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  1. #1

    enviro-tec VAV speed control

    I have quite a number of VAV boxes and all have speed control on them. All are 277volt and have model ETFC277-8 speed control boards. the problem is that the resistor and part Q2 keeps burning out. I am trying to find out what the specs are for this part Q2, it looks like a small diode but no polarity is marked. i am thinking that it may just be an overload protection. i would like to get these boards repaired if possible. Any help appreciated, thanks

  2. #2
    Join Date
    Jun 2006
    Location
    New Jersey
    Posts
    4,336
    Quote Originally Posted by SFRON View Post
    I have quite a number of VAV boxes and all have speed control on them. All are 277volt and have model ETFC277-8 speed control boards. the problem is that the resistor and part Q2 keeps burning out. I am trying to find out what the specs are for this part Q2, it looks like a small diode but no polarity is marked. i am thinking that it may just be an overload protection. i would like to get these boards repaired if possible. Any help appreciated, thanks
    If my memory is right, these are newer series or parallel boxes with 3 speed PSC motors and speed controller. Yes?

    I would focus on why you are losing speed controllers. What's the incoming voltage look like? What that static look like?

    I find alot of these with the motor set on high and the speed controller cranked down.....which is no good for motor or controller. Your better off with the lowest possible speed tap and the highest setting on controller.

    If these are ECM's, then I don't have any experience with them.

  3. #3
    These are burning out at different places throughout the 4 story structure. I don't find any voltage problems. The dampers are shutting and the boxes are zeroing out before startup. I have not checked the speed selection compared to speed controller setting, as I never thought this was a problem.
    I would still like to repair the controllers, if I could find info on the cicuit board or components.

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