VA-GA-GAS-THERMOM

Supported Applications

The Omega VA and GA series comprises remote vapor- and gas-actuated thermometers designed for temperature-indicating applications requiring panel installations or remote reading. These instruments utilize capillary lengths ranging from 1 to 100 feet, enabling the sensor bulb to be located away from the display dial. Vapor-actuated models (VA) are specified for use where excellent readings are required provided the measured temperature is above or below ambient conditions; these units feature progressive graduations and perform best when operating temperatures fall within the upper two-thirds of the dial range. Gas-actuated models (GA) employ Class IV thermal systems with gas coil technology, offering superior accuracy across the full measurement span compared to vapor types.

Operating Conditions & Performance

The series covers a broad temperature envelope from -320°F (-196°C) to 1200°F (649°C), with specific ranges selected via model codes. Accuracy is defined as ±1 scale division for vapor-actuated thermometers and ±1% of scale for gas-actuated models. Gas instruments provide a linear dial ensuring consistent accuracy across the full span, while vapor instruments utilize progressive graduations optimized for the upper two-thirds of the range.

Available temperature ranges include:

• Vapor (VA): -40 to 60°F (-40 to 15°C) through 200 to 450°F (100 to 230°C).
• Gas (GA): -320 to 100°F (-200 to 40°C) through 400 to 1200°F (200 to 650°C), with dual Fahrenheit and Celsius scales available on many ranges.

Higher temperature ranges of 300°F or above for vapor-actuated models, as well as all gas-actuated models, are offered only with stainless steel systems. Specific high-range configurations (e.g., -D or -E capillary codes) require specific process connections such as -L2 or -M2.

Configuration Options

The series is configurable across dial size, case material, lens type, temperature range, sensor assembly, and connection style. Model numbers follow the format: VA/GA – Case Style/Size – Temperature Range – Capillary/Bulb – Length (feet) – Process Connection – Thermowell.

Four dial sizes are available: 2", 2½", 3½", and 4½". Case materials include stainless steel, black aluminum (hinge ring type), and phenolic. Lens options consist of polycarbonate or glass.

• Rear Connection: Stainless steel cases with rear connection are available in sizes 2" through 4½" (e.g., codes 20FR, 35UR).
• Lower Rear/Bottom: Black aluminum hinge ring types and stainless steel bottom-entry options exist for larger dials.
• Turret Mounting: Phenolic cases with glass lenses are offered in a 4½" turret style (code 45TB).

The sensing element consists of a bulb connected to the dial via a capillary tube. The bulb outer diameter is ⅜".

• Materials: Copper or 316 SS (stainless steel).
• Protection: Options include no protection, bronze braid, or stainless steel armor.
• Lengths: Capillary lengths range from 1 to 100 feet. Bulb sizes (#1 through #5) vary by length and overall assembly dimensions.

Connections are selected based on the installation requirement, including plain bulb or union types:

• -J1: None (plain bulb).
• -K2 / -L2: ½ NPT union in Brass or 316 SS.
• -M2: ½ NPT union with jam nut and bendable extension (316 SS only; available for specific high-temp ranges).
• -J2 / -J3: Jam nut only, required when using a thermowell.

Optional thermowells are offered in 1/2" or 3/4" sizes with materials including 316 SS and Brass. Models vary by capillary length (e.g., U1 for 1–10', U8 for 76–100') and bulb type.

Key Product Differences

The primary distinction between the two product families lies in their actuation mechanism, accuracy profile, and temperature range coverage. Vapor-actuated (VA) models rely on vaporized liquid expansion with progressive graduations; they are best suited for applications where operating temperatures can be maintained within the upper portion of the scale. Gas-actuated (GA) models utilize a gas-filled system that provides linear dial readings and consistent ±1% accuracy across the entire span, extending to higher maximums up to 1200°F.

Material constraints differentiate specific configurations: ranges at or above 300°F for vapor types and all gas-actuated models are restricted to stainless steel systems (capillary codes -D or -E). Additionally, the M2 bendable extension option is available only with 316 SS capillaries. Lens material varies by case style; glass lenses require specific designation on certain phenolic cases, while polycarbonate is standard for most stainless and aluminum housings.