Dwyer 1638-0 Pressure Switch, Large Diaphragm, SPDT, 1/8″ FNPT, 0.05–0.25″ w.c.

Dwyer 1638-0 Large Diaphragm Pressure Switch Overview

The Dwyer 1638-0 is a precision large diaphragm pressure switch engineered for reliable detection and control in HVAC, building automation, and light industrial applications. Designed to work with air and non-combustible gases, this switch delivers consistent performance across a low differential pressure range, making it ideal for monitoring duct static pressure, filter status, fan operation, and airflow proving in commercial and residential systems.

Key Features

• Pressure range: 0.05″ w.c. to 0.25″ w.c. — ideal for low-differential pressure sensing
• Approximate deadband: 0.04″ to 0.05″ w.c. for stable, chatter-free switching
• Large diaphragm design for enhanced sensitivity at very low pressure differentials
• SPDT (Single Pole Double Throw) switch action — supports both normally open and normally closed circuit configurations
• Compatible with air and non-combustible gases
• 1/8″ Female NPT pressure port for easy inline installation
• Compact, rugged construction suitable for field installation

Specifications

• Brand: Dwyer Instruments
• Model / SKU: 1638-0
• Pressure Range: 0.05″ w.c. to 0.25″ w.c.
• Approximate Deadband: 0.04″ – 0.05″ w.c.
• Diaphragm Type: Large Diaphragm
• Switch Type: SPDT (Single Pole Double Throw)
• Port Connection: 1/8″ Female NPT
• Media Compatibility: Air and Non-Combustible Gases

Typical Applications

• Duct static pressure monitoring and control
• Air filter differential pressure sensing and clogged filter alerts
• Fan and blower proving in air handling units
• HVAC system airflow verification
• Building automation and DDC control systems
• Combustion air proving in heating equipment

Why Choose the Dwyer 1638-0?

Dwyer Instruments is a trusted name in pressure measurement and control, and the 1638-0 reflects their commitment to accuracy and durability. The large diaphragm construction provides exceptional sensitivity at the low end of the pressure spectrum, while the SPDT output gives installers maximum wiring flexibility. The 1/8″ FNPT port ensures compatibility with standard pneumatic fittings found throughout HVAC and mechanical systems.