Drying Saving:
Energy in the Process
By Richard Castellow

An example of a mechanical inlet restrictor.

Today’s systems are flexible: choose the number of producers and choose the number of arches on which to mount them.

Those of us who have been in the car wash industry for some time have noticed quite a number of changes these last few years. The proliferation of the express-exterior wash along with the declining numbers of available employees in some areas has been the impetus for one such change — the arrival of the “mega drying system.” Citing the need to offer the same drying performance as the wash down the street without the associated labor, operators are relying on more producers and higher horsepower to do the job. In some instances, the typical rules of thumb no longer apply. For example, the old formula of one horsepower for every car per hour has been increased in some cases to almost two.

Operating efficiently, or “getting the most from your drying system” no matter what the size, has become of great interest to most operators, and rightly so. As the single largest power consumer in most washes, and with the variety of energy-saving devices on the market, the air dryer is one of the easiest and best components for actively reducing your utility bill. Likewise, the range of producer horsepower and nozzle offerings furthers this effort by allowing operators to select the best producer/nozzle combinations and fan positions to maximize airflow — achieving superior drying results without necessarily relying on as many producers to do so.

As the cost of power continues to soar, more and more operators are going to realize the need to maximize the efficiencies of their drying system. Whether you are operating a modest dryer, or one of the newer mega systems, the following principals apply equally.

This discussion will now be broken into two parts: The equipment currently available to reduce power consumption and lower your power bill, and recommended dryer layouts to best utilize the available airflow.

EQUIPMENT

Lowering your power bill can be done one of two ways: lower your total consumption, or lower your peak consumption. Either one will give you less heartache when you open your next utility bill. If you can lower both, you will begin to see substantial benefits.

Power companies charge for kilowatt-hours used. They take the total number of kilowatt hours consumed and multiply it by the rate per kilowatt-hour to determine the bill. It is quite easy to see how lowering the kilowatt-hours can impact the bill. What is sometimes overlooked is how the rate is determined.

Some utility companies charge a rate based on peak demand. Peak demand charge is the amount charged for the highest average demand recorded over any fifteen-minute period within the billing period. The utility companies charge for peak demand in an effort to recover the cost of providing the infrastructure necessary to meet the peak requirements of the business regardless of whether it is a momentary or constant demand.

The task of lowering these variables may sound daunting, but fortunately there are a number of technologies currently available that used alone, or in conjunction with each other provide us with the means to reduce one or both of the critical factors affecting the utility bill.

First, here are a couple preliminary facts to aid in the understanding of power saving devices: A motor can draw up to 10 times the normal run amps under start up conditions. All motors have a limited number of times they can be started during a given hour. If the motor exceeds that number, you can expect to see premature motor failure. For the most part it is less expensive, and better from a maintenance standpoint, to leave a dryer motor running once another vehicle has entered the tunnel even if it requires several minutes for the vehicle to enter the dryer.

Each of the following technologies could fill an article itself. I will not attempt to delve too deeply into the innermost workings of each, but will provide enough information to help you understand what technology is available.

Soft Start
The first and least expensive is the soft start. The soft start replaces the conventional across-the-line starter, and provides a variable voltage ramp-up for the motors that substantially reduces the typical inrush of current that we see in a start-up situation. With soft starts we would typically see no more than five times the full load amps (FLA) as noted on the motor name plate. By employing a soft start, we minimally reduce the total consumption particularly in a very busy wash, but have reduced the peak demand enough to reduce the utility bill.

Variable Frequency Drive
Our next high-tech money saver — and the most expensive — is the variable frequency drive (VFD). Three-phase motors are designed to rotate at a specific RPM based on the frequency of the power utilized. Here in North America, we have 60 cycles per second or 60 htz. In Europe it is for the most part 50 htz. A VFD is an electronic device that converts the incoming power and outputs it to any desired frequency within its designed range. Like the soft start, the VFD ramps the motor up slowly, this time by changing the frequency, avoiding the huge inrush of current. Unlike the soft start, a VFD seldom exceeds the FLA draw on start up. One of the advantages of a VFD over a soft start is its ability to ramp down to an idle speed between vehicles to conserve total consumption, assuming a large enough space between vehicles.

Both the soft start and the VFD may qualify for a rebate from the utility company, so it would be wise to consult with them prior to making your final purchasing decision.

