HVAC Balancing

What does the TAB contractor have to say?

Never mind, I already know what he says. You can calculate all you wish, it will never be correct. This is why these specialized TAB contractors are used.

TAB = ? The last set of plans from 2004 include a statement the system shall be balanced, but apparantly this was not done. The owner is currently in litigation with the installation contractor over this issue.

Yes, TAB: Test, Adjust & Balance.

If it was not done, there are specialty contractors equipped to do so.

Stinks of homework.

It is not.

Time and materials...

Only somewhat facetiously...:

1. Open all registers fully.
2. Run system.
3. Anybody gets too cold, close their register some; too warm, open some.
4. Rinse and repeat, keeping notes and making each successive move half as far as previous move.
5. Cross fingers and hope this converges to a satisfactory result.

I don't think he's asking how to do the job, but rather how to bid the job....

Your step 3: registers cannot be opened some if all registers are open fully.

Thanks, energygod, GA. I see why your ratio of GA's to answers is so high.

Well I'm afraid you've left out the first basic step, which renders all other info useless...and that would be checking the units to see if they are working at capacity...for all we know from the information given the air filters may just need to be changed...or they may not have filters at all, and the evap coils could all be dirty....in any case, this would be the first step...Lack of routine maintenance accounts for about 99% of cooling problems...

You are correct. It was not stated by the OP what level of preliminary corrective action might have been taken.

However- once you started the "balancing" measurement effort, you would/should very quickly determine if plugging or related low airflow was a culprit. If you saw total CFM at less than about 375 per ton, it would raise a flag immediately and trigger a quick talk with the Owner.

The a/c units would have to be thoroughly checked to insure proper performance, checking the filters and coils would just be the first step....Once the units were thoroughly tested, depending on any problems found, then you would move on to the next step if necessary...Most of the time this would solve the problem, after all if this is an existing system it was probably working well at some time in the past...This would have been determined on the initial contact with the customer though, it would be one of the first questions to be asked....ie; Hey this system isn't working...Was it working in the past? The troubleshooting process begins with the first contact with the client...Once it's determined that all the systems are working properly, then you would check the ductwork for leaks or damage....This troubleshooting process would continue until the problem was solved...

First, you have to know what you're starting with. Determine that by hiring a a highly qualified professional balancing firm to measure total CFM, inlet and outlet air pressure, fan RPM and amperage draw, fan motor rated amps and voltage at each HVAC unit. Using colored smoke they can determine each of the office spaces served by each HVAC unit. This will be detailed on the to-scale drawings they will provide as part of their services.

By running load calculations on each space you can determine the CFM required by each space at peak load. This will also determine if the existing HVAC units are of suffiecient capacity.

If this building has variable air volume (VAV)boxes you are in luck. If each HVAC unit serves an area with mutiple spaces and only one thermostat, you are in for a lot of comfort complaints.

If you are an experienced HVAC design engineer you'll know what to do. If you aren't I suggest you retain one before taking the first step on this project.

Good luck,

Lou Bindner

check this

www.ft3.biz

Nobody likes a spammer.