AHU Fan Replacement

How replacing your AHU fans can get you up to 50% in energy savings

You could be saving millions.

Sorry, that previous sentence is wrong. Let me correct that now…

You should be saving millions.

Ok, this doesn’t apply to everyone, but if you own, operate, or manage a building that has Air Handling Units (AHU), then this definitely applies to you. If you fall under this prestigious group of chosen people or know someone who does, read on.

Most commercial buildings nowadays has an HVAC system that’s composed of chillers, fans, cooling towers, and pumps. Out of all these components, the chillers are the biggest energy consumers, and fans are a close second.

While it makes sense to target the chillers first when looking for energy savings, the truth is you or any sane building owner won’t likely change the chillers of a building within the first 5 to 10 years of the building’s lifetime. Unless, of course, your building’s needs have changed drastically or you just found an incredible solution that justifies replacing the chillers earlier than expected.

So what do you do? You target the 2nd biggest item in the list… and that happens to be the fans in your AHUs. And what a 2nd option it is. It’s not very often we find such a delicious opportunity in a secondary offering. Much like the Godfather II, you’ll find this sequel has almost as much or even more delightful moments compared to its predecessor (but if it applies in your case, we still strongly suggest you look into Godfather I, a.k.a. your chillers, and btw, you can skip Godfather III).

Why optimize fans?

Fans are notoriously inefficient, or at least they used to be. Depending on the type of fan that’s installed in your building’s AHU systems, the typical efficiency could vary from 60-75%. Not very impressive numbers.

To understand this better, let’s take a look at the 4 commonly used types of fans in the market. Your building’s AHUs probably has one of these 4 types installed.

  1. Centrifugal Fans
  2. Plug Fans with External Motor & Speed Controller
  3. EC Fans with Integrated Motor & Speed Controller
  4. Axial Fans

Centrifugal Fans

Centrifugal Fans are the worst of the lot. They suck air from the sides and propel it in a radial direction perpendicular to the fan’s shaft (what’s the opposite of streamlined?). It also makes use of a belt that only adds more things to maintain and more opportunities for inefficiency due to poor belt tension. Centrifugal Fan System’s efficiency typically ranges from 60-65%. If you recognize this picture to the right in your building, this is your lucky day because you have an incredible opportunity to save some money.

Plug Fans with External Motor & Speed Controller

A step above the previous type are Plug Fans. This type of fan has an external motor directly attached to the fan, no more belts (that’s one less thing to worry about), but it still propels air in a radial direction that’s perpendicular to the fan’s shaft (no luck there). It doesn’t have a dedicated housing like a centrifugal fan but instead makes use of the AHU’s housing as the enclosure. Efficiency for this type of fan system ranges from 62-68%, slightly better but still subpar.

EC Fans with Integrated Motor & Speed Controller

This type of fan is similar to the previous type, the main difference is that EC Fans make use of an Electronically Commutated (EC) Motor that’s integrated into the system. The problem with this type of fan is when the motor fails, you’ll have to replace the entire assembly (ouch!). Also, if you need to supply more than 10,000 CMH of airflow, you’ll need to install several of these bastards inside your AHU, and as you’ll see later, that’s not in your best interest. Efficiency for EC Fan Systems still ranges from 62-68% typically.

Axial Fans

Finally, Axial Fans, the best type yet. Axial Fans are also directly coupled with a motor (no belts involved) and it throws air in the same direction from where it is coming from –  a significantly more streamlined approach. Less resistance means less energy needed to deliver the same amount of airflow. This type of fan system has an efficiency of around 70-75%.

70-75% sounds ok, but still a bit underwhelming isn’t it?

That’s where Novenco comes in…

Introducing the Novenco ZerAx® Axial Fan

A reimagining of the traditional axial fan, the Novenco ZerAx® Axial fan improves on some of the features of a typical axial fan to further increase its efficiency. 

  • Minimized tip clearance reduces noise and turbulence
  • Unique blade design brings the efficiency of the fan itself to 90%
  • Guide vanes act as a means to minimize air rotation after the fan and they also serve as the motor mount, eliminating the need for a separate foot mount for the motor
  • Coupled with a high efficiency VFD motor, the aerodynamic efficiency of this system can reach up to 92%, or up to 49% better than centrifugal and plug fan systems

Plug Fans vs. Novenco ZerAx® Axial Fans

All those points above sound cool and all, but how does one fan really vary from another? They’re all just made up of the same stuff after all. Let us show you how.

    Radial Discharge

    For Plug and EC Fan Systems, air enters horizontally and discharges radially in a perpendicular direction. That means the airflow undergoes a 90-degree turn as it goes through the fan. If that doesn’t seem like a problem to you, imagine a 100m running competition, but instead of just a straight path for each contestant, there’s a 90-degree turn at the halfway mark. I don’t care if you’re Usain Bolt, you’re not finishing that race under 10 seconds. Not with the same amount of energy at least.

      Multiple Fans

      To further compound this problem, for some cases, there’s a need to install several fans to meet the required airflow for a system. And since air is thrown at the sides of Plug and EC fans, that means the air coming out of each fan will inevitably crash against each other. Going back to our race analogy, can you even imagine how that race would look like if the lanes are clashing against one another. Track and field gear will surely be different if so, I’m thinking football helmets and shoulder pads for starters.

        Airflow through a Plug Fan

        Here’s how it looks like inside an AHU with a plug fan. 

        The first thing you might notice is the placement of the fan, it is somewhat in the middle of the entire assembly and acts like a choke point between the two sides.

        Air flow accelerates as it gets near the fan’s opening and it is discharged perpendicular to its initial direction. As a result, air flow is very turbulent as it crashes to the enclosure of the AHU before it is pushed towards the ductwork. The more turbulence there is, the less efficient the system.

        Airflow through a Novenco ZerAx® Axial Fan

        Now let’s look at the airflow inside an AHU with a Novenco ZerAx® Axial Fan.

        Again, the first thing you might notice is the fan’s placement. Now it’s located at the end of the AHU assembly, just before the ductwork. The second thing you might notice is how uniform the airflow is. There’s no choke point in the middle of the assembly and no change in the airflow’s direction. Everything looks natural. Smooth. Doesn’t this seem like a more ideal scenario? Or do you prefer the chaos of the previous option? If so, then best of luck to you.

        To sum things up, AHU fans have gone through some major improvements over the last couple of years, and Novenco has been in the driver seat of that charge for a long time. With the Novenco ZerAx® Axial Fan, building owners like you now have an opportunity to optimize your AHU systems and start saving on energy costs without touching your chiller plant system. The best part is, with this type of investment that brings such profound results, it can pay for itself in as little as 2 years.

        And as big proponents of energy saving, we at G-Energy vouch for this technology and we would like you to take advantage of this incredible opportunity to save energy and some money.

        Contact us now to get a free consultation.

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