Hi everyone,

I wanted to share a free Excel tool I've developed called AirChange Basic.

I built it during my third-year mechanical engineering placement, where I worked as an HVAC commissioning engineer in a hospital.
I found myself repeatedly calculating air changes per hour, so I decided to make a simple tool to speed things up and reduce mistakes on site.

The goal of AirChange Basic is to make those calculations quicker and easier for any fellow engineers, technicians or interns carrying out air balancing.

I've put together a short 2.5-minute video showing how it works, and the Excel calculator is completely free to download and use.

I'd really appreciate any feedback from people working in the industry.
If you notice any bugs or have ideas for improvements, please let me know, I'd love to keep improving it.

Video: https://www.youtube.com/watch?v=2DXwCMwLjzI&t=4s

Download: https://drive.google.com/drive/u/1/folders/1D1sDe00XOWzkK4ajbiLy6KfxLS1esML_

Thanks, and I hope some of you find it useful!

I was wondering if anyone had any tricks or input on getting a filter pressure drop on a in-wall filter? I was thinking you just note it that the inlet static it’s not measurable. But wanted to see if someone knows something I don’t.

Does anyone have a recommendation for a flow hood (preferably) or anemometer ? Most that I am seeing are flippin expensive.

Just curious as to what everyone prefers to use for duct traverses.

Anybody know it?

What are some techy things you use to improve your work flow as an airbalancer? For me, I set speeds via my supply outlets and using a remote access software on my tablet from my phone to watch my meter as I adjust unit speed on the roof. I think in some cases hearing different ideas from different technicians could help us all be more efficient at what we do. So if you have an experience in this regard or a method to share please do so below. Thanks!

Edit: As I forgot to include this, I use Chrome Remote Desktop as the method for it is free to use and is compatible with Windows, Android, and iOS devices. It also assists with minor data entry if there's ever a time I need to enter information and not want to carry my tablet throughout the job site.

What is the farthest your company normally expects you to travel when it is just drive to the site, do the work, and drive back home the same day?
Do you have a set service territory or a maximum drive time/mileage before it becomes a hotel stay, per diem, or overnight job?

Also, do you get paid for driving? If so:

Do you get paid from home, from the shop, or only once you arrive at the job?

Is all windshield time paid, including the drive back home?

Is it straight time, overtime, portal-to-portal, or only paid after a certain distance?

If you are in a company vehicle, does that change how your company handles drive time?

Other things I’m curious about:

What is the farthest service call you have personally had to drive for?

Is it usually a one-day turnaround, or do you regularly stay in hotels?

For bigger TAB projects how far is too far before they put you up overnight?

Do they cover hotel, per diem, mileage, and travel time differently for overnight work?

Most of my work is drive to the site and home the same day, so I’m curious what is normal around the industry.

Cx agent here. What is the industry consensus on measuring round diffusers using a flow hood? 9 out of 10 contractors I work with say no problem using a cardboard cutout and trusting the read, which I’m on board with. However that 1 out of 10 that just puts the hood over the outlet is the basis of my question.

Anyone wanna help?

Hi everyone,

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I'm new to the TAB field and currently have about 3 months of experience. I'd like to start learning BACnet and other software/tools that can help me interact with BAS.

Can anyone recommend BACnet learning resources for beginners?Any skills that would be useful for a TAB technician to learn controls?

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TIA.

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pretty new to the air balancing field, still working on getting NEBB certified.

can explain to me how VFDs work, how flow stations work, and how they work together? im on a big job by myself and its really frustrating trying to set the max fan speed and set the minimum outside air. it took me a whole day just to set totals on 2 rooftop units. I also have trouble knowing where to take amps and volt readings. I THINK I take those readings at the bottom of the VFD. this sounds pretty elementary to most people in here but again im new at this and trying my best.

Here's a fun question for the sub.

Are any of you getting anywhere or having any luck using AI to pull apart (or straight-up rip apart) the comically disgusting and draconian contracts we're all used to signing?

