Category: Blog

Short-Cycling Furnaces and What to Do

Because winter is quickly approaching, you want to ensure your furnace is working properly at keeping your home warm and your family comfortable. If you feel like hardly any heat came from your vents and/or your unit shuts off shortly after firing up, it may be short cycling. Short cycling means that the furnace turns on and off very frequently with little time between on and off. This is a common issue that you may experience with your furnace this time of year. If you start having furnace problems (even if it doesn’t completely go out), go ahead and give us a call at Mainline HVAC in Alabaster, AL, so we can diagnose the problem and complete any furnace repair as soon as possible. We’ve already had some cold weather and are expecting more and we don’t want you to go without heat. Let’s take a look at the what and why of short-cycling– 

Why Does a Furnace Short Cycle? What causes it?   

Common short cycling causes include:

  • Overheating
  • Bad flame sensor
  • Dirty furnace
  • Blocked heat grates/ registers
  • Blocked exhaust vent
  • Thermostat is in the wrong location
  • Furnace is too big for your home

Thankfully, when we take a look at your system, we will be able to figure out which of these is causing the issues. You won’t have to worry about a thing, we’ve got it taken care of.


Like most equipment, furnaces have a way to shut off to prevent dangerous overheating and damage. Your furnace may turn off prematurely if it’s overheating, which is a good thing as far as safety goes, but bad for keeping your home warm. An overheating furnace can potentially cause cracks in the heat exchanger, which could cause carbon monoxide to leak into your home. You might be wondering, “Do I have to replace my whole furnace if it’s short cycling?” Not necessarily. There are many reasons a furnace may get overheated and cause short cycling and most don’t require a full replacement. Some of the causes actually require very simple corrections. Here are the most common reasons:

  • Blocked Registers

The registers in your floor, walls, or ceiling likely have a way to close them, allowing you to control which rooms get heat. If too many of these vents are closed your furnace can’t disperse enough heat, so the heat will build up in the furnace, causing it to overheat and shut down. Make sure that most of your registers are open and not being blocked by anything like furniture. If you make these adjustments and your furnace is still acting up, then this was likely not the main cause.

  • Blocked Exhaust Vent

This is a dangerous cause of overheating and short cycling since it can allow carbon monoxide through the vent. The exhaust vent becomes blocked by birds’ nests from birds, beehives, or something else. If you check it out and realize the cause is a nest, it may be best to have animal control or pest control handle the task.


  • Dirty Furnace Filter

A dirty filter can cause overheating, kind of like with a clothes dryer. A sign is that you feel hotter than usual air coming out of the registers- seems like hotter air would be nice when you’re trying to heat the house, but it’s actually a sign of overheating. If the furnace gets too hot, the switch will shut it off. A dirty filter in your returns prevents a flow of return air into the furnace, and will quickly overheat. The solution is super simple- change your filters out regularly (several times a year).

Can It Be Something Other Than Overheating?

Yes, sometimes short cycling can be as simple as bad thermostat placement. If your thermostat is getting warmed before the rest of the house, it will cause your furnace to turn off prematurely. This can be due to poor placement like right above a register or on the wall of the utility closet where the furnace is located. If placed here, the thermostat will heat quickly and reach its set point before it should. The solution is easy! Just relocate the thermostat to a location that isn’t near a vent or window.


If you read through this and realized it sounds like your current situation, your furnace may be short cycling or overheating. Contact Mainline HVAC for your furnace repair needs in Alabaster, AL and surrounding communities. While it could be something as simple as a thermostat issue, it could also be something more serious, so it’s always best to have our Mainline professionals take a look.

How to Prep Your House for Cold Weather

We’re starting to get a sneak peek of colder weather at night, even though daytime temperatures are still fairly warm…welcome to Alabama, right? As the weather starts the cooling trend, it’s so important to prep your house ahead of time to prevent issues and catch potential problems. The last thing you need is to frantically get things in order the day before a freezing cold night. And you definitely don’t want to be left in the cold if you have a faulty furnace that calls it quits- that’s why we offer furnace tuneups. Here’s easy, helpful list for what needs to be done:

Indoor Water Sources

  • Identify any problem pipes- consider areas that have been problematic in the past
  • Insulate said problem pipes with heat tape or other insulation products.
  • Instruct everyone in your household how to turn off the house’s water source in case you do experience a frozen or busted pipe and need to shut off the water until a plumber can come fix it.

