Which device proves purge air flow during light-off and damper position in burner operation?

Which device proves purge air flow during light-off and damper position in burner operation?

• A. High fire limit
• B. Low fire limit
• C. Flame safeguard
• D. Pressure switch

Answer: (A)

Proving purge air flow during light-off and confirming damper position relies on sensing the actual air flow and draft in the burner path. A pressure switch in the burner draft/vent system monitors the duct pressure during the purge cycle. When purge is underway, it must register the correct pressure range to show that enough air is flowing and that the damper is in the proper position to create the required draft. If the pressure isn’t within spec, ignition is delayed or blocked, preventing fuel from accumulating and avoiding a hazardous ignition. The high fire limit, by contrast, is a temperature safety device that protects against overheating and does not verify purge air flow or damper position.

Proving purge air flow during light-off and confirming damper position relies on sensing the actual air flow and draft in the burner path. A pressure switch in the burner draft/vent system monitors the duct pressure during the purge cycle. When purge is underway, it must register the correct pressure range to show that enough air is flowing and that the damper is in the proper position to create the required draft. If the pressure isn’t within spec, ignition is delayed or blocked, preventing fuel from accumulating and avoiding a hazardous ignition. The high fire limit, by contrast, is a temperature safety device that protects against overheating and does not verify purge air flow or damper position.