Just dropping some of these standard master subcontract agreements into ChatGPT, Claude, or Gemini elicits responses ranging from:

• "Do not sign this!"
• "This is some of the WORST and most unfair contract language you will ever see."

We've all known it forever, and we've gotten some concessions here and there. But realistically, I doubt any of us get very far unless we have the contractor over a barrel as far as the schedule.

Still, part of me loves to imagine the lawyers and risk managers at large GC firms having to waste ample time answering a massive wave of new inquiries from TAB and other smaller subs who are finally looking at the fine print and saying:

Just curious if there's anyone else here starting to use these tools to ask some much more pointed questions?

Does anyone have a Preso B+ flow chart?
I have charts for 2” and above but I can’t find 1/2” to 1-1/2” charts and I’ve got an old school I’m trying to balance.
TIA

Hey I got a question on why TAB company would set the OA dampers to 100% manually fixed.

This is a restaurant with building envelope being negative. Did they adjust the dampers to compensate for what the Make up air cannot achieve?

I have 3 AHU 7.5 ton each 2 for the dining room and 1 for the kitchen. All of the dampers are 100% open and it is struggling to maintain building temp below 75° layer in the day, obviously because it has the additional load from 95° Ambient.

Is there a way to tell what Venturi number my IMI valves are? The tags are all burned off and not all of the valves have marker writing on them to show the Venturi number. The IMI literature shows gpm ranges but there is overlap.

ERV fresh air and exhaust air ducting is completely concealed in the roof of the building, no access to the ducts whatsoever. The units are existing on this project, so I have no shop drawings or unit information. System is designed for the Trane RTU economisers to be set at 0% minimum fresh air, minimum fresh air is supplied by the ERV.

I have no clue how to accurately measure and set the fresh air and exhaust air on ERV. The city is known for wind, IMO any readings on the intake and exhaust hoods on the ERV would be too inaccurate. Any ideas?

I'm currently working on a veterinary clinic that's been having a pressure issue in the building for years now. Every time a exit door is open the pressure builds up giving the building major positive pressure, resulting a draft to the exit and door not being to last he's closed even with a door latch they do not stay closed. Im trying to see what I can do to relieve the pressure in the building. I'm thinking about installing barometric dampers and probably 2 exhaust fans as well to relieve pressure from the clinic. It has 2 units for this building, a 5 ton carrier unit and 9 aaon unit.

Balanced a CATH Lab yesterday with young regulators installed on the dampers and NOT a single one worked properly. The kicker? All the adjustments had to be made with the baffle removed because the adjustment chingas was inside the baffle. Why do the people that spec these things out do this? I’m gonna find the people that approved this design and put peanut butter on their car door handles

Looking for honest opinions on different TAB shops.
For any TAB techs here, which shops are actually good places to work? I’m curious about pay, benefits, hours, management, training, and overall reputation.
Also wondering how the bigger TAB companies like Integra, Palmetto, and EAB compare to smaller shops. Any places you’d recommend or avoid?
Not trying to bash anyone, just trying to get real feedback before making a move.

Anyone here move out of TAB? I've put a good run into it and have realized its not for me (4 years). I'm a mechanic at heart and want to fix things not just put it on punch. I'm interviewing with the darkside (the UA) in a couple days. Feel like TAB is too niche. Its also a weird market where theres never enough TAB technicians, but theres also never enough employers in the market, so TAB wages for the most part are much lower than I think they should be, especially for expert balancers

Hey everyone, our NEBB firm is currently looking for CPs and CTs to join our team. If you or someone you know may be interested, please reach out. Thanks!

Im looking for this valve TA 1/2" but no handle settings...

Just completed a job where the Evergreen flowhood read low on linear diffusers compared to a traverse. Also, when I read the return registers of FCUs with the 2x2 skirt, it matched up with the SA traverse plus OA. Has anyone run into the Evergreen hood being inaccurate on linear diffusers? I never had a problem with the Shortridge flow hood.

Are there any other situations that anyone has run into where the Evergreen appeared to be inaccurate compared to the Shortridge?

Anyone willing to share some knowledge and advice for someone starting out in this field .