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LEFOO · PRESSURE CONTROL

LEFOO LF31 Furnace and Air Proving Differential Pressure Switch

LEFOO LF31 original product photo
LEFOO LF31 · Manufacturer image and specification

LEFOO / Pressure Switches

LEFOO LF31 Furnace and Air Proving Differential Pressure Switch is a manufacturer source-supported switch family, distinct from continuous differential-pressure transmitters. The AirAlign selection analysis below highlights configuration and application differences rather than recopying the original catalog text.

Model specifications and engineering choice

FunctionVery-low-range pressure/vacuum furnace proving switch, SPDT or SPST, for gas-fired heating equipment
RangeMaker February 2026 LF31 PDF 0.15–34 in water column and setpoint around 0–3000Pa ordering choices, application-specific
Contacts5A max for silver resistive contacts but only 0.5A max for gold-platinum-silver; confirm type and inductive load
MountingMaker original datasheet requires diaphragm in a vertical plane; its CE certificate annex tightens mounting to within ±10° of vertical
Certificate boundaryProducer-hosted document MB 69258041 0001 LF31 annex limits −30…+85°C ambient, 50mbar maximum working pressure, rising trip 40–2500Pa and 23±7Pa differential: do not substitute broad family figures
Proof and burst100in W.C. (~3.6psi) proof and ≥5psi burst according to original maker PDF; different from switching setpoint
Selection valueFurnace safety interlocks may require gas appliance type approval; the manufacturer’s CE document should be used only for the models and conditions within its stated scope.

How to select and install

Calculate the intended differential between the high and low ports and confirm the static/differential maximum pressure, mounting orientation, switching threshold/hysteresis, contact rating under inductive load, actual terminal protection, media composition and any required gas appliance certification. An ON/OFF pressure switch must not be described as an analog differential-pressure transmitter.

Original LEFOO LF31 model specifications · Original manufacturer product/order PDF · Original maker certificate and scoped conditions

Related Pages

LEFOO manufacturer profile · Pressure Switches

LF31 — furnace pressure-proving safety distinction

LF31 is applied to furnace or air proving, where a discrete pressure contact may be part of an appliance’s ignition permissive circuit. Its installation and acceptable failure mode must follow the equipment’s certified design and relevant maker instructions; an ordinary pressure-switch component alone does not establish burner-system compliance. Document pressure tap placement, hose material temperature limits and required reset behavior before substituting another LEFOO LF3x model.