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I do a LOT of CX. That is why my handle is CXagent.

Do I know as much at the TAB, GC or Controls guys? On each job I probably do not know as much as the ones who installed and lived with making it work. But what I don't know I usually find out.

Oh, before I go very far - most of the problems I find are in the design. There are some construction/installation problems but most problems are in the design.

I never have time/budget to check everything. So I check the common problems and look for indications of problems. Zones where both the heating and cooling are on all the time. Exhaust fans that never shut off. Buildings that are depressurized - by design. Sensors that are way out of calibration or not working at all. AC's that will never get cold enough for the air to be dehumidified. Roof leaks. Plumbing cleanout missing or turned where they are unusable. I see those problems over and over and over.

And I get fooled by some problems. Like a supply vent that blows across a sloped roof and turned straight down onto the t/stat - by design. A RTU that will lock out every eighth time the reheat function turns on.

But the ones that keep me busiest are the ones that should never happen. Like ducts that were never installed (but TAB report shows proper flow). Or ducts that "fell off" the diffuser or start collar after TAB. Or RTU that never had power on them. Or split systems that have never had the refrigerant lines connected. Yes - I see those all the time too. And the TAB report shows them to be working when tested.

I have had many 'discussions' with design engineers, architects and contractors that I was not needed on a job. I just say "show the owner I'm not needed and put me out of business - please." Just like anytype of job, CX is only as good as the people doing it. That is true with TAB, mechanical contractors, control contractors, etc. I have worked with really good and really bad of each of those. CX is only as good as the people doing it.

What tells me I am doing a good job is the number of GC that hire me directly. They don't ask the Owner to hire me. The GC hires me directly.

Commissioning seems to be to out of a basic mistrust that the job was done right. I understand that. It's the last opportunity to see if things work as planned.
I A building in town came to mind. The county court house hadn't worked mechanically since built. A friend worked there and problems were reported from the beginning but no one could be pinned down to fix it.

I believe that many jobs might not be done right. We've all seen it in construction. I wouldn't buy a house w/o a home inspector. Not saying the guy knows his stuff or that there isn't a need to qualify the specialty. I remember not too long ago CA's were rare.
I could conclude it was out of necessity. Sometimes some might do a job half a$$ed because they know no one will find out.

I started to get certified in commissioning but after looking into it decided it was more paper work than substance. For that reason I never got certified. My opinion of it guys. The original intent attracted me because the original intent was to start when the design team started and work closely with them. By doing that a lot of problems can be avoided but every request I got was to do the work after the install was completed.
On one job where I was awarded the TAB work I called the CA and told him he needed to check the heat calculations on one of the RTU'S because as designed they would deliver 46 F air with an ambient of 0 F. He said they value engineered the job and there was no problem. You can guess what the email I got said when the ambient got to 0 F.
Sorry guys but I think CA is more feel good fluff than anything else. If you watch a lot of them sit down at the control computer and accept what ever it tells them. In my book that isn't the way it should be done.

I have not had to much trouble from CAs on mechanical jobs my company has performed. What is kind of funny is the CA always has less knowledge than the control guy, tab guy, and construction superintendent. But the CA is making sure they did it right.

I’ve heard there is a ca that works around here for the local schools that made ridiculous demands to change stuff after installation that had some minor flaw. Guys started putting clarifications in their public open bids to add 100k if this ca was involved.

NEBB does have a standard form for each application. I now have my own forms on the computer. I only had one set of instruments calibrated. I compared the other instruments to the calibrated ones. It takes some time but is well worth doing. My standard reference was the inclined manometer even though I had the other equipment calibrated.
Very few contractors care about anything but the report because the report gets their retainage released.

Wayne, we know many T&B reports are flawed one way or other. Along with this, reports have no easy way to compare them as there is no standard form. I remember one that used the formula for DC electricity to arrive at AC motor readings.
Parking lot reports.
I talked to one T&B company about how expensive having the instruments sent in for calibration. He said they didn't do that. They had one set of instruments calibrated and compared the others with that set. I didn't ask how that was done with accuracy.

Most jobs don't have someone follow up on reports. I once pointed a flaw in a report. The contractor said he didn't care. All he said he cared about was the NEBB cert. so he could get paid.

brad agree that is stupid but how and why did a competitor have that authority? I think a competitor would try that in an effort more to discredit than anything else. If there is a problem a representative sample should be good enough say 5 or 6 verifications.
I had a job with several 20 CFM exhaust grilles. I explained in the report summary that the only way to read airflows that low was to traverse the duct but the install didn't allow traverse of anything but the total exhaust. I further explained what I did to balance the system but the lady in charge of the facility wasn't satisfied. The design engineer fortunately understood the problem and when I told her to remove the grilles and add enough duct below the ceiling for me to traverse I would be happy to do it. That idea sounded good to her until she found out the cost of everything but the traverses were on her.
The engineer called me aside and said "don't be too upset with her because that is the only honest balance report she has ever seen".

