Backfeeding question

Discussion in 'Electrical Forum discussion & Blog' started by dcf1999, Nov 18, 2013.

  1. dcf1999

    dcf1999 Member

    Messages:
    31
    Location:
    Illinois
    Ahhhh... the common backfeeding forum post... Here it goes!

    I've beeing doing a lot of research on the topic (as I want everything to be safe). I know the correct way is to use a transfer switch, which I am going to do. I ordered the transfer switch and it will arrive tomorrow. Meanwhile though, I started doing the wireing for the transfer switch. I installed the 220 inlet outside where the portable generator will go, and ran the 10-3 (30 amp switch and gen) wire to the main panel. I need some elecricity right now, so I temperaraly installed a 30 amp double pole breaker and the 10-3 is wired to that so I can backfeed the panel.

    Now... before I get a bunch of backlash, I know to open the mains... It's only the wife and I in the house and she doesn't touch the box (I've explained the dangers and she really has no urge to play with the breakers). I only run the generator when I need it... taking a shower (on a well), running the heat for a bit to keep the house somewhat warm, etc.... I'm not running the gen 100% of the time on this setup. I've very OCD when it comes to safety so I triple check everything... my order is this... 1. Check mains and backfeed breaker are open. 2. start gen. 3. connect gen. 4. check to make sure main and all breakers are off (open). 5. check to make sure main is off (open). 6. Open backfeed breaker. 7. Open only needed circuits. Yes... I know it's illigal what I'm doing and potitatally unsafe... but if done corretly, it can be safe.

    My question is... I've been reading... and not quite got the right idea on how it works, but I've read that even with the mains off (open) you can backfeed through the neutral to the grid. Is this correct? I've also read, in order for this to happen, you have to wire the system wrong. Is that correct? My inlet plug is wired (W) - white wire (X) - Red wire (Y) - Black wire. At the panel, the ground and white wire go into the bonding stip and the black and red go into the breaker.

    Last few questions... If the system was wired wrong, wouldn't you notice it when the house is running on gen power? I mean if one hot leg was accedently attached to the netural bar & lets say the white wire from the inlet was wired to the breaker, wouldn't that cut power to that half of the panel? Lastley... does a transfer switch open the netural wire to the outside? It seems like this "feeding through the neutral" could happen even with a transfer switch if the switch is wired wrong.

    Sorry for the long post and any spelling errors... Thanks for everyones time.
  2. DonL

    DonL Out of the Trades

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    Location:
    Houston, TX
    The best bet is to use extension cords for what you really need.

    That is a lot safer then back feeding, and the problems that may come from it.


    Good Luck.
  3. Reach4

    Reach4 Active Member

    Messages:
    2,075
    Location:
    IL
    The neutral should not be a problem. "If the system was wired wrong", who knows what that would do.

    It is permissible to get an interlock sold by the maker of your panel to keep the top breakers from being turned on unless the main breakers are off. That normally takes up the top 2 breaker rows (4 slots), so you would have to move the breakers that were there down to make room. Not all panels have such kits available.

    I think the kit sold by http://www.interlockkit.com/ is not technically allowed because it is not being provided by the maker of your panel.

    http://www.homedepot.com/p/GE-PowerMark-Gold-Load-Center-Generator-Interlock-Kit-THQLLX1/100674082 would be an example of a permitted kit if you had a GE panel and installed the kit in accordance with the instructions.

    I am not a pro.
  4. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
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    Location:
    North Carolina
    Your installation is completely illegal even with your transfer switch

    408 of the NEC mandates that any back fed breaker be secured to the panel so it takes more than a pull to release the breaker.

    702 of the NEC requires a transfer switch and the listing of the generator see UL FTCN will require that transfer switch to switch the neutral or in other words a portable generator can be connected to your house as a separately derived system only.

    225 of the NEC requires that any feeder supplying a building to have a disconnect to disconnect all ungrounded conductors and this disconnect has to be suitable for service equipment. A cord and plug is not suitable as service equipment.

