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Thread: Help needed with a battery-inverter backup system

  1. #1
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    Help needed with a battery-inverter backup system

    All,

    I am putting together a battery backup system for certain circuits in my home, primarily for the steam boiler and a CPAP machine. I am not a licensed electrician. I did work for an REA and as an electrician many years ago. I try to keep abreast of code changes and have watched most of Mike Holt's videos.

    The system is described as follows: Four (4) 230 amp 6 volt flooded lead acid batteries connected in series/parallel, yielding 460 amps at 12 volts. Batteries sit in a battery box which will be vented. Charger/Converter is 55 amp, #4 MTW to the batteries. Battery cables are 1/0 welding cable. Battery to Inverter cables are 1/0 MTW/USE-2/THWN-2 (90 deg. wire), rated 270 amps in free air (not in conduit or raceway). Positive lead goes to 400 amp switch (Blue Sea Systems) and then to 200 amp ANL fuse and then to Inverter. Inverter is a 12 volt input Xantrex, 1800 watts continuous.

    I have two questions: 1) I want the Inverter output to go to a 6 QO breaker Square D box, from which I will wire in separate circuits feeding 15 amp outlots in various locations in my home. They will NOT be connected to the house wiring. The Inverter does not appear to have a hardwire option. Can I plug connect to the Square D box from the 15 amp GFI on the Inverter? Or, I could remove the 15 amp GFI and hardwire it.

    2) How/where do I terminate the EGC? It will run between the charger/inverter/breaker box. The only place the grounding conductor will connect with the house will be at the steam boiler, as I will probably install a 2 pole toggle between the house wiring and the inverter output at the boiler disconnect. The house has a 200 amp main, 2 subpanels in the house itself and one in the detached barn/garage. I could run the EGC to one of the subpanel without much trouble.

    Thank you for your attention.

    Bob W. (rjwinz)

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    Hard to help without knowing the inverter model..but if it does not have a hardwire option then it does not sound like it is intended for a permanent install. I'm not sure if it would be a violation to connect it permanently by plug (it might be) but I certainly think the NEC wouldn't allow modifying listed equipment. (And the inverter is required to be listed.)

    Your battery setup raises lots of questions for me, too.

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    Quote Originally Posted by rjwinz View Post
    All,

    I am putting together a battery backup system for certain circuits in my home, primarily for the steam boiler and a CPAP machine. I am not a licensed electrician. I did work for an REA and as an electrician many years ago. I try to keep abreast of code changes and have watched most of Mike Holt's videos.

    The system is described as follows: Four (4) 230 amp 6 volt flooded lead acid batteries connected in series/parallel, yielding 460 amps at 12 volts. Batteries sit in a battery box which will be vented. Charger/Converter is 55 amp, #4 MTW to the batteries. Battery cables are 1/0 welding cable. Battery to Inverter cables are 1/0 MTW/USE-2/THWN-2 (90 deg. wire), rated 270 amps in free air (not in conduit or raceway). Positive lead goes to 400 amp switch (Blue Sea Systems) and then to 200 amp ANL fuse and then to Inverter. Inverter is a 12 volt input Xantrex, 1800 watts continuous.

    I have two questions: 1) I want the Inverter output to go to a 6 QO breaker Square D box, from which I will wire in separate circuits feeding 15 amp outlots in various locations in my home. They will NOT be connected to the house wiring. The Inverter does not appear to have a hardwire option. Can I plug connect to the Square D box from the 15 amp GFI on the Inverter? Or, I could remove the 15 amp GFI and hardwire it.

    2) How/where do I terminate the EGC? It will run between the charger/inverter/breaker box. The only place the grounding conductor will connect with the house will be at the steam boiler, as I will probably install a 2 pole toggle between the house wiring and the inverter output at the boiler disconnect. The house has a 200 amp main, 2 subpanels in the house itself and one in the detached barn/garage. I could run the EGC to one of the subpanel without much trouble.

    Thank you for your attention.

    Bob W. (rjwinz)
    Going with a automatic backup generator will be cheaper and simpler.

    Although if you can't be dissuaded, you may have better luck for help with that type of system on one of the DYI/off grid solar forums like http://forum.solar-electric.com/
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

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    Quote Originally Posted by jaggedben View Post
    Hard to help without knowing the inverter model..but if it does not have a hardwire option then it does not sound like it is intended for a permanent install. I'm not sure if it would be a violation to connect it permanently by plug (it might be) but I certainly think the NEC wouldn't allow modifying listed equipment. (And the inverter is required to be listed.)

    Your battery setup raises lots of questions for me, too.
    Thank you for your reply. I will check with the local inspector about plug connecting - or I will get a different inverter. Its a Xantrex ProWatt 2000.

    Kindly let me know your concerns about my battery setup. If there are changes to be made this would be the time.

    Bob W.

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    Quote Originally Posted by electrofelon View Post
    Going with a automatic backup generator will be cheaper and simpler.

    Although if you can't be dissuaded, you may have better luck for help with that type of system on one of the DYI/off grid solar forums like http://forum.solar-electric.com/
    Thank you for your reply. I have a generator that can be used to power critical loads and recharge the batteries if necessary. I prefer to avoid the noise. The goal here is to have the boiler running off the battery/inverter system full time, so it will continue to run if power is out, and to have a few receptacles around the home to use if that happens. I want to add solar or wind later if practicable. This is a "test" system to see if it is all feasible.

    Bob W.

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