Combustion Air; Ducted Combustion Air; Benchmark Pump Relay - Watts AERCO Benchmark BMK750 Installation And Start-Up Manual

Benchmark 750-6000 with Edge [i]: Install-Startup Manual
SECTION 2 – INSTALLATION

2.13 COMBUSTION AIR

The Benchmark Venting and Combustion Air Guide, TAG-0022 (GF-2050) MUST be consulted
before any inlet air venting is designed or installed. Air supply is a direct requirement of ANSI
223.1, NFPA-54, CSA B149.1 and local codes. These codes should be consulted before a
permanent design is determined.
The combustion air must be free of chlorine, halogenated hydrocarbons, other chemicals that
can become hazardous when used in gas-fired equipment and other combustion products.
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 and warranty validation.
If combustion air is supplied directly to the unit(s) though air duct(s), see section 2.13.1 below.
If combustion air is not supplied through air ducts, it must be supplied to the unit(s) through two
permanent openings. These two openings must have a free area of not less than one square
2
inch (6.5 cm ) for each 4000 BTUs (1.17 kW) input for each unit. The free area must take
into account restrictions such as louvers and bird screens.
For Canada installations, refer to the requirements specified in CSA B149.1-10, sections 8.4.1
and 8.4.3.

2.13.1 DUCTED COMBUSTION AIR

For ducted combustion air installations, the air ductwork must be attached directly to the air inlet
connection on the sheet metal enclosure. Consult the Benchmark Venting and Combustion Air
Guide, TAG-0022 (GF-2050) when designing combustion air ducting.
In a ducted combustion air application, the combustion air ducting pressure losses must be
taken into account when calculating the total maximum allowable venting run. When using the
unit in a ducted combustion air configuration, the minimum diameter connection at the unit is:
TABLE 2-4: Air Duct Minimum Diameter
Benchmark Model
BMK750 – BMK1500
BMK2000 – BMK3000
BMK4000 and 5000N
BMK5000 & BMK6000

2.14 BENCHMARK PUMP RELAY

Benchmark units include a pump relay (P/N 69102-2 for BMK750 & 1000, 69102-3 for BMK1500
- 6000) as standard equipment. The pump relay allows the user to turn a pump on/off and
open/close a motorized valve as the boiler cycles on and off on demand. The Pump Delay Timer
feature allows the user to keep the pump running and keep the motorized valve open for up to 30
minutes after the boiler has shut down and the demand is satisfied.
The pump relay is attached to the outside of the power box, as shown below. Boilers equipped
with the pump relay have a label on the power box cover adjacent to the relay.
OMM-144_B • GF-217 •
5/25/2020
Duct Diameter
6 inch (15.2 cm) diameter connection
8 inch (20.3 cm) diameter connection
10 inch (25.4 cm) diameter connection
14 inch (35.6 cm) diameter connection
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