    DonL gave the best advice in this thread that you will ever get concerning portable generators
  5. dcf1999

    dcf1999 Member

    Messages:
    31
    Location:
    Illinois
    I do like the interlock idea the best because then I can choose which circuits I want running and which ones I don't... but they don't make the interlock for my panel so I'm doing the transfer switch.

    I don't like the extension cord idea because it just seems kind of foolish to cut the NM cabling for the well pump, install a 220 outlet on one end and an 220 plug on the other so I can run a 50' long 220 extension cord to power my well from my generator. Same with the furnace.. . I don’t want to cut the 110 line and install plugs. Do they even make a 50' long 220 extension cord? I've seen 20' ones.... or would I then have to make that myself also. Then it's running a bunch of 100' cords to power my fridge... etc... Just seems sloppy and a great tripping hazard having a bunch of cords running through the house... I'd much rather have my well and furnace hard wired into my panel (like they are) instead of plugging them into an outlet... Plus it seems a heck of a lot easier to install a 10 circuit manual transfer switch and isolate 10 circuits that I would want to have on when the power is out.

    jwelectric: So what you’re saying is the transfer switches made by generac and such are illegal? Because they say right on the box that they’re approved by the NEC? Also... electricians install those type of manual transfer switches all the time... seems if it's against code, they wouldn't do it. You would also think that, if those switches are illegal, the manufactures would make one that is code compliant... Honestly... from all the research I did on the manual transfer switches, you're the first one to say there illegal to have for the use of temporary power.

    Now… that being said… obviously the 30 amp breaker I installed to temporarily allow me to feed my panel would be removed, and the 10-3 cord from the outside inlet would then be correctly wired into the transfer switch therefore there would be no way to “illegally” back feed my panel anymore. That whole setup mentioned above was just an easy and safe fix to temporarily supply power. Now I say safe because the method I used, while illegal, does essentially the exact same thing an interlock does except there is no metal bar to prevent both the back feed breaker and main to be on (closed) at the same time. However, I’ve never seen a breaker (the main in my case) to switch itself on by itself. And it’s a hell of a lot safer than using a 220 “suicide” cord connected to a dryer outlet (like a lot of people do). As long as the main breaker is off, no power can get to the outside grid (theoretically… see original qustion).

    The switch I purchased is the Reliance Controls 31410CRK Pro/Tran 10-Circuit 30 Amp Generator Transfer Switch Kit. I’m installing it tomorrow.

    Now… all that being said… back to my original question (that still hasn’t been answered)… I’ll post it again… I've been reading... and not quite got the right idea on how it works, but I've read that even with the mains off (open) you can back feed through the neutral to the grid. Is this correct? I've also read, in order for this to happen, you have to wire the system wrong. Is that correct? My wiring is all correct btw. If the system was wired wrong, wouldn't you notice it when the house is running on gen power? I mean if one hot leg was accidently attached to the neutral bar & let’s say the white wire from the inlet was wired to the breaker, wouldn't that cut power to that half of the panel? Lastly... does a transfer switch (like the one I purchased) open the neutral wire to the outside? It seems like this "feeding through the neutral" could happen even with a transfer switch.

    I know for a fact I didn’t miss-wire anything. It’s just an honest question that I’m intrigued about…. It just doesn’t seem possible for power to back feed through the neutral if the mains are off… with the mains off, it’s an open circuit… like attaching the negative to a car battery but leaving the positive disconnected…. In that situation, no power is fed through the car’s electrical system.

