# 300ft, 200amp feeder run. What size wire would you run



## magicone2571 (Apr 29, 2021)

300ft from disconnect to panel. 200 amps. My calculations show 350 mcm Al for 3.46% vd. The client has a buddy that is a master electrician and is telling him to run 250/250/(4/0). I'm suggesting 350/350/350 as it's a long run and I don't think derating the nuteral is worth the few bucks of cost saving. 

What would you do?


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## Southeast Power (Jan 18, 2009)

magicone2571 said:


> 300ft from disconnect to panel. 200 amps. My calculations show 350 mcm Al for 3.46% vd. The client has a buddy that is a master electrician and is telling him to run 250/250/(4/0). I'm suggesting 350/350/350 as it's a long run and I don't think derating the nuteral is worth the few bucks of cost saving.
> 
> What would you do?


We usually see the wire size double at 300’.
I wouldn’t skimp,
Use Wesleyan.








350-350-4/0 Wesleyan Triplex Aluminum Conductor Underground Direct Burial 600V URD


Specifications : Size AWG : 350, Stranding : 37, Insulation Thickness (mils) : 95, Neutral Size AWG : 4/0, Single Phase Conductor Inches : 0.851, O.D. Inches : 1.736, Weight lbs./1000ft : 1.166 lbs, Ampacity : Direct burial : 345 Amps, Ampacity : In duct : 265 Amps. Standards : ASTM B-230, ASTM...




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## SteveBayshore (Apr 7, 2013)

Is the load 200 amps or is it a 200 amp circuit with a maximum legal load @ 80%; 160 amps?


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## Cow (Jan 16, 2008)

magicone2571 said:


> 300ft from disconnect to panel. 200 amps. My calculations show 350 mcm Al for 3.46% vd. The client has a buddy that is a master electrician and is telling him to run 250/250/(4/0). I'm suggesting 350/350/350 as it's a long run and I don't think derating the nuteral is worth the few bucks of cost saving.
> 
> What would you do?


What is the voltage and calculated load? 



SteveBayshore said:


> Is the load 200 amps or is it a 200 amp circuit with a maximum legal load @ 80%; 160 amps?


Where in the code book does it say a person can only use 80% of a 200 amp feeder?


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## magicone2571 (Apr 29, 2021)

Cow said:


> What is the voltage and calculated load?
> 
> 
> 
> Where in the code book does it say a person can only use 80% of a 200 amp feeder?


240 volt/1 phase 

I didn't think you could use the 80% rule on the feeder side, only service. 

As for load, it's a huge wood working shop. Numerous saws, air compressor, welders, lights. While I doubt there will be 200 amps at all times, I could see it pushing that at points. 

Another thing his buddy brought up was installing 2 ground grounds at the new attached building. Wouldn't that cause issues? I've just always sunk them at the service disconnect point.


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## oldsparky52 (Feb 25, 2020)

magicone2571 said:


> 240 volt/1 phase
> 
> As for load, it's a huge wood working shop. Numerous saws, air compressor, welders, lights. While I doubt there will be 200 amps at all times, I could see it pushing that at points.


I think your calculations are the minimum.


> Another thing his buddy brought up was installing 2 ground grounds at the new attached building.


Yup (but keep your neutral isolated from the new ground rods).


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## Cow (Jan 16, 2008)

In my opinion, it would be in your best interest, and the customers best interest, if you would perform a load calc. My gut tells me 250AL would probably run everything and then some, and still fit the 200 amp lugs, versus the 350AL you're proposing that may not be needed, and may require pin adapters/insulated taps to fit the lugs. But you need to verify it with a calc.

You also need to spend some time in article 250 to help yourself better understand grounding requirements for separate detached buildings.


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## magicone2571 (Apr 29, 2021)

Southeast Power said:


> We usually see the wire size double at 300’.
> I wouldn’t skimp,
> Use Wesleyan.
> 
> ...











