SENASYS
3/4″ Manual Reset Snap Disc Thermostat
Senasys manufactures a 3/4″ manual reset snap disc thermostat, 404 series. Our manual reset thermostat switches are ideal when you want to call special attention to a temperature malfunction. Because the switch needs to be manually reset, a human must interact with the switch and solve the problem before the equipment or appliance can work again.
CUSTOM OPTIONS
Designed & manufactured to meet requirements of original equipment manufacturers worldwide.
HIGH QUALITY
Senasys products are 100% tested before they leave our facilities.
CERTIFIED
All of our snap disc units are UL approved (USR).
MADE IN U.S.A.
Designed & manufactured in Eau Claire, WI, U.S.A.
The 404 series is our 3/4″ manual reset snap disc. This series is ideally suited for applications where you want to call special attention to a specific temperature malfunction. The 404 series feature a trip-free operation. Physical depression of the reset button holds the contact open and renders the device inoperative until the reset button is released.
Our 404 manual reset snap disc thermostats have a temperature range of 100-350°F, ±25°F. Many standard temperature options are available, or we can easily design a customer temperature range to suit your application requirement.
Product Specifications
- 3/4″ Bi-Metal Snap Action Disc
- Manual Reset
- Breaks on temperature rise
- SPST (Single Pole, Single Throw)
- 25 Amps @ 120VAC, 6,000+ cycles
- Temperature Range of 100°-350°F, ±25°F differential
- Available with exposed caps to provide a faster response time.
- Special black discs can be used to further improve the response to radiative heating in exposed units.
- Available with a variety of mounting brackets
- Variety of terminal options available.
- UL Listed
- Made in U.S.A.
For a more economical solution, Senasys has built relationships with overseas suppliers to provide our customers thermostats at a lower cost, with the same high quality as our snap disc thermostats built in the U.S.A.
Mounting Options
Select from a variety of mounting options below.

Standard Direct Mount

Electric Heat Direct Mount

Notched Bracket Surface Mount

Large Surface Mount

Small Flange Surface Mount

Airstream Mount
Terminal Options
A variety of terminal bends & orientations are also available. Our standard terminal bends are 0°, 45° or 90°.
For other custom options, please contact us.

1/4″ Quick Connect Terminals

Screw Terminals

Electric Heat Terminals

Standard Temperature Options
Below is a list of our common, off the shelf, bi-metal temperature options.
Custom temperature options available. Please contact us.
Disc Number
Temperature
546
Open 120°F ±5°F
525
Open 150°F ±5°F
523
Open 190°F ±5°F
514
Open 200°F ±7°F
541
Open 225°F ±7°F
515
Open 250°F ±8°F
516
Open 300°F ±8°F
521
Open 350° ±8°F
Frequently Asked Questions
YOUR QUESTIONS, ANSWERED.
One of the standout characteristics of an exposed cap is its’ use of a black exposed disc. This disc serves as a crucial element in sensing temperature fluctuations swiftly, enabling the switch to respond rapidly to environmental changes. This quick thermal response is especially important in applications where precise temperature control is paramount, such as in thermostats, industrial control systems, and appliances. The exposed caps are available for all non-epoxied snap disc thermostats within the Senasys catalog.
For more information on exposed snap disc caps, click here.
One of the key advantages of gold contacts is their significantly lower contact resistance when compared to high-current silver contacts. This low resistance translates into improved electrical conductivity, allowing for smoother and more reliable signal transmission. This is especially important in applications where even the slightest interruption or distortion in the signal could lead to critical errors or malfunctions.
For more information on when gold contacts should be used, click here.
Cross Reference
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BRANDS
Senasys
404 Series
Thermodisc
60T Series
Selco
SE/SES Series
3/4″ Bi-Metal Disc
Enclosed or Exposed
Manual Reset
Fixed Temperature 100°F to 350°F
Open on Temp Rise
Single Pole, Single Throw
SPST
25 Amps @ 120VAC
+6,000 cycles
Variety of Mounting Options
Variety of Terminal Options
UL Listed
Made in U.S.A.
Build A Thermostat
Follow the below nomenclature guide to determine the 3/4″ manual reset thermostat to meet your application requirements.
Request A Quote
Complete the form below with your application information, and a product specialist with follow up with you in 1-2 business days.