Stemco Capillary Switch

For manufacturers in diverse industries where precision is critical, maintaining consistent temperature control is essential. Due to recent shifts in the marketplace, many are turning to STEMCO Capillary Switch, a division of Senasys, for replacement Robertshaw capillary thermostats. If you have any immediate needs or specific requirements you’d like us to address, please contact us.  We’re here to help and would be happy to take a look and provide solutions tailored to your operations.

STEMCO Bulb and Capillary Thermostats

Regardless of the style or model selected, all our capillary thermostat switches function based on the same underlying principle. They contain a fluid sealed within a metal bulb that expands or contracts in response to temperature changes. This expansion or contraction moves a diaphragm that activates a snap action switch, either opening or closing a circuit.

American Made: All components are crafted at our Eau Claire, Wisconsin facility, where thermostats undergo 100% testing and ambient compensation before shipment.

Custom Options: If the standard models don’t meet your needs, our in-house machine shop enables us to customize thermostat switches to your specific requirements.

Certifications: All capillary thermostats are UL & cUL approved, ensuring compliance with industry standards.

Efficient Lead Times: We typically offer a lead time of just 4 weeks for developed switches, helping you maintain your production schedules.

Direct Customer Service: Experience personalized support—speak directly with a knowledgeable team member for assistance.

Quick Guide to Replacement Robertshaw Capillary Thermostats

Robertshaw 5300 Series (K & S) Electric Thermostats

354-1046 capillary thermostat Senasys is able to achieve a replacement option for the Robertshaw 5300 thermostats by using our 354 Series of capillary thermostats.

The 354 Series of thermostats are available field adjustable or fixed and can be either manually or automatically reset. These control and/or high limit switches are highly versatile, carrying up to 25 amps. The capillary thermostat has a temperature range of 0°F to 700°F, with a maximum ambient temperature of up to 250°F.

Robertshaw 5000 Series (D1 &D18) Commercial Electric Thermostats

352-39326 Capillary Thermostat

To replace the Robertshaw 5000 Series three-phase thermostats, our 352 Series of capillary switches are suitable. Our 352 Series features two SPDT microswitches, which replicate the three-phase function of the 5000 Series by allowing both switches to actuate simultaneously or with a differential.

The SPDT switches in our 352 Series can handle up to 25 amps (25/microswitch) and up to 277VAC. Configured as a double pole thermostat, each microswitch manages one leg. This series could also feature a unique ‘OFF’ position using the thermodynamic properties of the single diaphragm/hydrastat.

Robertshaw 275 Series Electric Thermostats for Residential Gas Ranges/Ovens

351-254326 capillary thermostat

STEMCO offers a direct replacement option to the Robertshaw 275 Series thermostats through our 351 Series Manual Reset thermostats.

The 351 Series Manual Reset Thermostats offer a temperature range from 0°F to 700°F. These thermostats feature SPDT switch action and can handle up to 25 Amps at 277VAC, with a maximum ambient temperature of 250°F. Available mounting options include panel, back, or side, with housing being optional. Terminals are located at the front, and adjustments can be made using a screwdriver or a D-shaft.


If thermostat issues are affecting your operations, or if you’re planning an upgrade to boost performance and reliability, consider STEMCO. Our solutions are designed for seamless integration, reducing downtime and enhancing efficiency across a broad spectrum of applications.

Send us your application details today!

Bulb & Capillary Thermostats

Original equipment manufacturers worldwide use thermostat switches designed and manufactured by STEMCO, a Division of Senasys. No matter which style or model you choose, all of the capillary thermostat switches operate using the same physics. A fluid is encapsulated in a metal and when the temperature changes the fluid either expands or contracts. This fluid change moves a diaphragm which is in touch with a snap action switch and either opens or closes a circuit.

Ambient Compensation

Our capillary thermostats can be ambient compensated to offset the differential in temperature which keeps our thermostat controls more accurate as it’s environment changes.

Custom Options

Capillary thermostat switches built by Senasys can also be built to customer specifications. This insures you get the exact control you want without paying for features you don’t need.