Dwyer Series H3 Explosion-Proof Differential Pressure Switches

 Dwyer Company Headquarters is in Michigan City, Indiana. Dwyer uses advances computer modeling software to simulate real world situations, creating more accurate measurement techniques in our products. Innovative product designs have been recognized by industry experts, including ACHR Dealer Design Awards in the Testing and Monitoring category for 2014 and 2015

Dwyer has invested in state of the art research and development facilities for best in class product testing and verification. Dwyer has a long history of innovation in designing and manufacturing our own measurement sensors that provide superior product performance.

Series H3 Explosion-Proof Differential Pressure Switches

Known for quality, reliability and accuracy, Dwyer designs and manufactures a full-line of Controllers, Data Loggers, Gages, Manometers, Monitors, Remote Displays, Switches, Transmitters, and Accessories to measure, monitor and control pressure, air velocity, flow, fan pressure, duct, and more.

Dwyer’s wide selection extends to Gages, Transmitters, Switches, Data Loggers, and Monitors for Differential Pressure. Dwyer manufactures a range of dial and digital gages to reliably measure and display pressure difference, between two pressure sources using gas or liquid in a process flow.

Sensors for air and non-combustible compatible gases have an electrical contact output at a specific difference between two pressures. Applications vary between the different types of differential pressure switches. A wide variety of switches and circuit styles enables control functions needed for any system.

Series H3 Explosion-Proof Differential Pressure Switch, heavy duty, industrial unit has a unique new design which provides sensitivity to differential pressures as low as 10 inches of water (254 mm w.c.), yet handles total pressure of 1500 psi (103 bar). Unlike common differential pressure switches that use a piston-type motion transfer, the Series H3 utilizes a rotary motion transfer shaft that prevents a change in total pressure from causing a set point shift. Unit yields dead bands approximately 5% of range, with zero set point shift due to variation in working pressures. Friction is minimized and repeatability increased by allowing range spring to act directly on diaphragm plate. Rolling diaphragm design maintains constant effective area to further reduce friction. Diaphragm is allowed to “seat”, allowing application of full rated pressure, up to 1500 psi (103 bar), on either high or low pressure port, without damage. Special over-travel feature prevents over tightening of range adjust screw.


  • Rotary motion design prevents set point shifts
  • Explosion-proof housing for use in applications where protection of process and personnel is needed
  • Option for use with water and water-based solution makes this a versatile switch


  • Water flow proving with an orifice plate.
  • Differential pressure across chiller.
  • Liquid filter status.
  • Perfect for monitoring differential water pressure on filters, chiller coils, and flow elements.

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Temperature Limit-4 to 220°F (-20 to 104°C). ATEX: -4 to 194°F (-20 to 90°C).
Pressure Limit1500 psig (103 bar).
Enclosure RatingStandard meets NEMA 4X (IP56); Drain option meets NEMA 3 (IP54). For hazardous use see "Hazardous Location Ratings Chart" on Catalog page.
Switch TypeSPDT or DPDT snap switch.
Electrical Rating5 A @ 125/250 VAC, 30 VDC.
Electrical ConnectionsSee Ordering page.
Conduit Connection3/4" female NPT.
Process Connection1/8" female NPT.
Mounting OrientationVertical.
Set Point AdjustmentInternal screw.
Weight4 lb 2 oz (2 kg).
Dead bandApproximately 5% of range.
Agency ApprovalsATEX (see "Ratings Chart" on catalog page), CE, CSA, UL.

Download Data Sheet: Series H3 Explosion-Proof Differential Pressure Switches

Ref: dwyer-inst.com