Series-1640

Supported Applications

The Dwyer® Series 1640 is a differential pressure switch featuring an SPDT floating contact (not snap action) that functions as a null switch. It is designed to position motorized dampers when static pressure in a duct system reaches a desired maximum and reposition them when the static pressure falls to a pre-established minimum. The series also controls air velocity and maintains a constant volume of air in a supply duct using a pitot tube sensing element.

Service is limited to air or compatible gases, specifically non-combustible, compatible gases as noted in specifications.

Operating Conditions & Performance

The Series 1640 operates within an ambient temperature range of -30°F (-34.4°C) for dry air or gas to 130°F (54.4°C), with process temperature limits cited as -30 to 110°F (-34.4 to 43.3°C). The switch is rated for a continuous pressure of 10 psig (68.95 kPa) and can withstand a maximum surge pressure of 25 psig (172.4 kPa).

Electrical ratings are defined by load type:

• Non-inductive loads: 2-1/2 amp at 110V A.C.; 1-1/2 amp at 220V A.C.; 1 amp at 24V D.C.; 1/2 amp at 110V D.C.
• Inductive loads: 1 amp at 110V A.C.; 1/2 amp at 220V A.C.; 1/2 amp at 24V D.C. (de-rate 70 - 80% for very slow pressure changes).

Due to the low electrical rating, the switch is almost always used with a relay that has suitable current carrying capability.

Variants and Ranges

The series offers five model numbers covering differential pressure ranges from 0.1 in. W.C. up to 12.0 in. W.C., each with an adjustable null span:

• Model 1640-0: Range 0.1 - 0.2 in. W.C. (2.482 - 49.77 Pa); Adjustable Null Span Min .01 (2.488), Max .03 (7.465).
• Model 1640-1: Range 0.2 to 1.0 in. W.C. (49.77 - 248.8 Pa); Adjustable Null Span Min .02 (4.977), Max .06 (14.93).
• Model 1640-2: Range 1.0 to 4.0 in. W.C. (248.8 - 995.3 Pa); Adjustable Null Span Min .03 (7.465), Max .12 (29.86).
• Model 1640-5: Range 2.0 to 6.0 in. W.C. (497.7 - 1493 Pa); Adjustable Null Span Min .03 (7.465), Max .18 (44.79).
• Model 1640-10: Range 3.0 to 12.0 in. W.C. (746.5 - 2986 Pa); Adjustable Null Span Min .04 (9.953), Max .20 (49.77).

Configuration Options

The Series 1640 features a single pole, double-throw floating contact switch that is not snap acting. The diaphragm moves in response to pressure changes, causing switching action at two preset points with no switching action between them. Visual set point adjustment is provided via screw type controls.

• Process Connections: 1/8" female NPT for both high and low pressure inputs.
• Electrical Connection: 3-screw type terminals (common, high, and low).
• Housing Dimensions: Overall height of 4 [101.60] in; diameter of 6-1/2 [165.10] in.
• Mounting: Requires diaphragm vertical orientation (consult factory for other positions). Includes four mounting holes with a spacing of 2 [50.80] TYP and a hole diameter of Ø9/32 [7.14].
• Conduit Connection: 1/2 conduit connection.
• Weight: 4 lbs., 13 oz. (2.18 kg).

Special models are available, including those with weather-proof or explosion-proof enclosures. Process tubing options and wetted materials require consultation with the factory.

Key Product Differences

The Series 1640 is identical to Dwyer® Series 1630 Large Diaphragm Pressure Switches except for its electric switch configuration, which utilizes a floating contact null mechanism rather than snap action. The 'high' circuit closes when rising pressure differential reaches the preset level, and the 'low' circuit closes when falling pressure differential reaches the preset level.

Model variations are distinguished by their operating ranges in inches of water column (in. W.C.) and corresponding adjustable null spans, as detailed in the variant table above. The series carries CE compliance marking.