Watts Aerco BMK 750 Guide

Heating and Hot Water Solutions
AERCO International, Inc. • 100 Oritani Drive • Blauvelt, NY 10913
USA: T: [phone] • Toll Free: [phone] • AERCO.com
Technical Support • [phone] • Mon-Fri, 8 am - 5 pm EST
© 2020 AERCO
Electrical Power Design Guide
Other documents for this product include:
OMM-0127, GF-205-K BMK750K-3000K Installation-Startup KOREA
OMM-0128, GF-206-K BMK750K-3000K Operation- Maintenance KOREA
OMM-0136, GF-210 BMK750-6000 Platinum-Edge Installation-Startup
OMM-0137, GF-211 BMK750-6000 Platinum-Edge Operation-Service
OMM-0138, GF-212 BMK750-6000 Platinum-Edge Reference Manual
TAG-0019, GF-2070 Benchmark Boiler Application Guide
TAG-0022, GF-2050 Benchmark Vent & Combustion Air Guide
TAG-0047, GF-2030 Benchmark Gas Guide
TAG-0048_P •GF-2060 •8/6/2020
Benchmark®and Benchmark
Platinum Boilers
Models 750 through 6000
Disclaimer
The information contained in this 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, not for incidental or
consequential damages occurring in connection with the furnishing,
performance, or use of these materials.

Benchmark Series Boilers Pre-Installation Electrical Power Guide
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1. General
Benchmark (BMK) Gas Fired Boilers are fully factory wired packaged units which require simple
external power wiring as part of the installation (Figure 1). This technical guide is intended to help
designers provide electrical power wiring (line voltage) to Benchmark units. Control wiring details are
provided in other publications, depending upon unit application. This document is intended only as a
guide and therefore cannot include all possible alternatives or unit applications. In order to comply
with all codes and authorities having jurisdiction, designers and installers must plan the electrical
wiring carefully and execute the installation completely. Emergency shutoffs, fusible fire switches,
break glass stations, and other electrical requirements should be considered and installed whenever
necessary.
2. Boiler Electrical Requirements
Benchmark boilers are available with the following power options:
BMK Model
Voltage
Phase
Amperage
BMK750 –1000 Domestic
120 V
1/ 60 Hz
15
BMK750 –1000 International
220 V
1/ 50-60 Hz
20
BMK1500 –2000 Domestic
120 V
1/ 60 Hz
20
BMK1500 –2000 International
220 V
1/ 50-60 Hz
20
BMK2500 - 3000 Domestic
208 V
3/ 60 Hz
20
480 V
3/ 60 Hz
15
BMK2500 - 3000 International
380-415 V
3/ 50-60 Hz
15
BMK4000 –5000N Domestic
208 V
3/ 60 Hz
40
480 V
3/ 60 Hz
20
BMK4000 –5000N International
380-415 V
3/ 50-60 Hz
20
BMK5000 - 6000 Domestic
208 V
3/ 60 Hz
30
480 V
3/ 60 Hz
20
BMK5000 - 6000 Canada
575 V
3/ 60 Hz
20
BMK5000 - 6000 International
380-415 V
3/ 50-60 Hz
20
Voltages lower than those specified in the table above will result in increased wear and premature
failure of the blower motor. Wire size and type should be made per the National Electrical Code based
on length and load.
For all Benchmark models, the power box for field wiring connections is located in the upper right
corner behind the unit front panel. All copper wire must be connected to the power box.

Benchmark Series Boilers Pre-Installation Electrical Power Guide
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Figure 1: Service Disconnect Switch Typical Location
Figure 2a: Power Box Components, BMK750 & 1000 –DOMESTIC
TERMINAL
BLOCKS
FUSE
BLOCKS
12V POWER
SUPPLY
TRANSFORMER
Service Disconnect
Switch
POWER
BREAKER
FLAME ROD SIGNAL
AMPLIFIER
24 VDC POWER
SUPPLY

