Murphy A20 Series - Manual

Bulletin AT-95026B page 1 of 4

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

®

mod-

els 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 pol-
ished 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.

Specifications

Dial:

White on black; U.S.A. standard scale is dual

scale °F/°C; others available.

Case:

Glass filled/Polycarbonate, corrosion-resis-

tant; 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, 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.

A20T Series
shown

**

AT-95026B

Revised 08-05

Catalog Section 10

A20 and A25 Series
Temperature SWICHGAGE

®