8 Reasons Hot Surface Igniters Fail

How Does a Gas Furnace Work

The Hot Surface Igniter has become an industry standard in gas heating systems in the Sacramento Valley.  To technicians and furnace manufacturers everywhere, the sequence of events that takes place for a gas furnace to start a flame that jets into the tubes of the heat exchanger is like a well-choreographed dance.  Stick around while we talk about an integral part of the sequence to bring heat into a home: the hot surface igniter.

Intro

As the winter season approaches, we are going to be using our gas furnaces more and more.  A lot of those furnaces won’t be lighting up when they’re turned on for the first time this season.  The hot surface igniters that start the flame in a gas furnace often fail.  It’s almost as common as replacing a capacitor in air conditioning systems all over the city every spring.

How They Work

Hot surface igniters are a resistance element made of silicon carbide or silicon nitride.  Anywhere from 80 to 240 volts are applied to the wires attached to the igniter.  A ceramic base insulates the wire connection to the carbide element which looks like the letter M on most applications. Spirals are another shape I see.  Most nitride igniters are formed in the shape of a 1.5-inch flat stick or a 2-inch long cylinder.

When the voltage is applied to the wires, the element starts to glow because of the resistance the carbide creates from one wire to the next.  When it glows long enough, gas is poured over it, and the flame ignites.

Hot Surface Igniters are Resistance Heaters

As mentioned earlier, hot surface ignitors, or HSI’s, are resistance heaters.  The element itself glows orange when the voltage is applied.  How hot that element gets depends on the voltage being applied to it.  A 120-volt HSI will glow at around 2500 degrees Fahrenheit.  Most gas fuels will ignite around 1100 degrees, so 2500 degrees is a little excessive.  A 240-volt igniter burns even hotter.  Several control boards these days are made to support an 80-volt igniter.  This way the carbide breaks down slower, adding life to the system.

Hot Surface Igniters are Better Than a Pilot Light

Before hot surface ignitors and spark ignition was around, we had gas pilot lights that would stay lit burning a 1 to 2-inch flame year-round whether the heat was on or not. When the heat was turned on, the gas valve would flow more gas over the pilot to ignite the burner assembly that carried the flame.

For a pilot to stay lit all year, it could cost up to $150 dollars a year depending on where you are in the US.  Some of you reading this post have pilot lights still going strong on your 35-year-old furnaces!  Although very reliable when needed, and not a truly major expense, it’s not a great use of resources to just let that gas flame just burn all year.

On-Demand Efficiency

You might be okay with a small pilot burning in your furnace all year, but it really freaks out some of our customers.  A lot of people don’t even know that new furnaces these days don’t have pilots anymore.  They come with on-demand ignition components like an HSI.  Meaning the ignitor only comes on when needed and even then, it only comes on for less than a minute at a time.

Hot Surface Igniters are Silicon Carbide

Silicon Carbide is one of the most common components that make up a hot surface igniter.  Not only are these igniters used to light gas furnaces, but they are used for lighting stoves, boilers and other appliances that heat things around your house. Carbide is used as an abrasive, as a cutting tool, and has some automotive applications as well.   The first carbide igniters were actually produced in 1969.  From then until now they have become one the main choices for manufacturers to use as their ignition source.  The other source being spark igniters, which we’ll talk about on another blog post.

How Long Do Hot Surface Igniters Last?

Just like most components on your HVAC system, these parts last about five to ten years.  Yes, you can get lucky and have one last for twenty years, but it’s few and far between.  Different hot surface igniters last longer than others.  The trend over the last five to ten years has been to use the more durable silicon nitride igniters.  They seem to be less brittle, making them better able to stand the test of time.

Why are Hot Surface Igniters Such a Common Replacement Item Each Year?

So why do these silicon carbide igniters break so often?  The fact is, a gas flame pours over these ignitors which applies a lot of damaging heat to them.  The same thing that makes them work also destroys them!

8 Reasons Why Hot Surface Igniters Break Down Prematurely:

1. Brittle HSI’s

Just today as I was called by one of my techs who said they accidentally broke an HSI as they were cleaning the burner assembly on a routine maintenance call.  It happens.  If you took your index finger and thumb and brought them together even somewhat quickly, that would be enough force to break the carbide tip of a hot surface igniter to pieces.

2. Overuse

A furnace that cycles on and off excessively will reduce the lifespan of an HSI.  Making sure the system is properly sized for the house is probably a good idea.  We say it all the time, but an improperly sized unit is going to cause all kinds of problems.  Maybe not in the first year of its life, but long after the contractor who installed it is gone, and not responding to the customer’s phone calls anymore.

3. High Voltage

If an HSI is exposed to higher voltages than it’s supposed to receive, they will surely break sooner than they should.  An 80-volt HSI should have about 80 volts applied to it.  Applying 120 volts to that HSI will cause it break, and sometimes almost immediately.  Having too low of voltage may not let the igniter burn hot enough.

Once, in my early service years, I replaced a 240 ignitor for a package unit with a 120 ignitor.  Not only did the HSI break on the first start-up, but the high voltage backfired to the control board and took it out as well, which put my employer in the position of having to now replace the customer’s control board.  I never did that again…

4. Contamination

Some field experts say that the oils on the hands of technicians will cause the carbide tip to break down earlier than it should.  Other experts say it won’t.  One thing is for sure, the fewer contaminants that touch the surface of this red-hot igniter, the better.  Other contaminants around the house that can get on the hot surface igniter are sheetrock dust, condensation, dirt, rust, and fiberglass.

