A20T / A25T (Mechanical Temperature Gauges)

Corrosion Resistant Polycarbonate Case Indicating Gage and Limit Switch Switch Can Activate Alarms and/or Shut Down Equipment Critical/High Temperature Limit Switch Is Visible and Adjustable (Most Models) Contact(s) Isolated From Ground

The A20 Series (2 inch/51 mm dial) and the A25 Series (2-1/2 inch/64 mm dial) Swichgage models are diaphragm-actuated, temperature-indicating gages, with built-in electrical switches for tripping alarms and/or shutdown devices.

Ranges are available from 32°-120°F (0°-45°C) through 300°-440°F (160°-220°C).

All models of these rugged, built-to-last instruments are fully sealed from the environment by the unique combination of a polycarbonate case and lens, a polished stainless steel bezel and O-ring seals.

These vapor/pressure actuated gages feature a sealed capillary tube and a sensing bulb. When subjected to heat, the liquid in the sensing bulb changes to vapor creating pressure against a diaphragm mechanism. The diaphragm translates this vapor pressure into a mechanical gage reading.

For series A20T and A25T, the gage pointer acts as a temperature indicator and as one switch pole which completes a circuit when it touches the adjustable limit contact. Contact(s) are isolated from ground. They have a self-cleaning motion to enhance electrical continuity.

Models A20TE and A25TE have internal snap-acting SPDT switches.

Gage-only models, without contacts (Murphygage®) are also available.

Applications for A20 and A25 Series temperature Swichgage instruments include: engines and equipment in the oil field, marine, irrigation, construction and trucking industries, monitoring engine coolant temperature, crankcase oil, transmission oil.

Base Models

Coolant or Oil Temperature
A20T and A25T Series Swichgage: For these models the gage pointer makes with an adjustable contact to complete a pilot-duty circuit.

A20TL and A25TL Swichgage: For use on Ford Worldwide engines. Supplied with special sensing bulb.

A20TE and A25TE Swichgage: A20TE (was A20ESR) and A25TE (was A25ESR). Models with internal SPDT snap-switches, instead of the single pole/pointer contact(s). When the switch closes on rising temperature, it becomes set. As temperature decreases the switch resets.
Model A25TE is CSA listed for non-hazardous areas.
Model A25TE-EX is CSA listed for Class I, Division 1,
Groups C & D hazardous areas.

A20TABS and A25TABS Swichgage: Same as A20 and A25T with internal SPDT snap-switch for pre-alarm.

Cylinder Head Temperature
A20TH and A25TH Swichgage: A20TH (was A20TL8133) and A25TH (was A25TL8133). For use on air-cooled engines.

Gage–Only Models
A20TG and A25TG Murphygage: Gage without contact(s).

Specifications

• Dial: White on black; U.S.A. standard scale is dual scale °F/°C; others available
• Case: Glass filled/Polycarbonate, corrosion-resistant; steel mounting clamp included
• Bezel: Polished stainless steel, standard; others are available.
• Pointer: Tempered nickel silver; red tip
• Lens: Polycarbonate, high-impact
• Sensing Element: Beryllium copper diaphragm
• Capillary: PVC armored copper; 4 ft. (1.2 m).* Stainless steel armor optional
• Sensing Bulb: Copper*
• Gage Accuracy: See accuracy chart
• Maximum Temperature: See Temperature Ranges and Factory Settings table
• Maximum Ambient Temperature: -40°F (-40°C) through 150°F (66°C)
• Adjustable Limit Contact (A20T and A25T):

 

• SPST contact; pilot-duty only, 2 A @ 30 VAC/VDC; isolated from case ground
• Closed when the high limit is met. Normally Open when pointer is in normal operating range. Contacts are gold flashed silver.

• Limit Contact Adjustment: by a 1/16 in. hex wrench through 100% of the scale.
• Wiring: A20T: Number 4 screw terminals; A25T: Number 6 screw terminals.
• Snap-Switch Rating (A20TE and A25TE):

 

• SPDT, 3 A@ 30 VDC inductive; 4 A @ 125 VAC inductive
• Wiring: A20TE: Number 4 screw terminals; A25TE: Number 6 screw terminals

• Unit Weight: A20 Series: 11.9 oz. (0.370 kg); A25 Series Models: 13.3 oz. (0.413 kg)
• Unit Dimensions: A20 Series: 4-3/4 x 4-3/4 x 3 in. (121 x 121 x 76 mm); A25 Series Models: 4-3/4 x 4-3/4 x 2-3/4 in. (121 x 121 x 70 mm)

 

*For optional capillary lengths, engine adapters, sensing bulbs and range combinations, see Murphy bulletin 8428.