Wiring Method for Mechanical Flow Switches‌

Here is the professional English translation of the mechanical flow switch wiring guide:

Wiring Method for Mechanical Flow Switches‌

The wiring of mechanical flow switches is based on their passive contact characteristic, requiring no external power supply. Fluid flow drives the mechanical mechanism to change the contact state for control. Specific wiring methods are as follows:

I. Core Wiring Principles

Passive Contact Characteristic‌

Mechanical flow switches (e.g., target/paddle type) rely on fluid force to actuate a micro switch. No external power is needed; only the contact's open/close state controls the circuit[1][2].

Contact Function Definition‌

Common Terminal (COM):‌ Common connection point for contact sets.

Normally Open Terminal (NO):‌ Open circuit with no flow; closes when flow is present[1][3].

Normally Closed Terminal (NC):‌ Closed circuit with no flow; opens when flow is present[1][3].

II. Standard Wiring Procedures

Single Device Control Wiring (e.g., Pump Start/Stop)‌

NC Mode (Recommended):‌

COM Terminal → Device Power Positive (or Control Loop Input)

NC Terminal → Device Control Terminal (e.g., Pump Start/Stop Signal Wire)

Principle: NC closes to start the device with no flow; NC opens to stop the device when flow reaches the set threshold[1][3].

NO Mode:‌

COM Terminal → Power Positive

NO Terminal → Device Control Terminal

Principle: NO closes to start the device when flow reaches the threshold[5].

Fire Protection System Extended Wiring‌

To simultaneously achieve device control and status feedback, use a relay:

Flow Switch Contacts → Relay Coil

Relay Contact Set 1 → Pump Start/Stop Control Line

Relay Contact Set 2 → Alarm Feedback Module (Requires series End-of-Line Resistor)[1].

III. Wiring Precautions

Direction Calibration‌

Ensure fluid flow direction matches the arrow mark on the switch during installation to prevent mechanical failure due to reverse force[1][5].

Contact Load Matching‌

Verify contact rating (typically ≤2A AC220V). Avoid directly driving high-power devices to prevent contact burnout; use a relay interface where necessary[4].

Circuit Protection‌

Secure exposed conductors with crimp terminals. Apply waterproof sealant to connections in damp environments[4].

IV. Function Verification Methods

Static Test‌

With no flow, use a multimeter to verify NC-COM continuity and NO-COM open circuit[3].

Dynamic Test‌

Simulate adequate flow (e.g., ≥1L/s for fire systems). Confirm NO closes or NC opens, triggering the connected device response[1][5].

Critical Note:‌ In fire protection applications, ‌strictly prohibit‌ powering the switch from the Fire Alarm Control Panel (FACP); independent power supply is mandatory for reliability. Industrial applications require setting the flow threshold via spring preload adjustment (knob/screw adjustment)[1].

Key Translation Notes:‌

Terminology:‌

无源触点 Passive Contact

靶式 Target-type / Paddle-type

微动开关 Micro Switch

常开/常闭 Normally Open (NO) / Normally Closed (NC)

公共端 Common Terminal (COM)

终端电阻 End-of-Line Resistor (EOLR)

弹簧预紧力 Spring Preload

报警反馈模块 Alarm Feedback Module

Voice:‌ Maintained the technical, instructive tone of the original.

Structure:‌ Preserved the logical hierarchy and numbered sections.

Accuracy:‌ Ensured technical terms align with international standards (e.g., NFPA for fire terms).

Clarity:‌ Used concise phrasing common in English engineering documentation (e.g., "Verify contact rating" instead of "Check...").

This translation accurately conveys the technical details and safety-critical instructions for wiring mechanical flow switches in various applications.