5. Gas valve pressure

An overfired gas valve will cause the flame to be hotter than it should be.  Any kind of heat is going to break down the HSI naturally.  It’s parts can last longer if you make sure the system is set up properly.

6. Faulty control board

In most cases the ignitor on the furnace is lined up with the flame that shoots into the heat exchanger.  It starts glowing red-hot when the control board tells it to come on.  If the board doesn’t tell the HSI to turn off, it will continue to glow red hot. You’d likely have a faulty board in this case, and that won’t be good for your HSI either.

That hot surface igniter will be energized in about a minute.  Most igniters achieve maximum temperature in less than 15 seconds.  Some ignition sequences can leave the igniter burning for about a minute.  The less the igniter has to be on, the longer the lifespan of the igniter.  Some things can’t be changed on a furnace such as this designed ignition sequence, so sometimes we’re just stuck with what we’re given.

7. Propane gas

Propane is a very viscous gas.  If you were to compare a natural gas furnace to a propane gas furnace after just five years of use, you would see the burner assembly on the propane system looks like it needs to be cleaned more than the natural gas burners.  I’ve seen hot surface ignitors that stand in the stream of a propane flame have the top half of the carbide tip ripped off after just 3 to 5 years.

8. Radiant heat

A heat exchanger that is overheated at shutdown could radiate extra heat on the ignitor to damage it or its ceramic base, especially in closed combustion systems like those Coleman or Intertherm downflow furnaces you find in modular and mobile homes.  A fan cools the heat exchanger once the call for heat has been satisfied.  Making sure the fan stays on for more than 90 seconds might be a way to correct this.

Standing pilot lights are a thing of the past.  Furnaces these days have spark igniters or hot surface igniters.  I don’t know that one is really better than the other.  Hot surface igniters are replaced about every five years.  Spark igniters have their downfalls too, though, which is why the industry hasn’t dedicated itself to one technology or the other.

Thanks so much for stopping by, and we’ll see you on the next blog post.

Heat Pumps vs Gas Furnace

Heat Pumps vs Gas Furnace

As an expert in the HVAC field, people ask me which is better:  heat pumps vs gas furnace?  

This is a question for the ages.  Predominantly, here in the Sacramento Valley, most people have gas furnaces.  This means they have a gas line plumbed from their meter on the side of the house that goes all the way up to the furnace in the attic, or closet or, or garage.  A smaller percentage of people in the Sacramento valley have all-electric heat pumps.  This just means electricity fuels all their heating needs.

So which is better? Let’s Explore Heat Pumps vs Gas Furnace

Well, if you put the two together and feel the heat coming out of the registers on an all-electric heat pump, and then feel the heat coming out of the registers of a gas-fueled furnace, you’ll feel the gas furnace has warmer air coming out of it.  This alone is the major reason people choose gas furnaces over electric heat pumps.  

Let’s assume the air in your house is 65 degrees.  The air coming into the system is 65 degrees.  A gas furnace will heat that air by about 30 to 60 degrees.  I find that temperature difference to be more in the area of 45 to 55 degrees most of the time.   This means you will have anywhere from 95 to 125-degree air coming out of your registers.  In the winter, gas furnaces feel very nice for this reason.  Your house will warm up quickly with warm air like that coming out.

An all-electric heat pump will typically take your 65-degree air and warm it up about 20 degrees.  This will warm up your house, but it will take longer.  A heat pump uses your outdoor condenser too, which is way more expensive to operate than a gas-fueled furnace.  You know how expensive it is to run your AC in the summer right?  Well, it will be equally as expensive, if not more, to run your heat pump in the winter.  You see, the heat pump alone can only heat your house until it’s about 45 degrees outdoor temperature.  When it gets colder than that, there is almost no heat in the outdoor air to convert into heat for your house, so the dreaded “heat strips” will turn on.  The heat strips will dramatically increase your 20-degree difference to 35 to 60 degrees but will take just as much electricity to run as it does the outdoor unit.  This means you will be using summer weather electricity to run the outdoor unit and equally as much electricity to operate those heat strips.  You will warm up, it’s just doubly expensive to operate the heat pump and your heat strips in the winter.

Here in Sacramento County gas furnace are much less expensive to operate.  

If you don’t have natural gas or propane run to your house, then you have no choice, you’ll have to get a heat pump.  But, if you do have gas to your house, I think it’s much wiser to switch to a gas-fueled furnace.  You’ll get warmer air out of it, which feels great in the cold December and January months.  

Feel free to call me anytime to discuss our questions on getting a heat pump or gas furnace for your next furnace replacement.  Our phone number is 916-877-1577 or you can email us.  

Troubleshooting a Furnace Gas Valve

Troubleshooting A Furnace Gas Value

10 Easy Things to Check When Troubleshooting a Furnace Gas Valve

Hey guys, today we’re going to talk about troubleshooting a furnace gas valve.   I wanted to expand on our recent gas furnace troubleshooting series by going into each part of a furnace sequence of operation.  I’ll describe what the gas valve does and why it’s important.  And towards the end, I’ll give you ten things to check when you’re troubleshooting a furnace gas valve.  That’s coming up here on Fox Family Heating & Air.

The Furnace Sequence of Events

First, as a technician, you have to know the sequence of events that occurs for a gas furnace to start up properly. It’s straightforward, and you should have this memorized before you can even consider being qualified for troubleshooting a furnace gas valve.

