Generator-ready subpanel question

Discussion in 'Electrical Forum discussion & Blog' started by charp, Sep 25, 2011.

  1. charp

    charp New Member

    Messages:
    19
    Location:
    Grass Valley, CA
    My last house had a generator ready Connecticut Electric 200 amp mechanically switched panel and I'd like to install one in our current house. My question is whether it's possible to downsize the main breaker in this type of panel to 100 amps since that is what the main panel is and that's what the underground service conductor is sized for. That would give me the ability to upgrade down the road if needed.
    The panel will be mounted on the exterior of the house and will have roof cover, in a breeze-way. Will it need to be rated for exterior installation? Any other panels I should look at?
    Last edited: Sep 25, 2011
  2. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,542
    Location:
    North Carolina
    1- Yes
    2- Yes
    3- many
  3. charp

    charp New Member

    Messages:
    19
    Location:
    Grass Valley, CA
    Got any recommendations for a panel? Is it possible to convert a standard panel?
  4. ActionDave

    ActionDave Electrician

    Messages:
    351
    Location:
    Colorado
    Are you wanting to transfer power to the entire house or set up a separate panel with some selected loads?

    Either way any off the shelf outdoor panel would do the job. Whatever brand is most popular in your area is what I would purchase.
  5. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,542
    Location:
    North Carolina
    1- no Whatever brand is most popular in your area is what I would purchase.
    2- yes
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,874
    Location:
    Cave Creek, Arizona
    Whatever panel you use it MUST have a positive interlock on the transfer switch so the two power supplies could NEVER be connected at the same time. Normally, the sub panel is wired to supply power to the more critical devices, NOT the entire house. In any case, it requires a city permit and inspection, and possibly an approval by the utility company, before being energized.
  7. charp

    charp New Member

    Messages:
    19
    Location:
    Grass Valley, CA
    The panel I had in the last house everything was powered when the generator was used. I had to manually shutoff non-essential breakers to not overload the generator. It was used to power the frig, and a light circuit or two. With the "new" house I will need to power the well - if I want water during a power outage.

    Anyone have experience with Interlockkit - a kit that converts a standard panel to generator ready?

    Permits and inspections - around here you probably need a permit to wipe your backside. Can't count the number of times I've had to wait on an inspector who then doesn't even do his job! I better stop now before I get worked up. I've had my fill of Government.
  8. drick

    drick In the Trades

    Messages:
    392
    I have used the interlock kit before. Its easy enough to install if you can measure and drill a hole (I think they even include the drill bit.) And its probably the least expensive way to manually transfer the entire load of an existing panel to a generator. As long as your comfortable with using your breaker panel as a switchboard to keep from overloading the generator I think you would be ok with it.

    It usually requires that you use the top breaker spaces next to the main breaker as your main breaker from the generator. You'll probably end up relocating a couple of existing breakers to open spaces lower down in the panel to make room for it.

    -rick
  9. ActionDave

    ActionDave Electrician

    Messages:
    351
    Location:
    Colorado
    The interlock kits are fine, but they are only useful if you are using a portable generator.
  10. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,542
    Location:
    North Carolina
    Why do you think that? It is a manual transfer and can be used with permanently installed generators.

    The small generators that come with the receptacles already on the generator require a special transfer switch that switches the neutral.
  11. charp

    charp New Member

    Messages:
    19
    Location:
    Grass Valley, CA
    So enlighten me on using a small portable generator in regards to the neutral.
  12. drick

    drick In the Trades

    Messages:
    392
    Check with your local inspector on the shared neutral issue. Gentran manual transfer switches don't switch the neutral and they are the most commonly installed transfer switch for portable generators in my area.

    -rick
  13. ActionDave

    ActionDave Electrician

    Messages:
    351
    Location:
    Colorado
    I'll amend my statement and say that they are most useful for portable generators.
  14. ActionDave

    ActionDave Electrician

    Messages:
    351
    Location:
    Colorado
    This gets into deep electrical issues that requires a common vocabulary shared mostly among electricians and electrical inspectors.

    If you have the generator you want to install in your possession post the make and model.
  15. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,542
    Location:
    North Carolina
    FTCN.GuideInfo
    Engine Generators for Portable Use

    GENERAL
    This category covers internal-combustion-engine-driven generators rated 15 kW or less, 250 V or less, which are provided only with receptacle outlets for the ac output circuits. The generators may incorporate alternating- or direct-current generator sections for supplying energy to battery-charging circuits.

