Your Trusted Manufacturer of High-Quality Heat Detectors
Thermotech Heat Detectors, Inc. — UL Listed, Factory Mutual Approved. The Model 302 series serves fire detection and alarm systems for commercial, industrial, and hazardous-location applications across the US and internationally.
Precision Rate Compensation Heat Detection
The Thermotech heat detector Model 302 is a normally open device designed especially for fire detection and alarm systems. These rate compensation type detectors are available in either 135°F or 194°F ratings.
All four basic models are self-restoring, non-ferrous, hermetically sealed, shock and corrosion resistant, and tamperproof. Thermotech heat detectors are not directionally affected — they can be mounted horizontally or vertically.
Refer to NFPA STANDARD 72 for application requirements, testing and maintenance.
Rate Compensation Technology
The Model 302 operates on the principles of a rate compensation detector. It consists of a high expansion aluminum tube encasing two insulation struts with opposing open contact points. The sensing shell and expansion struts have different coefficients of expansion.
Slow temperature rise: Heat penetrates inner struts — both expand until rated temperature (135°F/194°F) when silver contact points close, initiating alarm.
Rapid temperature rise: Heat doesn't penetrate inner strut — rapid shell lengthening brings struts together at a lower level, compensating for thermal lag. When air temperature drops below rated level, shell contracts, contacts open, and detector resets automatically.
Special Considerations
| Rating | Max Ceiling Temp |
|---|---|
| 135°F | 100°F max |
| 194°F | 150°F max |
Electrical Rating
| Voltage | Current |
|---|---|
| 6–125 VAC | 5 amps |
| 6–25 VDC | 1 amp |
| 125 VDC | 0.5 amp |
Never install in direct sunlight. Refer to NFPA STANDARD 72.
What Are You Looking For?
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American-Made. Regionally Trusted.
For decades, Thermotech has been the manufacturer of choice for fire protection professionals who demand reliability in every installation.
Made in the USA
Domestically manufactured in Ogden, Utah to rigorous quality standards. Every Model 302 unit is built to meet UL and Factory Mutual specifications.
Authorized Dealer Network
Find certified dealers and installation partners near you. Our network spans the US and extends internationally through trusted distribution partners.
Parts & Support
Full parts availability and technical support for every product line. Our team is ready to assist with specifications, installation guidance, and compliance questions.
Since 1970s
Detectors Built to Last.
Whether you're specifying for a new installation, replacing existing units, or sourcing for a large project, Thermotech has the inventory and expertise to support your needs.
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Our team in Ogden, Utah is here to help with specifications, pricing, and distribution.