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10 Furnace Maintenance Tips

10 Furnace Maintenance Tips

We oftentimes get asked by homeowners “What can I, as a homeowner, do or check on my furnace for furnace maintenance myself?”
So, we made a list of 10 things that a homeowner can do or check-in their furnace as preventative maintenance.
If you don’t come down and look at your furnace very often, we recommend you sometimes take a look at your furnace so you know where everything is.
So let’s get an overview of your furnace first before we proceed on our list.
The top door, the bottom door, and the vent.

If you have a steel vent that means you have a chimney. That vent goes out and out the top of your roof.

If you have a plastic vent, it’ll be two pipes going outside at the wall of your house – not out the roof.

Your exhaust piping should be in good condition especially the steel stuff. If it’s all rusted out and if you, for example, squeeze on it and your hand goes through it, that’s the worst-case scenario.

It should be sturdy and nothing should be rusting or corroding. If it is then there’s a problem and at that point, it’s better to call an HVAC technician and get an actual furnace inspection.
Do be careful if you have a steel pipe for exhaust. It gets very hot like 300-400 degrees so if your furnace was just running and you grabbed that, you’re going to burn your hand off so be careful. First, make sure it’s not hot.
Most people will also have central air conditioning and a lot of people don’t know this but actually, there’s a coil that sits on top of your furnace if you have an up-flow furnace which is part of your air conditioner.

It’s kind of looks like a letter A and it sits right on top like a big radiator.
It has a drain line and a drain pan on the bottom of it. Usually, it’ll be a clear hose or it’ll be a white PVC pipe.

All the humidity that it’s pulling out of your house during the summer runs down into the drainpipe or drain holes and down to your floor drain.
These are refrigerant pipes.

Here wherever you see the copper pipes, the thin copper pipe is always going to be bare whereas the thick one will have insulation over it. The reason is if it has no insulation, the thick pipe will sweat or condense and start to drip, and wherever it’s dripping, of course, it will cause rust or make spots in your ceiling if it’s towards the ceiling.
They run in a loop between your outside unit and your inside unit which is right on top of the furnace.

The refrigerant or the freon will just keep going in circles between the two when your air conditioner is running. And as we mentioned previously, this is an up-flow furnace which means the air comes in your furnace and it gets pushed out through the top.
There are also downflow furnaces. A downflow furnace will have the refrigerant coil called an evaporator coil.
That coil will be below the furnace and then there’s also the horizontal furnaces which are mounted horizontally usually in crawl spaces or attic units and in that case, the coil will be either on the left or the right side.

You’ll have your power coming in, it’ll either be a steel cable with the rigid cable or it’ll be solid.

A power switch either right at the furnace or the switch will be further down like at the wall or somewhere behind the furnace. If you trace the metal cable that’s running from your furnace, just track it down and you will be able to find where that switch is.
If there is no power switch, in that case, you would need to just turn off your circuit breaker to turn off the power to the furnace.
All gas and propane furnaces will have a gas supply line which will be black iron or copper and we know somebody’s going to say that copper is not code but at some places, copper is still code.

Another thing you should know about your furnace is how to take off your furnace doors. A lot of times there will be a handle on the top door, one way or another figure out how to take it out.
You have to press up and pull out.

A lot of Trane furnace would say you have to take the bottom door off first and then you can take the top off.
Sometimes, they’ll have knobs, sometimes the doors will be screwed in but to access anything inside of the furnace, you do have to take the doors off.
And just a fair warning, sometimes doors are pretty hard to put back in so pay attention as you’re taking them out for the first time.
For the bottom door, just pull it up. Usually, kind of wiggling it as you’re taking it out.

If wires are a mess you can zip-tie them to make it looks clean.
Another thing we want to point out is the door switch will typically always be on the bottom of the lower door. The door switch will either be in the middle, on the left or the right.

There is also a secondary power switch. All this does is when you take that bottom door off, this door switch usually pops up and disables the power to the furnace. That way, if homeowners start sticking their hands into the control board and stuff, they’re not going to get shocked.
Now that we’re done with the furnace overview, let’s proceed with the tips! But before you start freely touching anything inside your furnace, make sure it’s turned off to prevent accidents.
Tip 1. Change your filter regularly.
As simple as that sounds, a dirty furnace filter is a common problem. The furnace stops working or is not working correctly because the furnace filter is too dirty so make sure you change your filters regularly.
There are different styles of filters and a lot of times they’ll also have an arrow on the filter.

