PEECO Flow Switch

Technical Reference

How to Install a
PEECO Flow Switch

Proper installation is critical to accurate, reliable flow switch performance. Follow these guidelines to ensure correct actuation, long service life, and safe operation.

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Standard Mounting Configuration

Vertical mount on horizontal pipe — the default and recommended installation

10× Pipe Diameter
Upstream Straight Run
Minimum before switch
5× Pipe Diameter
Downstream Straight Run
Minimum after switch
Within 5° of Vertical
Mounting Angle
Standard configuration

Note: Switches will not work properly in turbulent flow. Always provide adequate straight pipe run. Other mounting orientations (horizontal, angled) must be specified at time of quotation and may require special configuration.

Installation Steps

1

Select the Correct Location

Install the flow switch in a straight run of pipe with a minimum of 10 pipe diameters of straight run upstream and 5 pipe diameters downstream. Avoid installing near elbows, valves, reducers, or other flow disturbances that create turbulence.

2

Verify Mounting Orientation

Standard installation is vertical mounting on a horizontal pipe run (switch body pointing up, paddle hanging down into the flow). Other orientations are available but must be specified at time of order. The switch must be installed within 5° of vertical unless otherwise engineered.

3

Install the Flow Switch

For threaded (NPT) models: apply thread sealant and hand-tighten, then wrench-tighten to the appropriate torque. For flanged models: align the flange, install gasket, and torque bolts evenly in a cross pattern. For wafer tee models: insert between flanges per the dimensional drawing.

4

Verify Flow Direction

Confirm that flow direction through the line matches the arrow or label on the switch body. Reverse flow will not actuate the switch correctly. For bi-directional (multiple action) models, flow direction is less critical — consult your order documentation.

5

Make Electrical Connections

Route conduit to the 1/2″ FNPT conduit connection (3/4″ and metric available). Connect wiring per the terminal diagram on the nameplate. Standard SPDT: N.O. (Normally Open), N.C. (Normally Closed), and Common terminals. Verify voltage and current ratings match your application.

6

Adjust the Set Point

All PEECO flow switches are fully field-adjustable. With flow established, adjust the set screw to the desired actuation point. The switch should actuate cleanly with less than 10% dead band between make and break. Re-check adjustment after system reaches operating temperature and pressure.

Installation Requirements

Minimum 10 pipe diameters straight run upstream
Minimum 5 pipe diameters straight run downstream
Install within 5° of vertical (standard configuration)
Flow direction must match switch orientation
All switches must be adjusted after installation
Third-party calibration available upon request

Important Warnings

Do not install in turbulent flow without appropriate options (Dash Pot, Stem Dampener)
Do not exceed rated pressure or temperature without consulting PEECO engineering
Explosion-proof models must be installed per NEC/CEC requirements for the hazardous location classification
Do not modify the switch body, bellows, or stem assembly
Verify electrical ratings before connecting to power

Field Adjustment

All PEECO flow switches must be adjusted after installation unless a third-party calibration has been requested and provided at time of order. The switch is fully field-adjustable across its entire operating range.

Water and nitrogen are used for factory flow testing to establish minimum activation and deactivation points. Field conditions (media, temperature, pressure, specific gravity) will affect the actual actuation point — use the velocity correction factors in the Flow Rate Table when working with fluids other than water.

Set Screw Adjustment

The set screw controls the tension on the return spring, which determines the flow velocity required to actuate the switch. With flow established at the desired trip point:

To raise the trip point (actuate at higher flow): Turn the set screw clockwise — this increases spring tension, requiring more paddle force (higher velocity) to trip the switch.
To lower the trip point (actuate at lower flow): Turn the set screw counterclockwise — this reduces spring tension, allowing the paddle to trip the switch at lower velocity.
Dead band (differential): The gap between the make point and break point should be at least 10% of the set point velocity. If the switch chatters or resets immediately, the dead band is too narrow — increase spring tension slightly.
Re-check after temperature stabilization: Thermal expansion of the pipe and switch body can shift the actuation point. Always verify the set point after the system reaches full operating temperature and pressure.

Spring Selection

PEECO flow switches are supplied with a standard spring matched to the ordered flow range. If the set screw has been adjusted to its full range and the switch still cannot be set to the desired trip point, a different spring rate is required. Springs are available in multiple rates to cover low, standard, and high flow applications.

Lighter spring (lower rate): Use when the set screw is fully backed out (minimum tension) and the switch still will not actuate at the desired low flow velocity. A lighter spring requires less paddle force to deflect, lowering the minimum achievable trip point.
Heavier spring (higher rate): Use when the set screw is fully tightened (maximum tension) and the switch actuates prematurely at high flow or cannot hold the set point against system pressure fluctuations. A heavier spring raises the minimum trip point and improves stability in high-velocity or high-turbulence applications.
Ordering replacement springs: Contact PEECO engineering with your model number, line size, and target flow range. Springs are not universal — the correct rate depends on paddle size, pipe diameter, and fluid density.

Changing the Spring

Spring replacement is a straightforward field procedure. De-energize and isolate the switch before opening the cover.

  1. 1Isolate the line and de-energize the switch. For E and H Series, follow hot-work procedures before removing the cover in a hazardous area.
  2. 2Remove the cover (slip-off for N Series; unscrew for E and H Series — five threads minimum engagement when reinstalling).
  3. 3Back the set screw out fully to release spring tension before attempting to remove the spring.
  4. 4Note the current spring position and orientation before removal.
  5. 5Remove the existing spring and install the replacement. Confirm the spring seats correctly against the actuator arm and the set screw bearing surface.
  6. 6Re-install the cover. Re-establish flow and adjust the set screw to the desired trip point.
  7. 7Verify actuation and reset at operating conditions before returning the switch to service.

Do not modify the spring by cutting, stretching, or bending it. A modified spring will not provide consistent force across its travel range and will cause erratic actuation. Always replace with a factory-supplied spring of the correct rate.

View Flow Rate Table & Velocity Correction Factors

Troubleshooting

Most field problems trace back to one of six root causes. Expand each symptom below for likely causes and corrective action.

Still having trouble?

Our engineering team provides free technical support for all PEECO installations.

201-419-6111 [email protected]

Ready to Order Your Flow Switch?

Every PEECO flow switch is custom-engineered for your application. Submit your process conditions and receive pricing and delivery typically within one business day.

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