Duct Built 0.5" S.P. SMACNA Table for a 2.5" + S.P. VAV System- Concers? Including the Obv

[CMK79]

Hi everybody,

I just started a new job as a Construction Manager and my first project was 90% complete when I got here and found multiple completed mechanical systems with questionable construction methods having been used. Specifically a system that was installed in a new building with a High Pressure VAV Trane 75 Ton 20,000 CFM Intellipak Scheduled to operate @2.5" S.P. and all Submittals and Plans confirm this operating S.P.

The concern is that the contractor installed 24ga Flat-Slip and Flat-Drive connections for Rectangular Duct-work on the high pressure side of the VAV's in the system. All ducting currently installed is interior, no exterior YET- The duct was built to a 0.5"S.P SMACNA Class/Table. The Project Specification Manual Calls for 4" S.P. Class Duct Construction and all SMACNA Tables Ive located show that TDC/TDF is used larger than 12"x12". All the Duct is 24GA,Flat S&D no beading or crossbreaking, no internal liner, and is externally wrapped. No stiffeners and an open ceiling return design with 55 VAV's and a thousand feet of duct.

Typical interior sizes are 20"x20, 30"x30, 30"x36"

I caught this when the installer brought out the rooftop duct built in S&D, 24 GA and using Flat S and Drive Stock in sizes from 20"x20", 30"x30" 30"x48", 48"x48" and 36"x72". All of the duct had to be sent back and rebuilt with Ductmate 35 Frames at the Transverse connection and some duct had to be remade in 22GA with Ductmate 35 using Mid Panel Tie Rod stiffeners to meet the 4" S.P. requirement. This caused me to look above the completed ceiling and find that all the installed ductwork in the high pressure side is built to a 0.5" or a 1.0" Table and again is all flat slip and drive construction. I am concerned that the ductwork is going to oil can and pop and make noise, or leaks in improperly sealed Ducts will squeal loudly as there are numerous joints I discovered completely unsealed. the current management doesn't want to acknowledge there's any issues, they don't even want to discuss it and say as long as it passed a leak test its fine, but I am concerned. The SMACNA tables require the heavier GA and Angle or TDC or Ductmate connections at the joints and not Slip and Drive for a reason.

Does anyone have any experience with a situation like this, or have any insight from an engineering standpoint, and what if any problems can result from this? Regardless of how obvious the issues might seem, please share.


Thanks in advance,

 

[Heaviside1925]

It sounds like a contractor was attempting to slip something under the radar. If the project spec says 4" S.P., then that is what should have been fabricated. I am unsure of what you meant by current management. Are you with an EPC with subs or are you a sub construction manager? If this is something your company is allowing to happen, I can almost guarantee that duct work is not the only area being shortcut. As far as issues go, I think you brought up the main one being the oil can and popping noises. There could be issues with other inline appliances such as louvers, registers, transitions, dampers that may or may not meet spec. I would assume there are permits involved and performance testing requirements that would likely be affected if not outright fail or not pass inspection. Honestly, what concerns me the most, is you, as a new construction manager, were doing your job and passed along what seem to be very valid concerns and you were ignored. At the very least, if your management did not think they were valid concerns, they should have pointed you to someone who could explain why they are not and instead you are stuck posting on a forum to solicit advice from strangers to validate something I think you already know is a problem.

 

[CMK79]

Thanks Heaviside1925.

I am unsure of what you meant by current management, re you with an EPC with subs or are you a sub construction manager?

I'll try to be a bit more specific. sorry about that. I was hired for a newly created position in the Department to Commission and hand over new buildings as they are finished and there's 12+ $20M-$25M buildings being turned over this year. The General Contractors hire all the Subs and work for my department. The existing managers in my department don't have MEP specific experience and have unfortunately let a things get past them. You don't know what you don't know, so.... they missed it. I know that the work is sub-par and will create issues,I just don't know how bad it will be. The people who missed it are sweeping it under the rug because they missed an equal number and severity of problems in a few previous buildings that are still experiencing closeout problems and they don't want admit the error and let the skeletons out of the closet. Even the engineer who drew the building is dismissive of this and I know its wrong but cant get a straight answer, or even an answer at all regarding any potential issues this will cause when the unit is fired up in 2 weeks. So that's why I came here. I found this forum and everyone seemed knowledgeable and helpful so I took a chance and threw this out to see what other HVAC Professionals would say. I want to be as prepared as possible for any problem that arises and start planning solutions ahead of time. Unfortunately because I'm getting stonewalled by the people who overlooked it in the first place I have turned to this forum for help.


