500 foot run

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highendtron said:
Well, I may have to step away from this because of the associated costs relative to what the owner can or wants to afford. The owner expects to run a heater and air conditioner in the respective seasons. He also will be using the barn as a small shop, ie; small tools. His current usage on his house is only averaging 60 amps (14400va)/month. I don't think he will use the barn as a full blown work shop but who knows! He runs a siding business out of his house. He had other bids based on the wire size for a 100 amp service 2,2,2,1. He was expecting $500 for a wire charge. I increased the wire size for the voltage drop , but still feel like $1000 for 1/0,1/0, 2,2. is too much money if the end result will be a 22 volt lose and the customer may be unhappy if he doesn't get the correct voltages at his new barn! I doubled the expected wire charge because I knew that the other bids would be too undersized unless the wire size was stepped up.
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This is where your salesmanship comes into play! I would do a real nicely laid calculation in easy to understand terms and try and sell my quote. I would explain about electric loads and voltage drop. Then show them on paper your calculations using your "proper" wire sizes and the other bidders "undersized" wire. Stress Undersized, just to get the cost down and get the job. Explain the other bidder is not looking out for their best interest and you are. Basically try and convince them to not base the job on numbers only but the correct installation.
 
One thing I have found is to keep in mind that startup current for motor loads can get you in trouble real quick if you don't include them in your calculations.
A typical 5 HP air compressor might only draw just over 15 amps running, but can draw as high as 80-90 amps starting up, this can easily cause it to stall or trip breakers, if there is loads already on the line when it tries to start. ever see those little 2, and 3 hp air compressors stall when a contractor tries to use a 100ft extension cord? same problem. but you don't have to use the full lock rotor current as most will still start up with half available current of the LR. When I know there will be motor loads I go an extra 25-30% of my calculated load to prevent this.

And as was said never use buck boost transformers to ever over come voltage drop when you don't have a fixed current load as you can damage equipment.
 
iwire said:
Thank you Captain Obvious. :D
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captobvious-738633-747223.jpg
 
the cheapest code compliant wiring solution

the cheapest code compliant wiring solution

ok being an electrical contractor im asked questions like this all the time. you want to scrap the conduit idea and run USE underground service entrance directly buried.WAY EASIER use schedule 80 pvc to sleeve wire at each end (schedule 40 against code exposed).To keep vd under code mandated 5% you will need to run 3 legs (2hots 1 grounded)of 4/0 alum to have 100a at the barn,then you will need to drive two new gound rods since you have created a new service.This scenario will give you 4.2% drop and 230v at 100a in the barn. hope this helps love the pic of capt obvious!!!!!!!!!!!
 
mike kiser said:
ok being an electrical contractor im asked questions like this all the time. you want to scrap the conduit idea and run USE underground service entrance directly buried.WAY EASIER use schedule 80 pvc to sleeve wire at each end (schedule 40 against code exposed).To keep vd under code mandated 5% you will need to run 3 legs (2hots 1 grounded)of 4/0 alum to have 100a at the barn,then you will need to drive two new gound rods since you have created a new service.This scenario will give you 4.2% drop and 230v at 100a in the barn. hope this helps love the pic of capt obvious!!!!!!!!!!!
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One thing that I would mention is that VD compensation is not required by the NEC.
 
mike kiser said:
you will need to run 3 legs (2hots 1 grounded)
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Only if these are still service entrance conductors, if they are after the main he will need 4 wires. but we do these installs all the time using a 200 amp or 320 meter socket with double lugs, stub back into the ground with a 3-wire to the garage and treat the panel as a service at the garage/barn. this way you don't need a OCP or disconnect at the house and the panel in the garage is treated just like a service, with a main, and grounding electrodes Etc...
as required in 230 which will also require the total calculated load not to exceed the rating of the main service. but still cheaper than running from the house panel, which would require 4 wires and follow 225 rules
 
Like I posted earlier, I probably will not get this job but if I do, I will put in a 100 amp disconnect at the house and run 4 wires (1/0,1/0,2,2). The house has a 320 meter can that has double lugs on it currently (has an existing shed with a disconnect). I would have to add a set of lugs for his new barn.
 
drbond24 said:
You would start with a 240/600 V xfmr at the front end. That is a 0.4 ratio, so the current on your 500 ft run is now reduced to 40 A thus decreasing your voltage drop a good bit. Now you can get by with #4 AWG and still have the same voltage drop as before (if you were OK with it to begin with). Another 240/600 V xfmr at the end will bring the voltage back to where you want it, and this time the ratio is 2.5 because you are stepping down. The 40 A you had on the run is increased back to 100 A.
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And you have the advantage of running just 2 hots and a ground. You can create an sds at the other end.
 
I would agree with Larry about stepping up the power to 600V. Hey, how is it a person can do thirteen postings a day? Over 30,000 in total? How can you even hold a job with that much posting?
 
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