New guy here, go easy on me!

alia176
alia176 Solar Expert Posts: 33
Hello folks,

I stumbled upon this site and am I glad I did! The info on this site has been extremely helpful with my imminent grid tie project. I wouldn't mind if the professionals on this site give me some constructive criticisms based on my design. I figure I should give you guys some background info before I ask my questions :roll:

So, without further ado, here's the spec on my system:

(24) Sharp 208-U1F panels
(1) SMA Sunnyboy 6KW inverter with DC disconnect
(1) 30 amp A/C disconnect
(1) Utility REC meter
(1) 200 amp load center with feed through lugs and 8 spaces

The plan is to install the panels on top of the future deck cover that I'm currently building. My deck faces due south so this would be a good way to protect the deck from sun damage as well as take advantage of the NM sun up here the house which is at 6800'.

Due to location of windows on the south side of the house, I'm forced to keep the angle of the panels at a bare minimum. Based on the angle of the panels, I'll have a power production loss of approx 10%. I do have plans to add four more panels in the future when the funds become avail again :cry:

A picture of the south wall of the house. I am building a ledger beam for the deck cover between the two rows of windows.

Deckviewlookingnorth_2.jpg

One line diagram of the system:

PHOTOBUCKETUPLOADONELINE.jpg


A plan view of where the new deck cover and solar panels will go:

PHOTOBUCKETUPLOADPLANVIEWWITHELEC.jpg

Comments

  • alia176
    alia176 Solar Expert Posts: 33
    Cont...

    This is where the electrical items will be located:

    ALIDECKCOVERPROJECT-FINAL10_30_11SouthElevwithelectrical.jpg

    Solar panels using Unistrut rack and clamps:

    PHOTOBUCKETUPLOADSOLARPANELSWITHRACK.jpg


    This is where the 200amp service enters the house into the basement. The service comes via underground from a power pole located about 300' from this location.

    serviceentrance.jpg

    A closeup view of where a future 200amp 8space load center will go using a TB conduit body. The previous owner took some liberties that I'll be rectifying with this project.

    serviceentrance_2.jpg

    This is a view of the existing 200amp load center inside the basement:
    Elec_panel_200Apic2.jpg

    As of now, the plan is to pull out the service conductors from the existing 200amp load center. Install a new 200amp/8space load center with feed through lugs on top of the 2" riser using a TB style conduit body. Run a new 2" conduit back into the house and run new conductors to the existing load center.

    I'm doing this for couple of reasons and please correct me if my thinking is not correct. The existing load center has no room for additional breakers needed for this PV project and I need to add few more 120vac circuits that the previous owners installed out of code and clean things up a bit. I need to read my NEC book as to how to handle this situation. I don't think I can have two 200amp breakers in tandem but don't quite know what the answer is either.

    Kind regards.
  • rollandelliott
    rollandelliott Solar Expert Posts: 834 ✭✭
    Re: New guy here, go easy on me!

    why don't you just replace some of your single breakers with double breakers thus freeing up more breaker slots. You can get them at home depot. basically two breakers that only take up one slot.
  • solarix
    solarix Solar Expert Posts: 713 ✭✭
    Re: New guy here, go easy on me!

    A 30A AC disconnect is too small for a 6kW Iinverter.
    6000 / 240 *125% = 31+ amps
    wire and breakers also should be for 40A

    Looks like you have a good handle on the project though.
    Modules are getting so affordable now that doing a suboptimal orientation for shade reasons is no big deal.
  • alia176
    alia176 Solar Expert Posts: 33
    Re: New guy here, go easy on me!
    solarix wrote: »
    A 30A AC disconnect is too small for a 6kW Iinverter.
    6000 / 240 *125% = 31+ amps
    wire and breakers also should be for 40A

    Looks like you have a good handle on the project though.
    Modules are getting so affordable now that doing a suboptimal orientation for shade reasons is no big deal.

    Excellent info, I'll bump it up to the 60amp, linkwhich I think is the next size at home depot. Copy on the wire size. My PV wires are 12 gauge USE2 outdoor ratd PV wires along with Tyco connectors, FYI.