"Honestly, what concerns me the most, is you as a new construction manager was doing your job and passed along what seem to be very valid concerns and you were ignored. At the very least if your management did not think they were valid concerns, they should have pointed you to someone who could explain why they are not and instead you are stuck posting on a forum to solicit advice from strangers to validate something I think you already know is a problem"

In regards to this - I know, its a problem, and you're right. I actually had an Engineer here tell me that the Project Specification Manual is "loosely written and open for interpretation and more of a suggestion" !!!! HUH!!WHAT!!! Isn't the name "Project Specification manual" meant to be "Specific"??? I had no idea I spent three decades following the Spec Book to the letter when I could have just done whatever I wanted.

You are correct I already know the answer. I'm not sure what to do except prepare for the worst and hope for the best.

Its been a challenge.

 

[Heaviside1925]

CMK79,
Thank you for providing more clarity of your situation. Since I've told you my engineering concerns, let me flip my hat around and talk from a PM perspective.

I hope I don't get flagged, reported, downvotes...whatever the process is here... for saying this but an axiom my father taught me was "Perfection is the enemy of done". You can look through designs from even the best engineers and find mistakes. They may be small or just grammatical but being in a field that prides itself on attention to detail, it's a proverbial fingernail on a chalk board. I have reviewed past design packages and thought "how the hell did this even get built" but somehow the contractor was able to muddle their way through it and in the end the customer was satisfied with the results. I've seen this on the other end, where a contractor is provided with a well-engineered design package but due to many times "low bidding it" results in the contractor taking liberties to reduce their cost but the end result is still the same, a satisfied customer. Even if one points out to the customer that the engineer firm or the contractor did not meet the original design specifications, many times they don't care because they are satisfied with the result or realize the cost and/or time for rework, provided they can even get the contractor to agree to it is not worth it, or not wanting a legal battle over contractual obligation.

Based on your last post, it sounds like a turn and burn on these building with specs and designs getting recycled. I am curious to know what you consider your professional liability on this is, if any, because it sounds like the person who engineered this had been made aware as well as your management. So, you have done your job, first, having caught the mistake and then reporting it to the relevant stake holders. I've been in similar situations and if you think your company won't use this negatively against you in the future, then I'd be inclined to make sure all of this is well documented and move on to the next mistake. That said, from a moral perspective, if I ever thought anything was going to be a life-safety issue or could fail catastrophically, I would stake my career on bringing to the attention of the AHJ if I'd exhausted all other methods. Alternatively, if the design does not function correctly or it looks shoddy, it sounds like you've done all you can in your capacity as a CM and it's between your company, customer and the subs.

I am looking forward to seeing if any other MEP engineers have a different take on short and long term issues given your description.

 

[HVAC-Novice]

It is specified (and was bid as) 4" . So providing anything less for the same money is fraud. it is not for the contractor to decide the customer doesn't "need" it. Maybe the fault will appear years later. What's next, we save on fire protection because 99.999% of the time it will not be a problem?
It is like the customer pays for a Lexus, the contractor gives them a Toyota. It does the exact same thing, so all is fine and the contractor deserves the Lexus money for the Toyota?

What if in 10 years they add capacity and install a fan that actually goes to 4"? Will that contractor than come back and replace the ductwork for free?

I don't know the contractual relationships. but you can test the system at 4" (close it off) and see if it fails. Do you have leakage testing specified?

Is there any documentation like a CB that the previous PM allowed the lower grade duct?

As for your employer or bosses ignoring you, just inform them of the issue and document that. Later on when that fails and everyone blames you, you have evidence.

 

[MintJulep]

Even the engineer who drew the building is dismissive of this

"... an Engineer here tell me that the Project Specification Manual is "loosely written and open for interpretation and more of a suggestion"

Assuming that these two are P.E. and you are not, then you will lose any pissing contest internally, and just get pissed on if (when) it becomes a lawsuit.

Sucks to be you, and I'm sorry that you find yourself in this situation.

Since you just started this job, perhaps you have your job searching stuff already spun up.