CleaverBrooks ProFire Q Series, Installation Operation & Maintenance

Page: 16 / 88

Introduction
1-6
750-437
Q Series Full Modulation
1.6 — Gas System
Gas is introduced into the combustion zone through multiple ports in the circular manifold. The full modulation
burner's LMV37 controls both the combustion air and fuel metering: it meters the fuel in proportion to fan speed
by adjusting the servo-driven gas metering butterfly valve.
Safety shutoff main gas valves are installed upstream of the gas-metering-butterfly valve and are controlled by
the LMV37 to open and close at the proper time in the operating sequence. The Safety shutoff valve models may
vary depending upon specific requirements.
1.6.1 — Main Gas Train Components
Depending upon the requirements of the regulating authority, the gas control system and gas train may consist of
some, or all, of the following items:
FIGURE 1-6.
Main Gas Train for Full Modulation (Q6-055 to Q8-250)
1.6.2 — Typical Gas Operation
Upon a call for heat and before flame ignition, the LMV37 flame safeguard starts the combustion air fan and
confirms the gas metering butterfly valve is in the low-fire position. When the combustion air switch proves
sufficient air, the control opens the gas safety shutoff valves. Provided the gas supply is connected and manual
cocks are open, gas then flows through the main gas train and gas metering butterfly valve into the burner gas
manifold. The gas streams out of the manifold through the multiple ports of the orifice plate (see Figure 1-5) and
mixes with the fan-fed combustion air.
Component Description
Gas Metering Butterfly Valve A servo-driven butterfly valve that controls the gas flow rate.
Gas Automatic Safety Shutoff Valves (SSOV(s)) Electrically operated safety shutoff valve(s) that open to admit gas to the burner. Stan-
dard U.L. burners include one diaphragm gas valve and one solenoid gas valve.
Gas Regulator Regulates gas train pressure to specified pressure required at the inlet of the gas train.
Input is set by the main gas pressure regulator adjustment.
Main Manual Gas Shutoff Valve A manual gas shutoff valve located at the gas train inlet (upstream of the regulator).
Main Manual Leak Test Valve A second manual gas shutoff valve located between the SSOV(s) and metering butterfly
valve. It provides a means of testing for leakage through the SSOV(s).
GAS
AUTOMATIC
SAFETY
SHUTOFF
VALVE
HIGH
GAS
PRESSURE
SWITCH
LEAK
TEST
VALVE
GAS METERING
BUTTERFLY
VALVE
GAS
AUTOMATIC
SAFETY
SHUTOFF
VALVE
LOW
GAS
PRESSURE
SWITCH
GAS
REGULATOR
MAIN
MANUAL
GAS
VALVE
MAIN
MANUAL
LEAK TEST
VALVE
TO BURNER
MANIFOLD
INLET
SUPPLY GAS
INTO GAS TRAIN
INLET
750-00529-000