Vfd's: A driving force for contractors

July 19, 2000
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Long ago in a galaxy far, far away, the consulting engineer specified everything in the commercial arena. He designed the hvac system for a building, he specified the components, and he recommended any upgrades a system might need, including energy-saving devices such as variable-frequency drives (vfd’s).

That’s changed dramatically in the last decade or so. Now contractors are running the show in many instances.

It’s true that engineers are often involved in new construction — designing the system, specifying equipment, etc. (although even that is changing in some cases). But once the building is finished, the engineer is rarely seen again, and the hvac system is in the hands of a contractor.

What contractors don’t seem to be realizing is that with the engineer out of the picture, it is their job to recommend upgrades. Contractors should tell their customers about upgraded filtration. Tell the customer about humidification-dehumidification equipment. And tell the customer how much energy can be saved by installing a vfd.

What contractors don’t have to tell the customer is the tidy profit they can make on these upgrades.

What's it all about?

Some contractors are reluctant to recommend any upgrades at all, because they’re uncomfortable in the role of salesman. They feel their job is to zip in, fix the problem, and zip out.

Getting a contractor to recommend a variable-frequency drive can be even harder, because the contractor may not be familiar with the technology.

But the drive itself is really quite simple. Basically a vfd is a motor controller that varies the speed of a motor. It works by generating variable voltage and frequency output in the proper volts/hertz ratio for the motors from the fixed utility-supplied power.

Vfd’s can save substantial energy when applied to variable-torque loads (such as fans and pumps) and result in reductions in electricity bills in most facilities.

While there are three major vfd designs, only one is common in the hvac world: the pulse width modulation (PWM) type. These work well in the 1/2- to 500-hp range and are considered to be reliable, affordable, and readily available.

The advantages of PWMs, according to the Federal Energy Management Program (FEMP), are low harmonic motor heating, excellent input displacement power factor, high efficiencies (92% to 96%), and the ability to control multiple motor systems with a single drive.

This may sound complicated, but it’s really not — especially if you find a reliable manufacturer to partner with, says Bob Keingstein, president, AFGO Technical Services, Woodside, NY, and also current president of Air Conditioning Contractors of America (ACCA).

Keingstein’s firm does only commercial work, and he often works with vfd’s. To make sure he’s specifying and installing the correct drives, Keingstein works closely with Paul Krasko, application engineer, United Electric Power, Hicksville, NY, a distributor of Siemens variable-frequency drives.

“Some contractors will go in, look at a job and because they don’t understand drives, they’re a little bit afraid to use them. What we try and do is help the contractor out by letting them know how they work, how to specify them, and what to do and what not to do,” says Krasko.

Keingstein adds that having a good relationship with a vendor makes the whole process easier. “Talk to your vendor, work with the vendor to do the right job for the customer. Some contractors out there have people in their offices who can do it all by themselves.

“But my personal feeling is, there’s no need to go this route by yourself. You partner with your vendor, the manufacturer, or whomever, and do the right job for the customer — do it once.”

Main benefits

Another reason why contractors may be reluctant to specify vfd’s is that not too long ago, the technology could be called “flaky.” In the last five to 10 years, though, great strides have been made in the reliability of vfd’s.

“The technology is absolutely reliable today, it absolutely works today. It’s a good piece of equipment virtually by any manufacturer because the technology is good,” says Keingstein.

Some contractors may also still be under the impression that vfd’s are only beneficial on larger horsepower applications. That’s not true anymore either. Costs have come down so much over the last few years that vfd’s can be beneficial on smaller jobs.

“Vfd’s are getting to be more and more cost effective on all motors, but especially on the small horsepower motors — down into the range of 10 hp and below,” says Peter Barr, commercial marketing manager, MagneTek, New Berlin, WI.

“For many years it was only cost effective to put a vfd on larger motors. But as time goes on, it’s getting more and more acceptable to apply them even to fractional-horsepower motors.”

There are many benefits to using a vfd, but the biggest one is that it will save the customer money. Savings, of course, will vary from application to application. Contractors can more accurately estimate energy savings by running calculations in the software programs offered free by most vfd manufacturers.

“If there isn’t a drive, that’s an opportunity for the contractor to sell a product. In almost every pump and fan application in an air conditioning application, if there’s no drive on there, there’s almost always the opportunity for the user to save money through energy savings,” says Richard Torbenson, vice president of sales and marketing, U.S. Drives, Niagara Falls, NY.

Besides saving energy, a vfd is a beneficial piece of equipment just for starting and stopping motors. If a customer has a fan that starts and stops multiple times per day, that can be very stressful on the bearings, belts, and everything else associated with that piece of equipment.

“A vfd can help in all those kinds of installations, because the drive acts as a soft start, slowly ramping the motor up rather than just banging it on full speed and letting everything else kind of catch up. It’s always beneficial in that scenario from a maintenance standpoint,” says Barr.

Less wear and tear means that the life of the equipment can be extended, resulting in lower operating costs and less maintenance.

Another vfd feature that often gets overlooked, says Krasko, is comfort. “A vfd is going to keep the airflow at a constant level all the time.

“If a contractor tells a commercial building owner-manager that tenants will be more comfortable because there are not going to be periods of hot and cold, a bell goes off in their head. They’re going to be happy they won’t have to listen to people complaining anymore.”

And if there’s a problem in the system, it is not difficult to “out” the drive as the culprit. Many drives have a screen that displays fault codes, so technicians doing normal preventive maintenance on a system can look at the display and see if there’s been a malfunction.

Selling no obstacle

It’s true that costs have come down on vfd’s, but that doesn’t mean they’re cheap. They can easily cost as much, or more, than the motor itself.

So what’s the best way to sell a vfd to a customer? Stress the payback, says Torbenson. “With software packages, it’s pretty easy to estimate an annual energy savings and a payback.”

Keingstein adds, “Do a good job and show the paybacks. Quite honestly, most of these products that do show paybacks sell themselves.”

The profit margin isn’t bad either, says Keingstein. “It’s like anything else. It’s what you make it and what the market will pay.” He adds that including another product line means another profit center in his company, “which keeps us with our customer, providing benefits and value.”

And these are the main reasons why contractors should be selling vfd’s anyway — to keep customers happy.

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