Description
Fixed Temperature Duct Limit Controls
The Firestat Fixed Temperature Duct Limit Switch is a UL Recognized manual-reset safety control designed to shut down HVAC equipment when duct temperatures exceed a factory preset temperature. Available in 125°F, 165°F, and 200°F setpoints, these controls are ideal for commercial HVAC systems, apartment buildings, air handlers, and OEM equipment requiring a non-adjustable temperature limit switch.
Designed for applications where a predetermined trip temperature is required, Fixed Duct Limit Controls deliver consistent, repeatable performance without the need for field adjustment. A helix bi-metal element senses a rapid temperature change. When the temperature changes the bi-metal expands and triggers a snap action SPST switch and opens a circuit. Once the control trips, it remains open until the overheating condition has been corrected and the manual reset button is pressed.
Senasys takes pride in quality control and reliable operation of our components. Every switch is individually 100% tested before it leaves the plant.
Key Features
- Temperature Settings: 125°F, 165°F, or 200°F (Factory Preset)
- Manual reset safety operation
- Precision helix bi-metal sensing element
- 5″ Insertion Element. Other lengths available, contact us.
- Fast, accurate response to rising duct temperatures
- Available with multiple sensing element lengths
- Rugged construction for long service life
- Meets requirements in Section 907.3.1. of the North Carolina Mechanical Building Code.
- Voltage: 120-240 VAC
- UL Listed
- Proudly manufactured in the USA
Typical Applications
Firestat Fixed Temperature Duct Limit Controls are commonly installed in:
How It Works
The sensing element continuously monitors the temperature inside the duct. When the factory-calibrated temperature is reached, the control opens the electrical circuit to shut down the heating equipment or associated control system. This helps prevent overheating, protects valuable HVAC equipment, and reduces the potential for fire hazards.
Because the control features a manual reset, it cannot automatically restart after an over-temperature event. An operator must first identify and correct the cause of the overheating condition before restoring the system to service, providing an additional layer of equipment protection.
Product Specifications
| Specification | Value |
| Temperature Setpoints | 125°F (52°C) , 165°F (74°C) or 200°F (93°C) |
| Reset | Manual |
| Contact Type | SPST |
| Action | Open on Temperature Rise |
| Voltage | 120-240 VAC |
| Probe Lengths | 5″ |
| Sensor | Helix Bi-Metal |
| Maximum Probe Temperature | 350°F |
| Enclosure Temperature | -40°F to 190°F |
| Country of Origin | USA |
| Certification | UL Recognized |
Adjustable vs. Fixed Duct High Limit Controls
| Adjustable Model | Fixed Model |
| Adjustable 100-250°F | Factory preset |
| Best for field service | Best for OEM |
| Multiple probe lengths | Standard 5″ probe |
| Custom temperature settings | Standard Temperatures |
| Learn More | Learn More |
Why choose a Fixed Temperature Duct Limit Switch?
A fixed-temperature model is ideal when:
- Building codes require a predetermined trip point
- Consistent activation temperature is important
- Equipment manufacturers specify a fixed limit
- Unauthorized adjustment should be prevented
- OEM production requires standardized components
If an adjustable model would be better suited for your application, learn more here.
Frequently Asked Questions
Here’s a list of commonly asked questions. Visit our FAQ page for more information.
- Why choose fixed instead of adjustable?
- Fixed duct high limit controls are a great solution for OEM applications to avoid user adjustment.
- Which fixed temperature should I order?
- That depends on the application requirements. Contact our technical support team to discuss.
- Can I order custom temperatures?
- Yes, please contact our technical support with more information.
- Which probe length should I choose?
- Probe length is dependent on the size of the air duct. Learn more here.
- Can I order custom probe lengths?
- Yes, please contact our technical support with more information.
- Is this UL Recognized?
- Yes.
- Does this replace older Firestat models?
- Yes. Our fixed duct high limit controls cross reference to part numbers 4PU53, 4PU54 and 4PU55.
- Does it require manual reset after activation?
- Yes. Learn more about how these controls work here.
Need OEM pricing or a custom fixed temperature?
Contact our technical support team for custom setpoints, private labeling, and volume pricing.
Prefer to work through a distributor?
Firestat duct high limit controls are trusted by contractors, manufacturers, distributors and maintenance teams across North America. If you prefer working with a distributor, visit one of our partner websites here.
Reviews
There are no reviews yet.