A little help for me and the electrician.

So I had an electrician over to give me an estimate to run 240V to my shed and 240V back to the house for connecting a grid interactive inverter. (Still haven't decided on which inverter yet) Anyway I do plan to set it up to sell power to at least lower the electric bill. Getting A/C power to the inverter is pretty clear. A/C out of the inverter will go to a sub panel that houses breakers for selected backed up loads. I would also like the sub panel to be powered from the main panel as well in case the shed burns down or for what ever contingency that might arise.

The house's existing A/C distribution box is an old Square D unit that I am currently back feeding through a 100 amp breaker because the box's main breaker is obsolete and can't be had so I am planning on replacing it in the process of wiring for the solar. I have come to find that there are "generator ready boxes" that are available and that have automatic or manual transfer switches that might let me eliminate wiring in a sub panel and still keep me from back feeding the grid during an outage.

Since this all needs to be inspected I am hoping to get some help in planning so I can inform the electrician so he can run the whole thing by the inspector for approval so I can move forward on this. I hope I have communicated this correctly, and am looking forward to ideas or better yet a clear diagram that I can print and show the electrician. There is not much Solar in this area. Hell i have never even seen a Solar power system up close unless a Harbor Freight kit counts.

Thanks

Dennis

Comments

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: A little help for me and the electrician.

    i hope i have this straight in my head of what you're doing. i gather this is to be a battery backed gt inverter(hybrid) and as such it already has the ability to stop sending power to the grid during an outage as it is called anti-islanding so no relays or switching over would be needed by you. the gt inverter with its built in switching will operate from the batteries during an outage automatically and will only send power to the circuits downstream of it.

    now it could get more complicated if you plan on a generator start as well, but some do have that ability usually with remotes and how they are wired in may depend on what the inverter + remote specifies. i wanted to show an example of how it's wired, but i'm not seeing one off hand. anybody have a good wiring diagram for them to follow?
  • bill von novakbill von novak Solar Expert Posts: 891 ✭✭✭✭
    Re: A little help for me and the electrician.
    verdigo wrote: »
    I have come to find that there are "generator ready boxes" that are available and that have automatic or manual transfer switches that might let me eliminate wiring in a sub panel and still keep me from back feeding the grid during an outage

    That's intended for a different purpose - connection of an alternative power source during power loss. All modern inverters on the market will drop the grid automatically when power goes out. A "generator ready box" will be useful to you if you want to use either a generator or additional battery-backed inverter to provide backup power, but you won't need it for a traditional grid-tie solar install.
  • verdigoverdigo Solar Expert Posts: 428 ✭✭
    Re: A little help for me and the electrician.

    This is an example of what they term a generator ready load center, and it takes the place of a typical A/C breaker box. Although it is intended for use with a back up generator I was wondering since I have to replace my house breaker box anyway if I would be able to use one of these http://w3.usa.siemens.com/us/internet-dms/btlv/Residential/Residential/docs_LoadCenters/SIE_SA_GenReady0609_low%20res.pdf and eliminate the need for a sub panel for loads backed up by my solar.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: A little help for me and the electrician.

    You'v never said what Inverter you plan on using. Yes, some Inverter's could be used with a box like that for standby power. A hybrid inverter that is Grid Tied is B-Directional, the ACin is also a ACout for the excess current you plan to sell. The actual ACout of the Inverter is for powering the sub panel / loads. If you want to be able to take the Inverter out of the loop, you do that with bypass breakers. Once the Inverter qualifies the incoming power, the transfer is made and the loads are pass through.
  • verdigoverdigo Solar Expert Posts: 428 ✭✭
    Re: A little help for me and the electrician.
    You'v never said what Inverter you plan on using. Yes, some Inverter's could be used with a box like that for standby power. A hybrid inverter that is Grid Tied is B-Directional, the ACin is also a ACout for the excess current you plan to sell. The actual ACout of the Inverter is for powering the sub panel / loads. If you want to be able to take the Inverter out of the loop, you do that with bypass breakers. Once the Inverter qualifies the incoming power, the transfer is made and the loads are pass through.

