Line Side Tap Wiring Question

Hi All

I'm new to the forum but have been reading heavily since deciding to do an 8.4 kW DIY Grid-tie system. I've learned a bunch on here (thanks!) and I'm hoping that some of the experts on here can help answer a few questions I have.

I'm trying to determine how best to tie everything together at my meter and main panel. For reference, outside I have a 200A Meter socket, feeding a 2" conduit into the basement and into a 200A Surface Mount Main Panel with a 200A breaker. Wire appears to be 4/0 AL and runs through about 2' of 2" conduit inside the basement before entering the top of the panel.

My original plan was to wire (2) Enphase micro-inverter branches into an AC combiner panel (2 20A breakers) and have that panel backfeed a single 40A breaker in the main panel. The problem with this is that I have CTs/Current Transformers on the 4/0 L1 and L2 conductors where they come into the panel. The CTs feed into an Eyedro device for logging electrical use in my house. If I backfeed the Main panel with the 40A breaker, the Eyedro device will measure current through the L1 and L2 wires but it does not know which way the current is going. This makes the data incorrect unless the solar system is not producing anything at all. I also plan to put a second Eyedro on the solar feed to track production on the Solar. Eyedro has a nice online tool for showing both usage and generation in real time on the same graph.

One obvious solution is to do a line side tap between the meter and the panel. The best place to do this appears to be at the meter socket itself by replacing the meter socket with one that supports double lugs like the Milbank K4977-INT or perhaps adding double lugs to the existing meter socket. If I did this I'm a little unclear on how best to connect this up...

It seems fairly common to run into the house, through a solar specific meter (if wanted/required), through a fused AC disconnect and then into an AC combiner panel, but I'm a little unclear on all of the details.

My questions are as follows:
  1. Is it a given that a line side tap is allowed by the utility and/or the AHJ?
  2. If I'm going to connect inside the meter socket panel, are double lugs the only option or is it allowed to splice into the line side conductors?
  3. If I did a line side tap in the meter socket panel can I just run the new wires into the house in an appropriately sized conduit for the conductors? The reason I ask this is I saw somewhere that a service entrance appeared to have a conduit sizing requirement independent of the service size.
  4. Instead of going from the solar meter (located inside the house) into a fused AC disconnect, can I just feed a 60A or 100A panel that would contain a main breaker and the (2) 20A Enphase branch breakers? If so, isn't this a cleaner way to do this instead of a disconnect and a separate AC combiner panel?
  5. Swapping out the meter socket looks pretty simple and materials seem to be less than $100. Is this fairly straightforward for an electrician to do, or maybe I'm missing something?
  6. Is adding double lugs to meter socket allowed or must the meter socket be specifically designed for it?

I'd really appreciate any input the forum has. It is entirely possible there is a better way to do this, so please feel free to tell me if I'm on the wrong track!

Thanks in advance,

Scott

Comments

  • PhotowhitPhotowhit Solar Expert Posts: 4,280 ✭✭✭✭
    Re: Line Side Tap Wiring Question
    SJKM wrote: »
    [*]Is it a given that a line side tap is allowed by the utility and/or the AHJ?

    In the US there is no DIY grid tied system that is legal, you should let the Utility company, AHJ(s), your insurance company and your mortgage holder if applicable.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • DanS26DanS26 Solar Expert Posts: 219 ✭✭✭
    Re: Line Side Tap Wiring Question

    I think you have the tail wagging the dog. You would be money ahead to scrap the Eyedro, use a load side breaker and install a TED5000 or other energy monitoring system that can separate the energy flows. Just my 2 Cents.
    18.2kW Kyocera panels; 2 Fronius 7.5kW inverters; Nyle hot water; Steffes ETS; Great Lakes RO; Generac 10kW w/ATS, TED System monitoring with PVOutput.org
  • SJKMSJKM Registered Users Posts: 4
    Re: Line Side Tap Wiring Question
    DanS26 wrote: »
    I think you have the tail wagging the dog. You would be money ahead to scrap the Eyedro, use a load side breaker and install a TED5000 or other energy monitoring system that can separate the energy flows. Just my 2 Cents.

    Thanks Dan. If the TED5000 is smart enough to read the current both ways, this is quite likely a better option. I appreciate your input.

    -Scott
  • SJKMSJKM Registered Users Posts: 4
    Re: Line Side Tap Wiring Question
    Photowhit wrote: »
    In the US there is no DIY grid tied system that is legal, you should let the Utility company, AHJ(s), your insurance company and your mortgage holder if applicable.

    I'm not sure what you're saying here. Can you clarify?
  • solar_davesolar_dave Solar Expert Posts: 2,331 ✭✭✭✭
    Re: Line Side Tap Wiring Question
    SJKM wrote: »
    I'm not sure what you're saying here. Can you clarify?

    1) The utility company will need to allow a back-feed electrical via your 40 amp breaker. Mine too has a an AC combiner back feeding a 60 amp breaker. The max without derating the main breaker is a 40 amp.
    2) your permitting agency (AHJ) will want a drawing and permit to attach. Usually they want and engineer sign off and a licensed electrician involved.
    3) you will want to inform your home owners insurance of your expensive addition to your property.
  • SJKMSJKM Registered Users Posts: 4
    Re: Line Side Tap Wiring Question
    solar_dave wrote: »
    1) The utility company will need to allow a back-feed electrical via your 40 amp breaker. Mine too has a an AC combiner back feeding a 60 amp breaker. The max without derating the main breaker is a 40 amp.
    2) your permitting agency (AHJ) will want a drawing and permit to attach. Usually they want and engineer sign off and a licensed electrician involved.
    3) you will want to inform your home owners insurance of your expensive addition to your property.

    Thanks! An earlier post mentioned the TED5000 which, now having read about it, is by far the easiest and most cost effective solution. I will go through the full process of permitting and inspection. I already spoke to my local code enforcement group and they seem quite easy to work with.
  • solar_davesolar_dave Solar Expert Posts: 2,331 ✭✭✭✭
    Re: Line Side Tap Wiring Question
    SJKM wrote: »
    Thanks! An earlier post mentioned the TED5000 which, now having read about it, is by far the easiest and most cost effective solution. I will go through the full process of permitting and inspection. I already spoke to my local code enforcement group and they seem quite easy to work with.

    Your next step is to talk with your utility about the net-metering plan offered and the interconnect agreement. This is where the rubber meets the road on your cost and return on investment.
  • TontwinsTontwins Registered Users Posts: 7 ✭✭
    What did you end up doing? I'm considering using Milbank K4977-INT
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