Informational Guide

What Is RTU in HVAC?

There are tons of different types of HVAC configurations, one of which being rooftop units or RTU. Learn more about these unique models with our guide.

by Josh M

Heating and air conditioning are pretty much an essential part of most of our lives and comfort levels. There are tons of different types of configurations, one of which being rooftop units or RTU.

These are significantly more sturdy and weatherproof, made to resist all kinds of weather conditions and outdoor situations. If you’re looking to learn more about them, including the cost, maintenance, and more, then our guide has everything you need!

RTUs (rooftop units) are self-contained units that offer both heat and AC for specific spaces (usually commercial spaces). They last anywhere between 10 – 20 years most of the time and require regular maintenance.

These units are ideal for big, open spaces like warehouses, large shopping centers, stores, markets, and similar layouts. However, they’re also made to work best with single-story buildings to make for the shortest travel possible and most effective temperature control. That’s not to say they can’t work with multiple stories, though. In fact, RTUs can work with buildings under 10 stories, so long as you can access the roof and ducts!

Another ideal application for RTU HVAC systems is restaurant kitchens, offering extra ventilation and conditioned air.

Units work as air enters the RTU through the air hood located on the side of the unit while keeping out rain and snow. As this air passes through, dampers regulate it, and air passes through the filters to eliminate contaminants. Once filtered, air is heated or cooled, depending on the system and operation. After this, it’s then circulated through the building ducts.

RTU in HVAC

3 Types of Rooftop HVAC Units

Fresh Air RTUs

These units involve zero recirculation, using solely fresh air. Most involve a refrigeration system for cooling and will feature 2 heat exchangers to offer both heating and cooling.

Recirculating RTUs

These units recirculate the internal air through return ductwork – much different from fresh air RTUs. These reduce the heating load by using some warm air return. The return damper works along with the intake damper. Of course, there will always be some fresh air coming in to keep air healthy and low on carbon dioxide.

Heat Wheel RTUs

These feature heat wheels built into the unit, making it more eco-friendly and better with energy and utility costs. This unit pulls air through the hood, passing through a filter to catch impurities.

Finally, it moves through the heat wheel, which takes the waste heat/cool and transfers it to the incoming fresh air with two air steams together. The heat wheel offsets heating/cooling in many cases, saving operation costs.

The Pros and Cons of RTU HVAC

What We Like
  • Lower Utility Bills
    As they use less energy to operate, they’re not only more eco-friendly, but the RTU HVAC cost is also easy on your bills!
  • Space Saver
    If your building is already tight on space and can’t afford the extra bulk that comes with most indoor HVAC systems, then you’re in luck. RTUs are all located on the roof (aside from the ducts), so you won’t have to worry about it taking up any room indoors!
  • Less Expensive Installation
    The good news is that RTUs are usually much cheaper and less difficult to install, further saving you time and money! Most of the hard stuff gets done at the factory, making it more convenient for everyone.
  • Chance of Existing Ductwork
    What makes an RTU even more convenient? Having existing ductwork already in place! That further facilitates installation!
  • Faster Diagnostic and Repairs
    As you have basically everything in one spot, it’s generally quicker and simpler for HVAC pros to figure out what the issue is and correct them. This will also typically end up in cheaper repair/maintenance bills.
What We Don’t Like
  • Difficult Access to Roofs
    If you can’t easily access the roof of the building in question, it may end up causing more issues than benefits. Not only that, but these units weigh quite a bit and can damage flat roof membranes if installation isn’t completed correctly.
  • High Heat and Extreme Cold Exposure
    It won’t be protected by a building when placed on the roof, so if you live in an area that gets either high heat or cold, it could become damaged due to this.
  • Possible Animal Infestation
    There’s the chance that critters may make their way inside to seek shelter or out of curiosity.
  • Not Suitable for Tall Buildings
    If the building stands 10 stories or taller, it won’t be easy to use. This is due not only to installation but because conditioned air will have to travel too far for adequate cooling, heating, and filtration.
  • Can Be Neglected for Maintenance
    As you don’t see the unit often, it can become easier to forget about maintaining it.

Core Components of HVAC RTU Units

Why is a rooftop HVAC unit sometimes referred to as a “packaged unit”? Because it comes with all components of an AC and heating unit in one.

