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  1. #1
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    Is Test and Balance Necessary??

    There is a lingering belief that HVAC TAB in new and existing buildings is optional. Removing a ruptured appendix is optional if you are willing to suffer the consequences. I have a building to straighten out that the HVAC systems have never satisfactorily conditioned. A few years ago the controls were changed out but the VAV and Fan Powered Boxes (There are many) were not calibrated. None of them were delivering design airflow and some were about half of design. The original design has one area that has a large exhaust airflow but no make-up air. The building is negative when those fans run. To fix the situation an expensive redesign was done and the building is now over designed.
    I probably could have saved them a lot of money if called in to troubleshoot prior to the redesign. I could go on but you get the point.
    No man can be both ignorant and free.
    Thomas Jefferson

  2. #2
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    I think to the majority they feel it is redundant. My point bob pays eddie’s engineering to provide xyz why should bob pay someone to prove or disprove he should get what was ordered and promised.If it was included ( free shipping) then I don’t think it would be scrutinized, but as you’ve said before the lowball or pencil balancing would win most if not all bids. When a customer sees the 200 ton ac that was specd he doesn’t know that their is more to the big picture. It seems many will step over the dollar to save a nickel if it’s not working it should be hot in here. They don’t realize the energy savings and equipment wear and tear imho
    Honeywell you can buy better but you cant pay more

    I told my wife when i die to sell my fishing stuff for what its worth not what i told her i paid for it

  3. #3
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    There was this one six or eight story building where the prior contractor didn't think TAB was the least bit important. The tenants kept complaining of bad temp control. We got called in, and long story short (it is a fairly long story), come to find out he removed every single minimum/maximum control on every single VAV in the entire building!

    D'oh !!
    If you were a real tech, you'd solder a relay on that board and call it good to go.

    I do a triple evac with nitro to remove non condensables.

    I use 56% silver on everything except steel.

    Did you really need the " If you were a real tech " ??

  4. #4
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    Thread Starter
    Do either of you guys think commissioning will get the point across that a legitimate balance is absolutely necessary for commercial buildings or do you think most commissioning efforts fall short?
    No man can be both ignorant and free.
    Thomas Jefferson

  5. #5
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    Tab, a very good and necessary part of a good project.

    Comishoning.... meh.

  6. #6
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    Thread Starter
    Scoobie what is your take on commissioning and why.
    No man can be both ignorant and free.
    Thomas Jefferson

  7. #7
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    I think it’s worth is only seen in extreme situations. If a customer perceives everything is fine you are seen as a snake oil salesmen. Especially if more money is needed to balance. On the other hand when a building is so far out of wack this shows the true talent and benefit to the customer.
    Honeywell you can buy better but you cant pay more

    I told my wife when i die to sell my fishing stuff for what its worth not what i told her i paid for it

  8. #8
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    Well, since you included me in the "either of you guys", commissioning would have had no effect on the results of my post / service calls on that building. Since the min/max controls were removed after the building was occupied and several years old.

    I think commissioning a building has more to do with the building. If you have a sprawling one or two story building with a bunch of RTU's, then a simple balance of air flow for each supply register on each RTU pretty well covers it. Because you likely won't know what a particular tenant is going to do.

    A building with a bunch of VAV's with a hot and cold deck, and nothing like hot water reheat, needs very little balancing at all.

    But a larger building, with one big azz supply fan for the air, and minimum positions at the VAV's for the hot water re-heat to work proper . . . Oh yeah, balancing to the print is very important. Both for comfort and energy savings.


    Quote Originally Posted by WAYNE3298 View Post
    Do either of you guys think commissioning will get the point across that a legitimate balance is absolutely necessary for commercial buildings or do you think most commissioning efforts fall short?
    If you were a real tech, you'd solder a relay on that board and call it good to go.

    I do a triple evac with nitro to remove non condensables.

    I use 56% silver on everything except steel.

    Did you really need the " If you were a real tech " ??

  9. #9
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    I agree crazy. I think it is often missed that TAB if done properly assures the most economical performance of the HVAC system. As long as there is no extreme discomfort all is assumed to be good.
    No man can be both ignorant and free.
    Thomas Jefferson

  10. #10
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    The biggest problems I have seen with VAV'S is the ones with electric reheat. I have seen a lot of them that wouldn't heat because there wasn't enough airflow to energize the heat coil. Eliminating the airflow set points and not calibrating the VAV'S is the worst single thing you can do or not do.
    No man can be both ignorant and free.
    Thomas Jefferson

  11. #11
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    That's pretty much what I was saying. With any VAV system with any sort of reheat, balancing is critical. Without it, you might have comfort, but at twice the operating cost. And those monies can add up FAST.


    Quote Originally Posted by WAYNE3298 View Post
    The biggest problems I have seen with VAV'S is the ones with electric reheat. I have seen a lot of them that wouldn't heat because there wasn't enough airflow to energize the heat coil. Eliminating the airflow set points and not calibrating the VAV'S is the worst single thing you can do or not do.
    If you were a real tech, you'd solder a relay on that board and call it good to go.

    I do a triple evac with nitro to remove non condensables.

    I use 56% silver on everything except steel.

    Did you really need the " If you were a real tech " ??

  12. #12
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    Thread Starter
    Agree BBeerme.

    No man can be both ignorant and free.
    Thomas Jefferson

  13. #13
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    Dec 2004
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    I think TAB is critical to proper performance, but more critical is a good design.

    Im in process of start up of a new school. Dual temperature, variable primary piping.

    The design premiss alone is idiotic.

    They allow for automatic transition from chilled water to hot water up to 6 times a day.

    The amount of system complexity added on the controls side alone, could have been better spent on a second piping set and a more simple and reliable design.

    KISS - thats my motto. Make things only as complex as is required, but not more.

    I got involved in the project after the crap hit the wall on the boiler side. Constant alarms, high deltas, etc... The boilers programing did not match the automation, the integral isolation valves were controlled open only when a burner was active, leaving nowhere for the water to go. The built in controls are incapable of providing the correct valve sequence, so I had to manually override one valve open at all times. Had to reprogram the boiler to recognize the automation signals for enable, and set point - this was after the Factory start up could not figure it out.

    I demanded copies of the balance report, and low and behold found the system pumps were never set for design flow because the boiler valves were erratic. So instead of making someone force the valves open, the balancer instead had the controls company set the DP setpoint based on when the last valve in the system had design flow.

    Which says to me, the entire balance is wrong, so what was the point?



    The chiller start up is tomorrow, I fully expect a whole new set of calamity.

    Im making the balance contractor come back out to set the pumps based on required chiller flow (with every zone valve open), and have the controls reset the DP signal to whatever that is. So at least total flow rate at design and target DP will be right. Still wont fix the rest of the system settings, but its a start. Also gonna have them calibrate the flow meter.

    Step one in water balance is open everything , and set the total flow.

    So when you blow that critical step, anything that follows is a complete waste.

    But my bigger point is, even if everything gets set the way it ought to be (which never happens), the system is so overly complex, and proprietary on the controls end that in 3-5 years time of lack of true system understanding and maintenance, the system will get even worse.

    End of Rant



    Sent from my iPhone using Tapatalk

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