Series-H2

Supported Applications

The Dwyer Series H2 is a dual-action explosion-proof pressure switch designed for sequencing work where two different actions are triggered as the pressure of a liquid or gas increases or decreases. The patented design utilizes two pistons in a concentric arrangement operated by a single diaphragm within one pressure chamber, allowing each piston to actuate a separate switch independently.

These switches permit control and protection for equipment subject to pressure variations. Applications include systems requiring setpoints that operate together, at opposite ends of the range, or at any two intermediate points. The unit is suitable for hazardous locations certified as UL Listed Explosion Proof, Class I, Groups B, C, D; Class II groups E, F & G.

Operating Conditions & Performance

The Series H2 operates within an ambient temperature range of -20 to 90°C (-4 to 184°F). The process temperature limit is rated at 275°F (135°C), with CSA approved construction available for specific temperature ranges. The maximum pressure rating is 1500 psig (103 bar).

Performance characteristics include a deadband of approximately 10% of range. The enclosure meets NEMA 4X (IP65) or IP66 ratings depending on the source specification, providing weatherproof protection. Electrical connections are provided via 18 AWG wire, 18" (460 mm) long.

Adjustable Operating Ranges

The series supports multiple adjustable operating ranges configured by model:

• H2S-1: Low range 3 to 40 psig (0.21 to 2.76 bar); High range 5 to 75 psig (0.35 to 5.17 bar)
• H2S-2: Low range 25 to 250 psig (1.72 to 17.2 bar); High range 30 to 400 psig (2.07 to 27.6 bar)
• H2S-3: Low range 100 to 1000 psig (6.89 to 68.9 bar); High range 150 to 1500 psig (10.3 to 103 bar)

Configuration Options

The Series H2 offers configurable options for wetted materials, switch types, and approvals to meet specific installation requirements.

Housing and Connections

• Housing: Explosion-proof aluminum housing.
• Process Connection: 1/4" female NPT.
• Conduit Connection: 3/4" female NPT electrical connection.
• Mounting Orientation: Any position; not affected by vibration per product overview.

Wetted Materials and Options

The standard wetted material configuration is a 316 SS chamber with FEP diaphragm and Buna-N O-ring. Alternative configurations include:

• Aluminum chamber with Mylar diaphragm and Buna-N O-rings.
• FEB (Fluoroelastomer) or EPDM O-rings as options.
• Gold contact snap switches for dry circuits (MV option).

Electrical Ratings

The switch type consists of two SPDT snap switches. Electrical ratings are 5A @ 125/250 VAC and 5A resistive, 3A inductive @ 30 VDC. The MV option provides a rating of 1A @ 125 VAC, 1A resistive or .5A inductive @ 30 VDC.

Key Product Differences

The Series H2 is distinguished by its dual-action capability and specific model ranges. The primary variations are defined by the adjustable operating range (H2S-1, H2S-2, H2S-3) which dictates the low and high pressure setpoints available.

Adjustment of the switches is performed via an internal nut mechanism accessible through a threaded top cover, allowing field adjustment or service without disturbing electrical or pressure connections. The #1 pressure adjustment controls the high range switch, while the #2 adjustment controls the low range; due to the concentric piston configuration, the #1 setting must always be higher than the #2 setting.

CSA approved construction is an optional feature that modifies the temperature limits and approval class for specific hazardous location requirements (Class I, Groups B, C & D; Class II, Groups E, F & G) with ambient temperatures of -20°C ≤ Tamb ≤ 75°C T6 or optionally -20°C to 40°C T5 Type 4.