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Thread: Neutral/ground at sub breaker panel

  1. #1
    DIY Member Cubey's Avatar
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    Default Neutral/ground at sub breaker panel

    I purchased a breaker box with 2 slots for a project I am working on for a portable outdoor 30 amp to 15 amp converter that features an outdoor breaker box with two 15 amp breakers leading to 2 duplex outlets with an in-use weatherproof cover, raised up off the ground by a stand. I will then plug in 12 gauge extension cords for extra amperage in my vintage travel trailer. This is my solution to the breaker question thread, but now I have a new separate question/problem.

    Anyhoo, the breaker box I purchased has the ground and neutral connected together. Is this normal for a sub breaker? Some websites I read say not to do it while others say its normal. Huh??

    If its not normal, how do I deal with connecting the ground? Do I splice the outlet's ground to the 30 amp service ground directly without going through the breaker's ground strip (which is very obviously also the neutral connection off to the sides) or what? That certainly doesn't seem right from what I read online since current going through ground has something or other to do with tripping the breaker.

    Can anyone clearify if its safe and normal for a sub breaker to have ground and neutral connected together, especially when it's going to be plugged into many different electrical systems. I need to know the universal way to wire the breaker box's ground & neutral in a safe fashion, if that is at all possible.

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    DIY Member Cubey's Avatar
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    Figured it out for myself finally! Isolate neutral from ground in a sub panel. Looks like I'll be going back to home depot for a grounding bar to put in.

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    In the Trades Bob NH's Avatar
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    What is a "portable 30 amp to 15 amp converter"? Are you using the subpanel to supply a couple of 15 amp outlets from a 30 amp breaker?

    Answers to your question:

    The neutral in a subpanel must be isolated from the ground.

    The usual practice is to have a ground bar separate from the neutral bar but you probably don't need a ground bar for two circuits (see below).

    The neutral bar is often mounted on an insulator and there will be a green screw, installed or furnished loose, that "bonds" the neutral bar to the enclosure. That screw is not used in a subpanel and must be removed if it is already installed.

    If the neutral bar is mounted directly to the enclosure (not insulated), then you will have to install an insulated bar for the neutral or provide another means to isolate the neutral.

    Then you will have to provide a ground point to connect the incoming and outgoing grounds to the enclosure. That could be a ground screw in the enclosure with the grounds all connected to it.

    Are you feeding the subpanel with a two-pole 240 volt breaker or a single 30 amp breaker?

    The outdoor receptacles will have to be GFI protected. The best way it to install a

    Are you running the wire from the main panel underground? UF or in conduit?

    Usual Practice:
    The usual practice with a subpanel is to run a 240 Volt circuit (from a 2-pole breaker) to the subpanel. If you want 15 amp circuits you would run #14 black and red (or two black) plus one #14 white plus a #14 green (or a 14-3 + ground cable) to the subpanel. Then you would run two separate #14 circuits (15 amp) to the outlets. You need only #14 because the neutral load cancels if both circuits are loaded.

    However, that won't work if the trailer is wired for only a 120 Volt supply.

    The way you have described your installation (30 amp circuit to subpanel) you will have to run #10 black, #10 white, and #10 green (or #10 cable such as UF) to the subpanel.

    Edit Postscript: You answered your question, a lot more succinctly than I did, while I was writing. I will leave this here in case there is information that may be useful to you.
    Last edited by Bob NH; 08-16-2007 at 09:05 PM.

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    DIY Member Cubey's Avatar
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    Quote Originally Posted by Bob NH
    What is a "portable 30 amp to 15 amp converter"? Are you using the subpanel to supply a couple of 15 amp outlets from a 30 amp breaker?

    Are you feeding the subpanel with a two-pole 240 volt breaker or a single 30 amp breaker?

    Are you running the wire from the main panel underground? UF or in conduit?
    It will plug into 30A service at an RV park and there is a 30A breaker on at the hookup pedistal. The purpose of this is so I can make use of the 30A service without using a $5 "cheater" adapter which can be a fire hazard if misused either on purpose or accident.