    Finally… with all this being said… my power is back on but while it was off… I did “illegally” back feed my panel… The linemen on my road fixing the lines didn’t die, nor did my house burn down. The generator was in plain sight from the power company working on the lines and they didn’t say or ask anything. I’m sure they test the lines to make sure there not hot before working on them. Just because something is illegal, doesn’t mean it can’t be done (temporally), or done safe for that matter. I bet 75% of electricians would, if in the situation where they needed electricity, back feed their panel. I’ve talked to a handful that have. They don’t tell people how, which is smart on their part, but they still back feed. But because they’re “electricians”, they feel comfortable doing it because… well… there electricians and they “know what’s there doing.” I didn’t ask if I should or shouldn’t do it, nor if it was legal to do… I knew it’s not the best option and that it’s against code… but I also followed all the precautions to make sure the gen power didn’t back feed to the grid (flipping the main). My question was about the neutral back feeding… and was purely out of curiosity… not because I feared I might be doing something wrong.
  6. dcf1999

    dcf1999 Member

    Messages:
    31
    Location:
    Illinois
    Thank you for not jumping all over me about the topic... I do like the idea of the interlock, but they don't make one for my panel. I opted for the Reliance Controls 31410CRK Pro/Tran 10-Circuit 30 Amp Generator Transfer Switch. It's easy to install, has good reviews.. and looks nice and clean. It also seems it will be easier for the wife to safetly operate if I'm not arround and the power goes out.
    Last edited: Nov 19, 2013
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,893
    Location:
    New England
    I think you're missing the point...a transfer switch must break all non-grounded conductors and a neutral is a conductor. Flipping a circuit breaker does not disconnect the neutral. IOW, you can't leave a neutral from one system connected so that it could be connected to the other system...current travels through neutral when you have any 120vac circuit hooked up. This could feed back and become dangerous to anyone downstream. The ground is a safety lead, and should only have current on it in a fault condition.

    ANy transfer switch you use must provide those capabilities, and it needs to break before making the alternate connection. Don't fry yourself or some lineman trying to fix your power...do it right or not at all.
  8. dcf1999

    dcf1999 Member

    Messages:
    31
    Location:
    Illinois
    I get the point... I know it's a potentially dangerous situation... I'm just trying to figure how it happens. The science behind it per say... When I read stuff like this, I get intrigued and want to learn about it (why it happens, how it happens, etc…). It's more of a thirst for how things work than "how can I rig this up."

    That being said, I’m starting to grasp the concept of how it could happen. So far this is what I gather. Let’s assume a generator is back feeding a panel, the main and all breakers are off except for the furnace… that one is on. The gen power flows through the 30amp double pole breaker to supply power to both lugs (or busses… whatever the correct term is). The current then flows through the furnace breaker to the furnace itself. Whatever current the furnace doesn’t use is then shed through the neutral to the neutral bus. That current then flows back out of the panel to the grid through the non-broke neutral connection. I also would guess a partial amount of that current is then routed to ground as well since the neutral bar is also connected to ground. So far is this all correct? If so… this is where I’m now confused… That excess current flowing through the neutral isn’t really dangerous until the circuit completes… where and how would that circuit complete? For example, let’s say you have a hot 14-2 wire. You can theoretically touch the white (neutral) wire all day long and nothing happens until you simultaneously touch the black (hot) wire. At that point the circuit completes and you feel get the shock. If you touch the white (neutral) wire and the bare copper grounded wire, nothing happens (assuming it’s a properly wired system and there are no shared neutrals). So the only way I could conceive a lineman getting injured in this situation is if there is current in the neutral wire on the pole (provided by the gen back feeding out of the panel over the neutral) and the feeder wires are energized. If the power is out and the linemen are out working on the lines to restore the power, I highly doubt (I could be wrong), those lines are energized therefore not providing an area to complete the circuit. Now… back feeding the grid because the main is on, current would flow out of the home to the grid where a lineman could easily touch a hot wire (energized through the back feed) and ANYTHING that’s grounded and have a very bad day. And it's undertood they have precautions for that even, however we must account for human error thus the precautions could fail.