  1. Power to the furnace control board
  2. Thermostat signals the call for heat
  3. Inducer motor kicks on
  4. Pressure switch proves the inducer operates correctly
  5. Ignitor activates
  6. Gas valve energizes
  7. Flame pours across burners
  8. Flame sensor proves all burners are lit
  9. The blower forces air through the ducts

First, the Inducer Motor Starts

When a furnace begins a new cycle, the inducer motor is the first thing you should see kick on.  One hundred twenty volts are applied through the wires coming from the control board.  This starts the inducer motor for up to 60 seconds before anything else even happens.

Next, a safety device called a pressure switch activates when the diaphragm inside it recognizes the inducer motor’s suction or purging action. 

When the “all clear” signal arrives at the control board, high voltage is sent to the ignitor – be it a hot surface ignitor or a spark ignitor.  The hot or sparking ignitor stands in the way of the gas that is getting ready to pour over it. 

This is Where the Gas Valve Comes Into Play

Modern gas valves typically have a printed circuit board in them that receive a 24-volt signal to activate the valve inside of it.  Remember the video I did on printed circuit boards?  If not, I’ll attach it below so you can brush up on what they are and the things that can go wrong with them.

This sequence will happen in three stages – and even if one step of this doesn’t perform, each part is still going to do its thing sequentially once the board gives the signal.

So, after the board senses the pressure switch and inducer motor are working:

  1. 120 volts is given to the ignitor (on some package units, it’s 240 volts.)
  2. 24 volts is given to the gas valve.
  3. The flame sensor starts detecting if there is a flame or not.

The ignitor is supposed to come on for a set amount of time: 30 to 60 seconds. (See our video on ignitors for an in-depth explanation of this topic.)

Next, the gas valve opens.  The gas coming from the utility company or the propane tank in the back yard is free to flow on to the ignitor.  That gas valve is what’s regulating the flow of the gas.

The flame sensor senses whether the flame is correctly burning.  At the opposite end of the burner assembly, the flame sensor also stands in the way of the flame.  The rod, which should be cleaned annually, by the way, will heat up and send a millivolt signal down to its ceramic base and on to the control board.

Only a certain amount of gas can be allowed to pass through the manifold and on to the burners.  The manufacturer of the furnace determines what that will be.  It is pretty standard, though—about 3.5″ water columns (wc).  The natural gas pressure coming from the street is somewhere around 7″-10″ wc, but the gas valve itself specifically allows that 3.5″ wc onto the burners. 

There are some situations and equipment where I’ve been told to bring the outlet pressure down to 3.25″ wc.  But I only did it on the advice from the technical support rep from that equipment.  Specifically, it was Ruud equipment.  The rollouts were getting too hot because the hood covering the flame would trap the heat and make the safety open.  Modifying the hood and adjusting the gas pressures were recommended to us, which seemed to fix it.

Furnaces differ, so please check your furnace installation and service guide for your system’s specifics.  This is something you don’t want to get wrong.

The gas valve is adjustable.  And usually, the installer of the equipment will dial in the outlet pressures on start-up.  Because the gas valve manufacturer – Emerson, White-Rodgers, Honeywell, and other valves makers will usually have it pre-set to that 3.5″ wc, some installers forget to do this.  We can’t assume the valve is correctly adjusted each time. That’s why you can have issues with your furnace related to your gas valve – because it wasn’t set up right by the installer during its first use.

Troubleshooting a Furnace Gas Valve

If 24 volts is coming from the board to the gas valve terminals and you don’t hear that little clicking noise the internal valve makes, you could have a bad gas valve.  To double-check, take the leads off to the gas valve and check there.  Got 24 volts?  Then something downstream of that 24 volts is not working. 

What’s the next thing that’s supposed to be working?  The printed circuit board or electric solenoid attached to the gas valve isn’t telling the valve to open, OR that gas valve board IS telling it to open, but the valve is stuck somehow.

If something is wrong with the internal components of the gas valve, it should be replaced. The gas valve cannot be repaired in the field. Only the gas valve manufacturer or someone certified by the gas valve manufacturer can make these repairs.

Some people will literally take a wrench and bang on the gas valve to get it to open up.  This is extremely dangerous.  Gas is nothing to toy with.  If you decide to try this and it kicks on, please replace the gas valve now rather than later. 

If we try to fix these ourselves and something goes wrong with the gas valve, and it somehow caught the house on fire, the investigation could come back to the furnace.  If they wanted to know who last worked on it and what was done to it, the gas valve manufacturer could claim innocence, and the homeowner’s insurance could deny the customer’s claim.  I know that sounds a little drastic, but it could happen.  Why put yourself in that situation?

I see people try to fix control boards, ignitors, and such, but we shouldn’t try to fix gas valves ourselves with such a sensitive instrument.

