Dwyer Instruments AVFS-2 | Thermo air flow switch | 24 VDC.
The Dwyer AVFS-2 is a 24 VDC thermal air flow switch that monitors duct airflow from 197 to 1969 FPM (1-10 m/s) without a moving paddle. Its titanium sensor, IP65 PBT housing and red/green status LEDs make it a low-maintenance solution for BMS, PLC and DDC control panels. Genuine Dwyer Instruments stock at General Tech Services LLC, Saudi Arabia, with free Saudi Arabia shipping. Request a quote in under a minute - call +966 569 289 544.
Product Overview
Traditional paddle-type airflow switches use moving parts that can wear, stick or become affected by dust and contaminants. The Dwyer AVFS-2 uses thermal dispersion sensing instead, providing airflow detection without a mechanical paddle.
A heated titanium sensor is positioned in the airstream and detects the cooling effect created by moving air. When airflow falls below the selected trip point, the switch changes the state of its 3 A N.O. SPST contact.
The AVFS-2 operates from a 24 VDC ±25% supply, making it well suited to low-voltage BMS panels, PLC cabinets and DDC controllers. Power consumption is approximately 3 VA, while the output contact is rated 3 A at 30 VDC or 250 VAC.
The unit provides ±5% full-scale set-point repeatability. Its response time is 3-60 seconds depending on airflow velocity and the selected set point, allowing fan-proving applications to accommodate normal fan start-up conditions.
Red and green LEDs provide an at-a-glance indication of airflow status, simplifying commissioning and troubleshooting. The PBT housing is IP65 rated for protection against dust and moisture, with an operating temperature range of -10 to 50°C. The AVFS-2 also includes a 2 m cable and has CE approval.
Key Benefits
- Solid-state thermal sensing with no moving paddle to wear or stick
- 24 VDC ±25% supply for BMS, PLC and DDC control panels
- Air velocity range of 197-1969 FPM (1-10 m/s)
- ±5% full-scale repeatability for consistent airflow trip points
- Flush titanium sensor helps limit dust build-up
- Red and green LEDs provide immediate airflow status indication
- IP65 PBT housing for protection against dust and moisture
- 3 A N.O. SPST output contact
- 3-60 second response time depending on airflow and set point
- CE approved
- 2 m cable supplied
- Genuine Dwyer Instruments stock with free Saudi Arabia shipping
Call +966 569 289 544 for pricing or assistance checking the AVFS-2 against your control panel requirements.
Who This Product Is Best For
- BMS and controls integrators working with 24 VDC field devices
- Facility teams replacing paddle switches in dusty duct environments
- Kitchen exhaust and car-park ventilation systems requiring airflow proving
- Clean-air and pharmaceutical HVAC applications where moving parts are undesirable
- Panel builders standardising on low-voltage airflow interlocks
- HVAC maintenance teams requiring a solid-state alternative to mechanical airflow switches
How to Use / How It Works
- Insert the probe into the duct using the appropriate mounting arrangement, with the sensor positioned correctly in the airflow.
- Connect the 24 VDC supply and wire the N.O. SPST contact to the controller, alarm or interlock input.
- Run the fan at the required operating airflow and adjust the trip point according to the application requirements.
- Check the red and green status LEDs while setting the airflow threshold.
- Reduce or stop the airflow and verify that the output contact and LED status change as expected.
Frequently Asked Questions
How does the AVFS-2 detect airflow without a paddle?
The AVFS-2 uses thermal dispersion sensing. A heated titanium sensor is cooled by moving air, and the switch detects changes in this cooling effect to determine whether airflow is above or below the selected set point.
What power supply does the AVFS-2 need?
The AVFS-2 operates from 24 VDC ±25% and consumes approximately 3 VA.
What air velocity range does it cover?
The AVFS-2 covers 197 to 1969 FPM, equivalent to 1 to 10 m/s.
How quickly does it respond to a fan failure?
The response time is approximately 3-60 seconds, depending on the airflow velocity and selected trip point.
What type of output does the AVFS-2 provide?
It provides a 3 A N.O. SPST contact rated for 3 A at 30 VDC or 250 VAC.
What is the difference between the AVFS-2 and AVFS-1?
Both models use the same thermal airflow sensing principle. The AVFS-2 is designed for a 24 VDC supply, while the AVFS-1 is intended for an 80-250 V AC/DC supply.
Does the AVFS-2 work in Saudi summer conditions?
The specified operating temperature is -10 to 50°C. The unit should be installed where the ambient and applicable operating conditions remain within this range.
Is the Dwyer AVFS-2 suitable for BMS and PLC applications?
Yes. Its 24 VDC supply and SPST output make it suitable for integration with BMS panels, PLC inputs, DDC controllers, alarms and fan-proving circuits.
Is the Dwyer AVFS-2 genuine stock?
Yes. General Tech Services LLC supplies genuine Dwyer Instruments products in Saudi Arabia with free Saudi Arabia shipping. Call +966 569 289 544 for pricing and stock availability.
Request a Quote Today
Get the Dwyer AVFS-2 thermal air flow switch delivered free anywhere in Saudi Arabia.
Call +966 569 289 544 | www.generaltechshop.sa