350-350-350-4/0 Slippery Rock Quadruplex Aluminum Conductor Underground Direct Burial 600V URD


350-350-350-4/0 Slippery Rock Quadruplex Aluminum Conductor 600V URD Allowable Ampacity for 350-350-350-4/0 Slippery Rock Quadruplex Aluminum Conductor 600V URD direct burial: 385 Amps Allowable Ampacity for 350-350-350-4/0 Slippery Rock Quadruplex Aluminum Conductor 600V URD in duct: 305 Amps...




www.nassaunationalcable.com





That's what I'm thinking. Not sure if it's worth saving a few bucks to derate the nuteral.


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## Dennis Alwon (May 9, 2009)

magicone2571 said:


> 300ft from disconnect to panel. 200 amps. My calculations show 350 mcm Al for 3.46% vd. The client has a buddy that is a master electrician and is telling him to run 250/250/(4/0). I'm suggesting 350/350/350 as it's a long run and I don't think derating the nuteral is worth the few bucks of cost saving.
> 
> What would you do?



Magicone are you not a licensed electrician? You're doing this work on the side????? Anyway you need an equipment grounding conductor to the separate structure. 350kcm would give you the full 200 amps at a 3% VD-- totally acceptable.

BTW, you only need 80% if the load is continuous. I am sure that they won't be running everything at once...


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## wiz1997 (Mar 30, 2021)

magicone2571 said:


> 300ft from disconnect to panel. 200 amps. My calculations show 350 mcm Al for 3.46% vd. The client has a buddy that is a master electrician and is telling him to run 250/250/(4/0). I'm suggesting 350/350/350 as it's a long run and I don't think derating the nuteral is worth the few bucks of cost saving.
> 
> What would you do?


I would go with the Master electrician's suggestion. 
He seems to know how to do the calculation better than you.
Ask the client who does he trust with the calculation.


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## Dennis Alwon (May 9, 2009)

wiz1997 said:


> I would go with the Master electrician's suggestion.
> He seems to know how to do the calculation better than you.
> Ask the client who does he trust with the calculation.



Actually the op's calc is just fine but it depends on the parameters that they used. If you want a full 200 amps and no more than 3% VD then 350 kcm is necessary


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## magicone2571 (Apr 29, 2021)

I am licensed but been a long time since I did something like this. Mostly do 200amp swaps or small stuff now days. I focus on consulting for construction mainly. 

But I'm finding there isn't a defentive answer, everyone interpets it differently. I personally like to over build than under hence why I am pushing for the 350mcm. The 250 will probably be perfectly fine.


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## oldsparky52 (Feb 25, 2020)

magicone2571 said:


> But I'm finding there isn't a definitive answer,


A good load calculation would take care of that.


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## blueheels2 (Apr 22, 2009)

For giggles I put this in the Southwire VD calculator. It says 500 MCM AL granted that’s a 200 amp load at the end and no more than 3% vd.


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## SteveBayshore (Apr 7, 2013)

Cow said:


> What is the voltage and calculated load?
> 
> 
> 
> Where in the code book does it say a person can only use 80% of a 200 amp feeder?


215.2(A) Feeders for continuous loads shall have an ampacity not less than 125% of the continuous loads. In my career I have only come across three circuit breakers that were listed at 100% continuous duty. The enclosures were about ten times the standard sized enclosures.


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## Cow (Jan 16, 2008)

SteveBayshore said:


> 215.2(A) Feeders for continuous loads shall have an ampacity not less than 125% of the continuous loads. In my career I have only come across three circuit breakers that were listed at 100% continuous duty. The enclosures were about ten times the standard sized enclosures.


You feel a 200 amp feeder to this woodworking shop based on the information provided qualifies as a continuous load?

*Continuous load. A load where the maximum current is expected to continue for 3 hours or more.*


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## oldsparky52 (Feb 25, 2020)

I think there is a good chance that this building could grow into a 200-amp service one day. 

I still think that one day you will wish you had installed the 350AL.