    I need this for long term use however I didn't want to have to haul the trailer to someone to have a hole cut into it for a 30A inlet, nor have to pay that since people around here charge an arm a leg for the most basic things so I figured it wouldn't be cheap.

    I'm far from good at simple wood cutting so I didn't dare try to do that myself. This seems like the safest and easiest solution for doing it all myself. I will have that breaker thing to carry around but I don't see that as a big deal. Doesn't weigh much and can be stored easily.

    I really only need it when 15a isn't enough, which is what the trailer's electrical system is designed for. I will need the extra amperage mainly in winter when I will need to run a heater or two. This will provide me with safe extra amperage for that. I suspect a single 1500W heater will keep me plenty toasty but I say "or two" since.. well, you never know! A second heater could be run at a lower setting (ie: 600W) as not to max out the hookup. Also, there will only be one duplex outlet per breaker so there definitely won't be any overloading. A single extension cord will be plugged into it and run into the trailer. In the case of needing two heaters I'd have to run another cord as well or just use it on a lower setting while plugged into the trailer's electrical system. As long as I count my amps I'll be fine though I don't wish to put much strain on the trailer's electrical system.

    This is actually also useful should I find an RV park or campground that lacks 15/20A outlets. I can haul out my converter and get separated, breakered 15A power without using a cheater adapter.

    The outdoor receptacles will have to be GFI protected. The best way it to install a
    I was thinking about that but wasn't sure. I guess I will do so.

    ....

    However, that won't work if the trailer is wired for only a 120 Volt supply.

    The way you have described your installation (30 amp circuit to subpanel) you will have to run #10 black, #10 white, and #10 green (or #10 cable such as UF) to the subpanel.
    Yes, that is what I will do. Home Depot has a #10/2 cable rated for outdoor use (not UF, it was black and insulated) that is flexible and the guy said that would be fine to use for wiring up to a breaker. I will only need about 4-5 feet of this as converter will be kept right at the hookup pedestal and 15A extension cord(s) run to the trailer from it's outlets.

    This may seem like a big waste of time an effort when I should just get a 30A system built into the trailer but eh, this seems kind if easier for me so thats what I went with. Easier, except I have to haul out a special convert box every time. Oh well! *lol* I could easily have 30A service put in later and reuse the breaker box and such if I find this to be too much trouble but I don't think it will be for my planned usage of it.

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    DIY Member Cubey's Avatar
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    Here is a photo of it so far. It will have a big #10/2 (plus ground) cable coming out the bottom of the breaker box of course but this how it'll look aside from that. The purpose of the stand is to keep it from falling forward or sideways. It will be braced against the electric hookup pedestal so it won't be able to fall backwards. A simple $2 lashing strap going around the pedestal and stand will keep it up just fine should there be some gusty winds.

    The stand legs are just leftovers from some poles I got used for making a rope & pole awning using a tarp. The stand is clamped in place and mounted to the back of the breaker box with screws & nuts.

    The weatherproof in-use outlets are attached to the box via screw in 2" nipple. I need to seal up all the caps and such before I start wiring it up.


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    Electrical Contractor/Instructor jwelectric's Avatar
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    What you have is a death trap in the making. When you get to the RV park find the space that you need.

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    Plumber Cass's Avatar
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    Could you expand on that statement.

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    Moderator & Master Plumber hj's Avatar
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    Either I am misunderstanding, or you made the project more complicated than necessary. It makes no difference whether the park has a 30 amp, or 100 amp at the connection, as long as the wire to your panel will handle it. YOUR breaker in the trailer then limits how much of that power you can utilize. It looks like you have to run an "extension cord" through the door to your subpanel.

  9. #9
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Cass
    Quote Originally Posted by jwelectric
    What you have is a death trap in the making. When you get to the RV park find the space that you need.
    Could you expand on that statement.
    To understand what is being talked about here one would need to take a look at this thread along with the one we are in now.

    It seems that this is going to be a Camper used for full time occupancy and more than what the unit is designed for is going to be used at one time.