Here are ten things we can check when we think we have a bad gas valve before condemning it:

  1. Check the wires to the gas valve.  Are they cracked or frayed?  That could mean a couple of things.  You have a REALY old furnace, or something could have scorched the wires—things like that.  Replace the wire and continue your diagnostic.
  2. Check the coil at the gas valve.  If you check the coil’s resistance by putting your two-meter leads on each terminal and you get a reading of OL, you have a bad coil. There are more complicated things here but let’s keep this straightforward. 
  3. The gas coming into the valve should be at utility line standards.  It’s around 7″-10″ wc for natural gas in my neck of the world. There’s a port on the inlet side to check it.
  4. You may have plugged burner orifices.  A furnace that’s been off all summer can be the victim of a spider spinning a web inside the burner orifices.  Now, that’s a tiny spider, I know, but I promise, it happens!  Take a small piece of thermostat wire and gently poke inside the holes of the orifices attached to the manifold and try to fire up the system again.
  5. The flame might be coming on for a few seconds but then shutting off.  Is there a dropout of voltage or gas pressure to the gas valve?  That’s something to check for sure.  And you can do that by putting a “T” fitting in line with the hose to connect to your manometer.  Check the inlet and the outlet side to see if the pressure is dropping on either side of the valve. 
  6. Another reason the flame could drop out after only a few seconds of burning is the flame sensor.  If the sensor doesn’t detect the flame, the control board will signal the gas valve to shut down.
  7. If the flame does anything but shoot directly into the hollow metal heat exchanger, a safety can trip.  One safety trip is the rollout switch.  Sometimes you’ll get a little part of the flame that drifts off to the left or right, sending the switch off.  That doesn’t mean you should remove the switch.  It means you need to fix the problem.  Clean the end of the burner assembly nearest the heat exchanger.  Rust will sometimes build up on the crossover channels.  Use a wire brush to clean and see if that solves it.  Then place the burner correctly into the channel.
  8. The other safety trip that can cause the system to cut the gas off to the valve is the high limit switch.  If the furnace runs for a few minutes, then shuts off, something could be causing the inside of the furnace to get too hot. The first thing I would check is to see is if the evaporator coil is dirty.   I have a great video that shows what a dirty evaporator coil looks like and what it takes to clean it.
  9. The other reason the high limit could open is the blower motor speed could be set too low.  Check your installation guide as a reference for where the settings should be.
  10. Check the ductwork too.  These last three have all dealt with airflow.  If the return duct is crushed, then we’ll have low airflow again.  Visually check the return duct and feel around it if it looks questionable.  If the duct is not perfectly round, then this could be the problem. The furnace is suffocating.

What else should folks check when troubleshooting a furnace gas valve?  Leave me a comment down below to share your expertise.

When you’re installing the new gas valve, there are few things to keep in mind. It’s a like-for-like change out, but gas leaks are a serious issue, so make sure to use some pipe dope or pipe tape to seal the fitting. 

Also, don’t bend the manifold when you’re trying to remove the gas valve or put the new one back on.  Use two wrenches to get a proper hold on the manifold and the gas valve.

I strongly recommend not over-tightening the gas valve to the manifold.  You could bend the manifold, but also remember, someone might have to get that thing off someday, and you’d be creating a challenging situation for a tech that has to come out and service it in a few months.  Some guys get a little over the top and really crank down on it.  Not necessary. 

Check for gas leaks with an electronic gas sniffer or soap bubbles.  This will assure you the fittings are snug and leak-free.  And don’t forget to check the outlet side when the gas valve is on.  It doesn’t help when the valve is off because no gas is flowing through it.

If it’s a natural gas set-up, the spring that comes inside the valve will already be the right one.  If you’re using LP gas, you’ll need to make sure you put the right spring in it. It’ll come in the box.  Check the manifold orifices to ensure they are the right ones for LP too. And put the sticker on the gas valve that says LP.  This will help future HVAC technicians when they service the furnace.

And lastly, check the gas pressure on the new valve after you’ve replaced it.  I can’t say it enough. It’s simple to do with the right tools, don’t just change the valve and not check the pressures.

When it comes to troubleshooting a furnace gas valve, there’s also a setting for low fire on two-stage units that needs to be checked.

If the gas pressure is too low, your furnace’s efficiency will go down.  More condensation than usual will build up because the air in the air-fuel mixture will be too high.  The condensation can cause corrosion, possibly creating the need for a heat exchanger replacement in the future.

High gas pressure can be just as bad for your furnace because it dramatically increases the furnace’s overheating risk. When this happens, high limit switches will start opening, causing intermittent operation.  It can also crack your heat exchanger since it’s only rated to handle a certain amount of heat.  And cracked heat exchangers can introduce the spent gasses inside the heat exchanger to be carried along with the heat blowing into the house.

So, to recap.  When a furnace begins a new cycle, the inducer motor is the first thing you should see kick on. A safety device called a pressure switch activates when the diaphragm inside it recognizes the suction or purging action of the inducer motor.   Next, the three parts of the ignition sequence begin.  The ignitor kicks on, the gas valve opens, and the flame sensor senses that the flame exists.  If this all goes well, you have heat blowing into the house about a minute later when the blower kicks on.

What else should folks check when troubleshooting a furnace gas valve?  Leave me a comment down below to share your expertise. Thanks so much for stopping by, and we’ll see you at the next blog post.

Don’t Miss Our Video Series on This Topic and Related Videos:

The Easy Guide to Diagnosing a Bad Furnace Inducer Motor

Inducer Motor Troubleshooting tips

Today I want to expand on our recent gas furnace troubleshooting series. “The Easy Guide to Diagnosing a Bad Furnace Inducer Motor” will fill you in on what the inducer motor does, why it’s important, the most common of ways I’ve found inducer motors fail, and how to let the customer know what you’ve found. That’s coming up here on Fox Family Heating & Air.

First, I want to give fair warning to anyone watching this that is not already an experienced technician in the HVAC industry.  This video is for educational purposes only.  Fox Family Heating and Air does not recommend anyone other than a professional to start opening the furnace up and trying to diagnose the failure going on with your system. 