Remember to keep faucets dripping and open the cabinets under your sinks when temperatures are below freezing at night. Put something under the faucet to catch the dripping water to use elsewhere the following day.


  • Disconnect water hoses and drain any leftover water
  • Store garden hoses and other outdoor equipment in a dry location ❏ Cover spigots- can use styrofoam kind or other available options ❏ Have in-ground sprinkler system blown out by professionals


  • Call​ Mainline Heating and Air for a furnace tuneup- we’ll check electrical components, pilot or flame sensors, safety controls, as well as inspect and clean the burners
  • Make sure vents are cleaned out and filters are replaced
  • Have furnace ducts sealed if they aren’t already- we can help with duct sealing as well

Remember to have a professional inspect and clean the chimney before use (if you have a wood-burning fireplace). This will help prevent health issues and​ ​hazardous accidents.

Windows and Doors

How to test for drafty doors and windows- light a candle (wick exposed, not the kind in a jar) and hold it in front of the door frame or windowsill. If the flame noticeably flickers, you have a bad seal. That means the quickly arriving cold air will easily be able to seep into your home and cause a higher energy bill.

  • Test door frames and window frames as explained above
  • Add (or replace) weatherstripping- your local hardware store should have several options available and can explain how to install them.
  • Install door sweeps where needed

Join our ​Maintenance Club​ so that you can get biannual tuneups without having to think twice about it. You’ll know with certainty that your furnace will get you through the colder months. We can also provide furnace repairs in Birmingham, AL whenever your system isn’t working properly.

Air Filters 101: What’s the Difference and Which one is Best?

If you’re about to go on a run, are you going to wear soccer cleats? What about wearing cowboy boots for a tennis match? No of course not, that would be ridiculous. Most shoes serve the same general purpose- protecting your feet, but obviously some are fit for specific situations or sports. It’s kind of the same with air filters. They all have a similar purpose- to keep your unit running at peak efficiency and improve air quality in your home. But some filters are better than others at specific tasks like allergen control. Did you know that there are more than seven different kinds of air filters? They’re made of different materials, for different purposes, and they’re not all created equal. Since there are so many different filters to choose from, how are you supposed to know which one you need? Is the kind you currently use the right for your system? Let’s discuss your options, the differences and similarities, and how to narrow down the right filter for your home. 


First, it’s important to note that filters are rated using the Minimum Efficiency Reporting Value (MERV), on a scale of 1 to 16 (16 being the most effective) for how well the filter can trap pollutants that are as small as 0.3 microns and as large as 10 microns. A lower MERV rating means that the filter is more effective at removing large particles- pollen, dust mites, and carpet fibers. A higher MERV rating means it’s better at catching small particles- smoke, bacteria, and viruses. 



  • Pleated filters


Material: polyester or cotton folds 

Uses: filtering dust and airborne pollutants; increased surface area helps trap more. 

Considerations: Puts more strain on the unit because it’s harder for air to filter through. 

MERV rating: between 5-11


  • UV light filters


Material: shortwave ultraviolet lights

Uses: Kills mold and germs; helps prevent disease and illness 

Considerations: Useless against common pollutants like dust; ineffective against fumes; costly installation

MERV rating:


  • HEPA filters


Material: uses static electricity

Uses: highest filtering (even bacteria); ideal for people with severe allergies or respiratory illness 

Considerations: May not help with odors or fumes

MERV rating: near 16


  • Spun glass filters


Material: spun strands of fiberglass; disposable and inexpensive

Uses: Good at filtering lint and dust; one of the least expensive options

Considerations: Doesn’t filter enough to make a noticeable difference in air quality, therefore not recommended for people with respiratory problems; can get clogged

MERV rating: 2-3


  • Washable filters


Material: differing materials; washable

Uses: Only has to be bought once; environmentally friendly option; durable

Considerations: must be completely dried after washing and before reinserting. 

MERV rating: 3-4


  • Electrostatic filters


Material: small paper and cotton fibers; can be reusable or disposable

Uses: Can improve air quality in the home; cost-effective

Considerations: Struggles filtering bigger particles like dust. 

