Pets & Pests vs Air Conditioners: How Animals Damage HVAC Systems

Pets & Pests vs Air Conditioners: How Animals Damage HVAC Systems
Joshua Rodriguez
Installation Manager

I am the Install manager at Fire & Ice, since 2017. I have spent 28 years in this business and have experienced nearly every aspect of HVAC from Industrial, commercial, and residential buildings. From design, install, service, or sales, if it moves air, I’ve worked on it.

About This Article

How can animals ruin HVAC equipment? You might be surprised at the number of ways.

Your air conditioner/heat pump was built to be outside. And being outside means that it has to put up with the best and worst of Mother Nature: hail, sleet, snow, ice, etc.

The good news is that HVAC equipment is built to withstand these conditions and tested to ensure that it will perform well for years in a variety of weather conditions.

But there’s a wildcard factor, as we have learned from service calls to repair air conditioners: Dog pee.

Also mice, snakes, spiders, and cats.

Some are lovable pets. Others are just pests.

This article will cover the unexpected damage that animals can inflict on your heat pump, furnace, or air conditioner. The damage can be slight: a small hole here, a chewed wire there. But the problem can quickly become major; some repair costs can run as much as buying a new unit.

If you’ve already had to deal with this, or want to reduce the possibility that something catastrophic will occur, read on

A Trane air conditioner.

Dog Pee Can Ruin Your AC or Heat Pump

You have two types of coils on your AC/heat pump. You have copper and aluminum, and then all aluminum.

On a spiny fin unit - such as Trane models - picture a tube with spikes going all around it. The spikes and the tube are both aluminum.

Dog urine is very acidic. That dog urine will destroy aluminum quickly and make a hole. If your dog’s urine hits the condenser coils, the corrosion could lead to a freon leak. If the leak is small and if you catch it early enough, you may get lucky and a professional may be able to find and repair the leak instead of replacing the coil. If the leak isn’t repairable, you might have to replace the entire coil.

You should replace the coil when dog urine has caused extensive damage to it, or more than 25% of the fins are missing AND:

  • Your air conditioner is still relatively new.
  • A replacement coil can be found and installed for no more than 50% of what it would cost to replace the whole outside unit.

To replace that coil could be anywhere from $1800 up. This depends on the amount of refrigerant it takes to recharge the system and the size of the unit.

If the AC Coil Isn’t Completely Ruined

If a few fins are damaged, your AC will still function, but it will transfer air at a slower pace. Your AC has to work harder without as many fins. This results in higher energy bills and an inefficient air conditioner.

If you have the copper and aluminum variety, the copper carries the refrigerant. The urine will dissolve the aluminum fins off of the copper. You’re left with copper tubes that aren’t going to transfer much conditioned air. You can see a lot of this on old air conditioners or heat pumps.

A repair technician may need to recharge your system with more refrigerant—and if your unit takes R-22 refrigerant (an old refrigerant that’s being phased out) this can end up costing you more.

An air conditioner.

How to Prevent Dog Pee Damage

Manufacturers try to protect the insides of outdoor units using louvered panels. The exterior is made of steel. They have a finished coat that protects the coil. It’s kind of like the coating on a car. It can stand up to urine, but it’s not going to prevent all of the damage.

So it’s important to train your animal to not go by there, or to put up some sort of fence. The fence needs a gate for access, and shouldn’t be right next to the unit. Your air conditioner/heat pump needs to breathe. If the fence restricts the air, the unit will suffocate, which could lead to another expensive repair. A mesh cage, provided it’s far enough away from the unit to prevent splashing, can work.

And even if you do manage to train your dog to stay away from your air conditioner, roaming neighborhood dogs won’t be so easily deterred.

This sort of damage is not covered under warranty because it’s a non-manufacturer defect. Nothing wore out or broke because of a deficiency. It is an unfortunate repair.

And if your fins or coils are ruined, and your AC is over 10 years old, it may be a better investment to replace the unit. Oftentimes, the cost to repair the fins and/or coils will be just as expensive (if not more so) than to replace the outdoor unit entirely.

If you’re looking to install a new air conditioner, you can ask about a wall rack that raises the unit above a dog’s pee range. Or you can place the new unit away from the dog’s fenced area. You can spray the exterior of the air conditioner with an odor that deters dogs to help prevent damage.

Rodents & Bugs can Infest Your Line Set Hole

Another area to consider outside of your home is the hole in the side of your house where the line set runs. A line set is the copper tubing that connects the condenser to the evaporator in your air conditioning system. More broadly, it’s the materials used to guide, protect, and insulate an air conditioner’s refrigerant line. It connects to your furnace.

