P-K MACH
®
Gas Fired Boiler
Technical Service 1.877.728.5351
Revised: January 3, 2020
Released: January 3, 2020
Patterson-Kelley 2020
All Rights Reserved.
1004905981 P-K MACH C1500H-C4000 Installation and
Owners Manual (Rev F Jan-2020).docx
Page 45
Fuel/Air Adjustments
The P-K MACH
®
boilers are equipped with a
gas/air ratio control valve and a gas safety shut
off control valve, combined into one valve
assembly. The valve functions in series with the
variable speed combustion blower to supply the
correct gas/air mixture for optimum firing
performance and efficiency. The combustion
blower speed is controlled automatically by the
boiler controller. The blower speed determines
the amount of air flow and the amount of
suction/negative pressure at the gas valves. The
gas valve adjusts gas flow to maintain the proper
delivery pressure at the outlet of the valve.
3.11.1 Gas Pressure Adjustment
See rating plate for the minimum and maximum
gas pressure of the boiler. The supply pressure
during main burner operation must be greater
than the
minimum indicated on the rating plate.
Nominal gas supply pressure is 7” W.C. for
natural gas. The gas pressure must not exceed
14” W.C. which is the maximum allowable
pressure on the gas train components. Each boiler is furnished with a manual shut-off valve which has
an integrated test port. This port is located on the upstream side of the valve body for measuring
supply pressure.
The air flow is pre-set at the factory prior to shipment. Gas flow is dependent primarily on fan speed
not upstream gas pressure. The automatic gas valve may have to be adjusted to obtain proper
combustion readings for specific local conditions. A combustion analyzer must be used. Combustion
must be set in accordance with the Recommended Combustion Settings for P-K MACH Boilers in
Section
Gas Valve w/ Test Port
