Murphy 20T / 25T Series Temperature Swichgage Gauge with Switch

Coolant and oil temperature gauge with a built-in trip contact

The Murphy 20T / 25T Series Temperature Swichgage is a vapor-actuated temperature gauge with an electrical switch built into the same case. The 20 Series has a 2 inch (51 mm) dial and the 25 Series a 2-1/2 inch (64 mm) dial. Ranges start at 32-120 F (0-45 C) and reach 300-440 F (160-220 C).

A sealed capillary tube joins the gauge to a sensing bulb. When the bulb is heated, the liquid inside it turns to vapor and presses on a diaphragm, which the movement converts into a dial reading. Enovation Controls recommends the series for industrial engines and equipment in oil field, marine, irrigation, construction and trucking service, and for monitoring engine coolant, crankcase oil and transmission oil.

Technical specifications

Values are from Enovation Controls bulletin 94031.

Models, options and ordering

Base models cover coolant or oil temperature (20T, 25T), Ford engines with a special bulb (20TL, 25TL), internal SPDT snap switch versions (20TE, 25TE, formerly 20ESR and 25ESR), a pre-alarm version (20TABS, 25TABS), cylinder head temperature for air-cooled engines (20TH, 25TH) and gauge-only MurphyGage versions (20TG, 25TG). Direct mount models 20TD and 20SD carry a short rigid bulb and are offered for 220 F (104 C) or 250 F (121 C).

The order code is built from the base model, an option string and the range, then the capillary type and length and the bulb thread. Options include black or alternative bezels, explosion-proof (EX) versions, high and low contacts, knob adjustment, silicone oil sealing and light pipe illumination for 12 or 24 VDC. Capillary lengths run in 2 ft steps to 20 ft, and the adapter nut must match the sensing bulb thread.

Setting and selecting the trip point

Select the scale so the normal operating temperature falls in the upper half. For adjustable switch models the trip point is adjustable only over the upper half of the scale, and for the 20TE and 25TE it cannot be set at the extreme ends because the reset differential must fit.

The contacts are for light duty. For inductive or high-current loads the bulletin recommends a magnetic switch, and for an alarm before shutdown it points to the 20TABS or 25TABS or to Tattletale models 760A and 761APH. Before ordering confirm range, capillary length, bulb thread and options. Enovation Controls lists this product family on its Legacy Products page, which describes those items as less popular or outdated but still available for purchase. Confirm current availability and any replacement part before ordering.

Where the Murphy 20T/25T Swichgage is used

• Oil field engines
• Marine engines
• Irrigation pumps
• Construction machines
• Trucking equipment

Selection checklist for the Murphy 20T/25T Swichgage

• Dial size
• Temperature range
• Capillary length
• Capillary armor
• Switch type
• Contact rating
• Mounting style
• Fluid being measured

Installation, commissioning and maintenance notes for the Murphy 20T/25T Swichgage

Fit the sensing bulb in the fluid and route the capillary clear of heat and sharp edges. Set the contact with the hex wrench. Check the dial, the capillary and the wiring at regular intervals.

Requesting a quotation for the Murphy 20T/25T Swichgage

Please send the range, the dial size and the capillary length. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

Murphy 20T/25T Swichgage gauge type

It is a vapor-actuated temperature gauge.

Murphy 20T/25T Swichgage switch

An electrical switch is built into the same case.

Murphy 20T/25T Swichgage maker

It is made by Murphy, part of Enovation Controls.

Murphy 20T/25T Swichgage 20 Series dial

The 20 Series has a 2 inch dial.

Murphy 20T/25T Swichgage 25 Series dial

The 25 Series has a 2-1/2 inch dial.

Murphy 20T/25T Swichgage dial colours

The dial is white on black.

Murphy 20T/25T Swichgage dial scale

The standard dial has a dual F/C scale.

Murphy 20T/25T Swichgage lowest range

The lowest range is 32-120 F.

Murphy 20T/25T Swichgage highest range

The highest range is 300-440 F.

Murphy 20T/25T Swichgage sensing element

The sensing element is a beryllium copper diaphragm.

Murphy 20T/25T Swichgage capillary

The standard capillary is armored copper, 4 ft long.

Murphy 20T/25T Swichgage capillary armor option

Stainless steel armor is optional.

Murphy 20T/25T Swichgage sensing bulb

The sensing bulb is copper.

Murphy 20T/25T Swichgage ambient temperature

The ambient limit runs from minus 40 to 150 F.

Murphy 20T/25T Swichgage limit contact

The limit contact is SPST and rated 2 A at 30 V.

Murphy 20T/25T Swichgage contact action

The contact is normally closed when the high limit is met.

Murphy 20T/25T Swichgage snap switch

The 20TE and 25TE use an SPDT snap switch.

Murphy 20T/25T Swichgage contact adjustment

The contact is adjusted with a 1/16 in hex wrench.

Murphy 20T/25T Swichgage case

The case is plated steel.

Murphy 20T/25T Swichgage bezel and lens

The bezel is polished stainless steel and the lens is polycarbonate.

Murphy 20T/25T Swichgage weight

The 20 Series weighs 12.7 oz and the 25 Series 13.8 oz.

Murphy 20T/25T Swichgage dimensions

Both series measure 4-3/4 x 4-3/4 in at the front.

Gauge records for the Murphy 20T/25T Swichgage

Record the contact setting, the range and the date of each check.

Choosing the right Murphy 20T/25T Swichgage model

Choose the range and the dial size from the fluid and the panel space.

Documents and quotation

The attached bulletin 94031 (revision 2014/11/13) is the source for the values above. Seven Star LLC supplies Murphy products as an independent supplier in Muscat. Send the full model code, range, capillary length and bulb thread with your enquiry. Related items are listed under temperature instrumentation.