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Air Conditioner and Heat Pump Noises: A Complete Guide

Is your A/C or Heat Pump making noise? We walk through what you can do to assess and fix the situation along with your HVAC service partner.

Air Conditioner and Heat Pump Noises: A Complete Guide

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Joshua Rodriguez


July 7th, 2020

Humming. Clicking. Buzzing. Clanking. Whirring. Crackling. Gurgling?!

Whatever the sound, these are noises that you don’t want to hear coming from your air conditioner or heat pump. Yet, they do occur, and so they must be dealt with swiftly. The alternative, which is not doing anything about it, can cause you discomfort and can sap efficiency and life out of your cooling equipment.

At Fire & Ice, we see noise issues in many different systems. The causes vary, and are often related to other technical issues, but the steps needed to proactively manage them are common to all homeowners.

This article is intended to do a few things. We won’t be able to tell you exactly what’s causing the noise in your system (hint: no one can without a complete, in-home inspection), but we may be able to narrow it down.

We’ll also show you how to proactively manage these issues, both with maintenance and with common sense practices around the equipment.

Lastly, we’ll discuss high-level options for dealing with a noisy air conditioner or heat pump. These options include moving the unit, having it repaired, or replacing it altogether.

That gurgle can’t wait any longer! Let’s get into it.

My A/C or Heat Pump is Making Noise...Now What?

The first step is to call your HVAC contractor ASAP. Anything else is simply wasting time and effort.

A good contractor is going to ask you a series of questions to try to hone in on possible sources of the noise(s). These questions can include:

  • Age of the system
  • Type of noise (clicking, banging, etc.)
  • Location and frequency of the noise
  • How long the noise has been occurring
  • Does it occur at startup, during operation, or only on certain settings or at certain temperatures
  • Type of refrigerant used

It’s important to note that, while they may offer a couple of theories on the source of the noise, this isn’t something that can ever be accurately diagnosed over the phone. There are simply too many moving parts in an HVAC system to be able to isolate a problem issue without inspecting it directly.

The good news is, these questions are still important, because they can reduce the time needed to identify an issue. Questions like the age of your system can also inform what the next steps should be. For example, if your air conditioner is 20 years old, parts may be harder to come by, or a repair may simply cost more than it’s worth. A conversation about replacing the unit entirely is probably warranted.

Conversely, that same issue in a 3-year-old system is probably worth repairing.

Noise-Causing HVAC Problems

The parts and potential sources of noise in a system are myriad. However, depending on the type of noise and age of the system, some are more common than others.

In a newer system, the compressor and outdoor fan are two common sources of noise.

In the example of the compressor, if the condenser coil is plugged or dirty, the compressor isn’t going to be able to pull enough air through the system. So it will increase the pressure to compensate.

This, in turn, can throw several systems off. Cooling systems are all about regulating pressure. The proper pressure to absorb heat from the evaporator coil in the indoor unit is not the same as the pressure needed to expel heat from the outdoor unit. Increasing the pressure at one point can and will have downstream effects. These effects can include decreased efficiency of the evaporator coil, resulting in poor system performance, or simply increased workload for the compressor, which will cause it to fail sooner.

Importantly, “failure” may not come for several months or even years in some cases. But during that time, you’re using more energy (i.e. higher energy bills) while getting less cooling benefits from your system (i.e. lower efficiency). And you’re probably sacrificing years off of the total life of your system unless it’s fixed.

It’s like having bad spark plugs in a car. Eventually, it’s going to mess up the whole system: your fuel mileage will suffer, how confidently it runs can fluctuate, and it can have downstream effects for larger parts like the central engine.

In practice, it can sound like your air conditioning system is ready to blow up, since the system isn’t designed to handle the type of pressure the compressor is creating. While the unit wouldn’t actually explode in this case, the actual worst-case scenario isn’t much better.

This is just one example, but it’s the type of thing a repair technician will be looking for and fixing if needed. If the noise is elsewhere, it could be another issue. The inside contactor, for example, is a voltage-control part. It can buzz when working improperly. If the blade in the outdoor unit is off-kilter, it can produce a loud hum. Or maybe something in the motor or fan is stuck, which can produce clanking.

Going exhaustively through each possible example would ultimately not be useful. Understanding the type of inspection that’s done, though, and how a single issue can affect multiple system parts, is the more important takeaway for a homeowner.

Are Systems Naturally Noisy?

The age of your unit will alter the answer here somewhat. Older systems weren’t designed to be as quiet as modern systems. As systems age, there can also be a slow, progressive increase in noise that isn’t related to a specific part. It could always be something worse, but perhaps it’s just missing a few screws that cause it to shake more.

That said, even an older system shouldn’t be waking you up at night or causing a distraction as you’re going about your day.

For most systems, though, the answer is: No, they should run very quietly.

Many modern systems run between 70-75 decibels, which is something you’ll be able to hear but that won’t cause a noise issue since the unit is outside.

