Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

1356710

Comments

  • a0128958
    a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    stephendv wrote: »
    ... I downloaded this version: http://www.sma.de/en/products/software/sunny-design.html

    "Sunny Design 1.51Komplettversion inklusive aller Standorte / complete package including all locations"

    Thanks. I too am running version 1.51.

    I figured out that city doesn't affect the string sizing part of the program (temps do, though).

    Best regards,

    Bill
  • a0128958
    a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    dwh wrote: »
    ... plastic box on a roof ... cock-eyed to boot...

    Thanks for the comments.

    With respect to the box, I think it's angled intentionally to help with water and ice not getting built up behind the box.

    Best regards,

    Bill
  • a0128958
    a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    ... PV system has a dedicated meter, power company pays you 7.5 cents kWr , you pay the lessee 70% of this ... is this correct?

    How do they know what your being paid from the power company?

    Who pays the taxes on your income selling power? as your technically a power producer and there is usually some taxes on this ( income taxes as well ? )

    What happens say in 15 years when you have to re-roof? does the lessee come out and pull the panels for you?

    Who is your installer? there was a picture with the name but looks like it was pulled?

    I will pay to the installer a monthly lease purchase payment based on the system's design kWh output. At the end of 10 years I have the option to purchase the system. The monthly payment, and 120 month purchase price are well stated in a lease purchase agreement.

    Design change actions now, like going from 4x9 to 3x12, will increase solar kWh harvest, which is mutually beneficial to the installer and me.

    I will receive a credit from TXU for any excess kWh I place onto the grid, at 7.5 cents.

    TXU will not pay me for kWh in excess of what I consume. I can't 'sell' to TXU more than what I consume. I.e., I can't get into an income situation.

    Removal of the panels to reroof would be at my expense. I have 40 year roof shingles, for which they're 15 years old.

    Noting that my installation currently is not starting off meriting 'wall of fame' comments here, I temporarily removed the image of the installer's company name. I'd like opportunity to work with the installer.

    Best regards,

    Bill
  • a0128958
    a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    niel wrote: »
    ... polyurethane sealant may not be tolerant of uv rays so a protective coating on it of some sort may be in order.
    ... using a construction adhesive for the seal, that a big issue, you will get leaks for sure, it is not intended for roofing! Companys web site says that's for panels!
    http://www.stickwithpl.com/Products.aspx?ID=fef65cc9-47bf-4802-aaa9-a343f2ef9458 . They should be using
    http://www.stickwithpl.com/Products.aspx?ID=Polyurethane-Roof-Flashing-Sealant
    icarus wrote: »
    ... I wouldn't allow any penetration that is not done with a proper flashing. Even roof grade silicone or tar is not a long term solution. Between temperature swings and expansion and contraction they will ALL leak, it is only a matter of when.

    Thank you for the comments regarding product used to seal roof penetrations.

    Now that I have construction adhesive used as a roof sealant, what's the corrective action needed? Remove the construction adhesive and then apply roof sealant? (A lot of work, and a lot more wear & tear on the roof shingles.)

    Or apply roof sealant on top of construction adhesive?

    Or something else?

    I'll look to see if I can learn what proper flashing would be.

    Many thanks.

    Best regards,

    Bill
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    a0128958 wrote: »
    Thank you for the comments regarding product used to seal roof penetrations.

    Now that I have construction adhesive used as a roof sealant, what's the corrective action needed? Remove the construction adhesive and then apply roof sealant? (A lot of work, and a lot more wear & tear on the roof shingles.)

    Or apply roof sealant on top of construction adhesive?

    I'd scrape as much off as comes off easily, and then use a can of Henerys and a putty knife, over it all. At least the panels will shade / protect the area somewhat.

    15 years into a 30 year roof, you can be pretty sure in 10 years, you are going to start needing re-roof on the exposed areas.
    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 ,

  • a0128958
    a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    mike90045 wrote: »
    I'd scrape as much off as comes off easily, and then use a can of Henerys and a putty knife, over it all. ...

