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Thread: My solar system

  1. #11
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    Your use of the PV 2K wire is at over the wire ratings. Is there some other rule that allows this?

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    Quote Originally Posted by Sierrasparky View Post
    Your use of the PV 2K wire is at over the wire ratings. Is there some other rule that allows this?
    Nope...Bad kitty I know. But from a practical perspective, the stuff is rated for direct bury so its "thicker than it needs to be" and has plenty of insulation if you compare it to similar cables such as L-824 5Kv airport lighting cable.

    In hindsight, I probably would have just ordered custom 2KV transformers. they are only about $1700 each. The reason its so tempting to use 2400 is its so common and they can be found surplus for really cheap, typically $300-$400 plus some freight. The thing I discovered though is the efficiency and no load losses is quite a bit more on older units, so I ended up replacing a few of mine anyway when some newer ones came along. So all in all Im not that far below if I had just bought the nice new ones with the correct voltage from the beginning. Live and learn.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  3. #13
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    Quote Originally Posted by Sierrasparky View Post
    Your use of the PV 2K wire is at over the wire ratings. Is there some other rule that allows this?
    Good question: 2280 RMS = 3225 Max Peak-to-Peak
    http://referencedesigner.com/rfcal/cal_04.php

    @ 150% over-voltage Megger-test log of 2kv DC cable should show any deterioration over time.

    If it fails underground the step potential above ground is what zaps walking animals.

    5kv triplex on power poles is probably cheeper
    Last edited by ramsy; 04-03-19 at 11:53 PM.
    Roger Ramjet NoFixNoPay

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    Quote Originally Posted by ramsy View Post
    Good question: 2280 RMS = 3225 Max Peak-to-Peak
    http://referencedesigner.com/rfcal/cal_04.php

    @ 150% over-voltage Megger-test log of 2kv DC cable should show any deterioration over time.

    If it fails underground the step potential above ground is what zaps walking animals.
    I dont think there is a different voltage rating for DC and AC conductors despite the peak AC being higher than RMS. Despite the fact that PV wire is usually used for DC, that doesnt mean it has a lower voltage rating (sorry if that is not what you were saying, sounding like that is what you were getting at). PV wire is covered under UL 4703 and UL 44. Note PV wire is also just type RHW-2 which is covered under UL 44: "Thermoset-Insulated Wires and cables".

    5kv triplex on power poles is probably cheeper
    There is nothing cheaper than using PV wire. Its say around .25 - .30 a foot for #10 (and as a MGN you can use 600V for the grounded conductor if you are really being cheap), and all you need is 3/4 conduit so you are looking at .80 a foot for everything. I guess it could be said that if you are not following the rules, then the world is your oyster as far as cutting costs
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

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    Here's one Residential Line Extension Estimator that shows $40k to extend distribution poles 2400ft in nearby Idaho.

    Another utility study estimates underground power is 4 to 14 times the cost of overhead lines of similar voltage and distance. That's when both projects are public works, with required engineering and standards compliance.

    There would be no comparison in cost between those public-works projects, and a home-made DIY conduit run that ignores burial depth requirements, with PVC conduit subject to the elements, or cracking in winter cold, or water intrusion.

    The NESC or other standard adopted at your State level, is what accident attorneys use in court to award property to injured clients. If trespassers can break that 3/4 PVC, and injure themselves, they 5-finger discount your estate. Permit violations are not necessary to prove.

    From a liability perspective, running your 2kv wire thru an electric fence with high-voltage placards may be better than ignoring duty of care to trespassers, or State level burial depth standard for 2kv in PVC. We'll be there next week, my cross-eyed cousin will work the shovels.
    Last edited by ramsy; 04-04-19 at 06:51 PM.
    Roger Ramjet NoFixNoPay

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    Quote Originally Posted by ramsy View Post
    There would be no comparison in cost between those public-works projects, and a home-made DIY conduit run that ignores burial depth requirements, with PVC conduit subject to the elements, or cracking in winter cold, or water intrusion.
    Of course not. Its all apples and oranges. We are getting off in the weeds a bit. We got on this because you said "5KV on poles would probably be cheaper." Maybe I am misunderstand what you were comparing against. For me, even done to code, underground would be way cheaper. I dont have the equipment to set poles, pull and tension wires, etc. I have the equipment to dig. 15 Kv primary is only low $2's a foot. Not to mention the cable route is through the woods and clearing a swath is out of the question. BTW the conduit is buried, and water doesnt matter, you know that.

    The NESC or other standard adopted at your State level, is what accident attorneys use in court to award property to injured clients. If trespassers can break that 3/4 PVC, and injure themselves, they 5-finger discount your estate. Permit violations are not necessary to prove.

    From a liability perspective, running your 2kv wire thru an electric fence with high-voltage placards may be better than ignoring duty of care to trespassers, or State level burial depth standard for 2kv in PVC. We'll be there next week, my cross-eyed cousin will work the shovels.
    I appreciate the concern, but worrying about getting sued is not even on my worry radar. IMO 2KV direct bury conductors in PVC buried 12" is safer that 15KV directly buried 36" which is what the utility would do. BTW it would be NEC compliant to install 2 KV in IMC buried 6", PVC 18" - its really not much different than LV.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  7. #17
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    Quote Originally Posted by electrofelon View Post
    ..For me, even done to code, underground would be way cheaper. ..BTW it would be NEC compliant to install 2 KV in IMC buried 6", PVC 18" - its really not much different than LV.
    Is that 18" PVC depth from NEC Table 300.5, which is limited to 1kv? Arn't you at 2kv?

    Underground-cost comparisons should use utility's figure of 36" deep, thru 2400 ft of roots & rocks, before assuming its less than overhead Residential Line extension estimator.

    I stand corrected, if your equipment & labor cost can do 36" deep for less.
    Roger Ramjet NoFixNoPay

  8. #18
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    Quote Originally Posted by ramsy View Post
    Is that 18" PVC depth from NEC Table 300.5, which is limited to 1kv? Arn't you at 2kv?
    yes, look at table 300.50 for over 1KV. The depths arent nearly as crazy as you might think: PVC even over 40Kv is only 30". RGS/IMc is 6" regardless of the voltage.

    Underground-cost comparisons should use utility's figure of 36" deep, thru 2400 ft of roots & rocks, before assuming its less than overhead Residential Line extension estimator.

    I stand corrected, if your equipment & labor cost can do 36" deep for less.
    Again, I dont really care about comparing anything with how a utility does or would do it. I am not disputing that overhead is cheaper for utilities for multi-MW distribution lines. My line is 15KW. FWIW, IMO just the work of removing a swath of trees would be more work than digging a 36" deep trench. If I needed to bring in a few MW for some reason, probably using poles and zig zagging up the driveway would be the most economical as it would minimize tree work, even though its 50% longer.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  9. #19
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    BTW Ramsy,

    If you didnt notice I had that thread "MV on poles" a while back

    https://forums.mikeholt.com/showthread.php?t=196761

    Might be best to move the discussion over to there as that is about running non utility MV.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  10. #20
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    Quote Originally Posted by electrofelon View Post
    yes, look at table 300.50 for over 1KV. The depths arent nearly as crazy as you might think: PVC even over 40Kv is only 30". RGS/IMc is 6" regardless of the voltage..
    Roger that, NEC Tbl. 300.50, 1-22kv = 18" deep in PVC.
    I could do that below $40k, even after breaking a few ditchwhitches.
    Roger Ramjet NoFixNoPay

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