There are high and low voltages that can shock a person.  There are also lots of moving parts that can damage body parts—namely, hands and fingers.  The furnace also produces hot surfaces within the furnace compartments and around the housing, which can cause severe burns.  An actual flame produced by the ignition and startup of a gas furnace can cause severe burns and damage to a person or property.

First, as a technician, you must know the sequence of events that occurs for a gas furnace to start up properly. It’s straightforward, and you should have this memorized before you can even consider being qualified to troubleshoot.

  1. Power to the furnace control board
  2. Thermostat signals the call for heat
  3. Inducer motor kicks on
  4. Pressure switch proves the inducer operates correctly
  5. Ignitor activates
  6. Gas valve energizes
  7. Flame pours across burners
  8. Flame sensor proves all burners are lit
  9. Blower forces air through the ducts

When a furnace begins a new cycle, the inducer motor is the first thing you should see kick on.  120 volts are applied through the wires coming from the control board.  This starts the furnace inducer motor for up to 60 seconds before anything else even happens. It’s a safety feature that creates a negative pressure or draft that purges the heat exchanger of any poisonous gasses, namely the combustion’s biproducts.  It makes the air inside the heat hollow tubes of the heat exchanger cleaner when the flame kicks on. With cleaner air inside the heat exchanger at the time of combustion, the furnace’s efficiency increases.

Without going into it too much, a safety device called a pressure switch activates when the diaphragm inside of it recognizes the suction or purging action of the furnace inducer motor. There’s another video called The Easy Guide to Diagnosing a Bad Pressure Switch, and I’ll make sure it’s attached to the end screen so you can check that out.  But first, you want to know more about the inducer more and how to troubleshoot it.

If the inducer motor doesn’t turn on when it’s supposed to, the furnace will recognize this and shut down.  It will wait a bit and try again.  If the motor doesn’t start after 3 to 5 tries, the control board will stop sending voltage to the inducer motor, and essentially locking it out from attempting it anymore.

Why Furnace Inducer Motors Fail

If the correct voltage is applied to the inducer motor and it’s not turning on, something’s not right. Let’s dig into why:

Unplug the furnace, which removes power to the system.

Is the base of the motor warm or hot to the touch?  This means it’s been trying to spin, but something is holding it up.  Is the flywheel on the motor or the actual squirrel cage unable to spin when you manually try to turn it? This can be a reliable indicator that the motor is bad and needs to be replaced.

Why is this happening?

One reason the motor’s shaft locks up is that the motor’s bearings may be seized, preventing it from turning.  Another reason has to do with the windings inside the motor.  One of them could be open—usually, the start winding in this case.  And finally, some motors have a capacitor that starts the motor and regulates the voltage while it’s running.  If it is a bad capacitor, a new one should get it going again.

One of the first indicators that a furnace inducer motor is on borrowed time is if it’s making odd noises.  Sometimes it’s a rattling noise, a clanking noise, chattering, pinging, shaking, a wobbling noise – you name it!  If it comes on and runs any other way than what you interpret as normal, based on your training and experience with properly operating furnaces, you can see if it’s something you can physically adjust.  If not, the inducer motor should be considered bad.  Why?  Because it’s not running to manufacturers specs.

Think Like the Furnace Builder

Think about it like this. Would the furnace’s builder, who takes a ton of pride in their system’s operation, send this out into the field to be installed, knowing the inducer motor is making a god-awful noise?  The answer is a resounding no!  And you should know that and be comfortable telling the customer this. 

Because many inducer motors are nearly impossible to rebuild, an entirely new unit must be purchased in most cases when one wears out. One of the exceptions to this is the occasional Carrier or Bryant units.

Ordering the Furnace Inducer Motor

So at this point, this is what I need my technicians to do. Inducer motors are ordered through the manufacturer. And since we have flat-rate pricing, which includes the cost of parts, labor, and warranty, if the motor is less than $100, it is a level 7.  Above $100 is a level 8. $200 and above, they need to call a supervisor for pricing.

Be Prepared with Information

You want to know the pricing and availability before you talk to the customer because you want to minimize the number of times you need to bring the customer information.  Coming to them and telling them the inducer motor is bad just to hear them say, “Okay, how much is it?” then means you must find out, come back, and tell them it’s the such-and-such price.  You get their approval on the price, but they want to know when the repair will occur. You’ll need to call back to your parts warehouse to ask when the part will be available.  You then must go back to tell them the part will be in around 5 to 7 business days from the factory. 

All of this back and forth can be avoided if you have all the necessary information upfront before even telling them about the diagnosis.  Even if they don’t go with your repair, you have the information and can log it in your file for the customer if they call back, approving the repair a month from now.

Communicating with the Customer

Once we determine pricing and availability, it’s time to talk to the customer about our diagnosis.  We explain what we found, let the customer know the price, and let them know when we can come back to repair the system.

Just a word to the wise:  good communication between you and the customer would mean telling them they need to change this part on the furnace before seeing if anything else is wrong with the system.  Sometimes you’ll get a customer that asks, “So this will fix my system and get it going again, right?” Well, you don’t really know because you haven’t seen what the rest of the startup sequence and the cycling off of the system is doing, have you?  

It’s very likely the rest of the system will work since multiple failures are pretty rare, but you’re going to feel like a jerk if you forget to tell them you have to see how the rest of the system operates after you replace the inducer motor.  Coming back to them after you’ve replaced the motor only to say, “Oh yeah, now your gas valve isn’t working, that’ll be another $600.” So just remember, without a properly functioning inducer motor, there’s no way to tell if the rest of the system is working to manufacturer specs. 

