External Static Pressure: Do HVAC installers actually measure this during normal installs?

biosopher

How important is it to have the external static pressure set properly for an HVAC system?

I ask because I don't recall my HVAC installer ever pulling out the instruments required to measure this. However I noticed that my HVAC has three selectable external static pressures: 0.30, 0.50 and 0.80 in. WG with 3 fan speeds at each static setting." The default is 0.5 in WG.

pecmsg

It's part of the start-up and commissioning of the equipment.

No, most do NOT do it!

ratio

The ductwork is sized around the engineers' choice of ESP. There are tables that show airflow resistance vs dimensions for various sizes. Using those, the lengths of the runs, & the equivalent length of the fittings (a transformation of the airflow resistance of the fitting), the ductwork is designed for a specific resistance at the required airflow; which, coupled with the airflow resistance of the unit itself & accessories, determines the ESP.

PC7060

critical when setting up high velocity system.

Teemok

Some companies have someone who does some math and has an understanding of the physics involved and the equipment's design principles and limitations. They pre install detail and post install check up on their installers, per job, on many important details. Actual static pressure vs design is just one of them. Some have a person or persons who learn the harder way and have developed rules of thumb or learned to copy someone else's rules of thumb. I've seen this first hand at a few companies. This second type relies on a form of cookie cutter design that is pushed or pulled to suit any new design problem. Generally it works well enough for standard design problems, as long as the rules are good enough and equipment doesn't change on them. They have happy customers and turn a good profit most of the time but they can't trouble shoot or avoid complex problems as well as the other types. Of course it's not black and white. Most of us are a variety of gray. Some are fairly static and know enough to do what they need to well, while others are always trying to get better. Toss in some glossy well developed sales technique training and it's harder to know who you are getting. Trouble is many home owners are completely unaware of the unique difficulties of their design problems and so are many sales guys and installers. Then awkward learning opportunities present themselves.

pecmsg

All this does come down to Money!

You will pay more up front for a contractor that takes the time to:

Properly size the equipment Manual "J"

Properly size the ducts Manual "D"

Properly select the equipment Manual "S"

Purging with N2 while brazing

600# pressure test overnight

Triple evacuation down to 500 microns

Weigh in refrigerant

Start up and commissioning

Teemok

@pecmsg I'm sure you are aware that the money a company charges doesn't guaranty that they do any of that. Lidar scans and ipad apps are cosplay for many. The Manuals can be garbage in and garbage out but you hit the nail on the head, if they do them, they probably care about getting it right. Manuals are great post install proof of due diligence and useful when trying to determine what went wrong. Many calls are made during work by installers that differ from plans on paper. It's tough out there to find high level skill for both ethical employers and customers.

DCContrarian

https://forum.heatinghelp.com/discussion/comment/1806060#Comment_1806060

What a lot of people don't understand is that installing an HVAC system isn't like installing a wall-mount TV or a microwave. It has to be engineered for the house, and every house is different. It's not just a matter of seeing if it fits in the space and hooking it up.

Not only does that engineering cost money, a lot of it has to be done before the job can be priced. How can you price the job if you don't know what size equipment it's going to take, or whether the existing ductwork is adequate for the job? But what customer wants to pay to get a quotation, and what contractor wants to do a whole lot of work on a job they may not get? Work that the customer can just turn over to a competitor?

So the pressure in the industry is toward not doing the engineering and just using rules of thumb, or replacing existing equipment with similar-sized replacement equipment.

EBEBRATT-Ed

Most residential contractors probably don't have a clue what static pressure is and don't have the equipment to measure it.

GothamairAZ

Setting the external static pressure correctly is crucial for HVAC system performance. It ensures optimal airflow and efficiency, preventing strain on the system and potential issues like reduced cooling or increased energy costs. If your installer didn’t measure it, it might be worth having a professional reassess to ensure everything is set up correctly. Proper adjustment can make a big difference in system longevity and performance.