Murphy A20, A25 User 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
®
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.
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 snapswitch 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
®
Bulletin AT-95026B page 2 of 4
Dimensions
A20 Series Models (typical) A25 Series Models (typical)
Ranges Available
Dual Scale Dial Single Scale
°Fahrenheit (°Celsius) °Celsius only
Std. Settings*
°F (°C) °C only
Max. Temp.
°F (°C)
20TABS and 25TABS Settings
Alarm** Shutdown
°F (°C) °C only °F (°C) °C only
Hi/Lo Settings
Low High
°F (°C) °F (°C)
32 – 160 (0 – 71) 0 – 70 215 (102) 150 (66) 66 32 (0) 150 (66) 140 (60) 60 150 (66) 66
32 – 120 (0 – 49) –– 185 (85) 110 (43) –– 32 (0) 110 (43) 100 (38) –– 110 (43) ––
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
160 – 320 (71 – 160) 70 – 160 370 (192) 300 (149) 150 200 (93) 300 (149) 290 (143) 145 300 (149) 150
140 – 300 (60 – 149) 60 – 140 340 (173) 275 (135) 130 200 (93) 275 (135) 265 (129) 125 275 (135) 130
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.
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 differen-
tial.
3. For adjustable switch models, the trip point is adjustable only over the upper half of the scale.
Temperature Ranges and Factory Settings
Temperature Accuracy Chart
32 to 120°F (0 to 49°C) ± 12°F (± 6°C) ± 5°F (± 2.4°C) ± 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)
Temperature Range Lower
1
/3 of Scale Middle 1/3 of Scale Upper 1/3 of Scale
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)
RANGE MAXIMUM PROCESS TEMPERATURE
≤250° (120°) 120% OF FULL SCALE
300° (140°) 350° (198°)
≥320° (160°) 120% OF FULL SCALE
MAXIMUM AMBIENT TEMPERATURE: -40° (-40°) thru 150° (66°)
Maximum Temperature
2-1/4 in.
(57 mm)
W
S
I
C
H
Y
G
H
A
P
G
R
U
M
160
130
60
TEMPERATURE
E
°F
®
210
230
250
100
80
120
°C
2-1/16 in. (53 mm)
Mounting hole dia.
Contact
Adjustment
1/16 in. hex
1/2 NPT
Adapter Nut
†
Standard combinations. See Murphy bulletin T-8428B for optional sensing bulb, engine adaptors and capillary combinations.
†
2-1/2 in.
(64 mm)
Mounting
Clamp
1-27/64 in.
(36 mm)
1-1/2 in.
(38 mm)
Sensing Bulb
Capillary
4 ft. (1.2 m)
†
†
long
5/8-18 U.N.F.
Union Nut
2-29/32 in.
(74 mm)
Y
H
P
R
U
M
160
130
80
60
TEMPERATURE
2-11/16 in. (68 mm)
Mounting hole dia.
Contact
Adjustment
1/16 in. hex
S
°F
210
°C
W
100
2-1/2 in.
(64 mm)
I
C
H
G
A
G
E
®
230
250
120
Mounting
Clamp
1-11/32 in.
(34 mm)
†
Capillary
4 ft. (1.2 m)
long
1-1/2 in.
1/2 NPT 5/8-18 U.N.F.
Adapter Nut
†
(38 mm)
Sensing Bulb
†
Union Nut
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