If it is a part that’s available for pickup, call the office to determine a date to pick it up and return and complete the replacement.  If it is a part that needs to be shipped, we want to let the customer know that the part should be arriving at said date and that we’ll call to schedule the appointment when the part arrives.  You’d also want to communicate to the customer and the office how long the repair will take. 

During the inducer motor installation, we need to either replace the gasket (usually comes with the new motor) or make a gasket with high temp silicone. Once installed, a good technician will test the system for proper operation to ensure there are no other issues with the furnace.

Diagnosing a Furnace Inducer Motor: A Recap

So, just to recap, inducer motors pull the flame through the heat exchanger and vent the exhaust through the roof. To determine an inducer motor’s failure, we need to verify the proper voltage is being sent to it. If the motor has proper voltage, the capacitor tests good and is not turning on, the motor is bad.  If it’s making a lot of noise, the homeowner should know the part is working but is on borrowed time.

Thanks so much for stopping by, and we’ll see you on the next blog post.

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How Does a Gas Furnace Work?

Easy Guide to gas furnace troubleshooting

 

Understanding How a Gas Furnace Works and the Sequence of Operation

Hey guys, how are you doing?  Today I’m going to describe for you the sequence of events that needs to happen for your furnace to start blowing warm air into your house. We’ll start at the thermostat and go all the way to the blower turning on, forcing air into the rooms of your home. Furnace troubleshooting is the topic coming up today on Fox Family Heating and Air.

Furnace Troubleshooting Safety

First, I want to give fair warning to anyone watching this that isn’t already an experienced technician in the HVAC industry.  This furnace troubleshooting video is for educational purposes only.  Fox Family Heating and Air does not recommend anyone other than a professional start opening up the furnace to try to diagnose the failure going on with your system.

There are high and low voltages that can shock a person.  There are also lots of moving parts that can damage body parts—namely, hands and fingers.  The furnace also produces hot surfaces within the furnace compartments and around the housing, potentially causing severe burns.  An actual flame produced by the ignition and startup of a gas furnace can cause severe burns and damage to a person or property.

When your house reaches a point where the heat needs to come on to keep you comfortable, a series of components work in a specific order to produce that heat.

The Thermostat

The thermostat is the first part of the sequence that engages, making the furnace work. There’s 24-volt power at the R terminal of the stat already.  Within the workings of the thermostat, 24 volts closes a switch at the W terminal.  That signal is sent to the control board back at the furnace.

The Furnace Control Board

The control board is a printed circuit board with various switches, resistors, and terminals that act as the quarterback of the heating system.  It calls the plays as they need to happen.

Low Voltage Wires

The control board has a terminal block with screws on it, with a set of thin low voltage wires coming from the thermostat.  Typically, the colors of these wires are red, yellow, white, green, and blue.  The wires are going to R (red), Y (cooling), white (heat), green (blower motor), and blue (common).

Note: the wire colors don’t matter here. They’re still copper on the inside of the sheathing.  So if we use a brown wire for R at the control board, brown needs to be hooked up to R at the thermostat.

The Inducer Motor

Once the control board receives the thermostat signal to turn the heat on, it tells the inducer motor to come on.  The inducer motor is a major component that removes the carbon monoxide from the flame of the gas furnace.  It draws the spent gasses into the metal or PVC flue pipe, which transfers those fumes from the furnace to the atmosphere through the roofline.  You may have seen the metal pipe sticking out of the roof of your house in the winter, exhausting steam into the air. That’s the exhaust we’re talking about here.

The Pressure Switch

This safety device proves that the inducer motor is on and doing its job properly.  If it’s not, the sequence shuts down and retries again.  This pressure switch is actually measuring the suction the inducer motor is producing and sends a signal back to the board, letting it know that startup is working so far.

Roll Out and High Limit and Pressure Switches

Meanwhile, other low voltage safety switches are sending a signal of all-clear back to the board.  There are a couple of “roll-out” switches and a high-temperature limit switch that must confirm to the control board all is well there, too.  The wires leading to the roll-out, high limit, and pressure switches are usually all wired in the same series circuit with each other as a safety control.  If any of these safety switches sense anything wrong with the heating system’s startup, the sequence stops, and retries.

The Ignition Sequence

Next, three components engage in lighting the flame and proving that it is lit. When the pressure switches and other safeties tell the control board all is well, the board starts the ignition sequence.  First, the board sends a signal to the ignitor.  This could be a hot surface ignitor that glows orange or a spark ignitor, which produces an arc between two metal forks lasting for several seconds.  (My blog post and video discussing why hot surface ignitors fail might be of use for you, too.)

Whether the ignitor glows or sparks or not, the next component, 24 volts, is sent to the gas valve, which opens the diaphragm inside of it. It opens, allowing natural or propane gas to flow on to through the metal burner assembly.

The Heat Exchanger

The gas now flowing through multiple orifices in the burner assembly reaches the ignitor, causing a flame to ignite and burn in a controlled fashion straight into the firebox or heat exchanger.  For the purposes of this post, we’ll call it the heat exchanger.

Crossover channels within the burner assembly allow the gas to flow from the first burner to the last one, where the flame pours over a thin metal safety rod called the flame sensor.  The flame meeting the rod creates a millivolt DC signal to the control board that allows the gas valve to remain open.  No flame being sensed means gas is flowing uncontrolled throughout the furnace cabinet, which is not good.

At this point, we have power, a good thermostat, a functioning inducer motor, ignition, flame, and flame sensor to verify it.

