David Richardson/NCI
Interior Hvac Diagram
David Richardson/NCI
If you know what to look for, a visual inspection provides clues to unsafe operation. It's never good for one package unit to exhaust into the economizer of an adjacent unit.
National Comfort Institute
Before you jump on the heat pump bashing bandwagon, look at your duct installation practices first.
Contracting Business/Kelly L Faloon
Ahr2023 Succession

4 Hours to Residential HVAC System Commissioning

April 1, 2011
HVAC commissioning can be done in four hours, and it's labor time well spent. Here's how it works

Residential HVAC replacement commissioning is often overlooked, and that's unfortunate, because it’s a powerful way to ensure customer satisfaction.

Commissioning must not be confused with equipment start-up, which is confirmation that installed equipment works the way that the manufacturer intended it to work. While equipment start-up could be considered a part of the commissioning process, it's really part of the installation process. HVAC commissioning is a process that goes beyond start-up. Commissioning is verification that what was planned is actually delivered.

Delivery of a plan is the key to successful product differentiation and ultimate customer satisfaction. A determined effort to deliver what was promised is the mechanism that makes a lasting impression on our customers. When we talk with customers about products and how they will work, we're making a promise that must be kept. Otherwise, what we said and did before and during the installation is nothing more than what the skeptical customer really expected: average performance.

HVAC commissioning can be done in four hours, and it's labor time well spent. Here's how it works:

HOUR 1: Interview and document for success.
In any endeavor, proceeding without a plan is hazardous, and commissioning is no exception. But don't be intimidated here, as a simple hand drawn floor plan is all that's needed. Make notations of the resources that you have to work with, including rough dimensions; the house's orientation; equipment model, serial number, and location; duct layout; duct sizes; register location and size; and windows and doors. Also, note anything that's standing in the way of good airflow, such as furniture or area rugs. Remember that you can't change the way people are going to live, so it's your job to design around how they live.

Now, involve your customers by taking them from room to room for input on how they live and whether they're comfortable from season to season. Make notations on the plan during the interview because it sends the message that you care, and that it's your intent to use this opportunity to improve their lives.

HOUR 2: Redesign for comfort and efficiency.
Redesign of an existing duct system doesn’t necessarily require removal of all components and starting over. In fact, most duct systems can be salvaged to a great degree. It's not unusual to find that supply ducts are sufficiently sized but return ducts are not; air filter surface area is almost always insufficient. Additional insulation may be required in hot or cold climates. This is one area where a detailed plan about what you have to work with can really pay off.

It's important that you pay particular attention to distribution of air volume according to how people live as well as how the home is built. Pay close attention to system zones so that negative pressure areas are not created. Ductwork and air filtration must be sized in order to live within the capability of the blower that's going to be used. Specify required air volumes on your plan, show how you would modify duct sizes, and show additional duct runs. Finally, carefully pick your supply registers. It's important that air is thrown with enough velocity to cause mixing of air across the room.

Now, put your team to work building your plan while keeping your eye on unforeseen problems that could cause the plan to change.

HOUR 3: Have a jobsite reality check.
Once the new air distribution system is installed, verify that you’ve achieved all that was planned. Start your reality check by measuring air volumes from room to room and comparing them to what you designated them to be on your redesign plan. If air volumes aren't right, figure out why, and then correct them. Volume dampers are cheap and make for fast volume adjustment, so use them wherever prudent.

The laws of physics are fast at work in an air distribution system. Every once and a while we have to change what we thought would work. Be prepared to change what isn't working. That's how you'll make customers excited to tell their friends about you.

While you're measuring air volumes, stop and listen for noisy registers. A noisy supply register is a register that has too much pressure difference across it. Noisy registers are resolved by either enlarging them or reducing the pressure difference across them. Remember that enlarging a return or supply register will affect total air volume as well as air balance; always measure system air volumes after making register changes or modifying duct layout.

It's amazing to think in these terms, but to live with a quiet HVAC system is actually unusual. The HVAC industry has installed so many undersized duct systems that air noise is now normal. When people have an opportunity to live with a quiet duct system — a new normal — they actually begin to notice noisy HVAC systems when visiting friends and family. Not only do they notice, but they also proceed to give testimony of how quiet their HVAC system is. I call this "new normal marketing," and it’s very effective.

Finally, measure total external static pressure, compare it to the rated fan capacity and calculate how many BTUs the system is delivering (delivered capacity) as compared to the rated system output. If you measured more than 90% of delivered capacity, then you're delivering an energy efficient system to the customer. Here’s a hint: If several of your registers are noisy, or if just one of your return registers are noisy, than you've probably already failed the delivered capacity test. If you're not familiar with the calculation of delivered capacity or air balancing techniques, seek out training. "Pretending" to commission a system or poorly commissioning one is worse than not commissioning it at all.

You might have noticed that there's a lot to do in hour three. With practice comes perfection, and it's definitely possible to verify air balance and measure delivered capacity within an hour. Practice will also diminish those occasions where you have to go back and fix what didn't work well. The process of documenting "before" and "after" system performance gives you insights over time about what is (or isn't) going to work.

HOUR 4: Conduct the exit interview.
Of all that you've done thus far, this is the most important step. Your customer can't know all that you've done for them unless you tell them. Just as you did in the first hour, take the customers from room to room and tell them what was done for their benefit. Show them how to operate the thermostat, advise them on the best way to use the system, and brag about the 95% delivered efficiency that you achieved. Equip them with an owner's manual, too: people like to be informed. Before you leave, let them know the best way to contact you if they have a problem. This way, you leave them with the unmistakable feeling that you never stopped caring, and that you'll continue to care in the future.

Bryan Lee is an HVAC contractor in Fresno, CA, and a trainer with NationalComfortInstitute.com. He can be reached at 559/227-9569 ext. 101, or by e-mail at [email protected] .

Another reason to Commission: PROFITS

Commissioning residential systems greatly enhances customer satisfaction. Now let's talk about another reason to commission your residential HVAC installations: profit!

Reduction in callbacks due to comfort concerns and air balance issues is an obvious reason to commission HVAC installations, but a less obvious reason is reduced marketing costs. Most HVAC contractors agree that a replacement referral is the best sales lead that can be had. Closure rates can be as high as 90%, and little marketing money is needed to create the lead. If you harvest replacement leads primarily through referrals instead of through marketing campaigns, marketing budgets can be cut in half, and that has a direct and positive impact on your gross margin.

The average sales lead costs $350 and about 4 in 10 of those leads will result in a sale. Assuming an average sale of $8,000, that’s $3,500 spent for $32,000 in gross sales. It's not unusual to achieve a 40% gross margin on an $8,000 residential replacement job. That means $4,800 is spent on labor, materials, subcontractors, tax, and advertising, with only $3,200 left to pay salaries and rent.

Now let's cut that marketing budget in half because you commission your jobs, keep promises, and your customers love to talk about you. The average cost per lead would now be $175. Using the same math, the average cost of sale would fall from $4,800 to $4,362, an increase of gross margin from 40% to 45%.

If you won't do commissioning to make your customers happy, consider doing it to make your wallet happy!