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Can Quality Maintenance Exclude the Duct System?

There’s lots of talk around the industry about Quality Maintenance. The struggle is to boil down ACCA/ANSI/ASHRAE 180 to something that can be used in the field. What impact would adding ducts to your service agreements have on the quality of your maintenance? Let’s take a look at how adding the duct system to your service agreements could have significant comfort and performance benefits to your customer, and to your bottom line.

To add the ducts to your service agreements, take a few minutes to measure total external static pressure. It’s a small thing that can bring great and immediate results. Static pressure is like a blood pressure test; a quick and painless way to assess overall system performance. Adding this simple test will pull your head out of the box and give you insight into the airside of the system.  

This simple test, if performed as a part of each service call, will open the door to duct system repairs and renovations that have often prohibited the equipment from operating as it could from the day the system was built.

By doing this your company will find opportunities to serve that you’ve been walking past for years.

Contractor Benefits

One contractor that added the ducts to his service agreements commented: “All we used to do is to fix the equipment, or replace the equipment. Now, that’s only half of what we do. Now we fix systems and no one can even think about taking our customers away from us.”

He went on for a half hour talking about building after building that they had “saved.” Not only by servicing the equipment, but by going into the ducting and repairing obvious defects that aren’t visible by servicing the equipment only.

His company had commissioned a municipal building and turned in a punch list of over 150 items that his service department had discovered. Each was critical to the performance of the system, but was outside of the equipment they had a service contract on. The result was a fat purchase order for the new work they had uncovered. The same opportunities are available in residential systems.

Here’s a list of typical income producing opportunities that you can discover by adding static pressure to your service agreements. Remember, these repairs may have gone undetected for decades and have been a sore spot to your customers for many years. The gross margins you need to receive for this type of work are in the 60% to 70% range. Don’t think of these as low margin nuisance work, or you’ll never be successful in implementing air diagnostics into your service department.

Static Pressure

It takes less than five minutes to measure total external static pressure. This pressure can then be combined with the fan speed to plot the airflow the fan is moving. Compare fan airflow to required airflow to evaluate the need system improvements that increase airflow.  

The pressure drop over a system’s filter or indoor coil can quickly reveal the restriction to airflow of the accessory. This practice will soon lead you to believe that filters with excessive pressure drop are the number one case of poor indoor or quality.

Any filter that reduces airflow substantially inflicts a significant energy penalty on that system and needs repair or replacement. You’ll also find that coils that may look clean, may not be. Compare actual coil pressure drop to original manufacturer’s specification to verify cleanliness and take appropriate action.

By measuring pressure in each plenum you can check the resistance of the duct system to airflow. Ideally, the supply or the return duct system pressure drop should not exceed 20% of fan rated static pressure. Most duct renovations require the addition of a large return duct sufficient to reduce system static pressure. 

Isn’t it strange that we only service the equipment, and assume the air distribution system automatically remains in tiptop shape all by itself? Consider adding the duct system to your service agreements to truly embrace quality contracting and differentiate yourself from your competitors.

Rob “Doc” Falke serves the industry as president of National Comfort Institute an HVAC based training company and membership organization. If you're an HVAC contractor or technician interested in a free static pressure measurement procedure, contact Doc at [email protected] or call him at 800-633-7058. Go to NCI’s website at for free information, articles and downloads.

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