Series-H3Configuration

Supported Applications

The Dwyer Series H3 Explosion-Proof Differential Pressure Switch is designed to actuate one or two single pole, double throw (SPDT) snap switches in response to increasing or decreasing pressure of compatible gases or liquids. The series utilizes a rotary motion transfer shaft design intended to prevent set point shifts caused by changes in total pressure. Applications include monitoring differential pressures as low as 10 inches of water column while handling total system pressures up to 1500 psig (103 bar). Standard wetted materials support general service, with an optional 316 SS chamber available for water and water-based fluids or harsher applications.

Operating Conditions & Performance

The Series H3 operates across four field-adjustable ranges: 10 to 180 in. w.c. (2.48 to 44.78 kPa), 0.5 to 15 psid (0.03 to 1 bar), 5 to 70 psid (.34 to 4.8 bar), and 10 to 200 psid (.7 to 13.8 bar). The device yields a deadband of approximately 5% of range with zero set point shift due to variation in working pressures. Process temperature limits are -4 to 220°F (-20 to 104°C); for ATEX models, the ambient limit is specified as -20 to 90°C (-4 to 194°F). The unit withstands a pressure rating of 1500 psig (103 bar) on either high or low pressure port without damage. Standard enclosures meet NEMA 4X (IP56), while the drain option meets NEMA 3 (IP54).

Configuration Options

The series offers configurable options for wetted materials, operating ranges, circuit types, electrical connections, and special service features.

• Wetted Materials: Aluminum chamber with nitrile diaphragm (Code A) or 316 SS chamber with fluoroelastomer diaphragm (Code S).
• Circuit Options: SPDT snap action switch rated 5 A @ 125/250 VAC, 30 VDC; DPDT snap action switch rated 5 A @ 125/250 VAC, 30 VDC.
• Electrical Connections: 18 AWG x 18 inch lead wires (Code L), UL and CSA approved internal terminal block (Code T), or ATEX approved internal terminal block (Code C).
• Hazardous Location Ratings: Models are available with approvals for Class I, Groups B, C & D; Class II, Groups E, F & G; and Directive 2014/34/EU ATEX Compliant construction.

Special options include the MV option (gold contacts on snap switch rated 1 A @ 125 VAC, 1A resistive or 0.5 A inductive @ 30 VDC), a Drain/Breather feature for condensate removal, and a VIT option providing fluoroelastomer diaphragm/O-ring where not standard.

Key Product Differences

Differences within the Series H3 are defined by model number segments corresponding to wetted materials, operating range selection (1 through 4), circuit type (S or D), and electrical connection method. The 'C' suffix denotes ATEX Compliant Construction with an internal terminal block; units without this suffix are not intended for use in potentially hazardous atmospheres in the EU under Directive 2014/34/EU, though they may be CE marked for other Directives. Models equipped with the Drain option feature an enclosure that meets NEMA 3 (IP54) instead of the standard NEMA 4X rating. The series supports vertical mounting orientation and includes a special over-travel feature to prevent over-tightening of the internal range adjust screw.