The quietest modern systems run as quiet as 40-50 decibels! 40 decibels is about the equivalent of reading in a library. These units will be difficult to hear at all unless you’re right next to them.

The same is true of ductless mini-split systems. These generally run 45-50 decibels on their highest settings, and even quieter at lower settings. If you’re alone in a room with a ductless mini-split and you’re browsing the internet, for example, you’ll be able to hear the unit, but it will be the equivalent of ambient or white noise, much like if a small fan were running.

We say all of that to say this: You should expect quiet operation. Now let’s talk about some ways to ensure that.

Raised, Plastic and Concrete A/C Pads

There are homes, usually built between 1990-2000, that have the outdoor air conditioner on a raised platform that’s attached to the home. The brackets that attach it to the home are attached to the home’s foundation. Especially as a system ages, but also at any point, the vibrations from the unit can travel through this connection, up the walls and into the home, producing noise.

So why would this be the norm for any home?

To get this out of the way now: it shouldn’t be like this. But the answer to why it happens lies in home construction. When a house is built, a hole is dug, and the foundations are set before the hole is back-filled. An HVAC installer can’t install a unit on the ground until this hole is back-filled, but that’s often one of the last stages of construction. So many began installing them on raised platforms to finish the job earlier.

This can increase noise, plain and simple. Even beyond the noise, many modern units are more efficient but also larger as a result. Most can’t fit safely on the raised platforms that were installed decades ago.

If you’re replacing a raised unit, do yourself a favor and talk to your contractor about removing the platform and installing it on a ground pad.

Speaking of the plastic pad that the outdoor unit should rest on, beyond being easy to install and durable, these pads can often absorb more vibration than concrete pads, which are another common method of installation.

Placement, Installation, and Location

We mentioned the increased size of many units, and this can occasionally make a difference. A 20-year-old outdoor air conditioner may have been below a first-floor bedroom window, for instance, but a new one might peek over the bottom of the window. This can have noise implications, so it’s best to consider the size of an incoming system when deciding where you would like it installed.

Some homeowners will also request a location that places the outdoor unit away from a deck, patio, or porch. It never hurts to consider location when replacing an old unit and installing a new one.

We also get questions about plants around the outdoor unit. The exact clearance guidelines will depend on the model being installed, but in general, you should be leaving 12-18 inches on all sides, and up to 36 if one side has a door or service panel.

Planting around a unit in this way may reduce the noise a little, but the bigger fear is that the plants prevent the proper operation of the equipment, which will increase the noise. Make sure you’re monitoring anything that’s near your heat pump or A/C.

Maintenance Solutions

We talked earlier about the questions that a contractor will ask over the phone. This is because if noise is a recurring problem for you, it’s almost certainly a maintenance issue.

The best way to prepare for unwanted noises is to have a maintenance plan with a trusted HVAC partner. Maintenance visits will prevent all kinds of problems and ensure the efficiency and longevity of a system.

By comparison, waiting until you hear gurgling noises every time you start up your air conditioner to call a service technician is not the right way to handle things. You’re going to end up paying more, and the problem is likely something that could have been prevented if caught earlier.

Repair, Replace or Move Your Noisy HVAC Unit

So you’ve got a noise, and you’ve scheduled a technician to visit your home. What are your options going to be?

Repair/Replace Parts

Repairing makes the most intuitive sense for noise issues, presuming that the system as a whole is still working. However, the age of your system plays a factor here, since some repairs can be surprisingly costly. If you’re within a few years of needing to replace the system altogether, repairing or replacing an expensive part can be more money than it’s worth.

Replace the Air Conditioner/Heat Pump

Replace the entire thing just based on some noise?! Not necessarily. But, as we mentioned above, say the compressor is more or less shot. Replacing that part in many systems can be a third (or more) the cost of a brand new system. Once you factor in the added savings you’ll get through the efficiency of a new system, a full replacement is often the less costly option. Just as importantly, it’s often the more comfortable option as well.

RELATED: Should I Repair or Replace My Air Conditioner?

RELATED: How Much Does a Heat Pump Cost to Replace?

Moving the Unit

Moving a unit to reduce noise can often be more hassle than it’s worth. For starters, moving and reinstalling equipment is a time-consuming, technical process that can incur significant labor costs. Second, it’s never an ideal solution to open a sealed system like an air conditioner or heat pump, and it is often better to simply consider one of the two options listed above.

If you really want to move your outdoor unit, it can be done. But generally, we find that the best reasons to move a unit have more to do with an upcoming installation of a deck, patio, or other home addition, not reasons related to noise.

Next Steps

If politely asking your system to stop making so much noise didn’t work, it’s time to call your HVAC contractor. If you have a maintenance plan with a licensed contractor, you’re set, and can prepare for their arrival.

If not, we’d love to help you out. At Fire & Ice, we service thousands of systems each year, and deal with a wide range of issues related to noise and any other area of HVAC repair. Start your scheduling process below and take the most important step toward a quieter, healthier air conditioner or heat pump unit.

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