    Thanks again.
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: New guy here, go easy on me!
    alia176 wrote: »
    Excellent info, I'll bump it up to the 60amp, linkwhich I think is the next size at home depot. Copy on the wire size. My PV wires are 12 gauge USE2 outdoor ratd PV wires along with Tyco connectors, FYI.

    Thanks again.

    You are going to have problems with the code guys if you do a 60 amp breaker for you backfeed. The issue is the buss bar in the panel is only rated @ 200 amps and NEC allows for a 20% "over rate" of you back feed breaker for a total of 240 amps, 200 amp main with a 40 amp back feed. You will either need to derate your main to 175 amps using the 60 amp or stick with the 40 amp and your 200 amp main.

    Look for a 40 amp as the path of least resistance.

    PS they don't actually care what the max input is to the 60 amp it is the breaker rating.
  • alia176
    alia176 Solar Expert Posts: 33
    Re: New guy here, go easy on me!
    solar_dave wrote: »
    You are going to have problems with the code guys if you do a 60 amp breaker for you backfeed. The issue is the buss bar in the panel is only rated @ 200 amps and NEC allows for a 20% "over rate" of you back feed breaker for a total of 240 amps, 200 amp main with a 40 amp back feed. You will either need to derate your main to 175 amps using the 60 amp or stick with the 40 amp and your 200 amp main.

    Look for a 40 amp as the path of least resistance.

    PS they don't actually care what the max input is to the 60 amp it is the breaker rating.

    Let's make sure that I understand what you're referring to.

    The 60 amp disconnect in the link above is strictly for the utility disconnect. Is that what you're referring to as well?
  • solarix
    solarix Solar Expert Posts: 713 ✭✭
    Re: New guy here, go easy on me!

    You want a 60A AC disconnect switch (I use SQ-D DU322RB), at least 8awg wire and a 40A dual breaker.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: New guy here, go easy on me!

    Generally, no.

    Usually, the system is setup as a branch circuit off of your main panel. You have a 200 amp main breaker, and a 40 amp branch circuit maximum (120% * 200 amp = 240 Amp maximum on bus in main panel).

    Some places do require to meters and two main panels... There the GT inverter has its own box and own meter for billing/rebate purposes.

    Double check the manual for the branch circuit rating of the 6 kW GT inverter you are going to install... It should list the appropriate breaker there.

    If you need more than a 40 amp service (40 amps * 1/1.25 * 240 VAC = 7,680 watts maximum), then you can install a smaller main breaker and install more solar power (say 175 amp breaker: 240 amp panel rating - 175 amps = 65 amp maximum total solar GT inverter worth of branch circuits).

    Note there are losses from panel ratings, inverter losses, and wiring losses... So most people install more panels than the listed inverter wattage rating (say ~7kW for a 6kW inverter). The inverter limits its output to the rated current, regardless of how many watts of solar panels are installed.

    There are times in cold weather with clear days where the system could generate more than 6kW--but the inverter is supposed to limit its output to its rated maximum current (32 amps maximum for a 40 amp branch circuit as an example).

    -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: New guy here, go easy on me!
    alia176 wrote: »
    Let's make sure that I understand what you're referring to.

    The 60 amp disconnect in the link above is strictly for the utility disconnect. Is that what you're referring to as well?

    Yeah I thought you were doing a 60 amp back feed breaker as well. If you use a 40 amp breaker to back feed you should be golden on a 200 amp panel.
  • alia176
    alia176 Solar Expert Posts: 33
    Re: New guy here, go easy on me!
    solar_dave wrote: »
    Yeah I thought you were doing a 60 amp back feed breaker as well. If you use a 40 amp breaker to back feed you should be golden on a 200 amp panel.

    Yup, that was the plan. Use a 60amp disconnect and a 40amp breaker in the load center to feed the grid.

    Thank you.
  • alia176
    alia176 Solar Expert Posts: 33
    Re: New guy here, go easy on me!
    solarix wrote: »
    You want a 60A AC disconnect switch (I use SQ-D DU322RB), at least 8awg wire and a 40A dual breaker.

