Profire V Burner Chapter 2
750-177 2-35
correction factors. To determine the required number of cubic feet per hour of gas, divide burner input (Btu/
hr) by the heating value (Btu/cu ft).
NOTE: When checking the input rate, Make sure no other equipment is operating on the same meter.
GAS COMBUSTION ADJUSTMENT
After operating for a sufficient period of tim
e to assure a warm boiler, make adjustments for most efficient
combustion.The butterfly gas valve directly controls the rate of flow. The low-fire light-off setting should be
regarded as preliminary until proper gas pressure for high-fire operation is established.
Determine the actual gas flow from a meter reading at
high-fire. With the butterfly valve open and with
regulated gas pressure set, the actual flow rate should be quite close to the required input. If corrections are
necessary, increase or decrease the gas pressure by adjusting the gas pressure regulator, following
manufacturer's directions for regulator adjustment.
When proper gas flow is obtained, tak
e a flue gas analysis reading.
With the high-fire air-fuel ratio established,
the gas pressure regulator needs no further adjusting.
Recheck low-fire and adjust if necessary.
Proper setting of the air-fuel ratios at all rates must be de
termined by combustion analysis.
NOTE: Check for CO through the entire firing range.
LOW-HIGH-LOW GAS BURNER ADJUSTMENT
The gas burner adjustments on a Low-High-Off system consist of the gas pressure
regulator, gas butterfly
valve, low and high gas pressure switches and an air damper assembly.
The auxiliary switch inside the M436 Mod motor makes or
breaks the high-fire gas. The Low-High-Low boiler
control energizes the M436 motor, driving it to high-fire. When the boiler control de-energizes the M436, a
built-in return spring drives it to the low-fire position.
All gas only (VG) V13-55 models use a butterfly gas valve
to control the gas flow to the burner. The M436
Mod motor controls the position of the valve.
1. Open the manual gas shutoff cocks.
2. Check the gas pressure at the inlet of the regulator and the
pressure downstream of the regulator. Make sure they
are in accordance with the regulator specifications. The gas pressure required at the manifold is the pressure that is
required to fire the burner at its rated capacity. To adjust the regulator, unscrew the cap located on the top and turn
the adjustment screw clockwise to increase pressure, or clockwise to decrease pressure.
3. Turn the burner switch to the “ON” position. The burner will start in the low-fire position.
4. After a few seconds, the O2 analyzer should have an accurate reading of the O2
present in the flue gas. Normally,
O2 levels are set between 4% to 6% at low-fire for standard turndown systems on gas and 6% to 9% O2 for high
turndown systems, with the target value of less than 50 ppm CO. To obtain the proper readings, adjust the air shut-
ter and low-fire regulator pressure.
5. Operate the boiler at low-fire until it is up to operating pressure
(steam) or temperature (hot water).
6. Bring the burner to the high-fire position. Adjust the high-fire gas
input to match maximum rating. At high-fire, the
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