MERV rating: 8-11


  • Media filters


Material: Some are carbon coated

Uses: Low maintenance; cost-effective; have a higher surface area so they’re able to filter more and keep dirt trapped; only has to be replaced one or twice a year.

Consideration: May need to be professionally installed

MERV rating: 11-13


So which one is right for your home? It depends on what you’re wanting from a filter, how much you’re willing to spend, and how often you want to mess with it. Media filters are a great, popular “best of both worlds” option. If you or a loved one has severe allergies, you might need to consider something more intense like a combination of HEPA and UV light filters. We want you to breathe in clean, cool air in your home and are ready to help that happen! Keep in mind that air quality checks and air purification solutions are just 2 of the many AC services that Mainline Heating and Air Conditioning offers in the Birmingham, AL area. Contact us today so we can make sure you’re using the air filter that’s best for your unit and your home.

These 3 Thermostat Habits are Costing You Money

Did your energy bills this summer make you want to cry? We get it…it’s extremely hot outside and you want to have a nicely cooled home, especially while you’re sleeping. Did you know that you may have some thermostat habits that are costing you money with no desired results? So if you are looking for ways to cut your energy use, making changes to your thermostat usage is a good place to start, considering that your HVAC usage makes up a good chunk of your monthly energy costs. If the following don’t apply to you, you made need AC service from your trusted experts here at Mainline Heating and Air in Birmingham, AL.But first, here are the 3 most common bad habits to break:


Habit 1: Attempting to cool your home “faster”

Setting the thermostat at 70° to get the temperature from 78° to your preferred 74° is surprisingly a bad idea, since it doesn’t actually speed up the cooling process like you’re expecting it to. Unless you have a two-stage unit, your AC only works at one set speed. Setting it lower to get to your desired temperature faster will only make the unit run longer at the same speed to reach the lower temperature setting. And when the AC runs longer…it’s going to cost you more money. So if you want it at 74° as soon as possible, just go ahead and set it to that. It’ll get there just as fast and save you money when compared to what you were doing!


Habit 2: Keeping your thermostat set at the same temperature 24/7

Setting the thermostat at a specific temperature and never touching it

Is the most energy-efficient way to do it, right? Actually, no. According to ENERGY STAR, you could be wasting as much as $180/year! Instead, you should change your thermostat setting whenever you leave

your home for 8 hours or longer, which is a normal work day for many. Essentially, you’re wasting money by cooling an empty house. Now, that’s  When your home will be empty for 8 hours or longer, set your thermostat

5°-8° higher in the summer. Then you can set the thermostat back to your comfortable setting when you get home. According to the U.S. Department of Energy, this can save you 5-15% on your yearly energy costs! 


What if you can’t remember to do that everyday? Or want to come home to a cool, comfortable home without waiting for your preferred temperature? Consider a programmable thermostat that can be controlled by an app or smart home device. You can set it back to something more comfortable on your way home from work, or the ball field, or wherever you’ve been. We would love to discuss these options with you! It could really help save some money on your energy bill and save you from potential frustration. 


Habitat 3: Adjusting the thermostat too much

Doesn’t this seem to go against the previous bad habit? You might be thinking, “So I need to adjust my thermostat daily, but not adjust it too often? Give me a break!” Adjusting it once in the morning as you’re heading out the door and then again after you get home is a good thing. Constantly adjusting it to get the optimal comfort is not ideal for your energy costs. Constantly changing the set temperature on your thermostat causes your

air conditioner to stop and start constantly, which causes them to run

inefficiently. Your AC should be running for longer, steadier times instead

of a constant “stop and go”. Think of it like your car- do you get

better gas mileage on streets with lots of stop lights or on the interstate?


So remember these 3 things to help you save money on your energy bills:

Don’t crank your thermostat way up or way down to heat or cool your home faster. Change your thermostat temperature setting when you’re away from home for 8+ hours. Ideally, 5°-8° higher in the summer. Don’t constantly change the thermostat setting when you’re home.


If you have good thermostat habits, but your home just isn’t getting cool (or that power bill isn’t getting any better), contact the AC professionals at Mainline Heating and Air Conditioning. We can evaluate your situation and devise the best solution. We want you to be comfortably cool for the rest of the summer and we’re available and able to help with your AC service needs in and around the Birmingham, AL area.