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Thread: VARI-TRAC

  1. #1
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    VARI-TRAC

    Hey balancers, what do I need to tackle a Trane Vari-trac system.
    Building is 5 years old, never been balanced. ( most max/min numbers in the "balance" tab were no where near the VAV design numbers. Negative building pressure.)
    I was there for a duct noise and got suspisious so they let me check a few things. Had a flowhood on the van that day and first box I measured was 45% low.
    Anyhow. Do I need some Trane software? Something special to connect to the VAVs?
    Can I connect thru the Vari-Trac control panel, or have to access each VAV? Where do I input and check flow for min/max/zero?
    Any pointers?
    I'm sure I can find manuals etc but always good to hear from others who've done this, and doubt there will be much balancing instruction.
    I know about initial total cfm setup and such. Just don't know how to work the VAVs.
    Thanks!

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  2. #2
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    Thread Starter
    Wow! A strikeout.
    Or more like a no-hitter!

    @WAYNE3298
    @Artrose
    You guys got anything.?

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  3. #3
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    Betting you need rover, or a functional workstation.

    Id be ready to get Trane or a Trane controls vendor on the job to assist.

    Thats the way everything is going anyways.

    Need 4 companies working side by side to swap a light bulb out anymore.


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  5. #4
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    @icy78,
    Questions:
    Are the Zone Damper Boxes Pressure Dependent (COBP) or Pressure Independent (VAV) ?
    Is there a Bypass and if so, is it controlled by Duct pressure ?

    I may be able to assist depending on the answers. Simple COBP is relatively easy, VAV with PI boxes not so much.

    Heatingman, I disagree, to a degree, about the "Need 4 companies..." part.
    If sense were so common everyone would have it !
    You cannot protect the Stupid from themselves !
    "Experience is the ability to recognize a mistake Before you make it again!" (Stolen Quote)

  6. #5
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    Quote Originally Posted by Cagey57 View Post
    @icy78,
    Questions:
    Are the Zone Damper Boxes Pressure Dependent (COBP) or Pressure Independent (VAV) ?
    Is there a Bypass and if so, is it controlled by Duct pressure ?

    I may be able to assist depending on the answers. Simple COBP is relatively easy, VAV with PI boxes not so much.

    Heatingman, I disagree, to a degree, about the "Need 4 companies..." part.
    These are PI I guess. They have flow rings. Trane thumb wheel zone sensors. They are also on a CV package unit with a static controlled bypass damper. No reheat.
    I dont think the bypass is setup correctly either as 2 units show 0.1" static Stpt and 0.2" static setpoint, and the 3rd is set at 1.2" static.
    I got suspicious about duct leakage there the other day. Totally calm outside and those attic ventilators, the natural draft ones, curved vertical fan blades, they were all spinning and I thought where the heck is that air coming from? So crawled up in the attic that day and the insulation is all bellied out on the ductwork. I poked thru the insulation and woosh! man what a mess LOL.

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  7. #6
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    Quote Originally Posted by heatingman View Post
    Betting you need rover, or a functional workstation.

    Id be ready to get Trane or a Trane controls vendor on the job to assist.

    Thats the way everything is going anyways.

    Need 4 companies working side by side to swap a light bulb out anymore.


    Sent from my iPhone using Tapatalk
    Man I'd really like to do it myself. Itd be interesting. May need 4 guys to help me tho!

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  8. #7
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    Quote Originally Posted by icy78 View Post
    Wow! A strikeout.
    Or more like a no-hitter!

    @WAYNE3298
    @Artrose
    You guys got anything.?

    Sent from my SM-G950U using Tapatalk

    You're probably not going to want to hear what I'm about to say.....

    If you are a balancer, and this was a controls job done by a Branch office, you'll need to contact the office for the software package. For Trane products, you'll need the correct version of Rover and a cable with the correct pinout. They can provide everything you will need.....

    But, in all likelihood, they will want to charge you.

    Be wary, vendor control products are often different software and hardware products. Depends on the product.

    Contact the Branch office, not a vendor, unless you know the product was installed by a vendor.

