footer-logo

photo of brightly colored fall leaves

It’s time for your Fall Furnace Tune Up!  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 Profressional Series gas & electric water heaters, and tankless water heaters.

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.

Fall Gas Furnace Tune Up — Why It’s Needed

  • A fall Furnace Tune-Up checks to ensure the furnace is heating properly and running safely. 
  • The Tune Up checks to see if cleaning of any component is needed (cleaning is sometimes an extra charge).  Cleaning dirty components ensures the furnace is heating at its peak ability & efficiency.
  • By far the most importance, a Furnace Tune Up checks the furnace to ensure it’s operating safely.

photo of standard efficiency gas furnace in attic photo of high efficiency gas furnace in attic

Shown: 80% Standard-Efficiency Gas Furnace    (Attic Installations)      95% High-Efficiency Gas Furnace

A Gas Furnace Can Heat While Operating Unsafely

Safety Monitoring Devices alert the furnace if something is wrong.  They operate during each heating cycle, checking for safe operation.  These devices can fail and the furnace won’t necessarily stop working.  This is discussed in detail later within this article.

Of Most Importance:

A furnace cannot determine if its heat-exchanger is cracked.  It will continue to operate and make heat.  A cracked heat-exchanger puts your safety at risk of carbon monoxide poisoning.  The burners create heat & exhaust gasses that pass inside the heat-exchanger.  While the burners are ignited, the furnace blower fan moves your home’s indoor-air along the outside of the heat-exchanger.  If the heat-exchanger is cracked, exhaust gases can mix with the home’s indoor air.  This is discussed in detail later within this article.

Shown: Gas Furnace Heat-Exchanger Diagram.

  • Combustion Gases (red arrows) flow through the inside of the heat-exchanger and are vented outdoors through the furnace’s flue pipe.
  • The blower fan moves air along the outside of the exchanger (cream colored arrows).

 

Gas Furnaces Include These Built-In Safety Features For Your Protection

Though deceiving in appearance, a gas furnace is quite sophisticated.   Using a computer type circuit-board (HVAC Term: Furnace Control Board) the furnace goes through several steps during each heating cycling.  In addition to creating heat, the furnace monitors for correct & safe operation the entire time it’s running.

All Furnace Safety Monitoring Devices Are Inspected & Tested During A Furnace Tune Up

  • Control Board:  Monitoring Furnace To Ensure It’s Working Correctly & Safely.  What happens if the control board isn’t working properly?

photo of furnace control board installed in furance

Shown: Furnace Control Board

If the control board gets a message something isn’t working correctly & safely, the control board shuts the furnace down.

This stops the the furnace from; creating a gas explosion, catching on fire, or allowing carbon monoxide into the home

(except with a heat-exchanger crack).

 

  • Burners’ Flames — Are They Ignited?  What the furnace does if burners did not light.

photo of a furnace flame sensor

Shown Above:  Flame Sensor (circled in red) checks to ensurese burners are ignited.

If the burners don’t ignite, the Flame Sensor tells the furnace control board, and it shuts the gas off & shuts down to avoid a gas explosion. 

photo of gas furnace burners operating properly

Shown: Property Ignited & Operating Burners

 

  • Burner’s Flames — Are They Only Where They Are Supposed To Be?  What if the burners’ flames are outside their correct location.

photo of flame rollout in a furnace.

Shown: Furnace burners’ flames outside their correct & safe location.  This can cause a furnace fire.

photo of furnace flame rollout switch with arrow point toward it

Shown: Flame RollOut Switch (arrow points to it).  Detects if burner’s flames are outside their correct area.

The Flame RollOut Switch tells the furnace if flames out outside their correct area.  The furnace shuts down to avoid a fire. 

 

  • Burners’ Flames — Is The Furnace Getting Too Hot?  What the furnace does if it’s too hot.

photo of gas furnace limit switch circled in green

Shown: Limit Switch (circled in green).  Monitors furnace temperature to ensure it’s not getting too hot.

If furnace is too hot, the Limit Switch tells furnace and it shuts down to avoid a furnace fire.

 

  • Are Exhaust Gases Being Vented Outdoors?  What the furnace does if they are not.

photo and labels show a furnace's pressure switch and draft inducer motor

Shown With Red Arrows:  The Inducer Motor moves exhaust gases outdoors.

And Pressure Switch checks to be sure inducer motor is working.

If Pressure Switch detects the flue gases are not being vented outside, it tells the furnace and it shuts down to avoid carbon monoxide poisoning. 

 

During A Furnace Tune Up, Heat-Exchanger Is Examined For Crack(s) 

During A Furnace Tune Up, The Technician Visually Inspects The Heat Exchanger For Cracks

PLUS

Performs A Combustion-Gases Analysis.  This analysis can also detect a cracked heat-exchanger.

photo with words cracked heat exchanger

photo of cracked furnace heat exchanger  photo of cracked furnace heat exchanger photo of badly rusted furnace heat exchanger

Shown: Three Severely Cracked Heat Exchangers. +  A Very Dangerous Furnace With A Heat-Exchanger Nearly Destroyed By Rust.

 

How An Exhaust-Gases Test Can Reveal A Cracked Heat-Exchanger

photo man drilling hole in furnace vent pipe photo of flue gases testing hole in pvc furnace vent pipe 

SHOWN: Holes Are Drilled Into Furnace Exhaust-Vent To Insert The Exhaust Gases Tester’s Prob (Probe Shown Is Sitting Along The Top Of The Yellow Tester).

