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Al’s Plumbing, Heating & A/C in Plano, Texas provides maintenance & repairs for all brands of Central A/C, Gas & Electric Furnace, and Heat Pumps.  Additionally we sell and install new HVAC Systems from American Standard (same company as Trane), Ameristar (same company as American Standard) and Coleman HVAC (same company as York HVAC).

Al’s also provides full service plumbing maintenance, repairs and replacements for every plumbing component in your home.  Al’s sells and installs Rheem Professional Series gas & electric water heaters, and tankless water heaters.  Al’s is near your home in Plano, Allen, and Frisco.  We service all homes in southern Collin and Denton Counties with no travel charges.

Call Al’s today to discuss any concerns or problems you have with your HVAC System or Plumbing.  We will arrange an appointment at your convenience and offer 24/7 Emergency Service.

photo of furnace control board

Image Source: Pexels.com

A Furnace Control Board Is Quite Similar To Any Printed Circuit Board (shown) Like You Will Find In Any Computer

This Is Part 1 Of A 3 Part Article About; Furnace Control Boards, How To Protect Them From Power Surges, + Other Ways To Minimize The Risk Of Early failure. 

  • Part 1: Furnace Control Board – Purpose And Functions
  • Part 2: Furnace Control Board – Power Surges Protection
  • Part 3: Furnace Control Board – Ways To Help Minimize Early Failure.

For Part 2 Of This Article Click Here: AlsPlumbing Furnace Control Board – Part 2

Al’s Plumbing, Heating & A/C in Plano, Texas provides maintenance and repairs for all brands of Central A/C, Furnace, & Heat Pump.  Additionally, Al’s sells & installs new HVAC Systems from American Standard (same company as Trane), Ameristar (same company as American Standard) and Coleman HVAC (same company as York HVAC).   Al’s also provides repairs & replacements for every plumbing component in your home.

Call Al’s today to discuss any concerns or problems you are having with your HVAC System or Plumbing.  We can arrange an appointment to meet your schedule.  We also provide 24/ Emergency Service.

A Furnace’s Control Board Is Its Brain

high efficiency gas furnace with two white pipes visible

Image Source: DreamsTime

A furnace control board is similar to a computer circuit board.  It’s the furnace’s brain.  It operates all functions, in the order they are to occur.  It controls everything the furnace does each heating cycle.  Because they are a sophisticated electronic, they can fail & must be replaced.  There are reasons why many fail early.

Replacing a furnace control board costs $600-$1,000, so it’s worth the effort to do what you can to ensure yours lasts as long as possible.  Within this 3-Part Article you can learn the more common causes of furnace and how to extend the life of yours.

The Control Board & The Heating Cycle

nest thermostat in heating mode

Image Source: ShutterStock

Shown: Nest Smart Thermostat

The Heating Cycle Begins When The Thermostat Calls For Heat

  • The Thermostat calls for heat.
  • The Induced Draft / Draft-Inducer Motor turns on upon receiving a message from the control board.  This fan removes exhaust gases to outdoors.
  • The Pressure Switch senses the drop in pressure (caused by the Induced Draft Motor).  It tells the control board the pressure dropped.
  • The Pressure Switch is a safety mechanism.  It ensures the furnace’s exhaust is being removed to outdoors before the burners are ignighted.
  • The Hot-Surface Igniter receives a message from the board and begins to heat up.
  • The Gas Valve (light blue knob) gets a message from the board to release gas to the burners.
  • The Burners ignite.  They don’t receive a message from the board to ignite, rather they ignite as gas is released to them.
  • The Flame Sensor senses the flame and tells the control board a flame exists.  With that message, the board continues to allow gas to the burners.
  • If the Flame Sensor does not sense flames, it tells the control board.  The control board turns the gas valve off to prevent a gas explosion.  The control board will also shut down the furnace.
  • The Flame Sensor is a safety mechanism.  It ensures a flame is burning while gas is being released.
  • The (Flame) Rollout Switches monitor the burner’s flames to ensure the flame is only where it belongs.   If a RollOut switch senses an irregular or oversized flame, it notifies the control board.  The control board shuts the furnace down to avoid a possible fire.
  • Flame Rollout Switches are a safety mechanism.  They cause the furnace to shut down if they sense flames are outside the correct area.  If flames were allowed to burn outside that area, they would likely cause a furnace fire.

NOTE:  Often times, owners discover they have a cracked heat-exchanger during a “no heat” service call.  Their furnace shut down because air (coming through the crack in the heat exchanger) was blowing flames outside their designated area.  The rollout switches sent a message to the control board, and it shut the furnace down.

  • The Limit Switch (see round white label) tells the control board the furnace is warm enough to turn the blower fan on.  It also monitors if the furnace is getting too hot.  It it determines that, it tells the control board.  The control board shuts gas off to burners, then often shuts the entire furnace down until it’s serviced.

The control board turns the Blower Fan on.  The fan moves air through the furnace, removing the heat and sending it into the house.

  • The Thermostat determines the home’s temperature matches its setting and tells the control board. The control board shuts off gas to the burners, then the induced draft motor, and finally the blower fan motor.  The heating cycle is complete.

The Control Board Also Helps Diagnose Furnace Problems.  

If a small indicator light on your furnace’s circuit board is flashing, it’s helping diagnose the furnace’s problem.  The flashing light is usually visible through a tiny window on the furnace door.

Click Below To See A Blinking Computer Control Board + An Index Telling What Each Blinking Pattern Means:

 DenGarden.com Blinking Furnace Control Board

The number of blinks between pauses represents a number corresponding to the furnace’s problem.  This number corresponds to a chart located somewhere on the furnace (usually on the removable doors on the front).

Example: “blink…blink…pause…blink…blink…pause…” would represent Item #2 on the chart.  The chart may say “Ignition Failure” or “Pressure Switch Open.”

The Control Board Helps Protect Your Safety  

The control board monitors each of the furnace’s operation for safe operation.  If it determines something is wrong, it will shut the furnace down to protect you.

Example:  If the burner igniter fails, the furnace’s burners cannot light.  When heat is needed, the control board opens the gas valve for the burners, then awaits a message from the flame sensor confirming that a flame exists.  If it does not get that message, it shuts the gas valve off to prevent a gas explosion.  It will also shut the furnace down until the igniter has been replaced.

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Al’s Plumbing, Heating & A/C in Plano, Texas provides maintenance & repairs for all brands of Central A/C, Gas & Electric Furnace, and Heat Pumps.  Additionally we sell and install new HVAC Systems from American Standard (same company as Trane), Ameristar (same company as American Standard) and Coleman HVAC (same company as York HVAC).

Al’s also provides full service plumbing maintenance, repairs and replacements for every plumbing component in your home.  Al’s sells and installs Rheem Professional Series gas & electric water heaters, and tankless water heaters.  Al’s is near your home in Rowlette, Murphy, and Wylie.  We service all homes in southern Collin and Denton Counties with no travel charges.

Call Al’s today to discuss any concerns or problems you have with your HVAC System or Plumbing.  We will arrange an appointment at your convenience and offer 24/7 Emergency Service.