Specifications

12/03/2013 Page 13 of 40
GF-2050
Benchmark Series Boilers
Venting and Combustion Application Guide
TAG-0022_0S
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913 • Ph: 800-526-0288
If an AERCO Boiler Management System II (BMS II) is being used to manage a multiple boiler
installation, the louver can be opened using the System Start Relay of the BMS II. Refer to the
BMS II Operations and Maintenance Manual, GF-124, for wiring connections and further details.
1.10 Direct Vent/Ducted Combustion Air
The Benchmark is approved for direct vent installation; i.e., it can draw all combustion air from
the outdoors through a metal or PVC duct connected between the Benchmark unit(s) and the
outdoors. This configuration is useful for situations in which room air is insufficient or otherwise
unsuitable for combustion. The minimum ducted combustion-air duct sizes for the Benchmark
boilers are as follows:
• BMK 750 = 6-inch diameter
• BMK 1000 = 6-inch diameter
• BMK 1500 = 6-inch diameter
• BMK 2000 = 8-inch diameter
• BMK 2500 = 8-inch diameter
• BMK 3000 = 8-inch diameter
• BMK 6000 = 14-inch diameter
In many installations, the combustion air duct can be manifolded for multiple unit applications.
If the system is designed around common air intake it cannot be common exhaust.
The length and restriction of the ducted combustion duct directly impact the size, length and
restriction of the discharge venting. The direct vent air intake should be located at least 3 feet
below any vent termination within 10 feet.
A screen with mesh size not smaller than 1” x 1” must be installed at the inlet of the ducted
combustion air duct.
IMPORTANT!
COMMON BREECHING OF AIR INTAKES CAN NOT BE
COMBINED WITH COMMON BREECHING OF EXHAUSTS.
1.11 Exhaust Vent and Combustion Air Systems
The Benchmark supports several venting and combustion air options, and although the
application parameters vary, there are basic similarities among all systems. Tables 1 through 5
at the end of this Guide address the pressure drop of most applicable vent and duct fittings and
sizes. The losses in the vent exit and air duct entrance are also included.
It should be noted that flow and vent or duct diameter have the most significant effects on
overall system pressure drop. When using fittings or terminations not listed in Tables 1, 2 and 3,
consult the device manufacturer for actual pressure drop values. If rectangular duct is to be
used, consult Table 5 for a round diameter duct size that has the identical pressure drop per
length of rectangular duct.
The pressure drop values in Table 1b and 1c are in equivalent feet of 8-inch diameter exhaust
vent. Note that 1 equivalent foot of 8-inch diameter vent is equal to 0.00546-inch W.C.