Okay, here’s what I’m wondering. PG&E is going to install a temporary/permanent service at the front edge of my property. I’m planning on a 200 amp service. The distance from the service drop to the main house will be approximately 300′. I plan on going underground and will be responsible for the conduit and wiring from the service drop to the house where I will install a subpanel. I’m wondering if the voltage drop will be too great…? Any thoughts? Any recommendations as to where I’d find information on sizing the wire, conduit, etc.?
I also understand that if I have PG&E provide 480 volts and then I install a transformer at the house the voltage drop issue goes away. Don’t know if I can get them to do that though.
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I had a similar issue with our property at the outset of development. Our service terminates 425 ft from the road. You need to have a careful discussion with the power utility about the line loss you will incur over distance. A certain amount can be mitigated with larger conductors, but that comes at a cost.
For us it was better to bite the $5K bullet and bring the 25KVA primary onto our property. We planted a transformer near the building with the main service panel.
Scott.
Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
Thanks for the input Scott. I've discovered a few sources on all this since posting here, one of which is a book I got through fine homebuilding some years ago called "wiring a house". (However, in the first chapter the author writes E=I/R which I believe is a misstatement of Ohm's law so I'm a bit nervous about the info in there).
Armed with new information I think I'm understanding that all I have to do is get PG&E to step the line voltage down to 480 instead of 240 at the property line/service drop, then I can take it from there. The higher voltage is much more efficient so the line loss problem is solved, not to mention the conductor cost problem. When I spoke with the fellow at PG&E he mentioned something about three phase which has requirements in the way of the load but it appears to me that 3 phase is unnecessary, I just need a higher voltage single phase service at the meter. Seems like that ought to be doable.
The main house is 300' away but I'm also thinking of the guest house at the top of the ridge, an additional 1000' beyond. That's a stretch.
all I have to do is get PG&E to step the line voltage down to 480 instead of 240
Dumb idea, I've explained this type trade so many times!
A 480/240 xfmr for household load and for only 300 ft. is a very costly proposition over time. The kW-hr rate you pay has a core loss factored into PG&E rates, you want to pay that twice?.
DO NOT FORGET THAT YOU WILL BE PAYING FOR THE TRANSFORMER CORE LOSSES OF YOUR 480 TO 240 TRANSFORMER 365/24/7.
This is such a basic calculation. My rate is about $200/hr to explain basics<G>
Often, a POCO will give a different rate for service at their distribution voltage, but 480 aint their dist. voltage.
BTW, you in Portland or similar area, please fill in profile (click on your name)
A 480/240 xfmr for household load and for only 300 ft. is a very costly proposition over time. The kW-hr rate you pay has a core loss factored into PG&E rates, you want to pay that twice?.
DO NOT FORGET THAT YOU WILL BE PAYING FOR THE TRANSFORMER CORE LOSSES OF YOUR 480 TO 240 TRANSFORMER 365/24/7.
Well that line got my attention. Do you mean that the transformer I install on my side of the meter to convert from 480 to 240 will have the core loss, which will be a factor in my bill?
I'm actually attempting to bring power 1300' from the service drop.
will be a factor in my bill?
Yep, big bucks over the years.
I'm actually attempting to bring power 1300' from the service drop.
Best to talk to PG&E on your options. When I first built my house power was 600 ft away, in today's $$ would likely be about $3K for POCO to drop 2 poles and string some 13.9 kV. Savings in the long run.
Lotta options. One EE I know in Colorado with a 1/4 mile run put in a dual feed system downstream of the meter. One feed for lights, etc, simple 2/0 Al feed for light loads. If he needed power for saw, range, or welder, he remotely connected a a 4.1kV step up xfmr to 4.1 kV feeder with a 2nd xfmr at the house. Not to big of $$ if one can DIY and find surplus UG HV cable, otherwise big $$$$$.
Like others said, if you need to ask, the HV option is not a DIY project without a lot of study and advice.
Well, I guess a quarter mile is about 1300'.
I am in contact with PG&E. Posting on here is part of the process of exploring the options. I'm sure I'll do it myself, partly because of cost, but mainly because I want to. I'm sure I won't proceed until I know exactly how it's supposed to be done, no matter which way I decide to go.
I do appreciate the input.
Voltage drop won't be an issue if you size the feeder correctly.
The NEC stipulates the minimum size for the conductors--Table 310.16, or 310.15 depending on how you set up the system.
Google "voltage drop" and you'll find several good calculators. NEC recommends keeping VD to less then 3 percent in feeders.
Conduit size? Depends on the type of pipe, and type of conductor and insualtion. See the NEC.
FWIW, the NEC allows 270 degrees of bend in the conduit. For the allowed wire fill, and a long run, more than 180 of bends makes for a tough pull. As in, a wire pulling winch or something similar is essential, and then you have to know what you're doing or you can damage the insulation on the wires.
Depending on the number and type of bends, I recommend going up at least one size to make the pull easier. And a lot of Yellow 77 lube--a five gallon pail wold be about right. Consider using rigid steel 90s at transitions from horizontal to vertical at the start and end of the pull. The wire can cut through the PVC sweep on a pull that long. If the condcuits willbe exposed above ground, Schedule 80 is required.
If all this is Greek to you--hire an electrician. There's a hell of a lot more to it than just sizing wire and pipe, stuff that if done wrong may work, but that could eventually kill someone or cause a fire.
As far as providing your own 480/240 stepdown transformer, I wouldn't. A 300 foot run isn't worth it. For a thousand feet or more, yes, and then I'd see if the PoCo could provide higher voltage than 480 (like 2500V).
Keep in mind that if you install a transformer, it's your responsibility. Damage due to lightning, voltage transient/surge, falling trees, all are your job to fix.
Cheers,
Cliff
Hi Cap,
Just noticed your post. I hear you on the 300' distance but I neglected to include my real concern in the original post, which is the guest house which is at a distance of 1300' from the service. I'll read your post carefully as I may have some questions. Thanks.
It all sounds doable and makes sense Cliff. I am wondering what that amount of wire will take in the way of pulling. That ought to be interesting. At least I can go with smaller conductor at the higher voltage.
2500V...? I'll ask about that.
you really need to get the utility HV closer to the house.
and forget about 480
because it seems that you know enough to be dangerous and 480 is NOT a voltage to play with, especially for folks who have read a few pages and think they have a grasp of the subject.
just a quick calculation and a WAG for a 100A circuit ......
at least 6oo kcmil for the guest house from the main service and that stuff wont fit under a ordinary breaker or 200 amp panel for that matter
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