Main Flame Establishment Period (Mfep) Fail - Beckett CG15 Manual

• Check manifold pressure in Low Fire.
— Typical light off pressure is between 0.8 in. W.C. and 1.1 in. W.C.
— If incoming pressure is too low gas will not reach the burner in time to light off, because low gas pressure will
cause the valve to open slower.
— If the incoming pressure to the gas train is too high, valve may not open. For some gas valves (4944B as an
example) if the gas pressure is >12 in. W.C. the valve may not open.
— See Table 4 on page 23 for more detail on recommended gas pressures to burner.
— Check distance from gas valve to burner manifold, see Figure 32 .
Figure 31 — Typical Gas Train Layout
• Check breech pressure
— Most commercial boilers request a positive 0.1 in. W.C. while in high fire, when the burner is in low fire, draft
reading is typically between positive 0.02 in. W.C. and 0.04 in. W.C.
— See manufacturer's spec for more information.
• Check exhaust system
— Install a dual acting barometric damper to alleviate draft fluctuations
— See Figure 5 and Figure 6 on page 11for recommended locations of barometric dampers.

Main Flame Establishment Period (MFEP) Fail

• Check valve timings
— If the high fire side of the valve does not open while high air is being introduced it can cause the MFEP to fail.
— See valve wiring diagrams for high and low side wiring.
• Check manifold pressure
— If manifold pressure does not change, make sure the orange cam on the damper motor is located between the
blue and red cam.
— See "Adjusting the Damper" on page 27 for detailed instructions.
— Check the 4062A motor to ensure it pushes on the plunger when going to high fire.
CG15, CG25, CG50 Burner Manual, Form No. 6104BCG50
Union on
Valve
Burner Manifold
Pipe Max
Size Length
1" 12"
1-1/4" 15"
1-1/2" 18"
2" 24"
Section: Troubleshooting — 39