So confused...wire size for 100 amp barn sub-panel 500 ft away

[teveritt]

I am so confused on the wire size I need to run for a 100 amp breaker panel in my barn being run underground from my 200 amp panel in the house. The distance is 500 feet which is the part I think causing confusion.
I checked out the forum here and there's a lot of good information, but I'm not sure how the distance affects the wire size?

My house has (2) 200A breaker panels in it and I want to install a 100A breaker panel in the barn to run various tools including an Air Compressor (20A @ 240V), pond aerator and fountain (1/2hp - 6A @ 120V), and a 50A motorhome receptacle. I'm planning on using the one house panel which powers a 60 Amp resistive heating element in the furnace when it's too cold for the heat pump to work. When it's that cold, I won't be working in the barn drawing a heavy load. So, it seems to be a nice trade off.

I've asked an electrical guy and he said to run 1/0 MHF Al. I went to the building department and they said I could run 2-2-2-4 URD Al which seems really light for a 500 ft run. I've come across wire size calculator telling me to run 250mcm. So, as you can see, I'm totally confused ont the wire size.

I'm at a point where I'll just have the electric company run 200A service, but really hate paying an extra meter fee every month.

Any idea what wire size would make sense on this? Thank you in advance.

 

[gnab2]

At 100A and 3% voltage drop you will have to run dual AL 400MCM. This will give you a Max distance of 507' for the load. One thing is how far is the house panels from the power meter? The calculation above is based on 120VAC @ the 100A breaker. If the meter is not close to the breaker you have to calculation that distance and voltage drop for the barn voltage drop. You have to size of the total load for that 200A panel. Many will argue that you don't need to do that since everything will not be on at the same time. But by chance it is do you want to burn stuff out that is running at the barn because the voltage drop is to low. You need to have no more than 5% voltage drop with feeder, main breakers and branch breakers. The main power feeder should be no more than 3% voltage drop.

Hope that helps.

Sent from my XT1650 using Tapatalk

 

[ard]

I've asked an electrical guy and he said to run 1/0 MHF Al. I went to the building department and they said I could run 2-2-2-4 URD Al which seems really light for a 500 ft run. I've come across wire size calculator telling me to run 250mcm. So, as you can see, I'm totally confused ont the wire size.

You are asking the wrong question...or not the full question.

When they give you the answer, the next question is 'what voltage drop does that give me? At 500 ft, 100A, 240 volts'

That 1/0 AL gives you 172 feet (at 3% drop, 240V, 100A)

The 2-2-2-4 gives you...nothing. It cannot handle 100A.

So, before you get a slew of 'what do you really need?' posts...the post above is correct: 400mcm ALUM to hit 100A at 500 ft...and I also get 250mcm Copper from the southwire caclulator

 

[lakeroadster]

The aforementioned calculator.....Voltage Drop Calculator

 

[pattenp]

For 100A at 500' I'd use 4/0-4/0-4/0-2/0 MHF. If you aren't pushing the full 100A you'll be fine on voltage drop. If this wire also needs to run inside URD can't be used.

 

[Dr Stan]

Just bite the bullet and have the electric company install a second meter which is what I did. 200A for the shop and 100A for the house.

Sure made life simpler. No digging, getting the wire under concrete, etc.

 

[ard]

What is the charge to install the second service?

Is there JUST a 'second meter fee'? Or is the rate you pay on the second meter higher?

Will the Poco string lines overhead, cut down trees? Is this a concern?

Have you priced 500 ft rolls of 250mcm copper?!?!

Do the math...prolly 15-20 years to break even?

 

[kd3pc]

What is the charge to install the second service?

Is there JUST a 'second meter fee'? Or is the rate you pay on the second meter higher?

Will the Poco string lines overhead, cut down trees? Is this a concern?

Have you priced 500 ft rolls of 250mcm copper?!?!

Do the math...prolly 15-20 years to break even?

the first few questions should go directly to your Power Company engineering staff, they will get you an answer and it should be good for a certain time period.

Copper is expensive, thus AL for a lot of this type of service. Then there is moving the roll and pulling it, not a one man task at all.

bests.

 

[Bert_]

4/0 Aluminum would work well even at a full 100A. It's also the most bang for your buck, it's a very common size so its relatively cheap. You could probably get by with 2/0 if you don't plan on loading it heavily. Your only allowed 80% continuous load anyhow.

In my opinion most are way to concerned about keeping voltage drop below that 3% number. The only thing you might have happen is minor dimming of the lights when large motors start up.

A second meter may be an option if the primary already runs near the barn. You will have a second meter charge but if their line does not run nearby it's likely you will have to pay the utility some amount to get them to run primary to your location. That gets expensive fast. But the only way to know is to call them and ask.

 

[theoldwizard1]

Is this really a "barn", that is used for agricultural/livestock purposes, even partially ? You might get a different rate from the POCO if they install a separate meter.

 

[teveritt]

Thank you for the responses. The "barn" is really a hobby building I guess? No livestock in it.

I like the idea of using 4/0 MHF, but don't like thinking about putting that size wire in due to it's difficulty of working with.

I did call the electric utility which is AEP here in Virginia. The guy just gave me a ballpark of $5K - $6K to run 200A service from the transformer. A local electric company quoted almost $9K to run a 100 amp sub panel feed, but no inside work on the barn...just for the wire which I thought was a bit high. Of course, about $1500 is for the horizonontal boring under the driveway.

I'm thinking of crying "Uncle" and just letting the utility run 200A service and then I would be done with it...in theory anyway.

 

[Mamrak76]

I know a trick I read about that allows you to use a large wire at 60deg C for a short run, then use a terminal block and switch to 90degC for your long run of 500 feet then transition back to 60degC when you reach your destination. Because service equipment has a lower terminal rating. It can save you lots of money, also don't forget your ambient temp ratings. Mike Holt has a great video on YouTube called Feeder Conductor Sizing.

 

[mm08822]

I know a trick I read about that allows you to use a large wire at 60deg C for a short run, then use a terminal block and switch to 90degC for your long run of 500 feet then transition back to 60degC when you reach your destination. Because service equipment has a lower terminal rating. It can save you lots of money, also don't forget your ambient temp ratings. Mike Holt has a great video on YouTube called Feeder Conductor Sizing.

You are right about that, but it wont help with the voltage drop issue. It would actually make it worse.

 

[Mamrak76]

Would a new service enterance to the build cost more or less if it was three phase? As far as conductor size and cost?

 

[AntonLargiader]

Looks like the majority of the cost is the trenching, but you can reduce it a bit by lowering your current need. How much does the RV really draw? If it hardly ever draws more than a few amps, you could get by with 60 and the 4/0 would work.

That distance is really a killer. I can use #6 Copper for 60A (rounding up from 55A), but it's only about 40 feet. You'd need 2/0 copper. 50A would be less, but I don't know if you can put a 50A recep plus other circuits on a 50A panel.

 

[nsula_country]

Our "Barn" is about 700'-800' from the main service to the house (320A). No way I would run that far for a sub-panel. Not cost effective to do it right.

POCO added a spur line, transformer, and pedestal to said shop, about 650' and 3 poles. Cost about $6000, in 60 easy payments of about $100/mo as the meter fee. Now have a dedicated 200A service to shop.

CT