Gas fireplace ignition systems determine how a unit lights, how it stays lit, how it behaves during power outages, and how its safety systems function.
While homeowners often focus on flame appearance or BTU output, installers and service professionals know that ignition type defines reliability, diagnostics, code compliance, and long-term service complexity.
This article explains the three dominant gas fireplace ignition systems in use today:
We’ll break down how each system works electrically and mechanically, how voltage is generated and used, how safety circuits are maintained, and where each system is best suited in real-world installations.
Ignition systems are not interchangeable. They affect:
From a service standpoint, ignition type dictates what fails, how it fails, and how it is tested.
A standing pilot system uses a continuously burning pilot flame to ignite the main burner and maintain gas valve operation.
Key components:
The pilot flame heats the thermocouple. When heated, the thermocouple generates a small DC voltage (typically 20–30 millivolts).
This voltage keeps the safety valve open. If the pilot flame goes out, voltage drops and gas flow stops.
This is a purely thermal-to-electrical safety loop.
No electronics are involved.
Standing pilot systems are mechanically simple but often flagged by local energy efficiency standards.
They remain common in older installations and some specialty off-grid applications like the Carol Rose Outdoor Linear Fire Pit (Manual Control models).
Millivolt systems expand on the standing pilot concept by using a thermopile instead of a thermocouple.
The pilot flame heats the thermopile, which generates enough voltage to power:
Unlike standing pilot systems, millivolt systems can operate the main burner circuit without manual valve engagement.
The system is self-powered.
Loss of pilot flame collapses voltage and shuts the system down.
Safety remains flame-based: Flame failure = voltage loss = gas shutoff. No electronic control board is required.
Millivolt systems are often preferred in remote locations or cold climates with outage risk.
Thermopile degradation is the most common service issue.
IPI systems eliminate the continuous pilot flame. Instead, the pilot ignites only when heat is called for.
Key components:
When a call for heat occurs, the control module sends a spark to the pilot.
Once the pilot flame is established, the flame sensor confirms ignition, and the main burner opens. When heat demand stops, the pilot extinguishes.
IPI systems are electronically managed.
Safety relies on flame rectification:
If the flame signal is lost, gas shuts off immediately.
IPI systems dominate modern installations. Service technicians must be comfortable with microamp flame sensing, board diagnostics, and wiring integrity testing.
Battery backup typically powers ignition and valve only, not accessories.
| System Type | Voltage Source | Typical Output | External Power |
|---|---|---|---|
| Standing Pilot | Thermocouple | 20–30 mV | No |
| Millivolt | Thermopile | 250–750 mV | No |
| IPI | Control Board | Regulated DC | Yes |
Standing Pilot
Check pilot flame quality, test thermocouple millivolts, and inspect mechanical valve.
Millivolt
Measure thermopile output under load, check switch resistance, and verify pilot flame engulfment.
IPI
Verify power supply, check grounding, measure flame rectification microamps, inspect wiring harnesses, and test control module logic.
Each system requires different test equipment and procedures.
From a technical standpoint:
There is no universally “best” system. The correct choice depends on site conditions, power reliability, code environment, and client priorities.
Gas fireplace ignition systems differ fundamentally in how they generate and use electrical energy.
Understanding voltage generation, flame sensing logic, and failure modes is essential for safe installation, accurate diagnostics, and long-term reliability.
For installers and inspectors, ignition type is not a feature — it is the foundation of the entire system.
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