Murphy ESPS-100 / ESTS Engine Pressure and Temperature Sender and Switch

Engine-mounted sender and fault switch in one body

The Murphy ESPS-100 and the ESTS-250 and ESTS-300 are engine-mounted sensors that combine a resistive sender output with a fault limit switch output. The ESPS measures oil pressure and the ESTS measures coolant temperature. Their sender characteristics match the Murphy ES series senders, so they can feed EG(S)21 series gauges or Swichgages, engine or genset controllers, or input/output modules such as a Murphy MeCAN interface.

The switch contacts are normally open at normal running pressures and temperatures. They close to the sensor body (case ground) when pressure falls below, or temperature rises above, the factory set limit. An external control device can use that signal to warn the operator or shut the engine down. The data sheet notes the contacts can be used in place of, or in addition to, EG(S)21 Swichgage outputs to give two staged limits for warning and shutdown.

Technical specifications

Values are from Enovation Controls data sheet ys6490, revision B dated 2023/03/07.

Ordering codes and quantities

The data sheet lists three stock codes: 05707753 for the ESPS-100 pressure sender/switch with a 1/8 in NPT thread, 0-100 psi sender range and 15 psi switch; 10703807 for the ESTS-250 temperature sender/switch with a 5/8 in-18 UNF thread and 105 C switch; and 10703808 for the ESTS-300 with a 130 C switch.

Enovation Controls prints a note that ESPS and ESTS orders are subject to a minimum order quantity of 100 units. Confirm this and current availability before committing to a project, because the manufacturer may change it.

Wiring and selection checks

Because the sender follows the Murphy ES characteristics, check that the gauge or controller input expects those resistance curves. The pressure sender resistance falls as pressure rises, from 240 Ohm at zero to about 33.5 Ohm at 100 psi, while the temperature sender falls with rising temperature. The switch is a separate output and is grounded to the case, so confirm the polarity and the load before connecting it to a controller input.

Select the temperature model by the sensor range and the alarm point your engine needs: 105 C switch on the 250 F range or 130 C on the 300 F range. For a different set point the data sheet does not offer an option, so ask for confirmation. 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.

How the Murphy ESPS-100 works

The sender changes its resistance as pressure changes. A gauge or controller reads that resistance as a pressure value. A separate switch inside the same body closes to case ground when pressure drops below the set point.

Where the ESPS-100 is used

• Engine oil pressure sensing
• Generator set engines
• Engine low pressure shutdown
• Engine warning circuits
• Engine controller inputs

Selection checklist for the ESPS-100

• Pressure or temperature sensing
• Pressure range
• Switch set point
• Thread connection
• Gauge or controller type
• Warning or shutdown use
• Electrical connection
• Mounting position

Installation, commissioning and maintenance notes for the ESPS-100

Fit the sensor into the engine port with a suitable thread seal. Connect the sender wire and the switch wire. Check the reading on the gauge with the engine running. Test the switch circuit at regular intervals.

Requesting a quotation for the Murphy ESPS-100

Please send the engine type, the range and the gauge or controller used. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

ESPS-100 sensor type

It combines a sender and a limit switch.

ESPS-100 measured value

The ESPS measures oil pressure.

ESPS-100 temperature versions

The ESTS-250 and ESTS-300 measure coolant temperature.

ESPS-100 sender match

The sender matches the Murphy ES series senders.

ESPS-100 gauge use

It can feed EG(S)21 series gauges and Swichgages.

ESPS-100 controller use

It can feed engine or genset controllers.

ESPS-100 interface use

It can feed input modules such as a Murphy MeCAN interface.

ESPS-100 switch action

The contacts are normally open at normal running pressure.

ESPS-100 switch closing

The contacts close to case ground when pressure falls below the set point.

ESPS-100 pressure range

The range is 0 to 100 psi.

ESPS-100 set point

The switch set point is 15 psi falling.

ESPS-100 connection

The connection is 1/8 in-27 NPTF dryseal.

ESPS-100 staged limits

The switch can give a second limit for warning and shutdown.

ESPS-100 contact rating

The contacts are rated 28 VDC and 200 mA.

ESPS-100 case

The case is zinc plate chromate.

ESPS-100 terminals

It has two 10-32 UNF studs.

ESPS-100 stud material

The studs are brass with tin plate.

ESPS-100 resistance at zero

The sender reads 240 Ohm nominal at 0 psi.

ESPS-100 resistance at 50 psi

The sender reads 103 Ohm nominal at 50 psi.

ESPS-100 resistance at 100 psi

The sender reads 33.5 Ohm nominal at 100 psi.

ESPS-100 ESTS-250 range

The ESTS-250 covers 38 to 121 degrees C.

ESPS-100 ESTS-300 range

The ESTS-300 covers 38 to 148 degrees C.

ESPS-100 ESTS switch points

The switch points are 105 degrees C and 130 degrees C.

ESPS-100 ESTS connection

The ESTS bulb thread is 5/8 in-18 UNF.

Sender records for the ESPS-100

Record the engine, the switch test date and the gauge reading.

Choosing the right ESPS-100 or ESTS model

Choose pressure or temperature sensing from the fault you need to catch.

Documents and quotation

The attached data sheet ys6490 is the source for the values above. Seven Star LLC supplies Murphy products as an independent supplier in Muscat. Send the model, thread, quantity and the instrument the sender will connect to with your enquiry. Related items are listed under pressure instrumentation; the temperature models also suit temperature instrumentation.