Series-DA-DS

Supported Applications

The Dwyer Series DA/DS Bourdon Tube Pressure Switches are designed for pressure control in HVAC systems, pumps, and compressors. These units utilize a visible calibrated dial to monitor setpoints and provide on/off indication of switch actuation. The series supports single or two-stage operation configurations.

Operating Conditions & Performance

The Series DA/DS operates within an ambient temperature limit of 180°F (82°C). Pressure ranges span from full vacuum to high pressure, specifically covering:

• Vacuum and low-pressure: 0 to 30 in Hg VAC
• Low-to-medium positive pressure: 1/8 to 15 psig through 10 to 200 psig (Brass)
• High-pressure ranges: Up to 800 to 8000 psig using 403 Stainless Steel or 316 SS Bourdon tubes

The series offers a repeatability of ±1% of full operating range, with DS-7300 models specified at ±1.5%. The maximum pressure rating corresponds to the upper limit of the selected operating range.

Configuration Options

Bourdon Tube Materials and Ranges

The series is available in three wetted material configurations, each supporting specific adjustable ranges:

• Brass Bourdon Tubes: Supports vacuum to 300 psig (e.g., Range Numbers 1 through 9).
• 403 Stainless Steel Bourdon Tubes: Covers vacuum/low pressure up to 8000 psig (Range Numbers with 'S' suffix, e.g., 25S through 16S).
• 316 SS Bourdon Tubes: Designed for corrosive service from vacuum to 2500 psig (Range Numbers with 'E' suffix, e.g., 26E through 13E).

Enclosure Types and Approvals

Housing options include General Purpose, Weatherproof (Series DAW), and Explosion-proof enclosures. The explosion-proof models are suitable for Class I, Groups C and D; NEMA 7; Class II, Groups E, F, G; Class III NEMA 9 and 9A, Division 1.

Approvals include UL listed, CSA approved, and FM approved (many models). Specific model suffixes denote these configurations:

• -W Suffix: Weatherproof enclosure
• -H Suffix: Explosion-proof enclosure
• -F Suffix: FM Approved models (e.g., DAF, DAHF)

Switch Types and Electrical Ratings

The series supports multiple switch mechanisms including SPST mercury switches, SPDT mercury switches, and SPDT snap-action switches. Circuit types include Single Pole Double Throw (SP-DT), Double Pole Single Throw (DP-ST), and Double Pole Double Throw (DP-DT).

• Mercury Switch Ratings: 10 A @ 120 VAC, 5 A @ 240 VAC for SPST; 3/4 HP AC.
• Snap Action Ratings (Code B): 5 A @ 120 VAC, 2 A @ 240 VAC; 1/8 HP AC.
• Circuit Codes: Suffixes such as -2, -3, -4 define circuit response to pressure increase (Open/Close).

Process Connections and Accessories

Standard process connections vary by enclosure type: General purpose units feature 1/4" male NPT or 1/2" male NPT; Weatherproof models offer 1/2" male NPT or 1/4" female NPT. Explosion-proof enclosures provide 1/2" male NPT and 1/4" female NPT.

Available accessories include remote connections (e.g., No. 49-62 for 300 psi, No. 49-62HP to 2500 psi), pigtail siphons (No. 42-52, No. 42-58), and mounting brackets (No. 33-25).

Key Product Differences

The Series DA/DS distinguishes between adjustable deadband models (DA) and fixed deadband models (DS). The DA series features two external adjustments: one for the high-pressure operating point and another for the reset point, allowing deadband adjustment over the full scale. DS models incorporate a fixed differential.

Model numbering reflects these distinctions alongside material and range codes:

• DA-70xx Series: Snap-action switches with adjustable deadband (e.g., DA-7031 for Brass).
• DS-72xx/73xx Series: Fixed deadband configurations.

Differential values vary by range and material. For example, the 403 SS Range 5S (2 to 60 psig) has a minimum pressure spread of 6 psig with a fixed differential of 1-1/4 psig for snap-action units, while mercury switch equivalents in similar ranges may exhibit differentials such as 4 oz or 7 oz depending on the specific range number.

Special service options include manual reset operation, two-stage controls (Series D-400), acetal bushed movement for high vibration/pulsation applications, and fungus proofing. For steam applications with ranges of 35 psi or higher, a siphon is required to prevent live steam from entering the Bourdon tube.