Mechanical Inlet Restrictor
Finally, we come to the mechanical inlet restrictor. Several manufacturers have begun to offer a device that restricts the airflow into the inlet of the dryer producer. Although this means of reducing power consumption is not new, it is only recently that we have seen widespread utilization of this principal. By reducing or shutting off the flow of air into the inlet of a producer, you significantly reduce the amount of current required to maintain the motor’s desired RPM. In most instances the amp draw is reduced by as much as 50 percent. By opening and closing the restrictor to allow the producer to draw the maximum amount of current only when a vehicle is actually in the dryer you can substantially reduce the total consumption while also reducing the number of starts per hour. Although this method does not reduce the peak demand, it is very practical and efficient at reducing the total power consumption. Unlike the VFD, the mechanical inlet restrictor valve is quick acting and can be utilized very effectively even on very busy days.

One added benefit to both the mechanical inlet restrictor and the VFD is the ability to reduce the airflow to the open bed of pickups. By either slowing the VFD down or closing the restrictor you can eliminate the torrent of spray that goes in every direction when a high-horsepower dryer enters an open pickup bed.

DRYER LAYOUTS

Once you have settled on a means to best conserve power you must maximize the airflow available. Today’s dryers are both a blessing and a curse. Twenty-five years ago we didn’t have the flexibility we have today. We can now have as many or few producers as we want. We have choices as to how many arches we want to mount them on. If, after we purchased our dryer, we decide we need more drying we can just add more producers. That flexibility is also our curse. How much dryer is enough? How much is too much? How do I configure what I have bought?

Unless you have an unlimited dryer budget, you are going to have to make some compromises; a single dryer configuration cannot dry every vehicle equally well. Remember what you are trying to accomplish: you want to have the greatest impact on the greatest number of vehicles. On more than one occasion I have seen an owner configure an entire drying system solely to maximize the dry of his vehicle at the expense of the majority of his customers’ vehicles.

Top Down
First rule in drying: dry from the top down. That applies to the sides as well as the horizontal surfaces. If you look at most effective dryer configurations you will find that they start with three to five producers in a chevron — or V — configuration on top. These first several producers are doing the heavy lifting. The intent of these producers is to rid the vehicle of large quantities of residual water. From that point on we can get down to the business of finishing off the vehicle to achieve the desired results.

Next give the water some place to go. Blow the water back, down, across, but blow it all in one direction. Too many times we see producers aimed straight at the vehicle. Water then doesn’t have a clear choice as where it is supposed to go. In many cases it goes in all directions — often right back onto an area that has already been dried. As in the case of the first top cluster, they should all be directed to sweep as much water off the vehicle either toward the back, bottom, or side.

Mistakes
Number one mistake: conflicting airflows. When the airflows of two producers converge, one tends to cancel out the effectiveness of the other. What you are left with is the water being trapped in the middle leaving little lines of water beads. I have seen these stripes chased all over the vehicle, but in the end they are still there.

The second most prevalent mistake is improper producer positioning. Remember we are attempting to get the maximum amount of available air onto the surface of the maximum number of vehicles while limiting conflicting airflows. Most large drying systems position the outside top producers too far off of the center line. In most cases the best results are achieved by positioning the center of the top outside producers directly over the drip rails of the average full size vehicle. This both blows the water out of the drip rail and door cracks, but also forces the water from the top of the windows down.

As is always the case when going large, there is a significant diminishing marginal return when you look at large drying systems. This is not an indictment of larger systems, but merely a statement of fact. The first three to five producers will remove the vast majority of the water. The remainder of the dryer will be dedicated to attacking specific areas as well as touch-up work, cleaning up the small drops of water thrown back on to surfaces previously dried.

Nozzles
Today there are a number of nozzle configurations available to choose from, as well as nozzles that oscillate and in some cases flip or pivot around to address specific areas such as mirrors and the back of vehicles. The types of nozzle configurations are too numerous to cover in this article and should be addressed by your equipment supplier. The programmable and oscillating nozzle can be very beneficial, but its use should be limited to areas where it is necessary to distribute the airflow over a larger area, and where conflicting airflows can be minimized. Keep in mind when employing this technology that a fixed volume is being distributed over a greater amount of area thus reducing effectiveness. These are best utilized to detail a large area that has had most of the water previously removed.

Extracting the best possible dry from your configuration is certainly possible, but it is not a given. Rome wasn’t built in a day. Those that have coaxed the maximum performance out of their dryer have done so over a period of time. In most cases, someone has spent hours standing at the exit end watching water being blown around the vehicle. A little change in positioning here, and a little change in angle there can yield unexpected results that please the operator, but more importantly increase customer satisfaction.

Richard Castellow is western regional sales manager for MacNeil Wash Systems Limited, headquartered in Barrie, Ontario. You can visit the company on the web at www.macneilwash.com.