168 can be utilized for
the Combination Mode, not the BMS II
(Model 5R5-384).
With a Combination Mode unit, field wiring is
connected between the unit’s I/O Box wiring
terminals, the CCP (Combination Control Panel),
and the BMS Model 168 (Boiler Management
System). The wiring must be done using a
shielded twisted pair of 18- 22 AWG wire and
polarity must be maintained. For further
instructions and wiring diagrams, refer to the
GF-108 Boiler Management System Operations
Guide and the CCP-1 data sheet.
2.7 I/O BOX CONNECTIONS
The types of input and output signals and
devices to be connected to the I/O Box terminals
shown in Figure 2.9 are described in the
following paragraphs.
CAUTION!
DO NOT make any connections to the I/O
Box terminals labeled “NOT USED”.
Attempting to do so may cause equipment
damage.
2.7.1 OUTDOOR SENSOR IN
An outdoor air temperature sensor (AERCO Part
No. 122790) will be required mainly for the
Indoor/Outdoor reset mode of operation. It can
also be used with another mode if it is desired to
use the outdoor sensor enable/disable feature.
This feature allows the boiler to be enabled or
disabled based on the outdoor air temperature.
The factory default for the outdoor sensor is
DISABLED. To enable the sensor and/or
choose an enable/disable outdoor temperature,
see the Configuration menu in Chapter 3.
The outdoor sensor may be wired up to 200 feet
from the boiler It is connected to the OUTDOOR
SENSOR IN and SENSOR COMMON terminals
in the I/O box (see Figs. 2.8 and 2.9). Wire the
sensor using a twisted shielded pair cable of 18-
22 AWG wire. There is no polarity when
terminating the wires. The shield is to be
connected only to the terminals labeled SHEILD
in the I/O box. The sensor end of the shield must
be left free and ungrounded.
When mounting the sensor, it must be located
on the North side of the building where an
average outside air temperature is expected.
The sensor must be shielded from direct sunlight
as well as impingement by the elements. If a
shield is used, it must allow for free air
circulation.
2.7.2 AUX SENSOR IN
The AUX SENSOR IN terminals can be used to
add an additional temperature sensor for
monitoring purposes. This input is always
enabled and is a view only input that can be
seen in the operating menu. The sensor must be
wired to the AUX SENSOR IN and SENSOR
COMMON and must be similar to AERCO
BALCO wire sensor P/N 12449. A resistance
chart for this sensor can be found in APPENDIX
C.
2.7.3 ANALOG IN
The ANALOG IN + and – terminals are used
when an external signal is used to drive the
firing rate (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 firing rate. The factory default setting
is for 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 Chapter 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 Fig. 2.9). 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.

INSTALLATION
2-8
Whether using voltage or current for the drive
signal, they are linearly mapped to a 40oto
240oF 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 ( 40oto
240oF), outlet temperature (30oto 240oF), or fire
rate (0% to 100%). This function is enabled in
the Configuration Menu (Chapter 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 500oF.
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. 2.9). 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 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.
2.7.9.1 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
(jumped).
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 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 (Chapter 3).
2.7.10 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
condition occurs and remains energized until the
fault is cleared and the CLEAR button is
depressed. The fault relay connections are
shown in Figure 2.9
2.8 AUXILIARY RELAY CONTACTS
Each Boiler 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 provided for the control of auxiliary
equipment, such as pumps and louvers, or can
be used as a Boiler status indictor (firing or not