How about the part where my buddy had to traverse 75 100cfm exhaust fans? Nobody sees a problem here? In my opinion when you make your competitor do something like that it's only to waste his time , hence the conflict.

hvacker when TAB instruments are calibrated a list of readings at various airflows for example are included with the report. There doesn't have to be a pissing match. When I was challenged I immediately called for a come to Jesus meeting on site. I informed everyone I valued my reputation above all and protect it with every fiber of my being. I was never challenged by anyone that pulled out their calibration report and that was the first thing I ask to see. Not one of them had the report and threw in the towel as soon as I pulled mine out. I told them I'll take the readings and you correct them.
I had one calibration company that didn't send the report and I called them and ask for it. They refused so I changed companies.
One of the big tricks the accusers tried to pull was using back pressure compensation. They would ask if I used it on the digital hood and no I didn't. I enjoyed that trick because back pressure compensation doesn't come into play until 500 CFM minimum. When I did compensate for back pressure I calculated it because the hood couldn't do it worth a damn.
I don't know if they have improved but digital flow hoods did not repeat well on low pressure systems. I would take at least 5 readings which were seldom close together and then ask if anyone could tell me the average.

bradluke0, there doesn't have to be a conflict of interests when instruments don't agree.
Most T&B people know how to affect instrument readings and also know some companies do this. Check to be sure your instruments recently calibrated so your sure your readings are OK.
He should have included his calibration dates for his instruments with his report.
It could be he wanted to make his company look better at your expense but maybe not. Assume the company did their job right and go from there.

I always included a disclaimer explaining how my readings were taken and how another reading at another time might be different. Most differences can occur after equipment has settled in. Mostly filters not being brand new but temperature and humidity can affect readings if your instruments don't adjust for them. Altitude also but your in Fla.

Urinating contests are often not worth it. I can understand why the owners seem to be taking sides. It's all about who seems to be an authority. If it appears you might loose future work I would probably pursue it. I might ask the other company for a bit of show and tell regarding comparison of instruments but w/o the owners. But I'd start out nice.

In situations like this I did learn from a lawyer to never ask a question you don't know the answer to. Never provide evidence you can't prove. Ducks in a row it's said. Then lock & load if necessary.
Know who is right first. Then there's those pesky calibration sheets that come with the instruments. Might want to check those first.

The problem with attacking the commissioning guys is that the owners back them all of the time . Some of them have been commissioning and balancing for a long time so they are not newbies . They are smart enough to know all of the points brought up above but they still will not admit that 3 months later being 6% from design is pretty dang good . My problem is that they financially benefit from making the T&B guy look bad . IMHO the CX guy should be an independent 3rd party with nothing to gain but protecting the owner . If you look up the definition of conflict of interest you can see this falls right there . I know some of you do T&B and commissioning but you are probably reasonable about things being just a few percent off . BTW....one of my T&B buddies had one of these guys CX their jobs . There were 75 100cfm exhaust fans on light switches in the bathrooms for a school . The CX guy made them go back and traverse all of them because of a blurb in the canned specs , the hood readings weren't good enough . He fought , but once again the contractor and owner made them go back . That's some serious BS .

CX = Commissioning.

Some good points here. I especially agree with Wayne - your integrity is everything. Defend it like your life depended on it. Ok - so only your livelihood depends on it.

Anybody that has done balancing for more than two jobs knows that balancing is an art. No two reading are the exact same even at the same conditions. And conditions change with time, temperature, etc. If a design / spec calls for tighter tolerances than the standard 10% I would ask for the tolerance on the equipment and sensors installed. A rule of thumb is to control to some tolerance you need to measure and control to 10% of the tolerance. So to get 5% tolerance you need to have sensor, fans, dampers, etc than can control to 1/2%.

As far as the CX guy making you look bad - turn the tables on them. Ask how long they have done CX. How long they have done TAB? What is most of their work (CX or TAB)? How accurate do they think they can measure and adjust? Where are their calibrations? Have they ever seen adjustments change over time. Etc. Then ask them if they think they could hold 5% tolerance 3 months after the original TAB was done? Do this patiently and professionally.

