Variable and Multi-Speed Blowers - What's the Difference?

Do you need a blower motor for your HVAC system? Do you know the difference between variable and multi-speed blowers? Are you asking yourself what even is a blower motor? The blower motor is the part of your HVAC system that sends conditioned air through air ducts to areas throughout your indoor space, ensuring the indoor temperature reaches the temperature set on your thermostat.  In this guide, we'll explain how a blower performs this function and discuss the different types of HVAC blowers available. We'll even provide some guidance on how to pick the best one for your home.

What Is the Role of the Blower in an HVAC System?

The blower, as the name suggests, blows air and is a critical component of the HVAC system — both in heating and cooling operations. Both variable and multi-speed blowers blow conditioned air through the air ducts in your home, delivering hot or cold air to different rooms in your home. The blower consists of two components — a blower motor and a blower fan, which are together frequently referred to as the blower.

How Does It Work?

When your HVAC system starts, it produces heated or cooled air. However, once this conditioned air is produced, it cannot go anywhere without a blowing mechanism. This is why a blower is required — the blower motor will turn the blower fan, which will push the cooled or heated air through the ducts and into all rooms in your home.

How Do Variable and Multi-Speed Blowers Differ From Traditional Blowers?

Years ago, only fixed-speed blowers were available. These blowers operated at only one speed, meaning that they moved the air with the same force from when they fired up to when they shut off again.

This blower type, which is considered the traditional blower type, has been around for many years because it was simpler to manufacture and required minimal maintenance. There were just two options — off or on. As you might imagine, however, this basic design also had some disadvantages.

The primary drawback of this blower type is its inefficiency. When they are on, regardless of how much air is required, these blowers roar to life, consuming large amounts of fuel and power. This all-or-nothing system meant that indoor temperatures would fluctuate significantly during each cycle. When they are off, air stops flowing completely, depriving you of the advantages that circulation provides.

However, in recent years, HVAC blowers have become more sophisticated and now can operate at multiple speeds. As you might have guessed, the two more modern blower types are variable and multi-speed blowers.

1. Multi-Speed Blowers

Multi-speed blowers feature two, sometimes three, fan speeds, which create better airflow and allow users to have more control over cooling or heating their environment. While a furnace with a multi-speed blower may still roar to life when turned on, it will quickly switch to a lower setting to bring your living space to the desired temperature more gently and quietly.

When a system with a multi-speed blower is on, it will spend most of its time on this lower setting. This means it needs less energy to run, which will translate to significantly lower energy bills. Operating at this slower speed setting also improves air circulation.

Following the advent of multi-speed blowers, more sophisticated circuit boards were created to tell the system when each speed should be used and how long it should be used for.

2. Variable Speed Blowers

Variable speed blowers are the most advanced blower technology to date. This sophisticated component uses an HVAC motor that can run at varying speeds, depending on what is required.

Considerably more advanced than the blowers that came before them, variable speed blowers come on quietly, ramp up slowly to the output needed, then fade gently into the background. These systems monitor your living space constantly and make necessary adjustments to provide the best climate control, air quality and circulation possible.

Variable fans don't simply heat and cool — they move air through your living space continuously. Due to the filters these systems use, the air quality in your home will significantly improve and humidity will be reduced in the summer. These systems operate at the slowest speeds possible, which helps you save on energy costs and causes less wear and tear to the unit.

Both multi-speed and variable speed blowers will adequately condition the air in your home. The best one for you will depend on what you're looking for in terms of performance, upfront cost and energy savings over the unit's lifetime.

What Are the Advantages to Installing a Variable Speed Blower?

Variable speed blowers offer several advantages thanks to their electronically commutated motor (ECM) or variable speed motor, which lowers the total electricity consumption of a furnace or AC unit and helps maintain adequate airflow throughout the system. For this reason, they are also called ECM blowers.

Some of the greatest benefits of variable speed blowers include:

1. Less Noise

If a blower is operating at a faster speed than necessary, this will produce a noise near the blower assembly that many people find distracting. Furthermore, this high speed may also produce a whooshing or whistling noise in the air ducts due to the high pressure.

While HVAC systems with variable-speed blowers don't necessarily operate more quietly at their top speed, they rarely reach their top speed when in operation. On all but the coldest and hottest days, a variable speed blower will run more quietly than one- and two-stage blowers. If you are annoyed or distracted by the noise of your HVAC system, you may want to consider upgrading to a variable speed model.

2. Less Energy Use

Few things will reduce your energy bills as dramatically as upgrading to a variable-speed blower. As traditional and multi-stage blowers often run faster than necessary, they frequently consume more energy than needed.

Variable speed blowers save you on energy costs because they allow the HVAC system to adjust the fan's speed — and therefore the amount of energy it consumes — to meet the temperature demands of your home. Furthermore, a variable blower tends to run for longer than its traditional counterparts, which actually reduces the energy your HVAC system uses by cycling the furnace, AC and blower on and off less often.

3. Better Air Circulation

HVAC systems are equipped with several components that treat the air as it travels through your house to make it more comfortable. High levels of humidity are a common source of discomfort, and many people turn up their AC higher than necessary to compensate for the humidity. However, the issue is often that the air doesn't spend sufficient time in the HVAC system's dehumidifier — and variable speed blowers can solve this problem.

