Universal Gas Safety Flame Sensor (Pilot Thermocouple Kit)
Gas safety is the single most important aspect of any heating appliance. The Hongtai Gas Safety Flame Sensor (technically known as a Pilot Thermocouple) is the industry-standard “Flame Failure Device” used to prevent dangerous gas leaks. Whether you are repairing a cozy gas fireplace, a commercial deep fryer, or a residential water heater, this sensor is the guardian that ensures the main gas valve only opens when a pilot flame is present.
Designed as a Universal thermocouple kit, this product is engineered to solve the “Pilot won’t stay lit” problem. It is a direct replacement for 95% of OEM sensors found in brands like Honeywell, Robertshaw, White-Rodgers, and SIT. By bundling multiple adapter fittings, one single kit can service hundreds of different appliance models, making it an essential inventory item for HVAC technicians and plumbers.
1. How It Works: The Physics of Safety
This is not just a wire; it is a millivolt generator based on the Seebeck Effect.
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Heating: The pilot flame heats the tip of the Gas fireplace thermocouple.
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Generation: The temperature difference between the hot tip and the cold junction creates a small electrical voltage (typically 20mV to 30mV).
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Action: This electricity travels down the copper capillary tube to the gas valve’s electromagnet.
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Safety: The magnetic force holds the spring-loaded gas valve open. If the flame blows out, the sensor cools down, voltage drops to zero, and the valve snaps shut, cutting off the gas supply instantly.
2. Key Features of the Universal Kit
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Multi-Fit Adapters: We include a comprehensive set of fittings (Split nuts, Snap-fit clips, and Threaded adapters) to ensure this Pilot light sensor fits into various pilot burner assemblies.
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High-Temperature Tip: The sensing tip is constructed from a specialized heavy-duty alloy designed to withstand constant flame impingement at temperatures exceeding 750°C without burning through or oxidizing.
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Flexible Installation: The copper tubing is annealed for extra flexibility, allowing it to be routed through tight bends in compact fireplace inserts without kinking or breaking.
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Standard Output: Calibrated to generate a strong 30mV open-circuit voltage, ensuring reliable operation even with aging gas valves.
3. Application Scenarios
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Gas Fireplaces & Log Sets: The most common failure point in gas fireplaces. If your pilot lights but goes out as soon as you release the knob, you need a new Gas fireplace thermocouple.
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Gas Water Heaters: Compatible with older style standing-pilot water heaters.
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Gas Furnaces: Used in pilot-ignition furnaces (not for modern Hot Surface Igniter systems).
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Commercial Kitchens: Essential for commercial griddles, fryers, and ovens.
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Patio Heaters: The tip-over safety switch in patio heaters is wired in series with this thermocouple.
4. Technical Specifications
| Parameter | Specification | Technical Note |
| Product Type | Gas Safety Flame Sensor | Thermocouple Type (1-Wire) |
| Standard Lengths | 18″, 24″, 30″, 36″, 48″ | 24″ (600mm) is standard |
| Output Voltage | 20mV – 30mV | Open Circuit Test |
| Internal Resistance | 0.02Ω – 0.05Ω | Low resistance is critical |
| Tip Material | High-Temp Nickel Alloy | Resists oxidation |
| Cold Junction | Split Nut / Coaxial | Standard connection |
| Adapter Kit | Included (M8, M9, M10, 11/32″) | Universal fitment |
| Response Time | < 30 Seconds (Cool down) | Safety requirement |
5. Troubleshooting & Installation Guide
Symptoms of a Bad Sensor:
The pilot flame lights when you hold the button, but the Pilot light sensor fails to keep the valve open when you release the button.
Installation Steps:
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Shut Off Gas: Safety first.
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Remove Old Sensor: Unscrew the connection at the gas valve and unclip it from the pilot bracket.
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Select Adapter: Match the old fitting with one from our Universal thermocouple kit.
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Position Tip: The tip of the new sensor should be immersed in the pilot flame by about 1/2 inch (1 cm). Do not let it touch the metal burner directly.
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Tighten: Screw the connection into the valve “finger tight” plus 1/4 turn with a wrench. Do not overtighten, or you will crush the insulator.
6. Frequently Asked Questions (FAQ)
Q: Is this a Thermocouple or a Thermopile?
A: This is a Thermocouple (it has 1 thin copper tube/wire). If your fireplace sensor looks thicker, has two wires, and generates 750mV to run a wall thermostat, you need a Thermopile (Powerpile). We sell those separately. Do not confuse them; they are not interchangeable.
Q: Why does the new sensor fail quickly?
A: Usually due to overheating. The pilot flame should only touch the top 1/2 inch of the tip. If the flame is “blowing torch” hot or touching the lower part of the probe, it will destroy the internal junction. Adjust your pilot flame size.
Need other gas parts?
Check out our Industrial Thermocouples for heavy-duty applications. For bulk OEM orders of gas safety valves, Contact Our Engineering Team.