What A Exhaust-Gases Analysis Checks

A Combustion-Gases Analysis checks for: carbon-monoxide, oxygen, and carbon-dioxide levels in the furnace’s exhaust.   These readings have normal ranges.  If any of these 3 gases is out of normal range, something is wrong with the furnace and it’s not operating correctly (and possibly not safely).

A Prime Example: If the heat-exchanger is cracked, some of the home’s indoor-air is forced into the combustion-chamber while the blower fan is running. .  If this occurs, an Exhaust Gases Analysis will show too much oxygen.  This alerts the Furnace Tech that the heat-exchanger may be cracked.  Further inspection of the heat-exchanger is required.

NOTE:  This Analysis also indicates when the heat-exchanger is NOT cracked.

NOTE: When oxygen is being forced into the combustion-chamber, it will distort the burners’ flames + change their color from nearly all blue to lots of yellow.

photo of a blue and a yellow fire flame

Shown: Blue Furnace Burner Flames Versus Yellow

1. This Video Shows Furnace Burners’ Flames Changing From Mostly Blue To Lots Of Yellow Once The Blower Fan Turns On:  

YouTube Video — Burner Flames Color Changes & Distortions Due To Cracked Heat Exchanger

Note:  You also see the flames becoming distorted due to air entering the combustion-chamber through the cracked heat-exchanger.

 

2. This Video Shows Using Combustion-Gases Analyzer To Test For A Cracked Heat-Exchanger. 

 YouTube Combustion-Gases Testing / Analysis

 

Want To Learn More About A Cracked Heat-Exchanger And What To Do If You Are Told You Have One?  Click

AlsPlumbing.com Signs You Have A Cracked Heat Exchanger

 

Why A Heat-Exchanger Cracks

Metal expands when heated.  Metal contracts as it cools.  This recurring expansion & contraction is part of a normal furnace heating cycle. All heat-exchangers eventually fail due to metal fatigue.  There is no way to determine how long a heat-exchanger will last, as many factors come into play.  The largest factor is typically how much the furnace gets used.  One home may have the heat set to 60 during the day (while owners are at work) while another home is always occupied and the heat is kept at 75 all the time.

A cracked heat-exchanger is not the only reason why an old furnace needs replaced.  The heat-exchanger can be ok, but other expensive components (such as the control board) can fail.  Replacing expensive components on an old furnace is often not wise, due to the age of all the components.  After replacing an expensive component in an old furnace, the likelihood that another expensive component can fail later is a key factor in the repair or replace decision.

One Definition Of “End Of Life” For A Furnace:  If the furnace is older than 2/3 of its normal lifespan (normal lifespan for a gas furnace in DFW is 15 years), and the cost of repairing it exceeds 1/3 of the cost of replacing it, careful consideration should be given to repairing versus replacing.

NOTE: Heat Exchanger Warranties Are Longer Than For The Rest Of The Furnace.  Example:  American Standard Gas Furnace Heat-Exchanger Warranty Is 20 Years (part only).  The (parts only) warranty on the rest of the furnace is 10 years if the warranty was registered.  If not registered, the (parts only) warranty drops to 5 years.

An older furnace may still have its heat-exchanger under warranty.  If this is the case, replacing the heat exchanger may be a viable option (it depends on the installation labor charge).  Furnace warranties are for parts only, the owner must pay the installation charge.

Some factors that can accelerate heat-exchanger failure.  These factors are usually:

  • How much the furnace is used
  • Poor Furnace Maintenance
  • Incorrect Furnace Installation
  • Furnace Design

Steps In A Gas Furnace Tune Up

  • Inspection: A technician inspects the furnace, tests it for proper operation and checks for any problems needing repair.stem from time to time.
  • Cleaning: Clean components (if needed) . A technician can remove any accumulations (additional clean charge may apply).
  • Adjustment: Checking for and correcting loose components plus other minor repairs (if needed).

These Items Are Part Of Typical Furnace Tune Up

  • Check Thermostat
  • Inspect Furnace Control Board and Test For Proper Operation
  • Inspect Gas Supply Line & Gas Valve
  • Verify Proper Burners Ignition
  • Check & Record Temperature Rise
  • Clean Burners & Adjust For Maximum Operating Efficiency
  • Clean The Flame Sensor.  A dirty flame sensor is one of the primary reasons a furnace shuts down.  Often this occurs during peak heating season.
  • Inspect Primary Heat-Exchanger
  • Inspect Secondary Heat-Exchanger (this extracts heat from exhaust gases in a high-efficiency furnace)
  • Inspect & Test Exhaust-Gases Draft Inducer Fan 
  • Safety Check All Controls For Proper Operation
  • Check For Gas Leaks (near furnace)
  • Test For Carbon Monoxide
  • Check Furnace Air Filter
  • Inspect Blower Fan Assembly Operation.  Lubricate & Adjust (if needed)
  • Check & Tighten Electrical Connections
  • Inspect & Clean Furnace Condensate Line (if needed)
  • Exhaust Gases Analysis
  • Inspect Combustion Air Intake & Exhaust Pipes (high-efficiency furnace).   Exhaust pipe only for standard efficiency furnace.

gas furnace 92% efficient

Shown: 2 White PVC Pipes For High-E Furnace.  One pipe brings outside-air in for combustion.  The other removes exhaust gases to outdoors.

gas furnace 80% efficient

Shown: 1 Metal pipe removes exhaust gases on 80% / standard efficiency furnace.  Standard efficiency gas furnaces draw combustion-air from the immediate indoor environment — directly into the furnace at the front.

 

footer-logo

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 Profressional Series gas & electric water heaters, and tankless water heaters.

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.