is volume damper upstream a terminal (VAV) box required
is volume damper upstream a terminal (VAV) box required
(OP)
should a branch duct with a terminal VAV box have a manual volume damper upstream?
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is volume damper upstream a terminal (VAV) box required
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RE: is volume damper upstream a terminal (VAV) box required
RE: is volume damper upstream a terminal (VAV) box required
If so, I have never designed for them there.
I do remember reading a case study from a military project which used it for a high pressure system, I will look for it.
knowledge is power
RE: is volume damper upstream a terminal (VAV) box required
RE: is volume damper upstream a terminal (VAV) box required
cry22, do you also mean no dampers at the diffusers? How is the system self-balanced?
I can see if there are two same-cfm-diffusers, say 500 and 500. The duct can be designed to keep the same static pressure to both. But what if it is 200 cfm and 800 cfm supply diffuser? Would sizing to the same static still keep the system self-balanced?
knowledge is power
RE: is volume damper upstream a terminal (VAV) box required
Opening all VAVs 100% prevents system balance. Because of the numerous ways that VAVs can be designed and implemented, the AABC National Standards book states that there is no "one size fits all" method for TAB. Each system needs to be understood and balancing has to be planned.
Unfortunately what I typically see is some TAB tech that has never seen the plans or the space show up at the job site after the mechanical is "done" and 2 days before the owner expects to get their CO. Then when I get the badly done TAB report I am the bad guy for not signing off and "holding up the project."
www.ellisconsultingengineers.com
RE: is volume damper upstream a terminal (VAV) box required
AnotherEllis: Yeah- it seems like that on every job lately....Owner wants to move in, General Contractor/Construction Manager is screaming at ME to sign things off when THEY haven't fulfilled THEIR contractual obligations.....Mech and Elec systems these days just aren't getting finished off - a construction site, at best, is Daycare for adults, and is basically an exercise in herding cats all the way through the process, and the shiny shoes MBA types that are all popping up as "Project Managers" these days couldn't project-manage their way out of a wet paper bag.
RE: is volume damper upstream a terminal (VAV) box required
RE: is volume damper upstream a terminal (VAV) box required
I always put dampers upstream of the VAV box because I don't have any idea how the system may change over time.
RE: is volume damper upstream a terminal (VAV) box required
RE: is volume damper upstream a terminal (VAV) box required
(PI) VAV boxes. Their installation in such a fashion actually would be a detriment to the system. The VAV box controls are effectively a dynamic balancing damper, absorbing the excess pressure available in the system as pressure and zone airflow requirements change.
RE: is volume damper upstream a terminal (VAV) box required
Making me think though. I'm going to go back through some project drawings. Good question and input from all. Also, I admit that I have personally never used the static-regain method in my life.
RE: is volume damper upstream a terminal (VAV) box required
RE: is volume damper upstream a terminal (VAV) box required
A VAV system is in essence self balancing but I have had issues where a VAV box (particularly the ones closest to the fan) can be noisy as they need to close too much to kill the duct pressure. Installing a VCD before the VAV box can assist in removing some of the static pressure.
RE: is volume damper upstream a terminal (VAV) box required
About the article:
As a lesson learned - Always add a note in your general notes saying that "in case of conflict between drawings and specifications, the highest cost item shall apply." It removes the stupid notes left out in details that are never edited, such as in this
In the case study, I see ovewhelming evidence that the A/E was right. I bet that the outcome will be in favor of the government.
The case references "high velocity" and is defined per SMACNA 1975. SMACNA 75 is absolute, we no longer talk of high pressure, low pressure, etc, we talk about 2", 4", 6" etc. Matter of fact, ductwork for VAV systems upstream of VAV boxes is considered "Medium pressure", not high pressure, thus the note referring to HP in the article is actually not applicable at all.
And finally, just because someone wrote an article about a case study involving a litigation and got "published" in ASHRAE does not mean that this is the new ASHRAE guideline -References to ASHRAE should be pulled from the 4 books, not from articles written by its members.
In my opinion, installing MVD's upstream of VAV boxes is simply stupid, it is stupidely expensive and useless on everyone, it would be buying disease with your own money.
RE: is volume damper upstream a terminal (VAV) box required