If the hole is big enough, that hole is an invitation for:

  1. Rodents and small animals
  2. Bug infestations, especially as the weather outside turns cold and insects look for a warm area to protect themselves

Do you want to patch it? An HVAC company can handle it, but it involves disconnecting the refrigerant line. To do that, the refrigerant has to be isolated and removed from the line, then recalibrated for proper pressures when it’s being reinstalled.

Then comes the sticker shock. The cost involved in fixing a small hole approaches the labor cost of a full AC installation. It’s best to find the right HVAC company that will ensure that hole doesn’t exist in the first place. For instance, the Airex Pro is a Positive Seal System for outdoor HVAC units and is an innovative solution to the problems created by poor air conditioner installation and ugly, inefficient line sets.

Pet Dander Can Clog Your Furnace Filter

Regrettably, you may be able to protect your outside heat pump/air conditioner, but still have to deal with your pets indoors. The problem there is pet dander, which floats around until it winds up on your furnace filter. The more pets you have, the worse the dander, the sooner your filter needs to be replaced.

You may have a filter that claims that it needs to be replaced every six months. If you have multiple pets, six months may be too long to wait. You might want to check your filter after four, no more than five months to see how dirty it is. Change it when it’s clear that it can’t trap much more airborne debris.

A technician installing a filter.

Your furnace is likely to continue to run for quite a while - perhaps even years - with a filter in need of replacement. But consider the consequences:

  • Airflow will eventually become very restricted, which will make it harder to heat your home. This could result in less heat, and it will cause your system to work harder, thus burning more energy to get the same level of heat. (It will have the same effect on your air conditioner.)
  • Your air quality will suffer, which opens your home up to allergens, dirt, dust, and other particulates. Any and all of these can exacerbate breathing problems, such as asthma.
  • Over time, these problems become worse. The difference between regular maintenance and a neglected system is the difference between one that will last you 15-20 years and one that will last 10-12 years.
Buy Your Filter

Mice Can Chew Through Wires

Chewing on electrical wires sharpens the teeth of mice. Biting on hard things makes their teeth firmer and stronger. Mice can gnaw the insulation on HVAC wires. That might fry the unit when it kicks on.

You may want to consider a duct-sealing service to keep not only mice but also bugs out of the ducts. You also want to inspect ductwork throughout your house, to see if there are any cracks between your ducts and the wall. A mouse needs only a tiny opening for it to be able to crawl through.

Once a mouse has found a place to call home, it will begin to build. Attic insulation and duct insulation are prime material for nests.

You may smell a pungent odor even if none of the pests have died and started decomposing; that odor is the smell of fermenting urine in the ducts. Not only can a rodent affect the aroma in your home, they can begin to affect the airflow of your HVAC system.

Almost no material is safe from rodent damage, but some are more susceptible than others. Some homes have ductwork made from fiberglass duct board or cardboard. These could easily become nest material and leave leaks in your HVAC system.

That's one of the benefits of regular maintenance. Mice (and other rodents) are in your ducts and furnace because it’s peaceful; nobody ever goes in there. If HVAC technicians get in there a couple of times a year, they can bust up that dark, cozy home.

Snakes feed on mice. Get rid of the mice, and the snakes will look elsewhere for dinner, hopefully away from your home.

HVAC Lines on the outside of a building.

Nests Can Block Your Furnace Exhaust

Unfortunately, birds and squirrels (yes, squirrels build nests, too) don’t always pick the best places to build their nests. Sometimes they build in the exhaust pipe of your heating system.

Your exhaust pipe’s job is to direct deadly gases, such as carbon monoxide, out of your home. If it’s blocked, the gas can’t get out. It comes back into your home, and you have a serious health hazard.

A visual inspection can confirm this. Or you can use a carbon monoxide detector if you suspect the damage has been done.

Next Steps

You can pet-proof/rodent-proof most of your HVAC yourself, provided you know what you’re looking for. We hope we’ve given you some clues about those strange noises you might be hearing in your ducts, and how to keep Rover from costing you a fortune on air conditioning repairs.

If you’re ready to talk to us about your HVAC needs and to schedule an estimate, check below to see if you’re in our service area. We look forward to helping you live in a more comfortable home.

Meanwhile, here are some related articles we hope you will find informative:

How Much Does a Heat Pump Cost to Replace in 2021?
How Much Does a New Furnace Replacement Cost in 2021?

Cost of a Air Conditioner Replacement in 2021

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