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  1. #1
    Join Date
    Apr 2016
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    Delta systems specifically a 4 wire one.

    I would really like to ask someone who can explain to me without all the math and explanations that go with it about why you don't see them much what the actual effect is of the way it is grounded. I am not an engineer or a master. I just ran up on this and saw it and no one even knew what it was and someone had to figure it out. I like it but I don't fully understand the way it is grounded. Because that's more like a neutral to me looking at it. It's grounded on a hot leg. It uses two transformers I could see them. I looked over the entire thing as I am maintence and I take care of things for him. Might as well know what I am looking at. So now I have a three phase compressor I just changed out and it says must be grounded. That ground leg is a hot leg for the three phase. I just don't think that's a good idea. I guess if the breaker tripped it would be ok. Pretty sure that's why they require a three pole. Has a wild leg too 214 specs say 208 so that's right in line we have 255 most places. Can someone just explain if there is anything else I need to know so I can tell the owner? We will eventually have to call an electrician in but it will have to be some one from out of town maybe. I know a few that have masters but I didn't even know this existed. Not that big a deal but I have been wiring and doing hvac for 25 years. I see things all the time I never saw before. I don't know where to find the information I looked. I have the code book and it tells me what I can and can't do how to figure loads but I can't seem to be able to find in simple terms what it actually does when you ground a hot leg like that. It shouldn't affect phasing should it? Is the other two are in phase then that one was I would think it was pumping. Anyway sorry this is so long but when friends of mine with a masters just shrug I figured maybe a bit more research couldn't hurt. Not like they wouldn't tell me. I am ok with driving a rod just for it if I need to. I am about to go read up and see what the manufacturer says but I want someone that knows power to at least maybe point me a direction I could look it up that would be appreciated. I don't mind doing the work. But all I can find is things that I laugh about and say yea right. Like the guys that design them do. Or basic information. Well I can follow the rules all day long and be fine but I want to know if there is anything specific that someone could get hurt doing they normally wouldn't. And not for me either. I check everything before I touch it. I also marked the boxes noting the high leg. Wouldn't want to wire up the microwave to 214 volts. Is there anything else I need to do for the lots of other people there that don't know? Other than common sense stay outa that? I kinda found that noticing things sorta makes you responsible for them. Thanks.

  2. #2
    Join Date
    May 2001
    Location
    Kansas City
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    If I'm understanding you what you have is called 240v grounded B phase, 3 phase power with only 2 transformers. It will read 240v between any 2 of the 3 phase conductors, 2 of the legs will show 240v to ground but the 3rd leg won't show any voltage to ground.
    The 4th conductor is your equipment ground. There is no neutral because there is no 120v available. It makes no sense but it works, you have 240v 3 phase power. Just make sure the transformer tap on the equipment is on 240v and not the 208v tap.
    You can hook up the 3ph conductors however you want as long as the phase rotation on the compressor has it running the right direction if its a Scroll. The condenser fan might be either 240v singe phase or might be 3ph.

    I'm not sure what your talking about a wild leg for? That's a different type of 3ph, that doesn't have a grounded (power) leg.

  3. #3
    Join Date
    May 2001
    Location
    Kansas City
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    If you really want to understand what you have call the P&L Co. and ask them to send a Lineman or Trouble Man out because you have questions, they will be glad to send someone out to talk to you.

  4. Likes Ernest Crossman liked this post
  5. #4
    Join Date
    Apr 2016
    Posts
    67
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    Thread Starter
    Quote Originally Posted by rsmith46 View Post
    If you really want to understand what you have call the P&L Co. and ask them to send a Lineman or Trouble Man out because you have questions, they will be glad to send someone out to talk to you.
    Thank you, I had someone answer the question. And it is a two transformer system with a wild leg. One of the panels told me the rest. I had never seen anything like it and seeing a hot leg also grounded kinda weirded me out. Electrician told me it balances it or something and not to worry about it, to just be careful. I went and marked everything so that's about all I have to worry about.


    Two wrongs don't make a right but three lefts do.

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