Results 1 to 7 of 7
  1. #1
    Join Date
    Mar 2016
    Location
    Pahrump, NV
    Posts
    1,677
    Post Likes

    Reminder to be safe with electricity

    I just picked up a new employee a couple of weeks ago. His experience is in sheet metal and roof penetrations. Those are both areas at which I am weak. So, he is a great addition to our skill set.

    I have been talking to him about visually assessing each job for safety as we walk up. He was about to lean on a package unit last week, and I told him to stop before he touched it because I saw a problem with the disconnect.

    Yesterday, we had a call from a homeowner who had bought the home about a month ago. They where planning to have a birthday party for their three year old in just a couple of hours. Her father-in-law had tried to get the condenser unit running the night before without success. So, when we got there the disconnect was already pulled, and the electrical access panel removed.

    It might have been an ICP NAC060, but the nameplate was virtually unreadable.

    I checked for voltage on the unit anyway.

    The father-in-law had replaced the dual run capacitor and wired common from the contactor to the HERM terminal, and compressor conductor was on the C terminal. Okay, simple fix, but I told my new employee that we needed to carefully check everything else before we restored power.

    There was an old transformer in the condenser unit. The low voltage conductors were isolated under wire nuts. It was no longer being used. The white line voltage terminal connector was stuck in a gap between metal panels. It was making contact with the metal panels.

    I asked the father-in-law where this wire was when he started working. He said it wasn't connected to anything. So, he stuck it between the panels to keep it out of the way.

    The black line voltage conductor to the transformer was still connected to the line-in side of the compressor contactor.

    Now, tell me if I am wrong.

    If we had energized the unit, without removing this old transformer, the black lead would have energized the the transformer with 120V to ground. The ground being the condenser cabinet and the line set to the indoor unit. This would not likely have tripped a breaker because the potential would have been through the transformer as a load (unless the transformer was already shorted to ground).

    I don't know how likely it would have been that any of the children at the party would have been hurt, but I do believe that it makes a good example of why it is important to continue investigating after you have found one obvious problem.

    PS: The homeowner eventually produced the original capacitor that had been removed. It tested within 6% of its listed rating. I still don't know why the unit wasn't running before the father-in-law started working on it.
    It's an upside down world we live in.

  2. #2
    Join Date
    Mar 2013
    Location
    Billington Heights, NY
    Posts
    20,923
    Post Likes
    It would have been fine unless you provided a less resistant path back to the pole transformer. The neutral from the 120v trans would have followed the metals parts/line set back to the furnace and completed the path via ground wire in the panel/driven rod.

    Im sure TB will come along shortly to tell me im full of BS

  3. #3
    Join Date
    Mar 2013
    Location
    Port St. Lucie, Fl
    Posts
    6,422
    Post Likes
    Quote Originally Posted by David Goodman View Post
    I just picked up a new employee a couple of weeks ago. His experience is in sheet metal and roof penetrations. Those are both areas at which I am weak. So, he is a great addition to our skill set.

    I have been talking to him about visually assessing each job for safety as we walk up. He was about to lean on a package unit last week, and I told him to stop before he touched it because I saw a problem with the disconnect.

    Yesterday, we had a call from a homeowner who had bought the home about a month ago. They where planning to have a birthday party for their three year old in just a couple of hours. Her father-in-law had tried to get the condenser unit running the night before without success. So, when we got there the disconnect was already pulled, and the electrical access panel removed.

    It might have been an ICP NAC060, but the nameplate was virtually unreadable.

    I checked for voltage on the unit anyway.

    The father-in-law had replaced the dual run capacitor and wired common from the contactor to the HERM terminal, and compressor conductor was on the C terminal. Okay, simple fix, but I told my new employee that we needed to carefully check everything else before we restored power.

    There was an old transformer in the condenser unit. The low voltage conductors were isolated under wire nuts. It was no longer being used. The white line voltage terminal connector was stuck in a gap between metal panels. It was making contact with the metal panels.

    I asked the father-in-law where this wire was when he started working. He said it wasn't connected to anything. So, he stuck it between the panels to keep it out of the way.

    The black line voltage conductor to the transformer was still connected to the line-in side of the compressor contactor.

    Now, tell me if I am wrong.

    If we had energized the unit, without removing this old transformer, the black lead would have energized the the transformer with 120V to ground. The ground being the condenser cabinet and the line set to the indoor unit. This would not likely have tripped a breaker because the potential would have been through the transformer as a load (unless the transformer was already shorted to ground).

    I don't know how likely it would have been that any of the children at the party would have been hurt, but I do believe that it makes a good example of why it is important to continue investigating after you have found one obvious problem.

    PS: The homeowner eventually produced the original capacitor that had been removed. It tested within 6% of its listed rating. I still don't know why the unit wasn't running before the father-in-law started working on it.
    I think it would have behaved like when you hookup a cheater cord between line and ground on 230V equipment. But... If it wasn't well connected to the ground, it would have sparked.

    That being said; I have had frightening incidents where I used a cheater cord to run a vacuum on the drain line next to the condensing unit, then gone to the air handler to pour water down the drain to flush the line, and the air handler was crackling from electricity moving through the cabinet.

    I believe these were incidents where the condensing unit high voltage was on the same circuit as the air handler, and I believe the raceway from the disconnect to the outdoor unit was used as the grounded conductor.

    Sent from my Moto Z (2) using Tapatalk

  4. #4
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    28,918
    Post Likes
    The cabinet and the equipment grounding conductor would have acted as a neutral to energize the primary of that transformer. However, the cabinet and the equipment grounding conductor should only become energized if there is a ground fault, so you are definitely correct to disconnect that transformer....and I probably would have physically removed the transformer from the unit if it's no longer in use.

    So....what was the problem that you found after you checked all the wiring?
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
    Member, IAEI

    AOP Forum Rules:







  5. #5
    Join Date
    Mar 2013
    Location
    Billington Heights, NY
    Posts
    20,923
    Post Likes
    ooo yay, I got it right

  6. #6
    Join Date
    Mar 2016
    Location
    Pahrump, NV
    Posts
    1,677
    Post Likes
    Thread Starter
    Quote Originally Posted by timebuilder View Post
    The cabinet and the equipment grounding conductor would have acted as a neutral to energize the primary of that transformer. However, the cabinet and the equipment grounding conductor should only become energized if there is a ground fault, so you are definitely correct to disconnect that transformer....and I probably would have physically removed the transformer from the unit if it's no longer in use.

    So....what was the problem that you found after you checked all the wiring?
    I did completely remove the transformer.

    The only issues I found on start up were low sub-cooling, high superheat and high suction line temp. (see screen shots).

    This was a home owner calling for service outside of their warranty company network. I told the customers that I wasn't willing to spend 45 minutes of unpaid time to deal with a warranty company about adding refrigerant and them wanting to know exactly how much refrigerant was needed.

    The suction line temperature was gradually coming down with the indoor load. Outdoor air was 104F.
    Attached Images Attached Images   
    It's an upside down world we live in.

  7. #7
    Join Date
    Jul 2018
    Posts
    41
    Post Likes
    Dang, I ***** if its over 85

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Related Forums

Plumbing Talks | Contractor MagazineThe place where Electrical professionals meet.