    I like that one, but holy moly, those are $$$$ :p

    Will this one do? Link
  • solarix
    solarix Solar Expert Posts: 713 ✭✭
    Re: New guy here, go easy on me!

    The TGN3322R is the GE version and should be fine to use. I didn't know HomeDepot had these. Probably cheaper at superbreakers.com though.

    Ya, isn't it wonderful what the utilities require when actually many GT inverters have a built in disconnect that they don't trust and when all inverters shut down automatically in event of an outage so no disconnect is even needed except for to assuage the "safety first" gods.
    These solar systems are so dangerous that there needs to be how many ways of shutting them off?

    1. Overcurrent protection breakers - needed to protect against fire.

    2. AC disconnect - required by utilities to provide a lockout tagout capability.

    3. Inverter disconnect - most brands provide a DC and or AC integrated disconnect in an effort to satisfy the authorities.

    4. Inverter ON control - Some inverters have an on switch that is actually the best way to shut the system down with out causing a DC arc.

    5. DC disconnect - most expensive of all, many places require a way to shut down the array - just in case.

    Mike Rowe: where are you?
  • alia176
    alia176 Solar Expert Posts: 33
    Re: New guy here, go easy on me!

    Thanks for your comments. I do understand the need for safety, I'm all in favor of going home to my family at the end of the day and I have worked with linemen in the past who were missing limbs due to electrocution accidents - all avoidable.

    Thanks for the heads up on superbreakers.com

    Attached is the shopping cart for my three items: load center, disconnect and a meter socket. Please let me know if I'm on the right track! I won't necessarily be purchasing from HD but wanted to make sure that I'm picking the correct components based on my design specs.

    Two pole vs three pole - my guess is that the three pole units are breaking Netural as well as the two hot legs as well?

    Thanks for everyone's input.
  • alia176
    alia176 Solar Expert Posts: 33
    System is online and producing power!!!

    well, it was about time I update y'all with the latest news. The system has been online since October and producing power, WOOHOO!!! The local AHJ signed off on the building and electrical permits and the local utility installed the REC meter in October.

    As some of you may recall, the solar panels are being used as deck shading while producing power. Our deck faced due south so we're using the panels as the roof of the deck shade. In order to keep the panels cool during the summer, a 3" gap is present on the sides of each panel. Due to our needs for passive solar heating during the winter, I was unable to tilt the panels to the desired tilt of 36deg. Instead, most of the panels are at 11deg tilt with the exception of six panels, which are at 36 deg. The eve of the house at the extreme East and West end forced me to tilt the panels at 36deg.

    28 sharp 230w panels are being used in a two string configuration. The North string is under the eve of the house and has too much shading during the summer to be of any use. I may have to consider going with Enphase inverters for these panels, not sure just yet. The South string has great exposure and produces around 22 kwh on the average during summer. Now that winter has arrived and the sun is lower in the sky, I was able to turn on the North string. Both strings combined are producing 24 kwh daily but I'm sure that number will decline as the days get shorter. Both strings terminate into a locally mounted small fuse box (DIN rail mounted) on the deck. I usually take my measurements and isolate the strings at this location rather go to the transformation station below the deck.

    As you know, projects like this can nickel and dime your pocket book to death and mine was no exception. In order to save money, I used Cooper B line struts for all mounting requirements. All hardware is zinc coated 3/8" nuts/bolts/T nuts. The SW doesn't get a whole bunch of moisture as of late so I opted not to go with the SS hardware. The mid and end clamps were constructed out of shallower height struts.

    I'm only getting $0.04/kwh from the local utility and as long as that pays for my minimum fee of $5.45, I'll be a happy camper. So far, the system has produced more power than we used and it's nice to see us banking the extra kwhs.

    Well, that's about it. Thanks for the bandwidth.
  • Surfpath
    Surfpath Solar Expert Posts: 463 ✭✭✭
    Re: System is online and producing power!!!