    15 years into a 30 year roof, you can be pretty sure in 10 years, you are going to start needing re-roof on the exposed areas.

    I 'misspoke.' I have Elk Prestique I High Def at 40 years, not 30. So I'll have to start re-roofing in 20 years.

    I'll edit my earlier posting to correct this.

    Thanks.

    Bill
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    For pipe penetrations I would use conventional pipe flashings: http://www.bestmaterials.com/penetration_seals.aspx
    http://images.google.com/imgres?imgurl=http://bestchoiceroofing.net/pipe_jack.JPG&imgrefurl=http://bestchoiceroofing.net/soil-collar-boots.html&usg=__yyL-F9s_GfkC6BjpI1h41mc0PJk=&h=480&w=640&sz=147&hl=en&start=2&um=1&tbnid=ZQrQInFWsZl05M:&tbnh=103&tbnw=137&prev=/images%3Fq%3Dpipe%2Bflashing%26hl%3Den%26client%3Dsafari%26rls%3Den%26sa%3DX%26um%3D1

    Like I said before, I wouldn't trust even roofing tar in the long term. Think about this, if you have a leak 5 years out, what a pain to take the array apart to get to it. I also wouldn't allow the penetration to be inaccessible UNDER the panels, I would feed it to the ends, even it it meant a bit more wire. That way, if it leaks, it is a simple process to repair.

    I also would only use mounting brackets that bolt UNDER the shingles. That would require some more extensive roof work, but I don't think I would trust a bolt through the shingle to seal from the weather for the life of the system. (I confess, I don't know of such a bracket, but I can almost guarantee that one exists, as they exist for all kinds of other mounting devices). Someone must make an L bracket that you can install by pealing up the shingle, bolt it down, then replace the shingle.

    The bottom line with all of this is that you are spending a considerable amount of money on an installation that is going to be in operation (hopefully) for a long time. I think that one has to temper the lure of a cheap price against the cost of repairs further on down the line. Remember, most roof leaks go undetected for a long time, even years, before they are discovered. Once they are discovered the potential for real damage, (wet insulation, mold, mildew, stained plaster/drywall etc) are way more expensive to fix, and I wouldn't count on your insurance to cover such damage, and who knows if the installer will still be around, or if his insurance would cover it.

    Tony
  • a0128958
    a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    stephendv wrote: »
    ... it will be interesting to see what you find when using the tool. The question isn't whether MPPT "works" or not, it's a question of how well it will work with your strings facing different directions. So when you do the simulation in the tool it will be good to see a comparison between using 1 SB7000 versus 2 x SB4000 (or whatever), 1 for each panel orientation.

    Stephen, thanks.

    The largest SB inverter that will work down at 9 panels / array (for my Astronergy 225 W panels) is an SB3000. It has a 250 Start Voltage, 200 Min. Operating Voltage, and 200 Min. Peak Power Tracking Voltage. The SB3000 has these 3 voltages 50 less than SB inverters starting with the SB4000 models.

    Thus, it looks like this could be a good option for the 9 panels (2.0 KW DC) that face SW that are on the garage (all in the same plane).

    The remaining area, on the house, facing South, again all in the same plane, could be set up as 2x12 (2.7 KW DC per array). While there's rail space currently installed for 27 panels, only 24 would be used.

    The smallest SB inverter that will appropriately handle 5.4 KW DC total is a SB6000. While some of the power numbers are cautionary, in fact, as has already been pointed out, it's unlikely that actual array power output will reach design power output.

    In summary, it looks like this is another option: 1x9 into an SB3000 inverter, and 2x12 into an SB6000. The numbers play nicely. My guess is the largest downsides to this option are the expense of adding another inverter, the expense of combining two AC circuits after the inverter, and the expense of using the existing SB7000 when an SB6000 would have sufficed. I'd also have rails showing for 3 unused panel areas.

    Thanks for offering this suggestion.

