It’s unlucky that some in our {industry} are comfy attaching new, high-efficiency tools to outdated, inefficient, and poorly put in duct methods. They simply assume every thing will work nice. If you’re one in all them, there may very well be two large duct system false assumptions you’re making. Let’s have a look at them and see what you is perhaps lacking.  

Assumption Quantity One: The Duct Design is Appropriate

If you wish to begin a battle amongst HVAC contractors, ask them the way to design a duct system. On one aspect of the dialogue, you’ll have  those that observe duct design guidelines of thumb that got here from earlier generations. These “guidelines”  in all probability got here from their dad or another person who taught them as they got here up within the commerce. To this group, disrespecting these guidelines is like spitting within the face of custom and on the identical degree as insulting their mother.

Who was the unique putting in contractor accountable for the duct system that you simply connected the brand new tools to? In the event that they’re a  contractor you badmouth for poor workmanship, congratulations – you simply joined their membership, as a result of you now personal their duct system.

On the opposite aspect of the dialogue are the duct design die-hards who observe industry-approved requirements. They’ll quote the formulation and  directions from these requirements by coronary heart, and so they have  disdain for these who use guidelines of thumb. Duct design die-hards don’t perceive why the rules-of-thumb group refuse to make use of {industry} accepted strategies and maintain going again to the beneficial residential setting on a duct calculator of .10-in. w.c. (inches of water column).

Relying on set up circumstances, each teams may be proper. Nonetheless, they might additionally each be improper. Design solely tells you what the meant final result of an set up must be. It doesn’t make sure the design will work. If you hook up new tools to a different contractor’s duct system, you assume they designed their ducts appropriately.

Assume lengthy and onerous about that final sentence after which take into consideration the final tools substitute job you probably did. Who was the unique putting in contractor accountable for the duct system that you simply connected the brand new tools to? In the event that they’re a  contractor you badmouth for poor workmanship, congratulations – you simply joined their membership. Why? As a result of you now personal their duct system.

design permits for the ducts to provide and return airflow from the air dealing with tools’s blower at a suitable static strain. These ducts may even ship the correct quantity of air to every room, however they aren’t self-balancing. So, in the event you imagine a six-inch duct all the time delivers 100 cfm (cubic toes per minute) of airflow, it is best to rethink.

Completely different duct sizes will ship completely different airflow quantity primarily based on the size of the run and becoming varieties you utilize. However you have to additionally take into account the set up, as a result of that’s what determines if the design will work within the area.

Assumption Quantity Two: The Duct Set up is Appropriate

If somebody advised you that your duct designs and installations didn’t work, may you show them improper? What may you do or say to defend your workmanship if somebody questions the outcomes? Holding your hand over the availability register and proclaiming it blows “good” isn’t sufficient.

Sadly, if an issue arises after you put in a new air-handler or gasoline furnace to another person’s duct system, chances are you’ll must present proof of correct operation. Whereas correct duct design is what ought to have occurred, the set up is what actually occurred. It’s the completed product. A number of elements to think about with an set up that’s put in appropriately are:

  • The ducts are tight and don’t leak air
  • All versatile duct is supported, straight, and tight, with no restrictions
  • Duct fittings don’t create extreme strain drops within the duct system
  • Duct insulation prevents extreme temperature losses to unconditioned areas like an attic or crawlspace. 

The set up crew’s skillset, workmanship, and consideration to element play an enormous half within the elements above. If the most effective set up crew was on this job, knew what to do, and had the best supplies, there’s a very good likelihood they’ll  full a profitable set up. Nonetheless, if the set up crew skips necessary steps and rushes by means of the job, there’s a very good likelihood they missed so much. The design, regardless of how good it’s, received’t carry out.

When You Measure, You Know

You’ll by no means know the way dangerous these assumptions are until you check. If you happen to don’t check, you’re blind to the outcomes of putting in new tools to current ducts. I as soon as heard Rob Falke say, “If you happen to don’t check a system you hook new tools to, you’re no higher than the installer who did it improper within the first place.”

If you measure, you may be certain the correct quantity of airflow makes it to every room; you don’t must guess. Additionally, you will know that duct pressures are inside design parameters and never double what they need to be. If you measure, you already know

Till I understood the idea of proudly owning an current duct system as soon as I attached tools to it, I by no means thought of what I used to be doing. As soon as I used to be uncovered to this line of pondering, it modified how I approached an current set up. I needed to ask myself, “Do you really need that unknown legal responsibility?” 

Why would we take that likelihood and play Russian roulette with our methods? It was a sport we used to playi. Generally we received and  different instances  we misplaced. Then we discovered a greater approach and  began to check so we may confirm the duct’s situation earlier than we offered somebody a brand new piece of apparatus. We didn’t need it to carry out poorly or  fail prematurely. So, if there have been points, we made the home-owner conscious of our findings and gave them choices. 

If you happen to promote new tools with the promise of effectivity after which connect it to an outdated, inefficient duct system, you could have unintentionally deceived that buyer. As a substitute, why not ensure you ship methods you possibly can show work as designed? Your skilled life will get simpler while you don’t assume the present set up works and undertake another person’s issues. 

David Richardson serves the HVAC {industry} as Director of Coaching for the Nationwide Consolation Institute, Inc. (NCI). NCI makes a speciality of coaching that focuses on enhancing, measuring, and verifying HVAC and Constructing Efficiency.

If you happen to’re an HVAC contractor or technician fascinated about studying extra about duct upgrades the proper approach, contact David at or name 800-633-7058. NCI’s web site is filled with free technical articles and downloads that can assist you enhance your professionalism and strengthen your organization.


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