A delay now occurs to allow the heat exchanger to warm up so cold air isn’t sent through the ducts and into the air.  The heat exchanger is a hollow metal box with individual chambers.  The flame pours into each chamber, warming the metal to an extreme temperature.

Once hot enough, the air that flows over and around the metal box warms quickly from room temperature to about 100 to 140 degrees.  The temperature is set by the manufacturer and must be closely adhered to.  This will keep the system operating safely and to proper specs.

The Blower Startup

After this delay completes, the blower starts up, sending forced room temperature air over the correct speed of the metal heat exchanger.  If the air is sent over too fast, the air entering the room won’t be warm enough.  Too slow of air or not enough air and the system gets too hot.  Too hot means the high-temperature limit we discussed earlier will open, telling the control board something’s not right. So, this blower motor has to be dialed in just right.

Furnace Troubleshooting Tips

Here are some things that can happen when the furnace isn’t starting up correctly.  The following troubleshooting tips are not all-inclusive and are not to be taken as scripture that what is going with the furnace you’re working on is the problem.  These are general problems only.

No power to the board – If the unit is plugged in correctly and the breaker at the main panel is in the on position, there should be power to the furnace control board.  A transformer can fail between the outlet and the control board, and they can and do regularly.  The board with proper power can send the high and low voltage signals it needs to be the quarterback and run the plays.

Power, thermostat, no inducer motor – Low voltage power is sent from the control board to the R terminal at the thermostat.  Assuming you have 24 volts there, the thermostat closes the W switch, which now has 24 volts applied to it.  If the 24-volt signal is getting back to the control board’s W terminal, the control board will send the high voltage signal to the inducer motor.  If voltage is getting to the inducer motor but it doesn’t run, you likely have a bad inducer motor or capacitor for the inducer motor if it has one.  If you’re not getting voltage to the inducer motor from the board, you have a bad board or faulty wiring connection between the two.

Power, thermostat, inducer, no ignition – If the inducer motor is running, the ignitor should start glowing or sparking.  The gas valve should open, allowing the gas to flow, the gas flame should crossover to the other burners in line, and a signal should be received at the flame sensor telling the board everything is good to go.

As with many components in furnace troubleshooting, if the part is getting power but not operating, it’s likely failed.  If it’s not getting power from the control board, it’s likely a bad board.  I have a great video on why control boards fail for more information.

Power, thermostat, inducer, ignition, flame, sensor, but no blower – If everything works as it’s supposed to, except the blower motor hasn’t turned on after the flame ignited after about a minute or so, something is going on there.  If the motor is getting power but not working, the motor or its capacitor may have failed.  If the motor is not receiving power from the board, the board is likely bad.  Not all blower motors have capacitors, either.  This is especially true for systems made in 2020 or later.

Power thermostat, inducer, ignition, flame, sensor, blower, shuts down on high limit or roll-out – Lastly, if the blower motor comes on and the system starts heating, but after a few minutes or even several minutes the system shuts down, the high-temperature limit switch may have opened causing the system to retry again, after the heat exchanger cools off.  If the chamber that houses the heat exchanger gets too hot, this high limit switch will shut down the system.

So What Causes a Shutdown?

First, we have to check that the blower speed settings are correct.  Next, the air filter could be dirty, ductwork could be too small or even collapsed, or the evaporator could be clogged with dirt. (Check out one of my most popular videos that shows what kind of problems a dirty evaporator coil can create.)

All of these items have one thing in common:  not enough air flowing over the heat exchanger.  This causes the inside temperature of the furnace to go over the recommended setting established by the manufacturer.

Although many things can go wrong with the gas furnace, sometimes in combination with each other.  Not much else can go wrong unless something in this sequence goes wrong.  I sure hope this answers some questions you have about troubleshooting a gas furnace.  Be safe and use your head out there. Don’t get in over your head if you don’t know what you’re doing.

Thanks so much for stopping by, and we’ll see you next time!

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Turning on the Furnace for the First Time Each Year

Turning on the Furnace for the First Time Each Year

What is that burning smell when turning on the furnace for the first time each year?

As the winter season approaches, a lot of you will turn on the furnace for the first time this year.  That can be a very intimidating situation for some people.  You may have just moved into your first apartment.  Or perhaps you’ve just moved into your new home this past summer.  The AC worked fine, but now it’s time to see how the furnace is going to work this winter.

Whether you walk over to the thermostat or turn it on manually, what’s that burning smell the first time you’re turning on the furnace for the year?  In this week’s blog, let’s break down the gas furnace, and some of the sounds and smells you get when it comes on for the first time each year.

About Turning on the Furnace

You should understand the nature of the furnace is to provide warm air for your home.  And it does that with a gas flame.  But that gas flame isn’t just flying around uncontrolled the way it does in a fireplace for example.  A very structured flame is sent into the furnace.  If the flame were to roll out or overheat the furnace, a series of safety switches will engage, turning off the furnace.

Whether you walk over to the thermostat or turn it on with your smartphone, the sounds and smells that you experience can be confusing.  That’s not how the air conditioner sounded when it came on, and that’s definitely not how the air conditioner smelled when it was working.

When the furnace gets turned on, the thermostat on the wall tells the furnace which is in your attic, your garage, or your closet in the hallway to initiate a sequence of events that will ultimately shoot a gas flame into the firebox, or heat exchanger.

Turning on the Furnace:  the Basic Parts

There are a few parts that come on before that flame starts to heat the home.  The thermostat tells the control board inside the furnace to come on.  The control board is the brains of the system that will control the following events.