    Best regards,

    Bill
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    You can go 2x13 and still use the SB7000 and go 1x10 for the SB3000

    On the 13 in a String , even down to -6F will be OK for the 600 VOC maximum ( calculator shows about 570V, but in real world you would never see this

    You will get better performance with the separate inverters as well
  • solartek
    solartek Solar Expert Posts: 69 ✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    a0128958 wrote: »
    Thank you for the comments regarding product used to seal roof penetrations.

    Now that I have construction adhesive used as a roof sealant, what's the corrective action needed? Remove the construction adhesive and then apply roof sealant? (A lot of work, and a lot more wear & tear on the roof shingles.)

    Or apply roof sealant on top of construction adhesive?

    Or something else?

    I'll look to see if I can learn what proper flashing would be.

    Many thanks.

    Best regards,

    Bill

    Bill,

    For composition shingle roofs, my one and only choice is Quickmount and GeoCell 2300 sealant. They're expensive, they're labor intensive to install, but they give me piece of mind. I don't own any part of the company, I'm just a happy consumer of the product.

    Scott.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    solartek wrote: »
    Bill,

    For composition shingle roofs, my one and only choice is Quickmount and GeoCell 2300 sealant. They're expensive, they're labor intensive to install, but they give me piece of mind. I don't own any part of the company, I'm just a happy consumer of the product.

    Scott.

    BINGO! That's what I am talking about,

    Tony
  • System2
    System2 Posts: 6,290 admin
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Just for clarification, this is one of our installations and the contract is a Lease Purchase with a guarantee that the monthly payment is not more than 70% of what the electricity would have cost. If there is an adjustment in the payment it directly impacts the Purchase Option for the customer. Yes that is correct our company is providing 100% financing for this and many of our other projects in the many states that we operate in.

    In this case, the project is one of the first installations in Plano (per the Plano Inspector) and will be included in the Solar Parade of Homes for his area and will be utilized in our regional advertising.

    The original configuration of the system was 3 X 12 but was changed to 4 X 9 to accommodate a customer request and with the approval of SMA. SMA made it clear that on very hot days > 115 degrees F, the system might fall below the VStart / Operating Voltage for the inverter. Yes sometimes we all try to hard to make a customer happy and this string design change could fall into that category.

    We are in the process of reverting to an alternate string design so this will not be an issue and could expand the system beyond its original 36 panel design with a Hot Tap so we are not limited by the 20% NEC back feed restriction through the BusBar of the main circuit panel.

    The mechanical engineer assigned as the project mgr and his second in command have over 130 installs between them so the crew is definitely one of the more skilled install teams in Texas.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    Infinergy wrote: »
    The mechanical engineer assigned as the project mgr and his second in command have over 130 installs between them so the crew is definitely one of the more skilled install teams in Texas.

    Yikes ! I guess I do live in a 3rd world country now.

    Perhaps you Infinergy should visit the jobsite, before the "crew" covers up all their "prep" work.

    Some/much of the documentation revealed some pretty bonehead work. If this was on my roof, there would be pitchforks, torches & tar and complaints to the contractors board .

    Maybe start by looking at the photos of overstuffed electrical boxes, and sheetrock adhesive used for roof penetration sealing.

    Maybe you are giving them an allowance for the proper materials, and they are buying other.
    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 ,

  • AntronX
    AntronX Solar Expert Posts: 462 ✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    I just want to say that you guys (icarus, niel, mike90045, Solar Guppy, BB., Windsun, Cariboocoot, dwh, solartek) are pretty awesome. What was going to be a nice little photo documentary of a0128958's solar install, turned out to raise a lot of questions that come up in even a vanilla install that has been performed many times before [Moderator: We try to educate and learn here--Did not intend to to take pot-shots at anyone. -Bill].

    AntronX edit: for the record, no indecent language was used. Just stating what's already on everyone's minds. [AntronX is correct. One of those "gray" moderation calls. -Bill]
  • a0128958
    a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Considerable discussion yesterday.