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Figure 2a: Power Box Components, BMK750 & 1000 –INTERNATIONAL
Figure 3a: Power Box Components, BMK1500 –2000 –DOMESTIC
TERMINAL
BLOCKS
FUSE
BLOCKS
POWER
BREAKER
12V POWER
SUPPLY
TERMINAL
BLOCKS
POWER
BREAKER
FUSE
BLOCKS
12 V POWER
SUPPLY
TRANSFORMER
FLAME ROD
SIGNAL
AMPLIFIER
TRANSFORMER
FLAME ROD SIGNAL
AMPLIFIER
24 VDC POWER
SUPPLY
24 VDC
POWER
SUPPLY
220 V Transformer
Harness
To 220 V
TRANSFORMER
For INTERNATIONAL units,
Molex is plugged into 220 V
Transformer Harness

Benchmark Series Boilers Pre-Installation Electrical Power Guide
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Figure 3b: Power Box Components, BMK1500 –2000 –INTERNATIONAL
Figure 4a: Power Box Components, BMK2500 –6000 –DOMESTIC
POWER
BREAKER
FUSE
BLOCKS
12V
POWER
SUPPLY
TRANSFORMER
24 VDC
POWER
SUPPLY
FLAME ROD
SIGNAL
AMPLIFIER
TERMINAL
BLOCKS
12 V POWER
SUPPLY
24 VDC POWER
SUPPLY
POWER
BREAKER
TRANSFORMER
FUSE
BLOCKS
TERMINAL
BLOCKS
For INTERNATIONAL units,
Molex is plugged into 220V
Transformer Harness
220 V
Transformer
Harness
To 220V
TRANSFORMER

Benchmark Series Boilers Pre-Installation Electrical Power Guide
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Figure 4b: Power Box Components, BMK2500 –6000 –INTERNATIONAL
3. Provisions for Service
Designers must provide emergency shutoffs and other devices to satisfy electrical codes. It is also
recommended to provide an electrical shutoff disconnect switch of suitable load carrying
characteristics near each BMK boiler. No electrical boxes or field components should be mounted to
the surface of the boiler or where they would interfere with the removal of the side or top panels for
maintenance. The service disconnect switch should be mounted near the unit, as illustrated in
Diagram 1. Wiring conduit, EMT, or other wiring paths should not be secured to the unit but supported
externally. Electricians should be instructed as to where the wiring conduit should be located, such as
away from the relief valve discharge, drains, etc. All electrical conduit and hardware should be
installed so that it does not interfere with the removal of any covers, inhibit service or maintenance, or
prevent access between the unit and walls or another unit.
TERMINAL
BLOCKS
POWER
BREAKER
FUSE
BLOCKS
12V
POWER
SUPPLY
TRANSFORMER
24 VDC
POWER
SUPPLY

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4. Boiler Wiring
A dedicated protected circuit should be provided from the power source to the boiler. No other
electrical devices should be permanently wired on the same circuit. The protected circuit and circuit
breaker switch must be sized for the amperage values below.
An emergency switch (electrical shutoff) must be wired in series with power to the unit. Connecting an
emergency shutoff switch (E-stop) to the main power terminals of the boiler is the recommended and
safest way to totally disable and un-power the unit. Use of the remote interlock, located on the I/O
board, is not recommended since it does not cutoff power within the unit, it only disables it. Under no
circumstance should the remote interlock of the BST Manager unit be used as an emergency switch
for the plant.
The following table lists the input power requirements for all Benchmark boilers, including the diagram
number of each model’s corresponding schematic diagram:
DOMESTIC UNITS
INTERNATIONAL UNITS
BMK Model
Diag.
Voltage/Phase/Frequency
Amps
Wires
Diag.
Voltage/Phase/Frequency
Amps
Wires
750 –1000
1a
120V / 1/ 60 Hz@
15 A
3
1b
220V / 1/ 50- 60 Hz
20 A
3
1500 –2000
20 A
2500/3000
2
208V / 3/ 60 Hz
20 A
5
3a
480V / 3/ 60 Hz
15 A
4
3b
380-415V / 3/ 50- 60 Hz
15 A
4
4000/5000N
7
208 V / 3/ 60 Hz
40 A
4
6a
480V / 3/ 60 Hz
20 A
4
6b
380-415V / 3/ 50- 60 Hz
20 A
4
5000/6000
4
208V / 3/ 60 Hz
30 A
4
5a
480V or 575V / 3/ 60 Hz
20 A
4
5b
380-415V / 3/ 50-60 Hz
20 A
4
For applicable wiring connections, refer to the schematic diagrams below.
Diagram 1a - BMK750 –2000:120 V / 1
 / 60 Hz Wiring Schematic –3 Wire –DOMESTIC
120 V / 1/ 60 Hz
DISCONNECT SWITCH
1 POLE 20 AMP
1 POLE 20 AMP
CIRCUIT BREAKER

