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Mercoid Series DA / DS Bourdon Tube Pressure Switches

Visible setpoint, adjustable deadband, pressure ranges to 5000psi (UL, SA & FM)

Customers tell us that this is the best pressure switch made. Our most popular, Model DA combines extremely high sensitivity and repeatability with easily adjustable set and reset points through non-interactive external adjustments. Visible calibrated dial for set points and on/off indicator to indicate switch actuation are included. Choose either high current snap-switch or hermetically sealed contact mercury switch. The DS Model has a fixed deadband.

DA Series is equipped with two external adjustments. One sets high pressure operating point, the other sets reset point. Deadband, or the difference between set and reset points is adjustable over the full scale. DS Series has a single external adjustment and fixed deadband. Visible calibrated dial, on/off indication. SPDT snap-action or sealed mercury switches. Minimum deadband obtainable at any point in range. Pressure Ranges vacuum to 5000 psig. U.L. and C.S.A. Listed. Many models FM listed. DPDT Snap Action switches are available. Larger Image

Note: See Other Mercoid Products

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See Models & Ranges
Select Operating Range and Deadband
Select Operating Requirement
Select Enclosure
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Physical Data
Max. temperature: 180°F. For higher temperature media applications, a remote connection or siphon (pigtail) should be used.
Pressure connection: 1/4" NPT. (1/2" on range 15S).
Housing: pressed steel with transparent cover.
Wiring connections: 3 screw type.
Wetted parts: same as Bourdon tube material.
Weight: 4 lb. (std); 6 Ib. (wea-proof); 8 Ib. (exp-proof).
Max. Press.: Max. adjustment operating range.
Suggested Specification
Pressure switch shall be Mercoid Series DA operated by a (brass) (type 316 stainless steel) (type 403 stainless steel) Bourdon tube actuating a (mercury switch) (snap-switch). Switch shall have deadband fixed or adjustable up to a maximum of 100% of switch range. Switch shall have calibrated dial and one or two pointers indicating set and reset points. Switch shall have visible on/off indication. Set points shall be adjustable without removing switch cover or shutting down process.
How to Order Mercoid Series D Pressure Switches
Select Operating Range and Deadband
Select Operating Requirement
Select Enclosure

The Mercoid Corporation manufactures one of the world's broadest lines of fine pressure switches. It is comprised of approximately 200 standard models and literally hundreds of variations. Whatever your application might be, it is most probable it can be fully satisfied with a Mercoid Series D pressure switch.

Because it is impractical to assign specific catalog numbers to such a diverse line, we have devised an ordering number procedure which, in effect, permits you to "build" or "design" your own standard pressure switch.

To help you do this, we would like to acquaint you with some basic terminologies and how they effect your ordering procedure:
Operating Ranges
Operation of the switch is adjustable within certain limits. This is indicated by an operating range number. DAW-33-2, Range No. 6 would mean adjustable within 5-100 psig. Select Operating Range and Deadband
Operating Requirements
D is the generic designation for a series of Mercoid pressure switches. However since they are available in a variety of functions, a second letter is added to D to define the type of deadband and/or adjustment. DA, for example, means a D pressure switch that is fully automatic and has a double adjustment.  Select Operating Requirement
A general purpose NEMA 1 enclosure is furnished as standard on all Series D pressure switches. However watertight, weather-resistant, weatherproof, and explosion-proof housings are optionally available. Adding a third character indicates an optional housing. DAW would indicate a DA switch with a watertight enclosure.  Select Enclosure
Mercoid offers Bourdon tubes constructed in a choice of brass, Type 403 stainless steel, and Type 316 stainless steel. Material is designated as part of the series number. A DAW-33 indicates a brass Bourdon tube. 
Switch Type and Action
Mercoid pressure switches are available with mercury or snap-action contacts which become an integral part of the ordering number. However switching action is designated by a circuit suffix number. For example, DAW-33-2 would indicate a SPST switch which opens upon an increase in pressure.
Electrical Ratings
The electrical characteristics of the switch are fixed by a code letter which is not necessary to specify. The code letter simply defines electrical ratings to assist you in selecting the proper switch for your application. For example, Code H tells you the switch is rated at 5 amps @120V AC.
1. 2. 3. 4. 5. 6.
  1. Indicates a Series D switch with a fixed deadband, fully automatic, single adjustment.
  2. Indicates an optional Class I, Groups C and D explosion-proof enclosure with switch an integral part of enclosure.
  3. Type number indicates snap-action contact, brass Bourdon tube, and Code E electrical rating.
  4. Indicates switch action, in this case SPDT, one opens as other closes.
  5. Indicates adjustable operating range of 1-35 psig.
  6. Options.
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