    Hi,
    Sounds like it was an adventure to put it all together. My panels will also be situated above my proch (a la Dutch gable). I will also likely use Unistrut.

    Could you post a few more photos regarding your panel mounting, perhaps showing how your panels were attached using those "Cooper B line struts" you mention?
    Thanks,
    -SP
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • alia176
    alia176 Solar Expert Posts: 33
    Re: System is online and producing power!!!
    Surfpath wrote: »
    Hi,
    Sounds like it was an adventure to put it all together. My panels will also be situated above my proch (a la Dutch gable). I will also likely use Unistrut.

    Could you post a few more photos regarding your panel mounting, perhaps showing how your panels were attached using those "Cooper B line struts" you mention?
    Thanks,
    -SP

    Attached are the pics of the mid and end clamps. The struts are lag screwed to the rafters using 5/16" hot dipped lag screws. The clamps are using 3/8" zinc hardware to attach themselves to the struts. The end clamps 90 deg units that are made by the strut companies.

    Home Depot and Lowe's carry "superstrut" and my local electrical supplier carrys Cooper B line struts. They're all similar look and appearance to the Unistrut brand from what I can tell.
  • Surfpath
    Surfpath Solar Expert Posts: 463 ✭✭✭
    Re: System is online and producing power!!!
    alia176 wrote: »
    Attached are the pics of the mid and end clamps. The struts are lag screwed to the rafters using 5/16" hot dipped lag screws. The clamps are using 3/8" zinc hardware to attach themselves to the struts. The end clamps 90 deg units that are made by the strut companies.

    Thanks, that was useful. I wish I could use the zinc stuff but humidity would soon rust it out. I'm thinking of just using the zinc unistrut (painted with anti-corrosion paint), together with galvanized clamps and lags.

    I also plan to use a lot of rubber where the zinc meets the galvanized accessories, & alu-zinc roof (I don't think the strut will touch the roof, but just in case it does). Insulated pipe tape was recommended to me. In order to slow down any galvanic (action) corrosion.

    For the mid clamps it looks like you used short peices of uni-strut on top to 'clamp' down the panels. Cool.
    -SP
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: New guy here, go easy on me!

    unless the unistrut stuff is aluminum then there will be galvanic reactions where it comes into contact on the pv aluminum frames.
  • Surfpath
    Surfpath Solar Expert Posts: 463 ✭✭✭
    Re: New guy here, go easy on me!
    niel wrote: »
    there will be galvanic reactions where it comes into contact on the pv aluminum frames.

    I wish I could buy aluminum unistrut (only the zinc kind is available to me)

    With this rubber strip, though, the panel and the zinc unistrut should not meet.
    However I wonder about some of the other connections. Here are the materials:
    Galvanized lag bolt goes through hardwood rafter through alu-zinc roof, through some kind of spacer (to keep the unistrut 3" off the roof), through corrosion painted unistrut. Then...
    Unistrut, covered with unistrut rubber then panel bolted down with unistrut solar clamps (SLR 100 mid clamp and SLR 150 end clamp).

    I guess the clamps will have to be Aluminum if they come into contact with the panels (or stainless)? But they also have to bot onto the painted zinc unistrut bar. What do you think?

    According to the unistrut page "Unistrut components are available in a variety of materials and finishes, including Pre-Galvanized (PG), Hot-Dipped Galvanized (HG), Stainless Steel (SS), Black Anodized and Clear Aluminum (AL)."
    Attachment not found.
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: New guy here, go easy on me!
    Surfpath wrote: »

    I guess the clamps will have to be Aluminum if they come into contact with the panels (or stainless)? But they also have to bot onto the painted zinc unistrut bar. What do you think?

    According to the unistrut page "Unistrut components are available in a variety of materials and finishes, including Pre-Galvanized (PG), Hot-Dipped Galvanized (HG), Stainless Steel (SS), Black Anodized and Clear Aluminum (AL)."

    Zinc coating is used (among other things) to reduce the galvanic corrosion effect when in contact with some other metals. In the case of aluminum touching iron/steel other than stainless, the corrosion is bad unless the iron or steel is galvanized. Since this is a coating, mechanical damage or pinholes can cause large corroded areas to grow under the plating.

