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  1. #1
    Join Date
    Jun 2012
    Location
    East tx
    Posts
    164

    Varitrane VPEF heat troubles

    I have a varitrave vpef vav box with a ucm4.2 board. This is a 460v 3 phase unit. On a call for heat the blower will come on, make the air switch and and go to the contactor that beings on the heat strips. This is a single stage unit. The orange wire(com/grnd) is not making a ground so the contactor won't pull in. The back of the ucm board looks good, no burnt connections. I havn't had a ucm board go bad on me yet but could this be? I can jumper the orange to a ground and contactor pulls in and all is well till it's suppose to satisfy lol. Is there a way to test the ucm board?Name:  ImageUploadedByTapatalk1355257057.549033.jpg
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  2. #2
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    4,470
    Does the common wire go thru any switches? Or does it come straight from common on board to contactor? I have had a wire break that still read voltage thru it but, wouldn't pull in a relay because no amperage could go thru it.

  3. #3
    Join Date
    Jun 2012
    Location
    East tx
    Posts
    164
    The common goes strait from board to contactor. Check wire continuity and a new temp wire from board to contactor. So im thinking it's internal to the board.

  4. #4
    Join Date
    May 2004
    Location
    SE Pennsylvania
    Posts
    1,010
    The UCM breaks the common. Can you see the status of the heat output through software? Are you meeting the min heat flow setpoint?

  5. #5
    Join Date
    Jun 2012
    Location
    East tx
    Posts
    164
    I will check that tomorrow. It is connected to tracer software, set to thumb wheel control. I have not verified actual cfm output but i do know blower is running wide open and nada.

  6. #6
    Join Date
    Jun 2012
    Location
    East tx
    Posts
    164
    On another note. What do the dip switches control on the ucm board?

  7. #7
    Join Date
    Jul 2007
    Location
    Mount Airy, MD
    Posts
    7,281
    Quote Originally Posted by hvac69 View Post
    The UCM breaks the common. Can you see the status of the heat output through software? Are you meeting the min heat flow setpoint?

  8. #8
    Join Date
    May 2004
    Location
    SE Pennsylvania
    Posts
    1,010
    Quote Originally Posted by Crazecodyk View Post
    On another note. What do the dip switches control on the ucm board?
    Addressing

  9. #9
    Join Date
    Mar 2011
    Location
    North Carolina Piedmont Area
    Posts
    451
    The dip switches are for software addressing 1 through 64 and E-ware address 65 through 127
    Attached Images Attached Images

  10. #10
    Join Date
    Jun 2012
    Location
    East tx
    Posts
    164
    So if the dips 5&6 are in the on position that should be the tracer address for that unit?

  11. #11
    Join Date
    Jun 2012
    Location
    East tx
    Posts
    164
    Ok. After looking at it today. Was able to bring it on via tracer system. I don't think the vav has been fully set up yet my the trane guys. So i've got it in manual mode till the rest of the construction finishes.

  12. #12
    Join Date
    Mar 2011
    Location
    North Carolina Piedmont Area
    Posts
    451
    The dip switches are a little tough to decipher, but here is a quick explanation.
    Each switch represents a value in the binary number system such as 1, 2, 4, 8, 16, 32, 64, and 128.

    Note: VAV UCM 4.2 only use 6 Switches
    Summing the switches that are in the on position determines the address.
    For example 1, 8, 32 are in the ON position = Address 41
    NOTE: This is the actual UCM address and will not always be the actual Tracer address listed for Hardware.
    This will be dependent on Comm such as Comm 3.

    You are using comm 4 most likely but will need to check.

    Trane Everyware Software:
    Must Add 64 to the base total:

    Example: 53 + 64 = 117
    or: 1+0+4+0+16+32+64 = 117
    or 1+4+16+32+64 =117
    or: 53 UCM Address + 64 E-ware address = 117

    As for the comm wire I see that they are on TB2-5 and TB2-6. I normally connect this to TB2-1 and TB2-2 and the daisy chain to TB2-3 and TB2-4. How ever there are others who connect the daisy chain to TB2-1 and TB2-2 as well. There is more than one way.

    Your connection may work but needs to be verified that it is correct. As for the shield it must be connected with one another and tapped back so as not to touch any ground or the metal cabinet.

    Have you set up the VAV's and verified that they are configured correctly.

    What do you mean that you have it in the manual mode? Are you saying that you have overridden functions?

    Hope this helps

    ________________________________________
    Trouble shooting is not part of the repair........understand the symptoms and you will find a solution.

  13. #13
    Join Date
    Jun 2012
    Location
    East tx
    Posts
    164
    I've installed theses VAVs in the past but never set one up to run off tracer. I would like to learn more of that. I have books that i am slowly reading through to self teach me.
    I was able to get into the tracer system ,click on the unit graphic, and overide the unit to come on(still unclear how i did this) they are haveing alot of communication issues with several of their units on several floors. Once all the construction is over, all the control guys are going to have to add all the new vavs to the system as well as troubleshoot the old ones as well. Wish i knew more about it. Will get there though

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