    New plan going forward: 1x9 (or 10) string for SW facing garage array into an SB3000, 2x13 strings for S facing house arrays into existing SB7000, all inverter output 'hot tapped' to electric service meter socket / no connection to service panel (circuit breaker box).

    Further, I firmly believe: Customer relationship with the profesional installer (any subject, i.e., building a house, pool installation, HVAC conversion to geothermal, solar PV system) will always more fundamentally influence project performance than any other single factor. And, the relationship is the customer's responsibility.

    No edits planned for anyone's previous postings - not into the 'blame game.'

    Design solution going forward is excellent, was initiated by proactive installer, and has full support of installer without hesitation. Dialog with installer has been constructive, productive, and positive.

    Best regards,

    Bill
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Good to hear things will be addressed. On the Hot tap, you still have to have breakers, all a hot tap does is allow a secondary breaker box for the inverters so you don't have the 120% rule issues to deal with on the main panel.

    You could also just have a sub panel off the 40 amp now installed, and the SB7000 and SB3000 on the 40 amp Sub as combined its no different than when you had the 7000 direct connected to the main. Your electrical inspector may like the sub-panel better than a line tap sub panel

    I would suggest you push for the 1x10 on the SW array, you have all the materials on-site, just have to move racking for a single panel
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    AntronX wrote: »
    I just want to say that you guys (icarus, niel, mike90045, Solar Guppy, BB., Windsun, Cariboocoot, dwh, solartek) are pretty awesome. What was going to be a nice little photo documentary of a0128958's solar install, turned out to raise a lot of questions that come up in even a vanilla install that has been performed many times before [Moderator: We try to educate and learn here--Did not intend to to take pot-shots at anyone. -Bill].

    AntronX edit: for the record, no indecent language was used. Just stating what's already on everyone's minds. [AntronX is correct. One of those "gray" moderation calls. -Bill]

    As I said, the critique offered has always been illustrative for both the OP as well as users in general. Advice is worth just what you pay for it, but if you are getting advice from folks with demonstrably more knowledge than yourself (not me!) then it is pretty easy to take. When people dig their heels in and chose to ignore the advice, the price they pay is their own.

    I don't think anyone here has a monopoly on good ideas, but clearly some folks here have "been there, done that".

    Tony
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Just to be clear--AntronX was very complimentary to everyone here.

    Regarding his comments about the installer--I made (perhaps it was a mistake) to soften AntronX's comment about the installer's issues.

    I can restore the comment assuming I was wrong--I was trying to keep the thread on-topic about the facts/issues of the install and avoid a pile-on regarding the installer.

    The installer is addressing the issues with "a0128958"/Bill. I don't want to interfere with the positive discussions/resolutions that Bill is having with them.

    None of the rest of us are directly involved and I would like to let Bill (and his installer, if he wishes) to have the last word concerning their business relationship.

    The moderation is my fault--No one else's here.

    Sincerely,
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    to help out here, in this discussion that has evolved, is not to degrade or gang up on anybody or anything. it is good to get concerns out in the open and discuss what is being done so that the best results can be had. nothing is quite written in stone and is why we discuss these things for understanding and possible better options. i see cooperation is going on between both installer and client and i feel they need to discuss things further between each other if only to enlighten if not change things before going on with the work as both have a stake in this. we here try to bring up good points and options to achieve a good if not a better result and we want to keep it that way. i understand why bb was concerned with the possible direction the thread was headed and i hope that you understand it too.
  • newenergy
    newenergy Solar Expert Posts: 291 ✭✭✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    In the junction box the conductors need to extend 3" from the opening (rule for <8" boxes - >8" the rule is conductors must extend 6" from where they enter).

    300.14


    I think wire-nuts are given a bit of a bad rap. If they are put on well they make a very very strong mechanical connection. I've been using some wire-nutted wire as a handle for a drill case for a year or so and it hasn't budged. A guy I work with used a wire-nutted wire to hold down his broken hood for quite a while.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Windsun also said earlier in this thread that they saw electrolysis problems with wire nuts as an issue too...
    Windsun wrote: »
    One of several problems with DC is that electrolysis is much more to worry about than in AC, and wire nuts + twisted wires are not reliable.

