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Thread: Can't get my 220V tools to work.

  1. #16
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    Quote Originally Posted by Mark Bolton View Post
    I would be more apt to blame your buddies doing his own wiring or some other event as opposed to the circuits being energized when he wasn't there. Tools, or proper wiring, don't burn shops down.

    If there's something in the circuit that's going to catch fire if left on you've got far greater problems than any switch will protect you from.
    Fire Inspector said it was the start capacitor in his belt sander. Professional shop. Professionally wired by an electrician. Fire inspector recommended kill switch for tools when away from the shop. But he's just the fire inspector. What does he know?

    Swapped out the tandem for a regular double pole and all is well. Not rocket science. I have a buddy who's an electrician. We wired my basement together a few years ago. I'll have him double check what I did.

  2. #17
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    Quote Originally Posted by Rob Price View Post
    Fire Inspector said it was the start capacitor in his belt sander.
    I'm not a sparky, but this sounds like a bad switch at the tool that leaked voltage/current, not a wiring problem? I understand you wanting to avoid that so you put in a switch to turn off the circuit. For peace of mind in that application, I would not use a simple toggle switch, but use a spring loaded knife switch designed to be a disconnect. I'm not sure you are gaining anything in robustness by using a toggle switch. (For toggle switch, I assume you are using one that looks like a light switch except rated for the voltage and current. I have one of those on my air compressor, but it is low amps at 220V).

    Mike

  3. #18
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    If you are concerned about fire risks, I would install heat detectors in the shop and have it wired so that you can hear the alarm in the night or have an alarm company respond to a problem.

    And, of course, have a couple of the proper fire extinguishers on hand.

  4. #19
    Quote Originally Posted by Jason Beam View Post
    I think the OP needs to call an electrician. There are too many signs of unfamiliarity with the way residential wiring works to trust that advice given over the internet would be safe.

    Oh Yes..... I pretty much have an idea what exactly went wrong for which I'll refrain from offering advice other than call a qualified electrician. It a very simple mistake that can have dire consequences.

  5. #20
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    Rob

    I'm fairly certain, like a lot of folks, that your culprit is the tandem breaker being installed incorrectly, just put in a standard 240 breaker. If you have the room in your box, and you don't violate the panel manufacturers loading instructions, then the 120/240 tandem breaker mentioned in a previous post could simplify things for you.

    The "Kill" switch is actually a very good idea, but you should have a device called a "manual disconnect", "electrical disconnect", "service disconnect", "circuit disconnect, etc, or something with those sort of word descriptors in the title between the breaker and your tools. It sounds as if you have a standard switch.

    Because someone has to bring it up, I will.
    Tandem breakers cannot be indiscriminately loaded into a panel. Virtually every panel manufacturer has a loading diagram that details which spaces, if any, can be utilized for a tandem breaker. Some panel manufacturers don't allow for any tandems installed in their panel. I know that a person can buy tandems at the 'Borg that fit, and work, but it's wrong, unless they are spec'd and installed per the panel manufacturer.
    The problem with indiscriminately installing tandems is that a condition can unknowingly be created whereas the neutral returns become unbalanced and or overloaded. It's especially easy to do it when sub panels are involved.
    Last edited by Mike Cutler; 08-15-2014 at 7:43 AM.
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  6. #21
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    Quote Originally Posted by Rob Price View Post
    Fire Inspector said it was the start capacitor in his belt sander. Professional shop. Professionally wired by an electrician. Fire inspector recommended kill switch for tools when away from the shop. But he's just the fire inspector. What does he know?

    Swapped out the tandem for a regular double pole and all is well. Not rocket science. I have a buddy who's an electrician. We wired my basement together a few years ago. I'll have him double check what I did.
    Glad to hear you have it fixed Rob!

    For safety's sake, I would have your electrician friend check your work.
    Ken

    So much to learn, so little time.....

  7. #22
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    Wade - you have hit the nail on the head. I tend to treat residential wiring with plumbing logic.

  8. #23
    Quote Originally Posted by Mike Cutler View Post
    The problem with indiscriminately installing tandems is that a condition can unknowingly be created whereas the neutral returns become unbalanced and or overloaded. It's especially easy to do it when sub panels are involved.
    Mike, would you mind expanding on this comment, please. I don't understand the problem you're describing.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  9. #24
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    Mike,

    The following applies to 120V circuits only; please pardon my simple description:

    On a 120V circuit, the current is supplied on the hot leg and returns on the neutral leg.

    If you have two 120V circuits with the same load, each on different hot legs, the effect is to neutralize the current load on the neutral. That is, the neutral carries the *difference* between the current in the two legs.

    When you install a tandem, both of those circuits are on a single leg. If you share a neutral, the neutral leg is carring the *sum* of the currents. This is typically not a problem from the neutral bus out (assuming you follow code), because code prohibits you from sharing a neutral in such an installation (assuming you know this), even though code permits sharing a neutral when the legs are on different legs (assuming there is a tie between the two breakers).

    If someone were mot to take this effect into consideration, they could find that they have an unbalanced load, leading to a high level of current on the neutral return home.

    The purpose of this post is to explain the phenomena, not to focus on legal vs. illegal. For that determination you need to talk to your local AHJ.