    A generator transfer switch is obviously the correct way to go (which is what I have) but the neutral (and ground) from that switch does get fed back into the main panel and is connected to the neutral bus. When you switch from “line” to “gen” it essentially turns off the outside connection (like turning the main off) and turns on the connection to the generator to prevent the back feed of gen power… but do those transfer switches also break the neutral connection to the outside world? Everywhere I look/read, it says they do not… so how are transfer switches any safer if the neutral is still closed and power can still back feed over the neutral? (Besides the obvious design of the double throw action preventing back feed through the mains)

    What I also gather is… the best transfer switch to have is one that is before the panel and breaks all three connections (the two hots and the neutral) to the panel. The neutral would then be supplied / connected via generator? I assume the automatic transfer switches you see on the whole house unites (generac for example) do this?

    All in all, it seems as if the potential for a dangerous situation via power backfed in the neutral seems close to nil because of what I described above (assuming what is described above is correct). Otherwise these generac and other brand transfer switches that don’t shut off the neutral would not be approved by the NEC as stated on their packages.

    Thank you for answering my question and your help in helping me understand this.
    Last edited: Nov 20, 2013
  9. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,531
    Location:
    North Carolina
    All current will flow back to its source including DC. The neutral being switched or not does not create a danger to a lineman. What causes a danger to a lineman is when the generator is feeding the hot conductors that are connected to the transformer. The transformer will step this voltage up to the primary voltage and the lineman is in danger.

    With a cord and plug generator the danger is to the person using the generator. A listed cord and plug generator will have the frame bonded to the neutral and when connected to a wiring system a parallel path will be established in the cord set causing the frame of the generator to be current carrying.

    If it is a new generator and the 240 volt receptacle on the generator is GFCI protected and new generators are required to have this, then when the neutral is not switched the GFCI on the generator will trip and the generator will be useless. Some older generators and non-listed generators will have the neutral “floating” or it won’t be connected to the frame and if the neutral is not connected to the frame it is dangerous. No bonded neutral and no current clearing of faults. No bonded generator and in the event of something going wrong with the windings and the frame could become part of a 240 volt path. Both of these scenarios have been documented and the reason that UL has required that all 240 volt receptacles on generators be GFCI protected.

    Panel front interlock kits are dangerous. When a breaker is turned off there is no way to know if the contacts of that breaker broke. There are documented cases where a breaker was turned off but the contacts did not open. When this happens the generator is back feeding the service conductors which is stepped up at the transformer causing much danger to the lineman. Power companies are starting or at least in my neck of the woods to bypass any place that has portable generators running in the yard just because of the danger involved.

    The NEC is a minimum safety installation guide. To do anything less than what is outlined in the NEC is an unsafe installation as well as being an illegal installation that could cause problems with your homeowners insurance.

    Unless the transfer switch is rated as service equipment and if it is it cost a lot of money, then a service disconnect is required between the meter and the transfer. Unless the generator has a service rated disconnect on it that is visible and within 50 feet of the building being served then a service rated disconnect is required between the generator and the transfer switch. I don’t think a cord and plug will fit the definition of service rated. This will mean that there will be a service rated disconnect on each side of the transfer switch, one for the utility power and one for the generator power. This is required by the NEC.

    I don’t know the law in the windy city but here in NC it is illegal to connect anything to a home that does not have a listing and label on it. If the generator is listed by UL then UL mandates that the generator is to be connected as a Separately Derived System (SDS). What this entails is the switching of the neutral in the transfer equipment. Switching of the neutral in no way makes it safer for a lineman but instead makes it safer for the user of the generator and anyone else coming into contact with that generator such as a neighbors kid which your homeowners insurance will not like should that kid need to collect insurance.

    Don gave you the best answer you will ever receive concerning that generator. Plug a cord into the receptacle of the generator and the other end into the appliance needing power and forget trying to connect it to your house. It will save you money as well as a lot of headaches should something happen and your homeowners insurance get involved.