The engineer of record has the responsibility of getting to the bottom of disputes like you have experienced. If you can't get resolution any other way file a complaint with the state board of technical professionals. I had to do that once and believe me it got the engineer's attention. Before you do that make sure you are mathematically correct and totally in line with the requirements of the cx agent's certifying agency and yours.
Low pressure systems are most likely where your readings will be challenged. Research these systems through ASHRAE because they are the final word and they have a lot to say about low pressure HVAC systems. They get into the meat of these systems like no other source I know of. Remember he who knows the most wins but not always in the first fight.
If you have an analog flow hood use it on the low pressure systems and compare those readings with the digital.
When I was in business there were two things nobody was allowed to doubt which were my integrity and total determination.
At one meeting my integrity was challenged and I stood up, looked all of them in the eye and told them "I don't know where this meeting is headed but it's not going anywhere until the question of my integrity is settled. I jealously guard my integrity and will not allow anyone to go un-challenge that questions it." The big mouth apologized immediately.
I had a client that wanted me to do balance and commissioning. I told them I wouldn't do it and recommended they not go that direction. They ask why and I told they if someone lies to you once they will have no problem doing it again.

C X ?

2 very thoughtful posts above . I am very strongly against a cx agent who is also my balancing competitor . It is conflict of interest if he works for the owner and can also benefit financially by writing up punch lists regarding the balancing report and not taking into consideration system drift , equipment differences , etc . The problem with challenging the cx agent ( Wayne made some valid points above ) is that in this part of the country the cx guy is always right ( and the good guy ) and we are always wrong ( and the bad guy ) as the readings might not fall into the +/- 5% or 10% range . You can call a meeting and try to explain system drift and equipment differences but at the end of the day the cx guy ( or at least the dicks that I know ) will not give in and the owner is going to back them . The owners , architects and contractors are simply not versed enough to understand that what we are saying here is correct . The same cx agent(s) I am talking about have also performed the balancing and cx on the same projects and that seems to be OK . Strange times indeed . Cheers . ( I have much more to say on this and I will post a recent situation that just transpired but I just got back from vacation and am a little whipped . I have to go back to work to get a little rest …. lol )

Plus or minus 5% to start with is BULL CRAP. Did the commissioning agent provide proof that his equipment was calibrated? How do you know that he actually used the calibration print out for his flow hood etc.? I'm willing to bet he didn't. The accuracy of a flow hood varies with flow quantity. If you are NEBB certified your readings should repeat within 5% and that makes the 5% specified total bull.
I would have insisted on an on-site meeting with all parties including the owner. At that meeting I would have taken pitot traverses with the electronic meters and the inclined manometer. Then measured airflow with an analog hood and digital hood. With all equipment properly calibrated you would have had 4 different airflow totals for any complete system.
The Shortridge meter or any other electronic meter would have been the highest pitot traverse reading but the inclined manometer would have been the most accurate. The electronic time weighted flow hood readings would have been higher than the analog hood but lower than the inclined manometer pitot traverse. You then ask the owner which set of readings do you want to rely on?
I would have also ask the cx for their calibration records including the list of readings when calibrated. I would bet they wouldn't have them with them on site. Without that list they only know what their hood is reading. The people that calibrated my flow hoods included a list of readings with variations for about 20 different airflows. You also have to factor in the accuracy of the flow hood used versus the system pressure.
Any commissioning agent should have known they had an obligation to have you take readings for them with your equipment. They should have ask for proof of calibration.
I never had a problem with cx agents but I'm not a fan of commissioning. I saw too much of it that was nonproductive paper work.

I do think they are probably doing as you say and justifying their purpose.

But as far as conflict, I dont really think so.

Most balance contractors also do commission work.

It would be a conflict if the same contactor did 2 functions.

Such as - install and balance

Or

Install and commission

Not that necessarily if something was found wrong it would not be addressed, its just the likelihood is much higher that it would be swept under the rug so to speak.


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commissioning / conflict?

Let me tell a story about cx . Some years ago we did a decent size school . It was all chilled water , vav and air monitors on the outside air . The spec was plus or minus 5% , the job was cx 3 months after we were done . The cx used his own instruments without us being present . We got written up for outlets being 6 - 7% out of tolerance , 2 air monitors 6% out , etc . Keep in mind that these are only 1 to 2 % over or under the 5% spec . We went back and found our readings were all mostly within 5%. We tweaked a few things and got out . Then we get another list . After much back and forth we refused to go back . The job was closed out and we never heard a peep afterwards. First of all , the cx should have been there with us , using our instruments . Second of all , the cx should have honest and informed everyone involved that flowhoods are plus or minus 3% , vav controls and air monitors are +/- 3% , etc . IMHO his agenda was and still is to make the TAB company look bad and justify his cost . This same cx guy also does TAB work and sometimes we bid on the same projects . Is this a conflict of interest for him ?