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Diagram 1b - BMK750 –2000: 220 V / 1
 / 50-60 Hz Wiring Schematic –3 Wire –INTERNATIONAL
Diagram 2 - BMK2500/3000: 208 V / 3
 / 60 Hz Wiring Schematic- 5 Wire –DOMESTIC
Diagram 3a - BMK2500-5000N: 480 V / 3  / 60 Hz Wiring Schematic- 4 Wire –DOMESTIC
220 V / 1/ 50-60 Hz
DISCONNECT SWITCH
1 POLE 20 AMP
1 POLE 20 AMP
CIRCUIT BREAKER
480 V / 3/ 60 Hz
208 V / 3/ 60 Hz

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Diagram 3b- BMK2500-5000N: 380-415 V / 3
 / 50-60 Hz Wiring Schematic- 4 Wire –INTERNATIONAL
Diagram 4: BMK5000/6000: 208 V / 3  / 60 Hz Wiring Schematic- 4 Wire –DOMESTIC
Diagram 5a: BMK5000/6000: 480 V or 575 V / 3
 / 60 Hz Wiring Schematic- 4 Wire –DOMESTIC
480 V / 3/ 60Hv or
575 V / 3/ 60 Hz
3 POLE 20 AMP
CIRCUIT BREAKER
DISCONNECT SWITCH
3 POLE 20 AMP
208 V / 3/ 60 Hz
380-415 V / 3/ 50-60 Hz

Benchmark Series Boilers Pre-Installation Electrical Power Guide
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Diagram 5b: BMK5000/6000: 380-415 V / 3
 / 50-60 Hz Wiring Schematic- 4 Wire –INTERNATIONAL
Diagram 6a - BMK4000-5000N: 480 V / 3
 / 60 Hz Wiring Schematic- 4 Wire –DOMESTIC
Diagram 6b- BMK4000-5000N: 380-415 V / 3  / 50-60 Hz Wiring Schematic- 4 Wire –DOMESTIC
480 V / 3/ 60 Hz
3 POLE 20 AMP
CIRCUIT BREAKER
DISCONNECT SWITCH
3 POLE 20 AMP
380-415 V / 3/ 50-60 Hz
3 POLE 20 AMP
CIRCUIT BREAKER
DISCONNECT SWITCH
3 POLE 20 AMP
3 POLE 20 AMP
CIRCUIT BREAKER
DISCONNECT SWITCH
3 POLE 20 AMP
380-415 V / 3/ 50-60Hv

Benchmark Series Boilers Pre-Installation Electrical Power Guide
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Diagram 7: BMK4000-5000N: 208 V / 3
 / 60 Hz Wiring Schematic- 4 Wire –DOMESTIC
5. Multiple Unit Wiring
Whenever multiple units are installed within the same mechanical spaces, electrical code requirements call for a
single electrical shutoff for emergency use. It is the responsibility of the electrical designer to comply with local
codes and regulations affecting an individual installation.
3 POLE 40 AMP
CIRCUIT BREAKER
208 V / 3/ 60 Hz
DISCONNECT SWITCH
3 POLE 40 AMP

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© AERCO International, Inc., 2020
Change Log:
Date
Description
Changed by
6/9/2020
Rev O:
Added BMK5000N information where applicable.
Linley
Thobourne, Chris
Blair
8/6/2020
Rev P:
Added diagram and description of E-Stop power shutoff switch
to Section 4.
Added 208 V row to BMK 4000/5000N –Domestic, changed
amperage from 15 to 20 in Sections 2 and 4. Added new wiring
schematic diagrams 6a, 6b and 7 for the BMK4000 & 5000N.
Chris Blair