Several times each year, PRIMUS receives temperature and pressure switches back from the field via a Return Material Authorization (RMA).

In the majority of cases, it was found that the switch seal was broken (the seal is comprised of a small set screw and a silicone bead around the entire periphery of the switch body).

These findings showed that the switches were improperly handled or installed by PRIMUS during factory assembly or in the field by Authorized Service Agents (ASA) or in-house maintenance technicians.

The seal protects the switch from any adverse conditions existing in the local environment.

These failures can be easily avoided as described below.

Switch Installation

Here is the proper way to install a switch:

  • Handle the switch only by its brass base!
  • Hand-start the switch and finish the installation with a wrench
  • Again, never twist the switch body as the seal protecting the switch from moisture and debris will be broken and the switch will fail prematurely

ADD PHOTOS Temperature Switches (Stainless and Brass)

Pressure Switches (Stainless and Brass)

Nason Switch Designs Ensure High Reliability

Nason is a 60-year-old company located in South Carolina.

All of Nason’s pressure switches use a snap-action electrical device activated by a precise elastomer diaphragm or piston offering a precise and repeatable design.

The Nason switches used by PRIMUS are proprietary. PRIMUS worked with Nason engineers to ensure the robustness and reliability of the pressure and temperature switches used in a steam sterilizer environment. These proprietary switches can be purchased on the SPIRE website or by calling PRIMUS Parts at 402-344-4200 Ext. 1010. They cannot be purchased directly from Nason.


Nason’s elastomer diaphragm, which moves a precise .040 of an inch, ensures accurate, instantaneous contact under all operating conditions. Nason tests 100% of its switches for accuracy.


Under most operating conditions, Nason switches have an operational life of over one million cycles.

Have a question or having difficulties? Talk to Dave Schall, our PRIMUS sterilizer expert who is here to assist you anytime at 877.679.7800 extension 1212 or email at

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