    You need your flowhood, a laptop with the correct software package, the style of vav, series fan, parallel fan, straight vav, whatever, and all the design numbers for the vavs. Cooling max/min, heating max/min, damper type stroke time, type of reheat, CW or CCW rotation for the damper, and much much more...... damper shafts tight and correct, flow ring piped correctly, etc., etc., etc.,.......as well as a thorough understanding about how your VAV's are designed to operate.....that's why you need somebody to teach you hands on....

    First time out the chute, hire somebody who knows how to do this work and help them, and learn exactly how to balance airflows, or hire a company and do the same.

    To attempt to do this cold with no experience is a failure straight out of the box.......

    And to actually be productive doing this specific work, a two man team is most efficient.

  9. #8
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    Quote Originally Posted by Artrose View Post
    You're probably not going to want to hear what I'm about to say.....

    If you are a balancer, and this was a controls job done by a Branch office, you'll need to contact the office for the software package. For Trane products, you'll need the correct version of Rover and a cable with the correct pinout. They can provide everything you will need.....

    But, in all likelihood, they will want to charge you.

    Be wary, vendor control products are often different software and hardware products. Depends on the product.

    Contact the Branch office, not a vendor, unless you know the product was installed by a vendor.

    You need your flowhood, a laptop with the correct software package, the style of vav, series fan, parallel fan, straight vav, whatever, and all the design numbers for the vavs. Cooling max/min, heating max/min, damper type stroke time, type of reheat, CW or CCW rotation for the damper, and much much more...... damper shafts tight and correct, flow ring piped correctly, etc., etc., etc.,.......as well as a thorough understanding about how your VAV's are designed to operate.....that's why you need somebody to teach you hands on....

    First time out the chute, hire somebody who knows how to do this work and help them, and learn exactly how to balance airflows, or hire a company and do the same.

    To attempt to do this cold with no experience is a failure straight out of the box.......

    And to actually be productive doing this specific work, a two man team is most efficient.
    Good input! Thanks.
    I am not a balancer. I worked for a balancer back in 94-99 so I do have somewhat of an understanding but NOTHING like what I read on here from accomplished balancers.
    However, I feel I can dramatically improve the situation with my bit of balancing background and my HVAC experience, combined with my innate desire to leave things better than I found them. Also, I have a controls friend who is somewhat versed in these. Together we'd do well I think.
    First is getting owner to agree.....it may stall there.

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  10. #9
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    Quote Originally Posted by Cagey57 View Post
    @icy78,
    Questions:
    Are the Zone Damper Boxes Pressure Dependent (COBP) or Pressure Independent (VAV) ?
    Is there a Bypass and if so, is it controlled by Duct pressure ?

    I may be able to assist depending on the answers. Simple COBP is relatively easy, VAV with PI boxes not so much.

    Heatingman, I disagree, to a degree, about the "Need 4 companies..." part.
    I was making a pointed joke, about how propriety everything is now days.

    Even “open” control systems I find to be excessively proprietary.


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  11. #10
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    Quote Originally Posted by icy78 View Post
    Good input! Thanks.
    I am not a balancer. I worked for a balancer back in 94-99 so I do have somewhat of an understanding but NOTHING like what I read on here from accomplished balancers.
    However, I feel I can dramatically improve the situation with my bit of balancing background and my HVAC experience, combined with my innate desire to leave things better than I found them. Also, I have a controls friend who is somewhat versed in these. Together we'd do well I think.
    First is getting owner to agree.....it may stall there.

    Sent from my SM-G950U using Tapatalk

    Icy....disregard about half of what I said earlier...

    I went back to your original post, and realized you were talking about an old Varitrac.

    We commonly refer to that system as a Poor Man's VAV.

    Often installed on Direct expansion, constant volume air handlers with a duct pressure controlled bypass in the supply duct.

    Be aware of the possibility of short cycling of conditioned air, or other, resulting in frozen DX coil.

    Since you are working on customer equipment, I would still contact the Branch for assistance.

    There are a couple basic sequence of operations for that design. Basically, a CV AHU maintaining a DAT, with supply duct pressure maintained by a supply duct pressure sensor that controls the bypass damper.

    Zone temp is maintained by pressure dependent VAV's. Switchover from cooling to heating is normally controlled by majority vote from the zone t-stats.

    Sorry I didn't read before speaking.

    I believe most of what you will need might actually be available on the internet.

    If I were you, I'd ask your question on the Controls section.

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