The first motor to come on will be the inducer motor.

Not a large motor by any means, but it’s the one that gets rid of the fumes spent by the flame that warms your home.  The control board and a pressure switch acknowledge that the inducer has come on and is working properly.

The ignitor will come on next.

Usually, it’s a hot surface ignitor made of silicon carbide that glows red hot.  About 2500 degrees.  The timer on the control board then allows the gas valve to open up and pour a controlled amount of gas over the red-hot surface ignitor.

Creating the Flame

This creates the flame we were talking about earlier, that shoots into the metal firebox, which is better known as a heat exchanger to us technicians. A small flame sensor then verifies the flame is on and sends a signal to the board that everything is burning properly, and the system is safe to continue heating the home.

Blower Fan Comes On

If the flame sensor says everything is okay, the control board then tells the blower fan to come on.  The sequence is complete.  Warm air will then start flowing into the rooms until it gets to the desired temperature.

That whole sequence of events that happens takes about 1 minute from the time thermostat tells the furnace to start, to the time the blower turns on and gives you heat through your registers.

When the thermostat senses the room’s warm enough, it tells the control board to end the call for heating, which then cuts the flame.  Meanwhile, the blower stays on just long enough to cool the furnace down quite a bit, about 60 to 90 seconds.  This helps extend the life of the system.

So how does the heat exchanger work?  Well, it “exchanges heat” by keeping the flame and its fumes inside the metal box while a fan blows air over the outside of the metal.  The heat that comes off that metal and the air from the blower is then carried into your rooms where you feel the warm air.

What’s That Burning Smell?

Folks call in every fall when they’re turning on their furnace for the first time and say the system IS working but there’s a strange smell coming through their vents. Almost like a burning smell.  When we get out to their home and verify all the motors are working properly, we let them know something most people don’t know until it’s happened to them.

So what’s that smell the first time you turn on your furnace each season?  It’s just a fine layer of dust that’s settled onto the heat exchanger.  The dust from your house has made its way past the air filter and blower assembly to the metallic heat exchanger.  As the metal heats up, the dust burns off and creates that burnt smell.  It can happen the first few times you turn the system on, but after that, you shouldn’t get that burning smell any more.

If the smell bothers you, you can just open the doors or windows to your house and let it vent out that way for about fifteen minutes.  But rest assured it’s not carbon monoxide.  That odorless gas can only be picked up by a carbon monoxide detector.

Safety First

If you do turn your furnace on for the first time or ANY time this year and your home’s carbon monoxide detector does go off, don’t just remove the batteries.  Don’t treat it like it’s some nuisance alarm, either.  Go ahead and step outside of the home and call the Fire Department.  Let them come out to make sure everything is okay before going back inside.  It might cause a big show for everyone in the neighborhood, but who cares?  It’s your family’s life on the line.

If you don’t currently have a carbon monoxide detector on each floor and the main hallways of your house, now would be a good time to pick those up from your local hardware store.

About Detectors

Speaking of detectors in your homes – if you haven’t done so already this year, it’s time to change out the batteries in those detectors around your home.  Your local fire department usually will come out for free and help you replace those batteries if you have trouble reaching those detectors on your own.  If they won’t and you’re in our area, just provide the batteries and we’d be happy to come out and change them for you.  Otherwise, any handyman in your area would be up to the task.

As a reminder, the single-most-important-thing you can do to keep your furnace clean is to change those air filters.  If the system can’t breathe in because of a dirty air filter, then it won’t be able to breathe out for you at the supply registers in your rooms either.  Again, if you can’t do it because you’re elderly or physically unable to reach the filter, give us a call!

Remove Flammables Before Turning on the Furnace

Another bit of advice we’d like you to consider is to make sure there are no flammables around the furnace.  Remember, we said that the furnace is either in the attic, the closet, or the garage. These are common places to store items that tend to be forgotten over time.

A metal flue pipe that gets very hot when the furnace is turned on can be dangerous if left unattended.  Broomsticks, cardboard, newspapers, clothing, and other materials can scorch over time if they’re resting on the flue pipe.  Setting away from the furnace any flammable varnishes, lacquers, oils, and gasoline will help keep your home safe.

Don’t Wait to Turn on the Furnace

Although you might be nervous to turn your furnace on that first time every year, do it.  Turn it on when it’s still mild outside.  Maybe don’t wait for the first winter snap to hit before finding out your furnace doesn’t work.  If you do wait, you might find yourself at the end of a long line.  Other homeowners and property management companies may be requesting service at the same time you are.

Taking Care the Easy Way

If you don’t already have someone coming out to your house each year just to make sure everything is running safely for you and your family, we’d love to be the company that gets to do it for you.  Fox Family offers an easy way to automate this. You won’t even have to remember to call us. We take care of it all.

Your furnace runs better when it’s been cleaned and maintained, much like your car. Every Fall or Winter is a good time to get the required maintenance done on your heating system. Don’t have a desire to be on an automatic program? Call for a furnace tune-up. A typical cleaning lasts 45 minutes to an hour and a half. It’s usually about a 30 point checklist, but I’ll go into that on another post.

Turning on the Furnace: a Recap

The nature of a gas furnace is to use a controlled flame to warm your house.  It’s done in a VERY controlled way by a series of safety switches.  Any unexpected events within the furnace components tell the control board to shut down the unit.

Thanks so much for stopping by, and we’ll see you on the next blog post!

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