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## Flyingsod (Jul 11, 2013)

Cow said:


> You feel a 200 amp feeder to this woodworking shop based on the information provided qualifies as a continuous load?
> 
> *Continuous load. A load where the maximum current is expected to continue for 3 hours or more.*


It could turn into that. If you’re not going to size everything for the max load then just make the system smaller. What’s the point of a 200 amp service that cannot reliably handle a full load?


Sent from my iPhone using Tapatalk


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## SteveBayshore (Apr 7, 2013)

Cow said:


> You feel a 200 amp feeder to this woodworking shop based on the information provided qualifies as a continuous load?
> 
> *Continuous load. A load where the maximum current is expected to continue for 3 hours or more.*


I didn't know it was a woodworking shop on my first post, I was suggesting to to use 80% for voltage drop purposes if the actual loads aren't known. Load would probably never come near 200 amps. I have done machine shops with 70 machines and 40 machinists. Set up a CNC machine and some can run for 5 to 10 hours making components. All of my projects are design/build. My current load calculation sheet is attached. All continuous and non-continuous loads are calculated at 100% and the largest motor is calculated at 125% for total calculated load. We are applying for a 2500 amp service.


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## Cow (Jan 16, 2008)

SteveBayshore said:


> I didn't know it was a woodworking shop on my first post,


Fair enough, I saw the guy had "residential" under his name and was asking about feeding a panel from a disconnect, I incorrectly assumed everyone else reading this would have probably made the assumption that he was asking about feeding a house or garage, etc, neither of which fall into continuous load territory. My mistake.


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## magicone2571 (Apr 29, 2021)

Appreciate the info. I had one of those crazy thoughts last night and after speaking with the poco it may work. The meter is on the east side of the property and to get to the new attached buildings panel would be the 300 ft mentioned above. 

Then I thought why don't we move the meter to the west side of the property and turn it into a 50ft run. The run to the existing house panel will now be 250ft but that will have a substantial less load than the shop. Poco agreed with me and are coming Monday to scope everything out. My hope was we could hang the meter right on the edge of the new garage but they are saying they only do lot line metering now. Luckily the lot line is only 50ft from the panel location. 

I feel a ton better with that on 250mcm than 300ft on 250mcm.


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## HAND (Jul 15, 2010)

(2) sets of 3/0 per phase, or 1#600 kcmil per phase , aluminium for each choice.
5 pc vd of course, nonmagnetic cond.


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## oldsparky52 (Feb 25, 2020)

magicone2571 said:


> I feel a ton better with that on 250*mcm* than 300ft on 250*mcm.*


How old are you?


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## HAND (Jul 15, 2010)

I will remark further that the voltage drop issue is not a mandate from the code, simply a recommendation (since it is written in the small print). If anyone can prove otherwise I would be interested in knowing where the Section is.


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## robmurray65 (6 mo ago)

magicone2571 said:


> 300ft from disconnect to panel. 200 amps. My calculations show 350 mcm Al for 3.46% vd. The client has a buddy that is a master electrician and is telling him to run 250/250/(4/0). I'm suggesting 350/350/350 as it's a long run and I don't think derating the nuteral is worth the few bucks of cost saving. What would you do?


 I'm a bit consternated at how difficult the basic concept is to find online. The above calcs, I think (...) are for 250MCM aluminum @ 68F. 1) What's the allowable voltage drop? Not a vague range. I think it's 3%. Maybe its 5%? I'm trying to find that... It's a number, not a range. 2) Do we calculate the voltage drop at the nominal 200A? Or at 80% = 160A. Or is our 200A service 80% of the design load of 225A? 3) I'm pretty sure everyone is on board with tge 2x wire-length, out and back. Do we take tge low-temp resistance, or the high temp. Table list resistances at 20C & 75C. What %V loss, from what current (+/- 20%?), at what temperature? ...


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## Dennis Alwon (May 9, 2009)

Rob This site is for professionals-- you can go to diychatroom.com for more info.


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