    On a side note; I have two generators that have been used in the past 12 years, one a Honda 5500 and the other a Honda 7500. One is for the well in order to water the horses and the other for the house but neither has ever been connected to my home. During a power outage I use two #12 100 foot cords for whatever I want to plug in in the house. My TV is not one of them but the reason is for another thread.
    Last edited: Nov 20, 2013
  10. dcf1999

    dcf1999 Member

    Messages:
    31
    Location:
    Illinois
    Thank you... that makes more sense now. I can see how the neutral would me more dangerous to the user than the lineman. I howerver, didn't know about the main breakers not fully opening... which obviously would be a danger to a lineman. I did know that the transformer does step up the backfeed (since current is going other way). I also heard about the bonding issues with the new generators. All in all, I'm considering having a whole house generator installed by an electrician. Where I live, it seems like a very good place to loose power to my place at least once a year. At one point, I did have a lineman come out to repair the feed to my house (lost power to half my panel which turned out to be a bad connection at the pole). He told me the biggest issue where I live was the guy down the street with all the willows that tend to cause problems with the lines during bad storms. He also said I'm on a main 3 phase line that is pretty high priority. However with the last storm, it took 48 hours to restore the power.

    I do have some other questions concerning future improvements to my electrical system, but I will start a new topic on that.

    Oh and let me guess... the TV reason is because the power from the gen isn't "clean" and can cause problems with sensitive electronics? Just a guess though.

    I didn't mean to get snippy with anyone, I honestly just wanted to know about the neutral backfeed thing because I didn't understand the physics behind it and wanted to learn more about it...
    Last edited: Nov 20, 2013
  11. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
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    Location:
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    In a 220/240vac circuit (at least in the USA), there is no connection to the neutral. Well, the ground and neutral are bonded at the panel, but that's a different issue. But, neutral is a current carrying conductor when using 120vac. The typical house feed is a center-tapped 220vac circuit...connecting one end to the neutral gives you 110vac. Back to the transformer, if the load on each end of the transformer is equal, then there's no current in the neutral there since they cancel out. That load is rarely balanced perfectly, though. That's one reason why the 110vac CB typically alternate which leg they are on, and a 220vac CB is wider so that it can connect to the two legs at the same time.
  12. Reach4

    Reach4 Active Member

    Messages:
    2,075
    Location:
    IL
    Are you saying a home generator transfer switch does not need to switch the neutral?
    Last edited: Nov 20, 2013
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
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    Location:
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    No, that's not what I said! I was just describing where and how current flows in the circuit.
  14. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Location:
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    The switching of the neutral in the transfer switch will be determined by the type of generator that is being installed.

    The type of generator you have mentioned in your original post would require the switching of the neutral but some generators does not require the neutral to be switched.
  15. DonL

    DonL Out of the Trades

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    Location:
    Houston, TX
    Last I checked All conductors that go to the pole need to be switched on a approved automatic power switch over system.

    And the generator will have its own grounding system and should not rely on the ground at the pole.

    The same applies to underground feeders.


    Water is about the only thing that a person really "Needs"
  16. guy48065

    guy48065 New Member

    Messages:
    111
    Location:
    SE and north MI
    How do I get water using an extension cord?
    Submersible pump, all wiring contained in conduit all the way back to the panel. Seems to my layman mind that anything I do to make that "extension cord ready" would itself be a violation.
  17. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,893
    Location:
    New England
    Couldn't you run the pump power to a junction box, add a plug and receptacle, and when you needed the generator, unplug from the line and plug it into the generator?
  18. guy48065

    guy48065 New Member

    Messages:
    111
    Location:
    SE and north MI
    Funny you should suggest that. My cottage boiler is wired exactly like that and I always thought it was about the lamest thing I ever saw. So people actually wire major circuits through SJO cord? I wonder how many of the other hacks I've discovered in my cottage are actually recommended practice?
  19. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,531
    Location:
    North Carolina
    If you have a well you will have a pressure switch located somewhere close to the storage tank. This is where I take a cord and connect my generator. Surely your pressure switch is not located in your panel so somewhere in that conduit there is a pressure switch that turns the pump on and off.
  20. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    Couldn't individual key items be fed through pull-out disconnect boxes? Have a tie-in point for an extension cord between the disconnect box and the item.
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