    These campers are set up from the factory with a distribution panel that is designed for the loads in the unit and it seems to me that the owner is wanting to add things that were not originally part of the unit ie; heat and AC.

    As has already been pointed out there will be cords passing through floors, walls, windows or doors which is a very big NO, NO!!!

    Quote Originally Posted by Cubey
    A single extension cord will be plugged into it and run into the trailer. In the case of needing two heaters I'd have to run another cord as well or just use it on a lower setting while plugged into the trailer's electrical system. I will only need about 4-5 feet of this as converter will be kept right at the hookup pedestal and 15A extension cord(s) run to the trailer from it's outlets.
    Instead of doing something to help this guy out anyone giving him help is only helping him burn his unit to the ground and I hope no one is inside when this happens.

  10. #10
    DIY Member Cubey's Avatar
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    Quote Originally Posted by hj
    Either I am misunderstanding, or you made the project more complicated than necessary. It makes no difference whether the park has a 30 amp, or 100 amp at the connection, as long as the wire to your panel will handle it. YOUR breaker in the trailer then limits how much of that power you can utilize. It looks like you have to run an "extension cord" through the door to your subpanel.
    Thats the thing. The wire between the 15A inlet to the panel is about 14 gauge. The insulation seems to lack any markings but its definitely not 10 gauge. In the 60s trailers came with 15A electrical systems, unlike now where they come with 30A or 50A. It would be a real fire hazard to use a cheater adapter which adapts a 30A outlet to 15A and runs through a 15A extension cord and plugs into a system designed for 15A only.


    Quote Originally Posted by jwelectric
    As has already been pointed out there will be cords passing through floors, walls, windows or doors which is a very big NO, NO!!!

    Instead of doing something to help this guy out anyone giving him help is only helping him burn his unit to the ground and I hope no one is inside when this happens.
    I guess I'm not understanding the problem with running in an extension cord. Whats the harm?

    It will be entering the trailer though a plastic dryer vent. When I removed the gas furnace that was missing parts and generally beyond repair, I first put in a small catalytic heater (which lacks low oxygen sensor so I want to use that sparingly) which requires a high pressure propane supply so I had to run a dedicated high pressure propane hose in so I put in a dryer vent with a hatch next to the entrance door and ran in the propane hose.

    I can also use this for running in the extra extension cord. It will have no pressure on it such as a door or window and will not be bringing in any water when it rains. It enters through the dryer vent and into a cabinet. I simply run the cord out of the cabinet and I have the added amperage I need. I don't see how that would be unsafe or a fire hazard.

    Here is a photo of the dryer vent with the propane hose entering through it.

    http://img.photobucket.com/albums/v2.../dyer_vent.jpg

    Seems perfectly safe to to me to do it in this fashion. I will be installing GFCI outlets for the converter and it will be double breakered (the 30A hookup breaker plus my 15A breakers). The box will be kept off of the ground so it won't be sitting in a puddle of water. I guess I'm not understanding the problem. I do see how I've greatly complicated things but my only solution would be to have someone cut the hole in the trailer for the 30A inlet. Seems like nothing in contrast to what I'm doing, I guess. Wish my logic didn't complicate things as it does.. But in any case I honestly don't see how this idea is dangerous. If you feel it is, please explain it.
    Last edited by Cubey; 08-17-2007 at 12:42 PM.

  11. #11
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Cubey
    I don't see how that would be unsafe or a fire hazard.
    The biggest danger lies with what you can't see as a danger.

    You must first learn that what works is not always what is safe.

    The fact that you have changed the heating unit for a high pressure unit is a big danger in and of itself.

    Now you are wanting to start adding cords through holes in the wall to add to the current load of the camper.

    Unless you are planning on having this camper tested with the remodel work you are doing I would highly suggest that you stop.

  12. #12
    DIY Member Cubey's Avatar
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    Quote Originally Posted by jwelectric
    The biggest danger lies with what you can't see as a danger.

    You must first learn that what works is not always what is safe.