This is because variable speed blowers tend to operate at lower speeds, meaning that the conditioned air spends more time passing through the dehumidifier. This allows the dehumidifier to remove more moisture from the air, meaning the air in your home will remain comfortable even at a slightly higher temperature.

Should You Upgrade to a Modular Blower?

If your HVAC unit is showing any of the following signs, you may want to consider an upgrade to a modular blower:

1. Low or Complete Lack of Airflow From the Vents

This tends to be the earliest sign of a malfunctioning blower motor. If the airflow from the vents is weak, this may mean your blower motor is struggling to push sufficient air through your ducts to achieve the air temperature you want. This issue could have several possible causes, including dust and dirt accumulation, a bad capacitor or an old motor. If your blower motor has a malfunctioning capacitor or is dirty, have an HVAC professional solve the problem, but if the motor is nearing the end of its useful life, consider looking for a better motor to replace it. Keep in mind that weak airflow may also be caused by leaky or dirty ducts or a clogged filter.

If there's absolutely no air coming out of your vents at all, this could mean the blower motor has an issue that cannot be fixed. If so, you'll need to replace it. However, an absence of airflow could also result from other factors, including a bad battery or relay, a problem with the fan control or a malfunctioning thermostat. It's best to hire a professional HVAC technician to perform an inspection and diagnose the issue properly.

2. Unusual Sounds

Strange sounds coming from your HVAC system may indicate an issue with the blower motor. While some issues causing strange noises can be fixed by a professional technician, others might require replacing the motor.

For instance, screeching and squealing sounds may indicate the blower motor has bearing issues or a damaged belt. These can be solved by lubricating the bearing or replacing the belt, respectively. If you hear clanking, rattling or banging noises from the motor, this could be caused by a broken or loose component. However, loud banging noises are a cause for concern. They usually mean something is disconnected or damaged and the blower motor probably needs to be replaced.

No matter what types of sounds are coming from your blower motor, you should always turn off your system right away. Be sure to contact an HVAC professional inspect your unit as soon as possible. They can determine whether your motor can be repaired or needs to be replaced.

3. Unusually High Energy Bills

Your blower motor is one of the major energy consumers in your HVAC system. This means it could easily be the reason for an unexplained increase in your energy bills. A motor that's aging, dirty or faulty must work harder to circulate air properly. This burns more energy. If your furnace or AC unit has seen better days or has a traditional blower motor, consider replacing it.  A more sophisticated variable speed motor can adjust its energy consumption automatically to meet the changing needs of your house. That will minimize the amount of wasted energy and lower your bills.

4. Frequent Breakdowns

As mentioned above, an old or faulty blower motor has to work harder to meet your home's needs. If it struggles too much, it may break down. Needing frequent repairs is yet another reason to consider upgrading your blower motor to a variable-speed model.

You should especially consider upgrading when you replace the air conditioner or furnace. You'll want a blower that performs to the standards of the new system.

What Size Blower Do You Need?

When it comes to variable and multi-speed blowers, getting the right size is critical. To determine the size of blower you need for your home, follow these steps:

  1. Determine the square footage of your home: This will tell you how many square feet of space your unit must serve.
  2. Figure out your climate zone for heating: To figure your BTU requirements, you need to know your climate zone. Warmer states like Louisiana and Florida are in Zone 1 and only require 30 to 35 Btu per square foot. Colder states like Minnesota and Vermont are in Zone 5 and require 50 to 60 Btu per square foot. If you live in a 2,500-square foot home in Zone 4, your heater needs to produce at least 112,500 Btu.
  3. Determine the tonnage required for AC: Air conditioners are sized by the ton. A 1-ton unit removes about 12,000 Btu per hour. A good estimate is 1 ton for every 600 square feet in your home. So that 2,500-square foot home in Zone 4 would need a 4-ton air conditioner.

At Ingram's Water & Air, our units have a flexible design to fit a certain footprint. An HVAC installation professional can help you size the blower.

Heating System Options for Your Blower

Two heating system options are compatible with variable and multi-speed blowers — gas furnaces and heat pumps.

  • Gas furnaces: In gas furnaces, gas burns on long ribbon burners, and the heat exchanger looks similar to a hollow, tall hair comb surrounding each ribbon burner on three sides. The heated gases travel up into the heat exchanger, eventually exhausting out through the vent pipe.
  • Heat pumps: These heating systems feature both air condensers installed outside of the house and geothermal condensers in water nearby or buried underground. Both utilize the same refrigerant used for air conditioning. Unlike traditional AC units, heat pumps can operate in reverse. Instead of heated air getting expelled from the home as waste heat, it's blown inside to provide heat. Heat pumps use compressor-condensing systems like regular AC systems — the only difference is that they're reversible. Geothermal systems function in practically the same way. However, instead of depending on the ambient air temperature to generate heat, geothermal units use the subsurface ground temperature. This environment is consistently cool, making it energy-efficient and reliable.

Shop Modular Blowers From Ingram's Water & Air

Browse our wide selection of modular blowers on our site, which includes industry-leading brands like GoodmanMrCool and Direct Comfort.

If you have any questions about our products, don't hesitate to contact us. You can use our form or just call us at 1-270-575-9595. Our sales representatives are true veterans of the industry and are happy to speak with you. Together, they will help you determine the best variable and multi-speed blower for your home HVAC system and your budget.

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