INSTALLATION
2-9
firing). Its contacts are rated for 120 VAC @ 5
amps. Refer to Figure 2.9 to locate the AUX
RELAY terminals for wiring connections.
2.9 FLUE GAS VENT INSTALLATION
The AERCO Venting and Combustion Air Guide,
GF-2050, must be consulted before any flue gas
vent or inlet air venting is designed or installed.
U/L listed, positive pressure, watertight vent
materials as specified in AERCO’s GF-2050,
must be used for safety and code compliance.
Because the unit is capable of discharging low
temperature exhaust gases, the flue must be
pitched back to the unit a minimum of 1/4" per
foot to avoid any condensate pooling and to
allow for proper drainage.
The combined pressure drop of vent and
combustion air systems must not exceed 140
equivalent feet of 8 inch ducting. Fittings as well
as pipe lengths must be calculated as part of the
equivalent length.
For a natural draft installation the draft must not
exceed -0.25”/+0.25" W.C. These factors must
be planned into the vent installation. If the
maximum allowable equivalent lengths of piping
are exceeded, the unit will not operate properly
or reliably.
2.10 COMBUSTION AIR
The AERCO Venting and Combustion Air Guide,
GF-2050, MUST be consulted before any flue or
combustion supply air venting is designed or
started. Combustion air supply is a direct
requirement of ANSI 223.1, NFPA-54, and local
codes. These codes should be consulted before
a permanent design is determined.
The combustion air must be free of chlorine,
halogenated hydrocarbons, or other chemicals
that can become hazardous when used in gas-
fired equipment. Common sources of these
compounds are swimming pools, degreasing
compounds, plastic processing and refrigerants.
Whenever the environment contains these types
of chemicals, combustion air must be supplied
from a clean area outdoors for the protection
and longevity of the equipment.
The Benchmark is UL listed for 100% sealed
combustion and can be ordered with a sealed
combustion option, or can be installed using
room air as long as there is an adequate supply.
(See paragraph 2.10.3 for more information
concerning sealed combustion air.)
If the sealed combustion air option is not being
used, an inlet screen will be attached at the
blower suction and the knockout at the top of the
unit will be and should remain in place.
The more common methods of supplying
combustion air are outlined below. For more
information concerning combustion air, consult
the AERCO GF-2050, Venting and Combustion
Air Guide.
2.10.1 COMBUSTION AIR FROM
OUTSIDE THE BUILDING
Air supplied from outside the building must be
provided through two permanent openings. Each
opening must have a free area of not less than
one square inch for each 4000 BTU boiler input.
The free area must take into account restrictions
such as louvers and bird screens.
2.10.2 COMBUSTION AIR FROM INSIDE
THE BUILDING
When combustion air is provided from within the
building, it must be supplied through two perma-
nent openings in an interior wall. Each opening
must have a free area of not less than one
square inch per 1000 BTUH of total boiler input.
The free area must take into account any
restrictions such as louvers.
2.10.3 SEALED COMBUSTION
The BENCHMARK boiler is UL listed for 100%-
sealed combustion and can be ordered with a
sealed combustion option or without. Units
ordered in the sealed combustion configuration
will come with an air inlet assembly installed on
the blower. The knockout at the top of the boiler
must be removed and the combustion air
ductwork must be attached to the 6" x 8" adapter
that is provided just below the knockout.
Remove and discard the screen attached to the
adapter.
In a sealed combustion air application, the
combustion air ducting pressure losses must be
taken into account when calculating the total
maximum allowable venting run. See the
AERCO Venting and Combustion Air Guide, GF-
2050. When using the boiler in a sealed
combustion air configuration, each unit must
have a minimum 8" diameter connection at the
unit.

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CONTROL PANEL OPERATING PROCEDURES
3-1
Chapter 3 - CONTROL PANEL OPERATING PROCEDURES
3.1. INTRODUCTION
The information in this Chapter provides a guide
to the operation of the Benchmark Boiler using
the Control Panel mounted on the front of the
unit. It is imperative that the initial startup of this
unit be performed by factory trained personnel.
Operation prior to initial startup by factory
trained personnel will void the equipment
warranty. In addition, the following WARNINGS
and CAUTIONS must be observed at all times.
CAUTION:
All initial installation procedures must be
satisfied before attempting to start the unit.
WARNING:
THE ELECTRICAL VOLTAGES IN THIS
SYSTEM MAY INCLUDE 460, 220, 120
AND 24 VOLTS AC. IT MUST NOT BE
SERVICED OR ACCESSED BY OTHER
THAN FACTORY CERTIFIED SERVICE
TECHNICIANS.
WARNING:
DO NOT ATTEMPT TO DRY FIRE THE
BOILER. STARTING THE UNIT WITHOUT
A FULL WATER LEVEL CAN SERIOUSLY
DAMAGE THE UNIT AND MAY RESULT IN
PERSONNEL INJURY OR PROPERTY
DAMAGE. THIS SITUATION WILL VOID
ANY WARRANTY.
3.2. CONTROL PANEL DESCRIPTION
The Benchmark Control Panel shown in Figure
3-1 contains all of the controls, indicators and
displays necessary to operate, adjust and
troubleshoot the Benchmark Boiler. These
operating controls, indicators and displays are
listed and described in Table 3-1. Additional
information on these items are provided in the
individual operating procedures provided in this
Chapter.
1
2
3
4
5
6
7
8
9
10
11
12
Figure 3-1.
Control Panel Front View