    The fact that you have changed the heating unit for a high pressure unit is a big danger in and of itself.

    Now you are wanting to start adding cords through holes in the wall to add to the current load of the camper.

    Unless you are planning on having this camper tested with the remodel work you are doing I would highly suggest that you stop.
    It seems you are completely misunderstanding what I'm doing.

    Regarding propane, I didn't "change" the pressure from high to low. The original furnace ran on the low pressure propane supply lines. The heater I bought needs high pressure as it was designed for 1lb bottles, but of course can safely run off of a bulb cylinder (kept outdoors, of course!) with the proper hose which is what I have done. The heater is connected to a bulk cylinder located out on the tongue of the trailer and the hose runs in to the heater. It is completely independent of the low pressure system of the trailer which the stove and fridge run off of. Perfectly safe.

    Now about the electrical stuff. I will NOT be adding any more load to the trailer's electrical system. Thats why I will be running in an extension cord, for the specific purpose of NOT adding excessive the load to the trailer's electrical system. The extension cord will have a heater plugged directly into it, completely separate from the trailer's electrical system. I will not be overloading anything anywhere. The trailer will have it's electrical system plugged in to one 15A outlet and the extension cord I run in will directly plug into a heater while being plugged into another, seperate circuit 15A outlet. Think of it as plugging in two extension cords on two seperate circuits in a house and using them. Thats bascually what I will be doing, except one of the extension cords plugs into the trailer's electrical system for its original 15A service. The other one will feed a heater. However the extra extension cord is plugged directly into the heater. I will not be combining two extension cords into the trailer's electrical system to pull 30A out of a 15A system which seems to be what you think I will be doing. I will simply be using an extension cord that is run into the trailer for plugging in a heater. I will get a 12 gauge cord so it can handle the load well.

    The only other solution I can come up with is to mount a 30A inlet box on the back of the trailer and have the box sticking out of the back instead of being flush on the side. It would be the same thing as I'm doing now except it would be built in. (Not sure why I didn't think of that before...) I suppose I could try to do that but really it would be the same difference as using an outdoor converter. Would mean less cords to deal with is all. Humm.. now I think I may do that. *grumbles* I'm about the worst in the world at making descisions.

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    Electrical Contractor/Instructor jwelectric's Avatar
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    Cubey

    Once again, What you are doing is building yourself a death trap.

    You are taking appliances that are not approved for what you are using them for and trying to install them in a tender box.

    The best and only advice I have for you is to either live with what you have or trade it in for something that you want before you kill yourself.

  14. #14
    DIY Member Cubey's Avatar
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    You are being very vague. You are not explaining anything. A statement that its a deathtrap tells me nothing about the WHY it is. Anyone can make a statement that something is dangerous but without the explaination as to why it is dangerous, how would anyone understand and not do it? Tell me WHY and WHERE it is dangerous.

    And what appliances are you talking about? A heater? Since when is a 1500W heater not supposed to be used on a 15A circuit?

  15. #15
    Electrical Contractor/Instructor jwelectric's Avatar
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    Well let's see how this works out.

    It is a resistive heating load that is to be calculated at 125% and I do believe that this will come to 15.625 amps. Now letís add a voltage drop from a drop cord and wonder where it will be?

    The NEC is a bare minimum safety rule book and it states;

    ARTICLE 400 Flexible Cords and Cables
    400.8 Uses Not Permitted.
    Unless specifically permitted in 400.7, flexible cords and cables shall not be used for the following:
    (1) As a substitute for the fixed wiring of a structure
    (2) Where run through holes in walls, structural ceilings, suspended ceilings, dropped ceilings, or floors

    Should I run into something like you are talking about doing in my jurisdiction there would be a power failure throughout the park in which this was found.

    Should a fire start and the insurance people find what you are describing then I doubt very seriously there would be a pay off.

    Should a fire start in your unit that caused damage in other units I do believe that you would be held liable.

    As to the new gas unit, was it purchased from a RV dealership or off the shelf at the big box store? There are some listing issues that would need to be addressed.

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