330' run 60 amps voltage drop

S

Stevenfyeager

Senior Member
Location
United States, Indiana
Occupation
electrical contractor
The on line calculator I use says for 330', 60 amps, 1/0 Al single conductors in pvc (already installed by customer) will produce 3.2% voltage drop. I think 3 - 5 % is considered acceptable ?
I usually shoot for 3%. Do these numbers sound correct ? Thank you.
 
LarryFine said:
Consider step-up/step/down transformers. The voltage drop at 480v or 600v is much less.
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For 330' it it more cost effective to increase the size of the conductor. The cost for transformers, additional materials and labor will eat up any savings from using smaller conductors. You also have the transformer losses.

In the OP's case the conductors are already installed. For a 60 amp feeder or even a 60 amp load I would not be worried about VD.
Utilities run hundreds of feed of overhead 1/0 AL bare feeding multiple 100 & 200 amp services on homes.
 
FYI California I don't think they have changed title 24 energy code 130.5 (c) Voltage Drop since it came out in 2013.

Your allowed to have a maximum combined voltage drop on both installed feeder conductors and branch circuit conductors to the farthest connected load or outlet of 5% of the full load amps or running load amps.
I omit and continuous / largest motor factors from the calculated full load amps and keep any demand factors.
There is no independent branch / feeder rules, just 5% total.
 
electrofelon said:
Yes the numbers seem correct. Is it a 60 amp load or a 60 amp circuit?
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This is kind of important. Just because one had 60 amp ocpd doesn't mean they have 60 amps of load.

Nothing wrong with considering future load either but if a rather fixed load on a 60 amp breaker all that really matters is what is actual load, along with acceptable amount of VD.

Efficiency wise the more usage the more important this might become, some cases it can depend on if it effects performance of whatever the load is.

If you are some place where AHJ's pay attention to energy codes it can be a big thing I would guess. Nobody enforces that aspect around here designer/installers may still take into consideration for performance reasons though or even how it might impact other loads on same service/feeder.
 
618electrician said:
Voltage drop stays the same !
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Not applicable to the current thread because the run is relatively short, but stepping voltage up prior to a long run then stepping down at the other end is a standard technique for reducing voltage drop.

For the same power delivery, higher voltage means lower current. And voltage drop in the wire is proportional to current. For a given fixed voltage drop, the higher voltage means a lower % drop. Net result is that if you double voltage the impact of the voltage drop is reduced to 1/4.

However the above analysis ignores the cost of the transformers and the impedance/voltage drop integral to the transformers themselves.

-Jonathan
 
One thing to consider with voltage drop is the actual voltage, which is almost certainly higher than 120/240

It's probably more like 123/246 and that can make a big difference on your voltage drop calculation

For instance, if you start with 240 volts and you want a 5% drop, the end result is 228 volts

But if you start with an actual voltage of 246, you can drop almost 7.5% and still be at 228

When you plug those numbers into your calculator, it might give you one size smaller wire
 
James L said:
One thing to consider with voltage drop is the actual voltage, which is almost certainly higher than 120/240

It's probably more like 123/246 and that can make a big difference on your voltage drop calculation
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Thats a good point, also if your in a area that has typically low voltages you might consider that.
I save the most by shaving off all the NEC fluff, I would never use a MCA in a voltage drop calc for example.
When I have to do a voltage drop for a 'Energy Code' I do stick with standard voltages from 220.5(A).
And if its close I do I shave off all the NEC fluff from the amps and note on my calc the voltage is from NEC 220.5(A) and load is the 'Running Load Amps' or Full Load amps of the equipment, not the MCA.
 
Another design consideration is to calculate the voltage drop for the largest transient load (for example motor starting current) to see if you will have acceptable performance (for example light flicker when a compressor starts or compressor starting performance).
 
winnie said:
Another design consideration is to calculate the voltage drop for the largest transient load (for example motor starting current) to see if you will have acceptable performance (for example light flicker when a compressor starts or compressor starting performance).
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Sometimes source impedance factors into how much voltage drop there is when starting a larger motor as well. Or sometimes things you don't have as much control over, like if POCO has long run of secondary conductors to your service. Good luck getting them to increase size of them or to place the source closer in some cases.
 
kwired said:
Good luck getting them to increase size of them or to place the source closer in some cases.
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Seems to all depend on how much money you are spending with them from some of what I see going on here lately. But for a home or small business owner, good luck
 
Joethemechanic said:
Seems to all depend on how much money you are spending with them from some of what I see going on here lately. But for a home or small business owner, good luck
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Some POCO's are better at working with you than others as well.

Had a shop several years ago that lights dimmed pretty bad (back when HID lighting was still common) when the air compressor started. There was probably 4-500 feet of overhead secondary conductor (likely was 1/0 aluminum) from the source before it hit the service lateral to this building. I figured they wouldn't do much for me when I asked but since there was primary line on the pole the lateral started at, they went ahead and put a transformer on that pole, no charge. Problem solved. I know another POCO in the area that would have balked hard on doing anything with this
 
kwired said:
Some POCO's are better at working with you than others as well.

Had a shop several years ago that lights dimmed pretty bad (back when HID lighting was still common) when the air compressor started. There was probably 4-500 feet of overhead secondary conductor (likely was 1/0 aluminum) from the source before it hit the service lateral to this building. I figured they wouldn't do much for me when I asked but since there was primary line on the pole the lateral started at, they went ahead and put a transformer on that pole, no charge. Problem solved. I know another POCO in the area that would have balked hard on doing anything with this
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Yeah, well around here is PP&L and PP&L is behind CanDo. CanDo is pushing all the industrial development in the area, so if you are in a Cando Industrial park, they kind of cater to you. But nobody like you or me is a CanDo industrial tenant

I'm still trying to figure out what this new 4 Gigawatt circuit is going to power
 
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