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Furnace flame sensors: How they work, when to repair or replace, and their cost


A flame sensor is among the so much essential security features of your furnace. This element is answerable for making sure that your furnace doesn’t create a perilous fuel leak or explosion.

Through working out why the furnace flame sensor is an important to the unit’s operation, you’ll be higher ready to acknowledge while a flame sensor is dangerous. Our information will stroll you thru cleansing the sensor and furnace flame sensor alternative.

What’s a flame sensor?

The flame sensor is a security part of a furnace situated at the inner of the burner meeting. It screens and verifies whether or not a flame is burning within the unit.

If the sensor does now not come across an lively flame, then it is going to close the furnace off to steer clear of a possible fuel leak. The furnace flame sensor is helping save you explosions that would happen if fuel have been allowed to proceed to float into the house in addition to carbon monoxide poisoning of the ones inside of the house.

The Facilities for Illness Regulate and Prevention document that no less than 430 other folks die within the U.S. from unintentional carbon monoxide poisoning each and every yr and a few 50,000 discuss with the emergency room as a result of the fuel. At the same time as house furnaces are chargeable for just a small proportion of those instances, it’s a the best reminder to put in a carbon monoxide detector on each and every degree of your house.

Flame sensor vs. thermocouple

A flame sensor and thermocouple are ceaselessly known as the similar or interchangeable portions, however that’s now not the case. At the same time as they each function a security function at the furnace, you would have to understand which you’ve gotten so as to exchange or restore the element.

A thermocouple is frequently discovered on older style fuel furnaces with a status pilot. It has a small flame that burns steadily, maintaining the highest of the thermocouple at a top temperature. If the flame is going out and the end of the thermocouple cools, it is going to routinely shuts off the furnace’s fuel valve.

Flame sensors are utilized in up to date furnaces that function by the use of an digital ignition fairly than a status pilot gentle. Those fashions use digital igniters to gentle the fuel. As discussed above, the flame sensors ensure that the burners are running correctly and feature ignited the fuel. If the sensor detects that the burner has failed, it’s going to flip off the fuel.

Furnace flame sensor region

While looking to decide easy methods to discover a flame sensor, you’ll need to dispose of the furnace get entry to duvet to start. Relying at the style of your furnace, you’ll have to take away screws or bolts to unlock the get entry to duvet.

The sensor is situated simply out of doors the burner meeting and seems like a small rod with porcelain surrounding the top that connects to the burner. A few furnace flame sensors are immediately at the same time as others bend at a forty five-level or ninety-level attitude. The sensor leads into the hearth chamber the place the flame burns.

Indicators of a nasty flame sensor

As with all different element for your heating and cooling device, the flame sensor can pass dangerous. In case your furnace stops running correctly, search for caution indicators that your flame sensor has failed:

  • Furnace burners activate however move out after a couple of seconds
  • Soot and different particles is overlaying the top of the sensor (cleansing the flame sensor would possibly restore this factor somewhat than a flame sensor alternative)
  • Tip of flame sensor is black
  • Porcelain/sensor casing is cracked

If a flame sensor alternative is important, it’s a low value restore that you’ll be able to most probably care for your self if you are feeling at ease running with the unit. So much furnace flame sensors value not up to $20, however for those who choose to have a qualified HVAC technician make the restore, you’ll be able to be expecting to pay among $seventy five and $250.

Flame sensor lifespan

In the event you’ve simply changed the sensor or had a brand new furnace put in, you’ll be able to be expecting the flame sensor to remaining for approximately 5 years. The typical lifespan of a furnace is 15 to 30 years, so you’ll be able to look forward to a flame sensor alternative a few times over the process your homeownership. 

To increase the lifespan of the sensor, seasonal furnace upkeep and cleansing the flame sensor is essential. Even though the furnace appears to be running easily, cleansing the sensor each and every yr can save you you from calling for emergency heating products and services in the course of wintry weather.

Furnace flame sensor cleansing

Sooner than you start the flame sensor cleansing procedure, flip the fuel and electrical energy off to the unit. The valve care for at the fuel pipe will will let you prevent the fuel go with the flow and turning off the furnace breaker at your electric field will make sure that all energy is close down.

If the furnace has been operating, wait no less than half-hour sooner than making an attempt those steps:

  1. Find the flame sensor (check with the furnace flame sensor region component above)
  2. Take away the furnace get right of entry to duvet, which would possibly contain freeing screws or bolts
  3. Unfasten/unscrew the flame sensor from the burner meeting
  4. Disconnect the wiring that ends up in the sensor and regulate field
  5. Loosen the screws and eliminate the flame sensor
  6. Use an emery fabric to softly get rid of soot and different particles from the sensor
  7. Reattach the sensor
  8. Reconnect the wiring to the sensor and keep an eye on field
  9. Safe the flame sensor to the burner meeting
  10. Reattach the furnace duvet get right of entry to  

Check the furnace to peer if cleansing the flame sensor used to be the answer you wanted. If the unit turns off and on correctly, a flame sensor alternative will not be important.

Exchange furnace flame sensor

Right through the sensor cleansing procedure, should you uncover the end of the sensor is black or the element is misshapen or damaged whatsoever, exchange slightly than restore the phase. Apply the flame sensor cleansing steps, however set up the brand new sensor as an alternative of cleansing the antique one.

Your furnace will handiest function with a undeniable form of flame sensor. Be sure the element you buy is suitable together with your unit. Test the landlord’s guide for steerage on the kind of sensor you wish to have.

If running with a furnace or coping with the fuel line isn’t inside of your DIY convenience degree, take the protected course and contact an HVAC professional. A furnace expert will check the flame sensor and substitute it if wanted.

To steer clear of being stuck in a state of affairs the place furnace carrier is wanted in an instant, time table regimen inspections. Seasonal upkeep can make stronger your unit in running correctly while you wish to have it so much and increasing the lifespan of the furnace. Discover our most sensible furnace manufacturers if it’s time to switch your unit. 

Updated: October 9, 2021 — 4:03 pm
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