Supply/load side connection (tap)

System
System Posts: 2,511 admin
My first post...I understand that NEC 690.64 allows for a load side connection...I could use some advice on the mechanics.

Situation:
Square D panel SC3040M200S 200 amp panel with 200 amp main breaker
Array size will be greater than 7.4 KW (max allowed 120% rule on load side connection)

Looking in my panel, the main breaker is supplied by exposed aluminum bars...I can access thes from the load side..what type of mechanical device would I use to connect the inverter to the supply side bars?

thanks

Comments

  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: Supply/load side connection (tap)

    I hope you have better luck with a load side connection than I did. Both our code and utility approvals nix the use of a LOAD side interconnect on a residential install. This forced a full upgrade to the service to dual 200 amp panels on a 400 amp service feed from the street. The cost was not trivial. It sounds like I had the same problem as you in overloading the panel buss bar and a entrance upgraded was all they would accept. In there defense they had not dealt with this size a system on a residential install.

    All this delayed my install for about 3 months of bickering back and forth about the load side connect.
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: Supply/load side connection (tap)
    Divenstuff wrote: »
    My first post...I understand that NEC 690.64 allows for a load side connection...I could use some advice on the mechanics.

    Situation:
    Square D panel SC3040M200S 200 amp panel with 200 amp main breaker
    Array size will be greater than 7.4 KW (max allowed 120% rule on load side connection)

    Looking in my panel, the main breaker is supplied by exposed aluminum bars...I can access thes from the load side..what type of mechanical device would I use to connect the inverter to the supply side bars?

    thanks

    Sorry one option is if you can derate your main breaker to like 175 amps you can use the excess to support the solar. That should get you (120% X 200 amp) + 25 amps. More than enough head room for the solar system. In my case, the Utility said this was unacceptable because of my load profile (breakers installed) in the existing panel.

    I didn't scream to hard as I am have a building being added to the property this summer and will need the extra panel capacity anyway. ;););)
  • System2
    System2 Posts: 6,290 admin
    Re: Supply/load side connection (tap)

    Thanks Solar Dave,...I am an all electric house...ac in summer and electric boiler/radiant floor in winter. I will have to review my load calcs....but I do not think I can derate to a 175 amp breaker...I am trying to get a hold of my Electrical inspector to ask....after that I will talk to my utility (Southern California Edison) I think I might max out on the load side (120%)...I am also planning to put in a shop and will probably upgrade at that time both the sservice and the solar

    thanks
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Supply/load side connection (tap)

    Is propane a reasonable alternative in your area?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • drees
    drees Solar Expert Posts: 482 ✭✭✭
    Re: Supply/load side connection (tap)

    Seems that if your meter was separate from your main load panel, that would give you the room to install a smaller box/panel where you could tap the solar in between the meter and main service panel.

    Or - what if you just install a main panel that has more capacity (300-400A?), but leave the main breaker at 200A?
  • Ravs
    Ravs Registered Users Posts: 13
    Re: Supply/load side connection (tap)

    250 amp bussing is a standard size for some commercial bolt-on breaker assemblies, so you could either go with that, or like the previous post, go with a larger residential type plug-in breaker assembly with derated main breaker. In the end the derated breaker might not be off-the-shelf item and might require a trip to your local electrical distributor instead of big box hardware.
  • System2
    System2 Posts: 6,290 admin
    Re: Supply/load side connection (tap)

    I went all electric to stay off propane, when I built my house...I was ignorant of the limitations and requirements to install a large grid tied system.

    I have a Square D All in one 200 amp panel....underground fed..I called Square D and they do not allow a line side tap...so my alternatives are go with max load side (120%) or upgrade the panel...I am going to contact SCE (utility) and see what I need to do to upgrade....any thoughts on a replacement panel that has a larger busbar capacity? thanks for all the advice
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: Supply/load side connection (tap)
    Divenstuff wrote: »
    I went all electric to stay off propane, when I built my house...I was ignorant of the limitations and requirements to install a large grid tied system.

    I have a Square D All in one 200 amp panel....underground fed..I called Square D and they do not allow a line side tap...so my alternatives are go with max load side (120%) or upgrade the panel...I am going to contact SCE (utility) and see what I need to do to upgrade....any thoughts on a replacement panel that has a larger busbar capacity? thanks for all the advice

    Here is what I did. This is a 400 amp service with a 200 amp mains panel and a 200 amp sub panel. All the loads are on the 200 amp main and the solar is wired to the 200 amp sub (derated with a 175amp breaker). We will soon add some loads to the sub panel for the new workshop building being constructed. The meter section of the panel is 400 amps and the utility pulled new wire to match that from the transformer to the meter. You can see the AC side PV disconnect and PV meter in the picture.