    When a portable generator is used to supply a building or structure wiring system:

    1. The generator is considered a separately derived system in accordance with ANSI/NFPA 70, "National Electrical Code" (NEC).
    2. The generator is intended to be connected through permanently installed Listed transfer equipment that switches all conductors other than the equipment grounding conductor.
    3. The frame of a Listed generator is connected to the equipment-grounding conductor and the grounded (neutral) conductor of the generator. When properly connected to a premises or structure wiring system, the portable generator will be connected to the premises or structure grounding electrode for its ground reference.
    4. Portable generators used other than to power building or structure wiring systems are intended to be connected to ground if required by the NEC.


    The UL listing requires that these type generators be connected to the house as a SDS

    [​IMG]
  16. Chad Schloss

    Chad Schloss Member

    Messages:
    330
    Location:
    USA
    THIS ONE - MAIN BRAKER INTERLOCK Siemens ECSBPK03 Generator Standby Power....jpg check around for other interlock kits if you are considering them. I was going to either make one or order the one from that site interlockkit dot com or something like that, but they were like $150... ouch.. it took some doing but I found one for my 200a siemens panel, all approved, no holes needed, made by siemens that stays in place and works even if you take the deadfront cover off for $100 less on Amazon last night.
  17. charp

    charp New Member

    Messages:
    19
    Location:
    Grass Valley, CA
    The generator I have is a Briggs and Stratton, model 030324 bought from Home Cheapo in 2006 for around $700. On a side note, went to our next job to set-up some special hardware for the foundation and the boss had his new Honda generator there - it was impressively quiet, wow. If only i had $3000 or so!

    So, to properly hook up the generator, do I connect the frame of the generator to the grounding rod for the house (don't yet know how the house is grounded) or do I connect the ground of the 30 amp receptacle of the generator to the frame? Also, connect the neutral to the grounded frame? Kinda makes the generator not so portable.

    Can't shop for the breaker set-up until I have a panel.
  18. drick

    drick In the Trades

    Messages:
    392
    You do not connect the generator frame to anything when using a transfer switch. Your house wiring already includes (hopefully) ground rod(s) by the electric meter. When you connect your generator's cord set to your house the grounding conductor in the cord set will connect the generator's grounding conductor directly to the grounding conductors in your breaker panel and out to your ground rod(s) at the meter. The grounding bolt on the generator frame is to be utilized with its own ground rod when there is no other grounding method available (like at a construction site - not that anyone actually uses it)

    Also - keep in mind that if you are planning on using that generator to start a deep well submersible pump its going to be a close call on 5500 watts. It will probably do it, but make sure that its only pulling a minor lighting load - at least the first few times you try it anyway.

    -rick
    Last edited: Sep 29, 2011
  19. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,542
    Location:
    North Carolina
    The device pictured above is not for the type generator you have. The generator you have should never be connected to your house unless you are going through a three wire transfer switch. Here is the User Guide Infomation that is in the UL Whitebook

    FTCN.GuideInfo
    Engine Generators for Portable Use
    GENERAL
    This category covers internal-combustion-engine-driven generators rated 15 kW or less, 250 V or less, which are provided only with receptacle outlets for the ac output circuits. The generators may incorporate alternating- or direct-current generator sections for supplying energy to battery-charging circuits.

    When a portable generator is used to supply a building or structure wiring system:

    1. The generator is considered a separately derived system in accordance with ANSI/NFPA 70, "National Electrical Code" (NEC).
    2. The generator is intended to be connected through permanently installed Listed transfer equipment that switches all conductors other than the equipment grounding conductor.
    3. The frame of a Listed generator is connected to the equipment-grounding conductor and the grounded (neutral) conductor of the generator. When properly connected to a premises or structure wiring system, the portable generator will be connected to the premises or structure grounding electrode for its ground reference.
    4. Portable generators used other than to power building or structure wiring systems are intended to be connected to ground if required by the NEC.

    Now the question is, are you wanting to do it right or are you just trying to make something work?
    If it is the latter then a couple of #12 drop cords is the cheapest way out and still be safe. If safety is not a issue then do it how ever you wish.

    At any rate the generator is a listed ungrounded device and driving a ground rod at the generator is not needed no matter how you wire it to your house.
  20. Chad Schloss

    Chad Schloss Member

    Messages:
    330
    Location:
    USA
    the panels I see for sale for portable gen sets do not switch the neutral. I think my 15kw propane generac xfer switch did though. what is incorrect without switching the neutral? people have been doing it for years. safe? you don't think it's safe to have the main breaker OFF and backfeed the panel with an interlock device as pictured above? again, people have been doing this for years, even without an interlock switch.
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