4.2.3 Accessing the Analyzer Probe Port
Benchmark units contain a 1/4” NPT port on the side of the exhaust manifold, as shown in
Figure 4-2. Prepare the port for the combustion analyzer probe as follows:
1. Refer to Figure 4-2 and remove the 1/4” NPT plug from the exhaust manifold.
2. If necessary, adjust the stop on the combustion analyzer probe so it will extend mid-way
into the flue gas flow. DO NOT install the probe at this time.
Figure 4-2: Analyzer Probe Port Location (BMK1500 shown)
4.3 FUEL TYPES and COMBUSTION CALIBRATION
All BMK Platinum models are preconfigured at the factory to use either natural gas or propane
gas, and BMK models 1500 to 6000 are available in dual fuel versions (natural gas and
propane).
Both fuel types require different combustion calibration values, and so care must be taken to
ensure to follow the instructions for the fuel being used.
• Natural Gas combustion calibration: Section 4.4.1
• Propane combustion calibration: Section 4.4.2
Instructions for switching between fuel types in dual fuel models are presented in Section 4.6.
4.4 COMBUSTION CALIBRATION
The Benchmark boiler is combustion calibrated with either standard combustion (NOx emissions
of <20 ppm) or Ultra-Low NOx (NOx <9 ppm) on the BMK750 to 2000 only at the factory,
whichever was ordered, prior to shipping. The gas pressure must be within the ranges shown in
Table 4-2 for each model of boiler at full fire.
Recalibration as part of initial start-up is necessary due to changes in the local altitude, gas BTU
content, gas supply piping and supply regulators. Combustion Calibration Test Data sheets are
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