Northeast Controls Inc.

PEECO Flow Switches

Glossary & FAQ

Terms, definitions, and frequently asked questions

Glossary of Terms

Dead BandThe difference in flow velocity between the point at which the switch actuates (trips) and the point at which it resets (resets). A wider dead band reduces nuisance cycling; a narrower dead band provides tighter control. PEECO switches have an adjustable dead band.
DPDTDouble Pole Double Throw. A switch configuration with two independent sets of contacts, each with a common, normally open (NO), and normally closed (NC) terminal. Allows simultaneous control of two separate circuits from a single flow event.
Explosion ProofAn enclosure design that contains any internal explosion and prevents it from igniting the surrounding atmosphere. Achieved through a machined, close-tolerance threaded cover (flame path). PEECO E Series and H Series use explosion proof enclosures rated NEMA 7, Class I, Div. 1, Group D.
Flame PathThe machined thread interface between the cover and body of an explosion proof enclosure. The long, close-tolerance thread cools any hot gases from an internal explosion before they can escape and ignite the surrounding hazardous atmosphere.
Flow VelocityThe speed at which a fluid moves through a pipe, typically expressed in feet per second (ft/s) or meters per second (m/s). PEECO flow switches are calibrated to actuate at a specific flow velocity, not a volumetric flow rate — the set point must be converted based on pipe size.
Heat DissipatorA finned body extension installed between the process connection and the switch housing on high-temperature PEECO switches. The fins dissipate heat from the process fluid before it reaches the micro-switch, allowing operation in process temperatures up to 2,000°F.
Micro-SwitchThe electrical switching element inside a PEECO flow switch. A precision snap-action switch that provides a clean, reliable contact closure when actuated by the flow-sensing paddle or piston. Available in SPDT, DPDT, SPST-NO, and SPST-NC configurations.
NEMA 4A National Electrical Manufacturers Association enclosure rating for indoor or outdoor use. Provides protection against windblown dust, rain, sleet, and hose-directed water. Not rated for hazardous locations.
NEMA 4XSame as NEMA 4 but with additional corrosion resistance (typically stainless steel construction). Used on PEECO N Series slip-on covers.
NEMA 7An enclosure rating for use in Class I, Division 1 hazardous locations (flammable gases or vapors). Requires an explosion proof design with a machined flame path. Used on PEECO E Series and H Series threaded covers.
Normally Closed (NC)A switch contact that is closed (conducting) when the switch is in its normal (un-actuated) state. Opens when the switch is actuated by flow. Used for fail-safe applications where loss of flow should de-energize a circuit.
Normally Open (NO)A switch contact that is open (non-conducting) when the switch is in its normal (un-actuated) state. Closes when the switch is actuated by flow. Used to energize a circuit when flow is present.
PaddleThe flow-sensing element on a paddle-type PEECO flow switch. A flat plate inserted into the flow stream that deflects when flow is present, actuating the micro-switch. Available in various sizes and materials to match pipe size and fluid compatibility.
PistonThe flow-sensing element on a piston-type PEECO flow switch. A cylindrical piston that moves axially in response to differential pressure created by flow, actuating the micro-switch. Used in high-pressure and high-velocity applications where a paddle would be damaged.
Set PointThe flow velocity at which the PEECO switch actuates. Adjustable in the field by changing the spring tension on the sensing element. The set point is expressed in feet per second (ft/s) and must be converted to volumetric flow rate (GPM, SCFM, etc.) based on pipe size and fluid properties.
SPDTSingle Pole Double Throw. The standard switch configuration on most PEECO flow switches. Has one common terminal and two output terminals (normally open and normally closed). Allows the switch to simultaneously open one circuit and close another when actuated.
SPST-NCSingle Pole Single Throw, Normally Closed. A switch with one common and one normally closed contact only. Simpler than SPDT; used when only a break-on-flow function is needed.
SPST-NOSingle Pole Single Throw, Normally Open. A switch with one common and one normally open contact only. Simpler than SPDT; used when only a make-on-flow function is needed.
Tee MountA PEECO mounting style where the flow switch body is a tee fitting installed in-line in the pipe. The sensing element extends into the flow stream through the tee. Available as screwed tee (NT/ET/HT) or flanged tee (NT-F/ET-F/HT-F).
Wetted PartsThe components of a flow switch that come into direct contact with the process fluid. For PEECO switches, the wetted parts are typically the body, paddle or piston, stem, and any seals or packing. Material selection for wetted parts is critical for chemical compatibility and corrosion resistance.

Frequently Asked Questions

What is the difference between a paddle switch and a piston switch?

A paddle switch uses a flat plate (paddle) that deflects laterally in the flow stream to actuate the micro-switch. It is the most common PEECO type and works well for most liquid and gas applications. A piston switch uses a cylindrical piston that moves axially in response to differential pressure. Piston switches are preferred for high-pressure, high-velocity, or abrasive service where a paddle could be damaged or deflected by turbulence.

How do I convert a PEECO set point from ft/s to GPM?

Flow rate (GPM) = Velocity (ft/s) × Pipe internal area (ft²) × 448.8. The pipe internal area depends on the pipe schedule and nominal size. Northeast Controls Inc. can provide a conversion table or assist with set point calculations for your specific pipe size.

Can I use an N Series switch in a hazardous location?

No. The N Series uses a slip-on cover rated NEMA 4X (general purpose). It is not rated for Class I, Division 1 or Division 2 hazardous locations. For hazardous locations, you must use the E Series (NEMA 7, Class I Div. 1, Group D) or H Series (high pressure, explosion proof).

What is the maximum temperature for a standard PEECO switch?

Standard PEECO switches are rated for process temperatures up to 300°F. For higher temperatures, a heat dissipator (finned body extension) is required. With the appropriate extension length, PEECO switches can operate in process temperatures up to 2,000°F.

Can PEECO switches be used for gas service?

Yes. PEECO offers gas-service switches with lightweight internals and calibrated springs for low-density fluids. Standard liquid-service switches may not reliably actuate in gas service due to the lower force exerted by a gas on the paddle. Specify gas service when ordering.

How do I adjust the set point in the field?

The set point is adjusted by changing the spring tension on the sensing element. On most PEECO models, this is done by turning an adjustment screw accessible after removing the cover. The switch should be adjusted with flow present and verified with a calibrated flow meter. Contact Northeast Controls Inc. for detailed adjustment instructions for your specific model.

What electrical rating do PEECO micro-switches have?

Standard PEECO micro-switches are rated 15A at 125, 250, or 480 VAC and 1/2A at 125 VDC. Higher-rated switches and hermetically sealed switches are available as options. See the Electrical Data page for full ratings.

Are PEECO switches available with 4–20 mA output?

Standard PEECO switches provide a dry contact (switch) output only. For a 4–20 mA analog output proportional to flow, consider a PEECO air-operated option (pneumatic output) or a separate flow transmitter. Contact Northeast Controls Inc. to discuss your requirements.

1-201-419-6111 · [email protected]

Request a Quote
Request PricingCall