The arrow says the direction of the airflow.
The airflow needs to go towards the furnace or the arrow is supposed to be pointing towards the blower motor in your furnace.
A lot of times the furnace filter will be on one side of the furnace either left or right in the return duct but there are others where it’ll be inside the actual furnace and you need to take the bottom door off to find that filter.
As for how frequently filters should be changed, if you have a 1-inch filter, many techs will say that they last three months but the only time filters are lasting three months is in the fall, when you’re barely using your air conditioner or your furnace.
In those cases, your furnace filters do last longer but if it’s negative 30 degrees outside and your furnace is running all the time, your filter is going to get plugged up in like three or four weeks.
A filter with looks of a nice white color could also be dirty. There could be like a white powder over the filter and this is plug the filter.
Furnaces are overheating with these filters. These filters caved in because the furnace is straining for air so it is pulling the filter in because the blower motor is having a hard time trying to suck the air through a dirty filter.
Another indicator is if your furnace is making whistling sounds and right when you take that furnace filter out everything stops, that’s a good indication that that filter is dirty as well.
In general, you should be replacing 1-inch filters every month or two.
Tip#2. Duct cleaning.
This is very important. When you have some kind of a home renovation going on, if you’re remodeling your kitchen or something, especially if you’re doing sheetrock, flooring, carpeting, that will get your ducts dirty especially the coil that sits on top of the furnace.
And if you’re not replacing your filter regularly, that coil is going to start to get dirty.
Unfortunately, duct cleaning is not something you could do yourself. You have to hire duct cleaners but a few pointers on that if you’re doing some kind of remodeling, make sure you’re replacing your filter a lot more frequently because that will get dirty a lot faster.
And after you’re done with all the remodeling, we do recommend getting your ducts cleaned and the most important part about that is to get your coil cleaned – the evaporator coil or to a coil that’s part of the air conditioner.
Operationally, the coil is the most important part. The ductwork does not matter as much as the coil itself. So, if you do hire some duct cleaners, make sure you ask them to clean the coil along with all the ducts.
And one last note about the duct cleaning, after they clean your ducts, all the dust and debris that they stir up, usually they never suck all that stuff out so after the duct cleaning your filter will get dirty a lot faster than it normally would.
So, if you just replace your filter and got your ducts cleaned, keep in mind that you may have to replace it like a week later or your furnace is going to start to overheat.
Tip#3. Keep Returns and Vents Open.
Keep your return grills always open not blocked by anything and to keep most of your supply registers opened up as well.
Some people like to close off the supply registers like in the basement or the upstairs room because it gets too hot. The rule of thumb for that is you don’t want to close off more than one-third of all the supplies in your house.
If you have, let’s say twenty-one registers, seven is the absolute maximum that you should be closing. But, optimally, you should keep them all open.
As for return grills, they’re usually bigger and they will never have shutoffs on them. You can’t close a return grill.

One thing to watch for is you don’t have any couches or shelves in front of those return grills so nothing is blocking them because they’re sucking the air in.
If you have some of those return grills blocked then your furnace will overheat as well. So, make sure they’re open and they’re clean.
If you can see a lot of dust, you can get a vacuum cleaner and just vacuum it all out. If inside you see that it’s all hairy and dusty too, you can just take the screws out that hold the return grill and vacuum there too.
If it looks really scary then you might need to hire subduct cleaners.
Tip#4. Thermostat Batteries and Program.
A lot of thermostats will have batteries and some of the customers are not aware their thermostat has batteries.
Usually, there will be a low battery symbol that appears but unfortunately many people miss that little notification until their furnace stops heating.

At other times, the low battery symbol doesn’t always appear when the batteries get weaker.
Before you start having problems, check out your thermostat, pull it off the wall and look for its batteries. There usually AA or AAA.

