Pilot Ignition; Fuel Types And Combustion Calibration - Watts Aerco Benchmark OMM-0124 Installation And Start-Up Manual

Benchmark 5000-6000 Boiler Installation & Startup Manual
SECTION 4: INITIAL START-UP

4.3 PILOT IGNITION

Benchmark 5000 and 6000 boilers are equipped with an interrupted pilot ignition system. The
pilot is ignited by a spark discharge within the Pilot Burner inside the combustion chamber. The
input of the Pilot flame is approximately 18,000 BTU/hr. (5.3 kW). The Pilot Burner flame will
stay ignited until the main Burner flame has stabilized and FLAME PROVEN appears in the C-
More Controller's display.
A Pilot gas supply regulator reduces the supply pressure from line pressure to 4.9" W.C. (1.2
kPa). An orifice (0.073" dia., 1.85 mm) further restricts the gas flow to the Pilot.
The Pilot Burner should be inspected at the beginning of each heating season, or every 6
months for continuous operation. It is constructed of high quality, heat resistant stainless steel,
however some darkening of the metal is expected. No adjustment of the Pilot should be
required, however the gas pressure downstream of the regulator should be checked if an
ignition issue is encountered. Refer to Figure 4-1 for test port location.
The Pilot flame is proven by two Pilot Flame Detectors, located above and below the Pilot. The
two Pilot Flame Detectors are optical sensors inserted into tubes with quartz windows; they
observe the Pilot through holes in the refractory. They have a red LED which changes from
flashing to steady-ON when they encounter the flicker of a flame that meets or exceeds the
internal sensing threshold. (Only one of the two detectors needs to sense the pilot flame
throughout the ignition period). The holes in the refractory should be checked annually to ensure
that the optical path to the Pilot Burner is clear.
NOTE:
The pilot flame detectors switch the signal to neutral when the flame is proven.

4.4 FUEL TYPES and COMBUSTION CALIBRATION

Benchmark 5000 and 6000 models may be ordered from the factory to use natural gas only,
propane only, or in a dual fuel version that can be configured on site to switch between natural
gas or propane gas.
Both fuel types require different combustion calibration values, and so care should be taken to
ensure the appropriate instructions are used for the fuel being used. Combustion calibration
instructions for natural gas are presented in Section 4.5.1 and for propane in Section 4.5.2.
Instructions for switching between fuel types in dual fuel models is presented in section 4.7.
CAUTION!
Ensure the appropriate combustion calibration instructions are used for the fuel being used in
the boiler.
OMM-0123_E • GF-207 • 12/17/2019 Technical Support • (800) 526-0288 • Mon-Fri, 8 am - 5 pm EST
Page 50 of 95