    My installer used copper crimp rings (of some sort) for our DC panel connections.

    DC is a different animal from AC.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • newenergy
    newenergy Solar Expert Posts: 291 ✭✭✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Are you guys really really sure the wire nuts have been a problem?

    I use good wire nuts (Scotch-lok).

    I'm not really sure why DC would be so much different and wire nuts are used pretty widely.

    I've used crimpers too (seen people do too many bad crimps) and insulated connector blocks (huge and expensive), but I always seem to end up back with wire nuts.

    I suppose I'd be willing to try out some different crimping equipment and some X-treme Tape (http://www.vyparproducts.com/) which I saw at the last Solar Power International conference.
  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Wire nuts as such are not really the problem if done right, what I had a problem with was the sheer quantity of them stuffed into a single j-box.
  • newenergy
    newenergy Solar Expert Posts: 291 ✭✭✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    I forgot about this, but I started a thread on this subject once before.

    http://forum.solar-electric.com/showthread.php?t=5904

    I think on my next job I'm going to connect with MC connectors inside the j-box. We do a lot of MC connectors anyway, we have the equipment up there on the roof, it makes a solid, water-tight connection and is disconnectable.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Wire nut suffer when the strain of the wires pulls on the wire nut rather than the twist of the wires before the wire nut. In the case of short wires/overstuffed boxes, trying to get larger gauge #10 and larger to stay together all while being stuffed in the box with such short leads. At least if the leads are long enough to put a couple of twists on the wire, the strain is on the twists rather than the nut as you try to fold the whole mess in the box. How many times have you made something up, crammed it into the box hoping that it would stay together? Too often in my case, and each time, it is telling me to leave longer leads, and/or use a bigger box, regardless of the box fill calc.

    Tony
  • newenergy
    newenergy Solar Expert Posts: 291 ✭✭✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    The stranded wires don't really twist very well. Maybe a good taping?
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    newenergy wrote: »
    The stranded wires don't really twist very well. Maybe a good taping?

    NO ! Twist and tape is bad. Use a split nut and tape. You need something to keep the wires pressed together well.
    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 ,

  • newenergy
    newenergy Solar Expert Posts: 291 ✭✭✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    mike90045 wrote: »
    NO ! Twist and tape is bad. Use a split nut and tape. You need something to keep the wires pressed together well.

    I didn't mean just twist and tape, I just meant the pre-twisting before wire nutting.
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area
    newenergy wrote: »
    I didn't mean just twist and tape, I just meant the pre-twisting before wire nutting.

    Pre-twisting before wire nutting SHOULD be standard practice. For me it *always* is. I never depend on the wirenut to make a good connection - for me it's just a way to cover and protect a twisted connection.

    I know, the picture on the wirenut package shows the wires just held parallel and then wire-nutted together and lots of people actually do it that way. When I was an apprentice my journeyman would have slapped me silly if I even thought about not twisting the wires first.

    For up to #10 then yes, twist and wire-nut is fine. Anything bigger and I prefer split-bolts. Split-bolts are technically supposed to have three tapes - first rubber, then plastic, then friction.

    I normally only tape over wirenuts for outdoor work. Then I fill the wirenut with Led-Plate, screw it on to the pre-twisted wires, tape around it and place the whole shebang pointed up so that the wirenut cannot ever become a cup that holds water.

    One common problem with wire-nutted connections is hot-spots created when the wires inside the wirenut just barely touch. This was a HUGE problem back when aluminum was allowed for branch circuits and was the cause of many fires because even a well twisted connection could and would become loose over many heating/cooling cycles.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Illustration of 8 KW (DC) GT Solar PV System Install for Residence in Urban Area

    Note to the original poster: What is the status, it seems like you have been away a while and I am curios to see/here about any progress,

    Tony