If you have a programmable thermostat, learn how that programming works because if your thermostat accidentally gets bumped into the program mode instead of the manual hold, your temperatures can be jumping around all over the place.
Even if you don’t like to use the programming feature on your thermostat, you must still learn it just so you’re aware of how it works and if something like that does start happening, you’ll be able to realize what’s going on.
Tip#5. Humidifier Panel, Damper, Settings.
Not everybody will have a whole house humidifier but there are quite a few furnaces out there that do have them and the only thing you should be aware of about the humidifier is replacing the water panel. The water panel is the filter for the humidifier.
Most of the covers will come off pretty easy, for some, there might be screws holding it but for the most part, they do come off pretty easy.

If you use your humidifier, the water panel will get dirty.

If you press on it and your finger just crumbles right through it, that means you should replace that water panel.

Usually, the frame will stay, the top comes off and the panel slides out. You can slide a new one in and you’re good to go.
Most humidifiers will also have a damper. Some have a damper right on the side, other humidifiers will have a damper built in the little round duct further down the line.
What the damper does is closing and opening the air supply to the humidifier. In the winter when you use your humidifier, you want that little duct to be open. In the summer when you’re not using the humidifier, you want this damper to be closed.
And also, be aware of where your humidifier control is or the humidistat. Once again, in the winter you want this thing to be on and in the summer, you want it to be off or at least on if you’re going to be using it.
A quick note on that, it has a bunch of numbers usually it’ll go from like 50 to 10, you can turn it up as high as you want. Of course, the higher you’re setting it, the more humidity to the point where if your windows are fogging up that means you have too much humidity.
You can turn up as high as you want until your windows start to fog, if they’re fogging up like you wake up in the morning and your windows are all watery then you have it set too high you want to turn that down.
For most people, the comfort level is about 35-40 percent.
Tip#6. Carbon Monoxide Detector.
In most states, by code, you should have a Carbon Monoxide detector on every single living floor of your house – no more than 10 feet away from bedrooms where people sleep.
There are standalone carbon monoxide detectors and there’s also the duals where it’s a smoke detector and a carbon monoxide detector in one.

We recommend you get the ones that have a digital display on them so you can see a live reading of the carbon monoxide reading in your house.

It is because most carbon monoxide detectors are only going to sound an alarm if there are 50 parts per million carbon monoxide in your home already, which at those levels, you’re probably already going to start to feel a little bit dizzy and maybe even nauseous.
So, we’d like you to have the little display and that display should always be zero so whenever you’re walking by it, you should always see a zero there.
And one last note about the carbon monoxide detectors, Fire Department’s recommend you replace the CO detectors every five to seven years. Replacing the batteries does not help because the actual carbon monoxide sensor inside of those little detectors are the ones that fail.
If you have old carbon monoxide detectors, you better be getting some new detectors in your house because carbon monoxide is a deadly gas and is fatal if the worst were to happen.
Tip#7. Know Where Your Shut-offs Are.
Every homeowner should know where their power and gas shutoff from their furnace is. Look on the sides of your furnace you will see a junction box or the power switch and if the power switch is not at the side of your furnace then just follow the cable that comes out the side of your furnace.
It is either a rigid cable or a solid one, just follow it where it goes and a lot of times, the power switch will be wherever that cable is going.
Some junction boxes will have mounted transformer for your humidifier but most people will not have that and usually, the junction box is just a standalone box.
Of course, you can just turn off the breaker going to your furnace.
For gas supply line shutoff, some are conveniently right next to their furnace. If it’s a valve, what you have to remember about these valves is if it makes a cross that means that’s off and if it goes with the pipe that means the gas supply is on.

The shutoff valve will not always be close to the furnace and if yours is not just follow the piping coming from your gas valve going outside the furnace. Just like the power cable, just track down the piping, follow it, and find out where to shut off is.
By code, every furnace should have a shutoff in the gas piping going to the furnace and there’s also an on/off switch on every single gas valve in a furnace as well.

It’s just a little switch, usually, they are pretty tiny switches that says on/off. And you can turn off the gas supply to the furnace just by turning that gas valve off as well.
Tip#8. Check Intake and Exhaust Pipes.
Tip number eight involves only high-efficiency furnaces. So, if you have the plastic PVC exhaust pipe and intake pipe, a good thing to check for is to go outside where those pipes go out at the side of your house and make sure that those pipes are not covered in snow, especially if you live in an area where you get a lot of snow.

