A20 AND A25 SERIES TEMPERATURE SWICHGAGE®

2 and 2-1/2 in. (51 and 64 mm.) Dial

• 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

Description

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) thru 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 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

Applications for A20 and A25 Series temperature SWICHGAGE® instruments include: engines and equipment in Oil Field, Marine, Irrigation, Construction and Trucking industries. Monitoring Engine Coolant temperature, Crankcase Oil, Transmission Oil.

SWITCH/ORDERING DETAILS

Description

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).* Galvanized and stainless steel armor optional.
Sensing Bulb: Copper.*
Gage Accuracy: See accuracy chart, on page 2.
Maximum Temperature: See Temperature Ranges and Factory Settings table on page 2.
Adjustable Limit Contact (A20T and A25T):SPST contact; pilot-duty only, 2 A @ 30 VAC/ VDC; isolated from case ground. Normally 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 thru 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.).

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 20 and 25T 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).

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

* * Products covered by this bulletin comply with EMC Council directive 89/336/EEC regarding electromagnetic compatibility except as noted.

Dimensions

 a20

a25

Temperature Ranges and Factory Settings

NOTES

1. Values in () are mathematical conversions from °F to °C–they do not reflect actual second scale range. U.S.A. standard scale is °F/°C.
2. For models A20TE and A25TE; the switch trip point cannot be set at either the low or high extreme of the scale. The trip point must allow for the reset differential.
3. For adjustable switch models, the trip point is adjustable only over the upper half of the scale.

Ranges Available

Max. Temp.

Std. Settings*

Hi/Lo Settings

Low High

20TABS and 25TABS Settings

Alarm**  Shutdown

Dual Scale Dial

°Fahrenheit (°Celsius)

Single Scale

°Celsius only

°F (°C)

°F (°C)

°C only

°F (°C)

°F (°C)

°F (°C)

°C only

°F (°C)

°C only

32 – 120 (0 – 49)

––

185 (85)

110 (43)

––

32 (0)

110 (43)

100 (38)

––

110 (43)

––

32 – 160 (0 – 71)

0 – 70

215 (102)

150 (66)

66

32 (0)

150 (66)

140 (60)

60

150 (66)

66

130 – 220 (54 – 104)

45 – 100

260 (127)

210 (99)

85

160 (71)

210 (99)

200 (93)

80

210 (99)

85

130 – 250 (54 – 121)

50 – 120

310 (154)

210 (99)

97

160 (71)

210 (99)

200 (93)

95

210 (99)

100

140 – 300 (60 – 149)

60 – 140

340 (173)

275 (135)

130

200 (93)

275 (135)

265 (129)

125

275 (135)

130

160 – 320 (71 – 160)

70 – 160

370 (192)

300 (149)

150

200 (93)

300 (149)

290 (143)

145

300 (149)

150

180 – 350 (82 – 177)

––

400 (209)

330 (166)

––

240 (116)

330 (166)

320 (160)

––

330 (166)

––

300 – 440 (149 – 227)

––

500 (260)

400 (204)

––

300 (149)

400 (204)

390 (199)

––

400 (204)

––

* Standard setting for A20T, A25T, A20TE and A25TE models.
** SPDT snap-switch is the alarm switch.

Temperature Accuracy Chart

Temperature Range

32 to 120°F (0 to 49°C)

Lower 1/3 of Scale

± 12°F (± 6°C)

Middle 1/3 of Scale

± 5°F (± 2.4°C)

Upper 1/3 of Scale

± 6°F (± 3°C)

32 to 160°F (0 to 71°C)

± 20°F (± 10°C)

± 8°F (± 4.4°C)

± 7°F (± 4°C)

130 to 220°F (54 to 104°C)

± 6°F (± 3°C)

± 3°F (± 1.6°C)

± 4°F (± 2°C)

130 to 250°F (54 to 121°C)

± 9°F (± 5°C)

± 5°F (± 2.4°C)

± 4°F (± 2°C)

140 to 300°F (60 to 149°C)

± 10°F (± 5.2°C)

± 6°F (± 3°C)

± 5°F (± 2.4°C)

160 to 320°F (71 to 160°C)

± 10°F (± 5.2°C)

± 5°F (± 2.4°C)

± 5°F (± 2.4°C)

180 to 350°F (82 to 177°C)

± 12°F (± 6°C)

± 5°F (± 2.4°C)

± 5°F (± 2.4°C)

300 to 440°F (149 to 227°C)

± 9°F (± 5°C)

± 5°F (± 2.4°C)

± 4°F (± 2°C)

Maximum Temperature

MAXIMUM AMBIENT Temperature -40˚ (140˚) through 150˚ (66˚)

RANGE

250° (120°)

MAXIMUM PROCESS Temperature

120% OF FULL SCALE

300° (140°)

350° (198°)

320° (160°)

120% OF FULL SCALE