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How does a single wire flame sensor work?
A furnace flame sensor works by detecting the presence of a flame within the furnace. The sensor is a short length of thin metallic rod that creates a small current of electricity in order to confirm there is fire burning within the furnace.
How do you test a single wire flame sensor?
You can measure flame signal by putting your meter (capable of measuring micro amps) in line between the flame sensor and the wire that was connected to it (see picture). If you are reading anything under 5 uA (micro amps), it is likely that your flame sensor is dirty.
How does a thermocouple flame sensor work?
Thermocouples are used on standing pilot furnaces that have pilot lights. The thermocouple sits near the pilot light and gauges whether it’s working properly, while the flame sensor detects that the burners are lit once they start to emit gas and the igniters light them up.
How does flame detection electrode work?
Flame rods work due to the ionization / rectification process to complete a circuit. When the flame rod is energized the current produces a positive charge that attracts the negative ions in the flame. This produces the direct current signal that is used to indicate the presence of flame.
How do you test a flame current?
Technicians can measure this flame current by placing a meter that measures DC microamps in series with the flame rod. The ignition controller is programed to look for this DC current and make a “go – no – go” decision based on the strength of this current.
How do you know if a flame sensor is bad?
Signs of a bad furnace flame sensor are:
- The furnace lights but then shuts down after a few seconds (short cycles)
- The porcelain on the flame sensor is cracked.
- The flame sensor is sooty or corroded.
How is a thermocouple connected to a gas flame sensor?
Some gas fired heating equipment relies on an electronic ignition to ignite the flame. Those devices generally will not use a thermocouple. If a thermocouple is used you’ll see a small copper tube (or in some devices an electrical wire) connecting the flame sensor to the valve.
Where is the thermocouple located on a gas fired water heater?
Remove access covers as needed: on a gas fired water heater you will need to remove the manifold door at the heater bottom in order to access the end of the thermocouple that mounts on and monitors the pilot flame. On a gas-fired furnace you may need to remove first the furnace cover and then a flame shield. Keep any mounting screws for re-use.
How does a thermocouple respond to temperature change?
A thermocouple is an electrical device that responds to temperature change by a change in voltage output. A thermocouple works to produce a small electrical voltage output by connecting two dissimilar metals or two wires forming a measurement junction at the sensor tip of the device.
Can a bad thermocouple cause a gas furnace to stop working?
A bad thermocouple itself can prevent a gas furnace or boiler from working – if you can light the flame at the pilot manually but then the flame goes out when you release the manual gas feed valve, the thermocouple is probably bad. What’s the Difference Between a Thermopile and a Thermocouple?