If those pipes get covered by snow so will be the exhaust and intake then your furnace is going to stop working, so make sure the area underneath those pipes is shoveled so the snow is not getting too high.
Also, the exhaust pipe creates condensation. The exhaust fumes coming out have a lot of moisture in them so an icicle usually starts to grow on the bottom of the exhaust pipe and sometimes they get really big and if they reach the exhaust pipe, they start to build up and start closing off that exhaust pipe as well.

So, if you see a big icicle on the bottom of your exhaust pipe, clear that off so it doesn’t bring you problems later on.
So that’s the outside portion, as for the inside we’re the intake pipe comes in, there’s usually going to be a burner box, it’ll be sealed off.

It’ll have like a cover door with about six or eight screws holding it on. You can just take all those screws out and you can take that burner door off. If you haven’t taken it off in a long time, it can be pretty hard to pry off.
Once you take that off, a lot of times the intake pipe will suck-in stuff from the outside like grass, bugs, and leaves. Those kinds of stuff will start to settle inside of your burner box, you can just take a vacuum cleaner and maybe a brush and just get all that stuff out of there.
And clean your furnace as well, if there are dust and debris inside, you can just clean and vacuum all that up so there’s not a lot of stuff inside of your furnace.
Tip#9. Check for Leaks.
Open up your furnace doors and inspect for any kind of water leaks. So, if you’re seeing any frost build-up especially if you’re seeing freshwater, try to figure out where the water is coming from. This will mostly pertain to high-efficiency furnaces that condense or create water.
80% of furnaces with the steel vent do not create water so the only time any water can leak over them is if the air conditioner, for some reason, is leaking over your furnace. A water leak could also be from the humidifier.
Tip#10. Clean the Flame Sensor.
Occasionally, every couple of years, clean the flame sensor. A dirty flame sensor happens to be the number one furnace problem so periodically cleaning it will prevent it from causing you trouble down the road.
Many of the modern furnaces will have a hot surface igniter, that igniter will have two white wires going to it.

Whereas the flame sensor will only have one white wire going to it.

So, that’s an easy way to tell on which side the flame sensor is.
Or you can just look back there and try to find the metal rod. Of course, when you’re doing this, you have to switch off the furnace power.
Usually, it’s going to be just 1/4 inch screw holding the flame sensor in, you take that screw out and just wiggle that flame sensor out.

It’s just a metal rod. It has different shapes, sometimes it’ll be a straight rod, they can be long or short.

Also, there will be dust and other debris that settles on most furnaces.
Cleaning the flame sensor is very easy. All you need is like a dishwasher scrubby, a Scotch Brite pad.

It’s not recommended to use sandpaper on them. You don’t want to scratch it because then it seems like the dust settles on it a lot faster than it normally would.
So, you just take a Scotch Brite pad or whatever it is that you’re using, any kind of a scrubby pad should work.
The main part is to just grip the flame sensor rod real tight. If you’re just lightly brushing it, you’re not going to get much stuff off. You have to press down on it pretty firm.

Press down and just polish it up, make sure you twist the scrubby pad so you get all the sides there. After you scrubbed it all off, the flame sensor will not give you any trouble for the next couple of years.
Just make sure you put it back in place. Usually, there’s only one screw hole so you can’t put this thing back wrong. It’s the most common furnace problem but also happens to be the easiest furnace problem to fix as well.
And those are the 10 furnace maintenance tips that we had for you and as a bonus, we also want to mention that most furnaces have the owner’s manual. If you happen to have that book from your furnace still those owner manuals will have a maintenance checklist provided in that manual of things that you can check in your furnaces.
Usually, it will look like the image below.

But you have to be a service technician to be able to check some of what’s on the list like checking and adjusting the gas pressure for example, but a homeowner can check and do themselves many of the things on this list.
Don’t worry If you can’t find your owner’s manual. Most of the major manufacturers like Carrier, Bryant, etc. will have the owner’s manuals online that you could lookup.
Just go to google and type in the brand and the model number owner’s manual. The model number of your furnace is usually going to be somewhere inside of your furnace cabinet or at the back of your furnace door.

You should be able to find your manual online but most of those checklists are pretty similar.
We hope you find this read useful. Check out more of our articles for more tips.

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