    Electricity can be confusing and the code even more so. As others have said, if you are unsure, check with a qualified electrician. If the electrician is unsure, consult with a qualified electrical engineer.

    Jim in Alaska
    Last edited by Jim Neeley; 08-15-2014 at 2:37 PM.
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  10. #25
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    Quote Originally Posted by Mike Henderson View Post
    Mike, would you mind expanding on this comment, please. I don't understand the problem you're describing.

    Mike
    Mike

    Each tandem, as you know, is attached to single stave of a pole of the 240 coming into the panel as they distribute down the backplane of the panel. If they're installed per a panel manufacturer's direction they can only be installed in a manner that facilitates splitting the loads equally between the two poles. If you place them just anywhere in the panel, to many the phases could now be in sync, depending on the poles they are attached too.
    In a main service panels it's not as big a problem as a sub, as the wiring size of the sub makes an assumption for a balanced neutral return to the main panel so as not to over ampere the neutral return. Too many tandems on the same pole will not have the canceling effect of the different angles of two opposite poles and can cause an overloaded, or unbalanced neutral return. The more evenly distributed the hots, the more enhanced the effect of canceling on the neutral return. If the sides becomes unbalanced the neutral return may theoretically see an entire side (pole) of current.

    This is the way it was taught to me many years ago.
    Last edited by Mike Cutler; 08-15-2014 at 2:59 PM.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  11. #26
    Quote Originally Posted by Mike Cutler View Post
    Mike

    Each tandem, as you know, is attached to single stave of a pole of the 240 coming into the panel as they distribute down the backplane of the panel. If they're installed per a panel manufacturer's direction they can only be installed in a manner that facilitates splitting the loads equally between the two poles. If you place them just anywhere in the panel, to many the phases could now be in sync, depending on the poles they are attached too.
    In a main service panels it's not as big a problem as a sub, as the wiring size of the sub makes an assumption for a balanced neutral return to the main panel so as not to over ampere the neutral return. Too many tandems on the same pole will not have the canceling effect of the different angles of two opposite poles and can cause an overloaded, or unbalanced neutral return. The more evenly distributed the hots, the more enhanced the effect of canceling on the neutral return. If the sides becomes unbalanced the neutral return may theoretically see an entire side (pole) of current.

    This is the way it was taught to me many years ago.
    Okay, I understand. But I'm not sure it would be a problem. Let's say that you have a subpanel and you wire it up with 4 gauge wire. So that's a 4 gauge for each hot, a 4 gauge for the neutral, and maybe a 4 gauge for ground.

    Then, let's say that someone had a bunch of 120V circuits and they put them all on one side of the line (one hot essentially unused and the other one carrying all the current). Let's say that the total load on the single side is 25 amps and everything is turned on so it's drawing 25 amps.

    You'd have 25 amps through one hot, zero through the other hot, and 25 amps through the neutral. The wire sizes are okay for that. The neutral is not going to be overloaded, it's just carrying the same current as the hot.

    And if there were any circuits on the other hot, the current through that hot will subtract from the current in the neutral. So in my above example, let's say the other hot is now carrying 5 amps. The current in the neutral will now be 20 amps.

    I understand the problem of someone using something like 12/3 to wire up multidrop circuits and "sharing" the neutral on that wire - if the two circuits are now on the same side of the line. In this case, the currents in the hots will add in the neutral so it would be easy to overload the neutral.

    But for something like wiring a subpanel, I don't see a problem with the current in the neutral.

    Mike

    [I never heard of being able to downrate the size of the neutral to a subpanel. Is that really code? How much can you down rate it? When I installed my subpanel, with an electrician, he put in all of the wires the same size and never suggested that the neutral could be smaller. Seems to me that downrating the neutral would be dangerous.]
    Last edited by Mike Henderson; 08-15-2014 at 4:16 PM.
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  12. #27
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    Wow. Talk about off topic- but good info. No sharing of neutrals here. The panel is full on one side and has open open slot on the other. Trying to keep it balanced just because.

  13. #28
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    Quote Originally Posted by Mike Henderson View Post
    [I never heard of being able to downrate the size of the neutral to a subpanel. Is that really code? How much can you down rate it? When I installed my subpanel, with an electrician, he put in all of the wires the same size and never suggested that the neutral could be smaller. Seems to me that downrating the neutral would be dangerous.]
    Me neither but I have heard of being able to downrate the green/bare ground.
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  14. #29
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    Quote Originally Posted by Rob Price View Post
    Connected the white and black wires to the breaker, ground to the ground bar and ran the wire inside. From there it goes to a 20A double pole switch so I can turn everything off and on from inside the shop.
    My gut reaction is that your circuit is undersized if everything is running off of a single 20A breaker.

  15. #30
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    Oh no. I have one breaker for DC, two breakers for shop tools (one for each side of shop), one double pole for 220, one for lights and one for AC. The 220 has the switch. Planning to add switches to the other tool circuits. Prob overkill, but that way no circuit ever has more than one thing running on it at a time and my lights stay on if I trip something. My only 220 tools so far are lathe and table saw. Haven't figured out how to run both yet simultaneously. Hoping to add a jointer/planer to that list.
    Last edited by Rob Price; 08-15-2014 at 7:04 PM.

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