    This is news to me. I had not realized that the A/C in was bi-directional. I had assumed that A/C out was feeding loads and selling power. You have no idea how much frustration you have just alleviated.

    Never Mind :roll:
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: A little help for me and the electrician.
    verdigo wrote: »
    This is news to me. I had not realized that the A/C in was bi-directional. I had assumed that A/C out was feeding loads and selling power. You have no idea how much frustration you have just alleviated.

    Never Mind :roll:
    I don't have one hooked up to the grid, but thats how my Outback GFX works. Some can be back driven when AC coupled in a mini grid, thats over my head.
  • bill von novakbill von novak Solar Expert Posts: 891 ✭✭✭✭
    Re: A little help for me and the electrician.
    verdigo wrote: »
    This is an example of what they term a generator ready load center, and it takes the place of a typical A/C breaker box. Although it is intended for use with a back up generator I was wondering since I have to replace my house breaker box anyway if I would be able to use one of these http://w3.usa.siemens.com/us/internet-dms/btlv/Residential/Residential/docs_LoadCenters/SIE_SA_GenReady0609_low%20res.pdf and eliminate the need for a sub panel for loads backed up by my solar.

    You could but it's awkward and requires a physical switchover. In general if you are doing the work anyway it is a lot easier to put in two standard load centers - one for essential loads and one for all other loads. Then you connect one circuit of the main panel to the inverter input, you connect the subpanel to the inverter output, and the inverter's internal transfer switch does everything automatically.

    The above requires a battery backed inverter. If you are going for a straight grid tie (which is the most common) you cannot get backup power to your panel. At most of you go with the "secure power" line of SMA inverters you can get 1500 watts or so to an outlet, but you can't power your house when the power goes out - so no need for a separate panel (or even a 'generator ready load center.')
  • verdigoverdigo Solar Expert Posts: 428 ✭✭
    Re: A little help for me and the electrician.

    I am teetering between an XW (Schneider) or Outback GVFX inverter. One of these generator ready load centers might make sense for me. I need to give it some more thought, and run the idea by my electrician.
  • n4wffn4wff Solar Expert Posts: 48 ✭✭
    Re: A little help for me and the electrician.

    Dennis, I have 2 - 240v AC lines to and from my barn so it is a similar to yours. My service from the power company is 325A which is overkill, but it allows me to split 200A to the house and run 100A to the barn. Originally I had a generator in the barn and a 200A transfer switch on the house to switch between the grid or generator. Now that I have solar, I reused the 100A wire from the generator to the transfer switch and attached it to the load output from the XW6048. Now, during normal operation, the inverter sees no loads and keeps the batteries hot, everything else, minus losses is sent back to the grid to sell, or at least slow my meter spinning. The advantage to this is we can use more KWs than the XW is rated for, since no house power passes through the inverter. When we lose grid power, I go outside and flip the manual transfer switch to the backup power position. I just have to remember to turn off my upstairs air conditioner when on backup power.

    Attachment not found.
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: A little help for me and the electrician.

    Just a general note:

    Backup power is one thing, and PV is another. A lot of folks go through a lot of gyrations (not to mention expense) to ensure that their PV system continues to provide power during an outage. IMO it is prudent to take a hard look at that and decide if it is really necessary. A grid tied PV system is a long term strategic tool. It will lessen your electric bill over months and years. If outages are rare (at my house in Austin I estimate that my power has been off less than an hour per year over the last 25 years) it would not be worth it to double the cost of a PV system just to have it run during an outage because the contribution to the bottom line would be minuscule. If you are concerned about power during outages and outages are rare and fleeting, it would be much better, economically speaking, to have a PV system for the long haul and a generator to get through the outages.
  • verdigoverdigo Solar Expert Posts: 428 ✭✭
    Re: A little help for me and the electrician.

    Your absolutely right. My entire electric bill divided into kwh used comes to a little shy of 12 cents per kwh, and the service is very reliable. It doesn't make sense for me to have either.
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