  • AC Evaporator Coil
    These hold the chilled refrigerant, which a compressor moves into it. When the air moves over the coil, the refrigerant takes out of the heat from the air.
  • AC Condenser Coil
    The condenser coil is almost the opposite of the evaporator coil. The condenser releases heat while the evaporator kind of “absorbs” it. When the blown air moves over the condenser coil, heat is dispersed into outdoor air.
  • AC Compressor
    This is the heart of the unit and serves to circulate the required refrigerant needed to exchange heat through the coils, as well as applying energy to the refrigerant.
  • AC Expansion Device
    These remove pressure from liquid refrigerant to facilitate expansion or change from a liquid to vapor.

How Much Does a Rooftop HVAC Unit Cost?

At this point, you may be wondering how much an HVAC RTU costs. There are some slight variations, of course, but generally, it’ll be anywhere from $5,500 to $11,000. These are for the full package, including all necessary components that are usually connected right into a ductwork system.

For installation, the cost will depend on the area you’ll be addressing.

  • 700 – 1,000 sq. ft.: $2,200 – $3,300
  • 1,200 – 1,400 sq. ft.: $3,000 – $3,800
  • 1,500 – 2,000 sq. ft.: $3,500 – $4,300
  • 2,000 – 2,500 sq. ft.: $4,500 – $5,000
Rooftop HVAC System

HVAC Rooftop Unit Maintenance Checklist

Why does regular maintenance of HVAC RTU matter? It will make sure that your RTU lasts as long as possible while giving you the least amount of issues that saves you time and money. How often is the RTU’s regular maintenance? Ideally, you’ll get maintenance done at least once yearly. This will help prevent any possible issues before they happen!

Air Filter Inspection

Dirty air filters negatively affect the air you breathe and can even clog up the HVAC unit if it’s not tended to regularly. Clean or replace it regularly, or hire a professional HVAC technician to do so.

Clean the Fan and the Motor

Make sure both are located properly in the center, ensuring neither is placed too close to the housing unit sides. As time passes, blades can start rusting due to exposure to moisture, so you’ll have to get these cleaned/replaced regularly, too.

The motor can begin to make weird noises and require the bearings to be lubricated every 6 months or so.

Inspect the Heat Exchanger

These components heat the air and should always be operating properly. Even small damages like cracks/corrosion can seriously contaminate your air supply, so this is a very delicate matter that should be taken seriously.

If you hear vibration, roaring noises, smoke coming out, etc., these are huge warning signs that something needs addressing.

Clean the Coils

Both sides of the coils need to be cleaned at least once yearly, making sure dust doesn’t build-up, which can reduce heat transfer and air quality.

Clean the Drainage System

The drainage system can become clogged with grime and dirt, thus requiring regular cleaning.

Check the Voltage

Improper voltage balances can result in many issues, from overheating to much more serious incidents. Ensure your HVAC tech revises the highest and lowers voltages, ensuring they don’t exceed around 4% of the lowest voltage whenever running.

Replace the Drive Belt Annually

These wear down naturally with use and should be replaced once a year.

People Also Ask (FAQ)

What is the difference between RTU and AHU?

The Air Handling Unit (AHU) has heating/cooling elements, blower/fan, filters, mixing chambers, vibration isolators, humidifiers, heat recovery devices, and controls. An RTU is no different, except for the fact that it’s placed on the roof!

What is an RTU panel?

This is a space where a technician can access filters and other essential components of the RTU.

Why can’t RTUs be used in buildings higher than 10 stories?

It’s simply too challenging and inefficient to push air through the ducts and reach every space it should when a building is taller than 10 stories.

How long do rooftop units last on average?

Usually around 10 to 20 years, with proper maintenance, of course.

Conclusion

Now that you know pretty much everything you could ever want to about RTUs, have you decided to get one for your building? We hope that our guide has been able to answer any questions you may have.

RTus are incredibly useful, and we’re sure that with proper maintenance, you’ll find that out for yourself!

Josh M

My name is Josh and I am obsessed with the HVAC industry. I created this website to help HVAC techs of all levels get the best out of their heating & cooling systems. I have spent thousands of hours studying air conditioners, heaters and home air products so you can learn & buy with confidence. Learn more about the team here.

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