Thermocouples consist of a single pair of dissimilar metals and are typically used for direct temperature measurement and safety controls. In contrast, thermopiles are made up of multiple thermocouples connected in a series, resulting in higher sensitivity and voltage output.
The main difference between Thermocouple and Thermopile is their method of measurement. The thermocouple is a thermoelectric instrument, while the thermopile is an instrument that modifies thermal energy into electrical output.
This piece of equipment tells a technician if there is sufficient gas pressure to supply the fireplace. Problems that occur with low pressure include low flame, sooting, and outages of pilot and burner.
No. If the thermocouple is bad, the system sees the failure as a pilot light gone out, and shuts off the gas.
Technically it has a thermocouple and a thermopile. The thermocouple is a pilot safety which shuts the unit down if the pilot goes out. The thermopile generates all the power required to operate the gas valve (< 1 volt).
They are not interchangeable with each other although they are similar, they do two different things in gas-fired systems.
Common Signs of a Failing Thermocouple
Here are some common indicators: Difficulty Lighting the Fireplace: If you struggle to light your fireplace, or if it takes several tries to keep the pilot lit, it could suggest that the thermocouple is not sensing the flame correctly and is failing to keep the gas supply open.
The Pilot Lights But Won't Stay Lit
If the flame lights and goes out when you release the gas control knob after holding it in for the recommended 20 to 30 seconds, that's the sign of a thermocouple malfunction.
Due to the function of your thermocouple and thermopile, it's only logical that they will build up carbon deposits from burning all the time. This build-up can very well limit their effectiveness. Although it's cheap to replace both probes, it's far cheaper to clean them first.
If your pilot is lit and the fireplace isn't igniting when you push the button or flip the switch, the igniter may be dirty or defective. Clear away any dirt or debris that may be in the way between the igniter and thermocouple or thermopile.
As long as they are used correctly and maintained properly, thermopiles can last for years or even decades and remain in good working condition.
Professional Furnace Thermocouple Replacement
For those who prefer not to attempt a DIY repair, hiring an HVAC technician is a safer option. The cost for a professional furnace thermocouple replacement usually ranges from $80 to $150, depending on your location and the specific HVAC company.
Once you have replaced the thermocouple, turn on the furnace and check to see if the pilot light stays lit. If your pilot light doesn't stay lit, it may be due to something blocking the thermocouple. You can try cleaning or replacing it, but if that doesn't work, you may need to call a professional.
Thermopiles can be constructed with a single thermocouple pair, composed of two thermocouple junctions, or multiple thermocouple pairs.
Universal Thermopile Works With Most Gas Fireplaces – Fire-Parts.com.
The thermocouple is what controls the unit's main gas valve. If the pilot is out or the thermocouple doesn't detect the heat from the pilot flame, the gas valve won't open and the unit won't ever turn on. Although the thermocouple is fairly sensitive, it needs to directly touch the pilot flame to work properly.
Once all that is complete, use a thin strip of emery cloth or 320 grit sandpaper to polish the thermocouple & remove soot. When the probe has become semi-shiny, your work is done.
Clean the thermocouple - using the emery cloth sandpaper, sand the ends of the thermocouple and then give it a finishing touch with the lint-free cloth. Hopefully, you can get to the ends of the thermocouple without having to detach it from the assembly, but you may have to do that.
The thermocouple is a safety device designed to shut off the gas valve if the pilot light goes out. Although, if your thermocouple is old, worn, damaged, wrongly positioned, or malfunctioning, it could have wrongly shut off the gas valve and prevented your pilot light from staying lit.
The best way to verify that you need a new thermocouple is to see if your pilot light is lit. If the pilot light can't hold ignition, that means either a problem with the gas supply or, more likely, the need for thermocouple replacement.
You can clean the thermopile easily by shutting off the gas supply and using a small stainless-steel brush and fine-grit sandpaper. Use your multimeter again to get another reading. If it's still low, then you'll need to replace the thermopile.
Common Gas Fireplace Issues and Repair Options
Relighting is typically inexpensive unless the thermocouple requires replacement, which can range between $120 and $300.