Delta Mobrey 721 Series Temperature Switch


Delta Mobrey 721 Series Temperature Switch Temperature switches comprise an armored capillary attached to the sensing bulb via a semi-rigid extension on which a compression gland slides to enable various depths of thermowell (pocket) to be accommodated. This sensor is coupled to the microswitch via a precision stainless steel mechanism, the combination of which helps deliver the market-leading performance customers can expect from the Series.

Designed in the mid-1970s and developed over subsequent years, the Performance Series switch range offers users the broadest range of options, the highest levels of set-point repeatability, and the confidence of long-term performance that a mature product such as this can prove. The model 721 Gas Filled Temperature Switch has a flexible thermal system and is suitable for setpoints between -50°C and 300°C with maximum working temperatures up to 310°C.

  • Ranges available up to 300°C
  • Weatherproof IP66 enclosures in zinc alloy or stainless steel
  • ATEX and IECEx Ex d Flameproof models available
  • Environmentally and Hermetically sealed switch options
  • Set-point adjustable over the full range against a calibrated scale with the tamperproof adjuster

Delta Mobrey 721 Series Advantages:

  • Better than 1% set-point repeatability
    • Users can expect a set-point repeatability performance better than 1% on all configurations with some configurations being significantly better
  • Extensive range of options
    • The Performance Series switches are available with an extensive range of materials, process connections, switch types, electrical entries, etc., and offer customers millions of different possible configurations.
  • More than 35 years of experience in the field
    • Installed in a wide range of applications from nuclear power plants to offshore oil rigs, the Performance Series’ long experience in the field offers customers the reassurance that they can be relied upon to survive the test of time in the harshest environments.


  • Precision stainless steel mechanism for arduous atmospheres and high humidity.
  • Hermetically sealed microswitch option
  • Models for fixed switching differential, adjustable differential, and HI-LO operation.
  • Ranges available up to 230 to 300°C (450 to 580°F). Maximum working temperature up to 310°C (600°F).


The 721 Performance Series is suitable for a wide range of applications:

  • Oil & Gas
  • Chemical
  • Petrochemical
  • Refining
  • Power
  • Food Industry

The choice of models available ensures that the 721 Performance Series is suitable for use in:

  • Corrosive atmospheres
  • Resistant to chemical attack

Delta Mobrey 721 Series Specification:

  • Accuracy:
    • Set point repeatability ± 0.5% of span at 20°C / 68°F ambient.
    • Scale accuracy ± 2% of full scale.
    • Models 721 scale accuracy will be affected by the relative position of the head and sensing bulb i.e., sensing bulb 1 meter above/below head = set point shift ± 1% of full scale approx.
  • Storage Temperature: -25 to +60°C / -13 to +140°F
  • Ambient Temperature:
    • -25 to +60°C / -13 to +140°F
    • On models 721-3, 781 it is advisable to avoid the condition where the ambient temperature is within ± 5°C (± 9°F) of the set point.
  • Maximum Working Pressure: System sensing probes for both the capillary and rigid stem versions are designed to withstand 100 bar (1500psi) without thermowell.
  • Enclosure classification: IP66 / NEMA 4X / Flameproof Ex d
  • Switch output:
    • SPDT or DPDT snap-action microswitch (standard)
    • Hermetically sealed (optional)

Process Connection: 3/8 NPT External Sliding Gland, ½ NPT External Direct mounting. Approximate Weight: Enclosures: “W & N” 2.5kg / 5.5lb (models 731-4 2.2kg/4.8lb); “A & O” 3.5kg /7.7lb (models 731-4 3.2kg/7.0lb); “H” 4.0kg/8.8lb; “K” 8.7kg/19.1lb

Download Data Sheet: 721 Temperature Switch


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