    As long as your unistrut is zinc coated, touching aluminum without coating damage will not cause major problems. Using Stainless steel for fittings removes this dependence on the integrity of the coating, but costs a lot more.
    SMA SB 3000, old BP panels.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: New guy here, go easy on me!

    If you use stainless bolts and nuts--Make sure you use get some Anti Seize compound (used for spark plugs and bolts at the auto-parts store).

    Many types of stainless steels will "gall" (cold weld nut to bolt) at the drop of a hat if there is no lubrication.

    Stainless
    Steel Galling / Locking Up / Freezing Up


    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: New guy here, go easy on me!
    BB. wrote: »
    If you use stainless bolts and nuts--Make sure you use get some Anti Seize compound (used for spark plugs and bolts at the auto-parts store).

    Many types of stainless steels will "gall" (cold weld nut to bolt) at the drop of a hat if there is no lubrication.

    Stainless
    Steel Galling / Locking Up / Freezing Up


    -Bill

    The elderly machinist's theme song: "Sliver Threads Among The Galled"
    SMA SB 3000, old BP panels.
  • alia176
    alia176 Solar Expert Posts: 33
    Re: New guy here, go easy on me!

    Hopefully the zinc coated hardware and galvanized struts will play nice with the Alum panels but I'm not too worried. Moisture is not a problem here in the SW. I wish I could've swung Unistrut's own mid and end clamps, maybe some day. These are Alum pieces with SS handware, pretty schwanky.
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: New guy here, go easy on me!

    I've been told to use different SS mixtures to help prevent the 'cold welding' I had no issues with the first mounting that I did this with then messed up this time and got the same mixture and they bind very easily and have been using antiox, the only grease I had around, and they quit binding, don't know how easy it will be to remove once the grease has been reduced over the years.

    Since you had the under side of the panels available, I don't understand why you didn't use the mounting holes under the panel, particularly since the home made mounts stand above the panels and will shade them when the sun isn't at optimal angles.

    You may find you don't have problems in the south west, but I would stick to SS and aluminum in damper climates, some have suggested roofing felt as a barrier between non common metals. On my current wood mounted panels, I decided after seeing what minimal oxidation between the aluminum mounts and the pressure treated wood on panels I had mounted 6 years ago, to not bother with a barrier between the pressure treated wood and the thick aluminum mounts (1/4") but I'll use a barrier with the thinner aluminum material I have coming in. I would worry about galvanized metal and the new pressure treating woods having seen single dipped galvanized screews stripper of their zinc coating over night.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • alia176
    alia176 Solar Expert Posts: 33
    Re: New guy here, go easy on me!
    Photowhit wrote: »

    Since you had the under side of the panels available, I don't understand why you didn't use the mounting holes under the panel, particularly since the home made mounts stand above the panels and will shade them when the sun isn't at optimal angles.

    That's a good question. At the time, I wanted to keep my hardware count down and doing what you suggested would've doubled the hardware count. As you said, it'd have been nice to not have any shading from the mid clamps. I may do as you suggested now that the system is up and running.
  • Surfpath
    Surfpath Solar Expert Posts: 463 ✭✭✭
    Re: New guy here, go easy on me!
    alia176 wrote: »
    That's a good question. At the time, I wanted to keep my hardware count down and doing what you suggested would've doubled the hardware count. As you said, it'd have been nice to not have any shading from the mid clamps. I may do as you suggested now that the system is up and running.

    Yes, you are right about hardware costs

    In many ways it was good that you just needed galvanized lag bolts for your open roof assembly. On a metal corragated roof like mine I have to keep the panels raised a few inches above the metal roof to accommodate the ridges, to keep the panels cool and to stop debris collecting at the unistrut.

    I have looked at using adjustable lag bolts. It looks like my options are to either go for fancy engineered bolts like this EJOT one (~$8 a bolt):
    Attachment not found.
    Or to use stainless hanger bolts like this one (~$4-$5 a bolt):
    Attachment not found.
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.