How a Pilot Light Works
Most Pilot Lights consist of 3 parts. The Pilot Hood:
Note: many pilot assemblies look different but all function in the same way.
This is where the flame comes out, which will usually shoot out in 2 or 3 directions (notice in this example the pilot hood is bent so that the flame shoots out 3 directions). Once lit, one part of the flame will engulf the thermocouple sensor:
When heated, this sensor automatically creates a small amount of voltage (20-30 milivolts which is 1/500 of a volt). This small amount of electricity is sent to the main control valve (the same control valve that you use to light your pilot) and is just enough power to signal the valve to keep releasing gas to the pilot. This is why you keep the pilot knob held in when you first light the pilot but after 30 seconds or so, the pilot stays lit on its own.
If we look at the picture, on the opposite side of the pilot hood is another sensor called the thermopile:
Your pilot assembly may or may not have this. One way to tell this is that If your fireplace normally turns on from a wall switch or remote control, you will have a thermopile sensor. If you turn your fireplace on by reaching into the fireplace and turning a knob, you may not.
Basically, the thermopile sensor is the same as the thermocouple sensor, except its larger. And because it is larger, it creates a larger amount of electricity ( about 300-500 milivolts or 1/2 of a volt). Most of the time, this sensor only controls the main burner flame. But if you do not have a thermocouple, this will control the pilot flame as well.
Here is a short video that explains the thermocouple and thermopile:
November 13, 2012
I have a DVT6-CMNS Superior fire place. The pilot flame barely reaches the thermocouple therefore I suspect that is causing its failure to remain lit. Is the hood removable for cleaning and if not how do I go about cleaning. Also my tank is about a third full so is there any other reason for such a short flame. The flame is about the same for all three exit ports on the hood. Can you help. Thank you Hank C
November 15, 2012
Hi Hank,
I would recommend replacing the pilot assembly rather than cleaning it.
Once the metal in the hood and orifice deteriorate, you can clean it with a wire brush, but it will get dirty again rather quickly. Cleaning it would be a temporary fix. Replacing it is more permanent.
Superior is owned by Lennox Hearth Products. I would go to their website and locate a dealer near you. You can purchase a new pilot assembly from them.
November 30, 2012
Hello,
My pilot light would not stay light so my husband clipped the I think it’s called the pilot tube thinking he was clipping the thermocouple, the other metal tube (not the thermopile). Do you know where I could find this part?
Thanks,
Tiana
December 1, 2012
It would depend on what type (brand) of control valve you have. Each one has a different style fitting that will screw onto the pilot assembly. Since you have to change it anyway, I would take it out and bring it in to a local fireplace shop or HVAC company and they should be able to match it. Pilot tubes are usually around $8-$10. You can use the “Find Certified Technicians” section on the top of the page to find one near you.
September 9, 2013
I can see the blue light is lit in my fireplace but when I flip the wall switch, it doesn’t turn on. For some reason, the glass is cloudy–any idea what the problem might be?
September 9, 2013
Start here: Main Burner Troubleshooting
Start with diagnosing your wall switch.
As for the cloudy glass, that is a calcium deposit that can be cleaned off. See the How to Clean Your Fireplace Glass Section
May 1, 2015
You most likely have a hole or crack in your pilot tube. This part would need to be replaced.