    The second photo is the old service, single 200 amp.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Supply/load side connection (tap)

    Have you done all of the conservation measures that make sense for your home (high SEER/COP heat pumps) and possibly a stand-a-lone heat pump hot water heater?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: Supply/load side connection (tap)
    BB. wrote: »
    Have you done all of the conservation measures that make sense for your home (high SEER/COP heat pumps) and possibly a stand-a-lone heat pump hot water heater?

    -Bill

    If that was directed @ me here is what we have done so far.
    1) added attic insulation mostly over 24 in deep
    2) added solar power attic fans
    3) replaced all light bulbs with CFL
    4) replaced all computers with MAC mini's (normal draw about 18-25 watts)
    5) replaced 1 of 2 AC units with high seer model, hoping for another rebate to do the other.
    6) replaced deep freeze with Energy Star model
    7) contract pending for solar hot water heater includes ultra high efficiency gas hot water heater and 80gal solar hot water storage. (up to 80% rebates and tax incentives)

    To Do items:
    1) replace 13 yr old fridge, would love another round of rebates first.
    2) add reflective solar film to the south and west facing windows.
    3) replace electric stove with Gas unit.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Supply/load side connection (tap)

    Solar Dave,

    Actually, I intended to ask Divenstuff--but your reply is great too.

    And Dave, how much power (% and/or kWH per month) do you think you have saved through conservation / turning stuff off?

    I have been telling people--If they have not yet worked on conservation, it is not unreasonable to try for a 50% reduction in their electricity use through conservation/energy star/lighting changes/downsizing computers/turning DVR etc. off when not used, etc...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: Supply/load side connection (tap)
    BB. wrote: »
    Solar Dave,

    Actually, I intended to ask Divenstuff--but your reply is great too.

    And Dave, how much power (% and/or kWH per month) do you think you have saved through conservation / turning stuff off?

    I have been telling people--If they have not yet worked on conservation, it is not unreasonable to try for a 50% reduction in their electricity use through conservation/energy star/lighting changes/downsizing computers/turning DVR etc. off when not used, etc...

    -Bill

    I would say at least a 30% reduction, some of the actions are fairly new but we kind of took the shot gun approach when the electric bill in mid summer hit $650+. Last month the bill with PV was $22 and of that only $4.40 was electric generation for off peak and we banked quite a bit of on peak. This month we moved the Swimming pool onto on-peak mid day to run it off the solar. Watching the numbers real close to see how that plays out.

    I think the replacement of the other old 10 seer AC unit will help a lot, but I burned all the rebates and tax credits available, the first one was on the agenda to be replaced when the compressor failed, it just hastened the inevitable. Same with the old fridge, waiting on some kind of better incentive, maybe 2011.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Supply/load side connection (tap)
    solar_dave wrote: »
    This month we moved the Swimming pool onto on-peak mid day to run it off the solar. Watching the numbers real close to see how that plays out.

    Bank your expensive peak hours, and split the pool time to before peak and/or after peak. That leaves you headroom to run the HVAC a bit. Most pools are over filtered
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: Supply/load side connection (tap)
    mike90045 wrote: »
    Bank your expensive peak hours, and split the pool time to before peak and/or after peak. That leaves you headroom to run the HVAC a bit. Most pools are over filtered

    Yeah the peak bank is OK with about 2500 kWh for on peak, but we have been consuming all our off peak, hence sliding the pool to the on peak. Pool gets 4 hours a day now. However when Monsoon season hits in Aug, lots of nutrients hit it and 6-8 hours a day with a good shot of chlorine is required to keep it from going green. Water temps over 85F in the pool is the perfect soup for the algae. Pool temps will be well into the 90F range soon.

    The plan is:
    1) bank about 800 kWh for each summer month, June-Sept.
    2) watch June usage to see if 800 kWh for on-peak is enough to break even with the addition of what we generate.
    3) try and bank some off peak cause mid summer AC usage is 7x24.
    4) the bank will be better next year, just added 2160 watts of panels on May 1

    At the end of the year my fall excess is bought back by the utility @ $0.065 kWh.

    Here is a shot of the last 48 hours with the pool pump on day shift, with no need for AC usage. Hehe, :D don't yah just hate electric dryer @ 4-6 PM on peak, but happy wife is happy life.
    red = load, green = solar, blue = net, yellow = voltage.


    In any case, the on peak has to always be the priority to hold the bill.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Supply/load side connection (tap)
    solar_dave wrote: »
    Yeah the peak bank is OK with about 2500 kWh for on peak, but we have been consuming all our off peak, hence sliding the pool to the on peak. Pool gets 4 hours a day now. However when Monsoon season hits in Aug, lots of nutrients hit it and 6-8 hours a day with a good shot of chlorine is required to keep it from going green. Water temps over 85F in the pool is the perfect soup for the algae. Pool temps will be well into the 90F range soon......


    Yikes !! +85F in a pool. You need an ozone bubbler, drop the airstone in the deep end, and no chemicals.
    http://www.tank-depot.com/product.aspx?id=1207
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,