Parallell 430' Aluminum Cables for 400amp Single Phase Service

[powerplay]

Due to many large trees being in the Way and cost, Primary power was not sent to the back of a farm to keep Secondary 240 volt supply close to the area needing Electrical Service.

The voltage drop calculation for 160amp on each conductor calls for Parallel #750 kcmil Aluminum for the 430' run. I have looked at Transforming to 600 volts and drop back down to 240 volts at the Load end, but the cable would still need to be 4/0 aluminum and the Transformers are expensive for that single phase voltage that will take time to build and ship to Site. If we used #750 kcmil paralleled to supply an 80% load of 320amps, would there be issues with voltage drop even when using such large cable? At that distance I could see a lot of line loss at 240 volts?

Thanks for your feedback!

 

[charlie b]

Before I give my response, please clarify something. Why are you saying that there is 160 amps on each conductor and that you are supplying an 80% load of 320 amps? If there is a current of 160 amps on each conductor, then you have a load of 160 amps. You don't add the two currents together to get a total. Presuming for a moment that you have balanced loading, the 160 amps that leave the source on the Phase A conductor will return to the source on the Phase B conductor. It is the same current. There is no such thing as a "total" current.

So what is the load? Is it 160 or 320?

 

[powerplay]

Before I give my response, please clarify something. Why are you saying that there is 160 amps on each conductor and that you are supplying an 80% load of 320 amps? If there is a current of 160 amps on each conductor, then you have a load of 160 amps. You don't add the two currents together to get a total. Presuming for a moment that you have balanced loading, the 160 amps that leave the source on the Phase A conductor will return to the source on the Phase B conductor. It is the same current. There is no such thing as a "total" current.

So what is the load? Is it 160 or 320?

load is 320amps.

parallel 750kcmil with 160amps each conductor.

 

[petersonra]

Due to many large trees being in the Way and cost, Primary power was not sent to the back of a farm to keep Secondary 240 volt supply close to the area needing Electrical Service.

The voltage drop calculation for 160amp on each conductor calls for Parallel #750 kcmil Aluminum for the 430' run. I have looked at Transforming to 600 volts and drop back down to 240 volts at the Load end, but the cable would still need to be 4/0 aluminum and the Transformers are expensive for that single phase voltage that will take time to build and ship to Site. If we used #750 kcmil paralleled to supply an 80% load of 320amps, would there be issues with voltage drop even when using such large cable? At that distance I could see a lot of line loss at 240 volts?

Thanks for your feedback!

My guess from your 80% load comment is that you are setting a 400 A panel there. I would be looking at what the real load is likely to be as opposed to the rating of the panel board. What does your load calculation say the load is? Personally I would base the conductor sizing for voltage drop at some percentage (like 50%) of the calculated load rather than the panel board rating.

this is what the southwire voltage drop calculator says.

limiting the VD to 5%
1 conductors per phase utilizing a #1000 Aluminum conductor will limit the voltage drop to 4.64% or less when supplying 320.0 amps for 430 feet on a 240 volt system.
For Engineering Information Only:
445.0 Amps Rated ampacity of selected conductor
0.027 Ohms Resistance (Ohms per 1000 feet)
0.037 Ohms Reactance (Ohms per 1000 feet)
12.0 volts maximum allowable voltage drop at 5%
11.127. Actual voltage drop loss at 4.64% for the circuit
0.9 Power Factor

limiting the VD to 3%
2 conductors per phase utilizing a #750 Aluminum conductor will limit the voltage drop to 2.71% or less when supplying 320.0 amps for 430 feet on a 240 volt system.
For Engineering Information Only:
385.0 Amps Rated ampacity of selected conductor
0.034 Ohms Resistance (Ohms per 1000 feet)
0.038 Ohms Reactance (Ohms per 1000 feet)
7.199999999999999 volts maximum allowable voltage drop at 3%
6.49. Actual voltage drop loss for each cable at 2.71%
12.980633599999999 volts Total maximum allowable parallel voltage drop loss for the circuit
0.9 Power Factor

If you had a specific question we could probably answer it, but just asking for "feedback" is pretty vague.

Is the transformer supplied by the POCO? If so would they be willing to give you 480V single phase instead of 240V? That way you could just add one xfmr near the panel board.

The other thing you could do is have them wire the taps so the voltage at the xfmr is at the high end. Have to be a little careful about that as you don't want a real high voltage at the other end.

 

[oldsparky52]

deleted

 

[powerplay]

My guess from your 80% load comment is that you are setting a 400 A panel there. I would be looking at what the real load is likely to be as opposed to the rating of the panel board. What does your load calculation say the load is? Personally I would base the conductor sizing for voltage drop at some percentage (like 50%) of the calculated load rather than the panel board rating.

this is what the southwire voltage drop calculator says.

limiting the VD to 5%
1 conductors per phase utilizing a #1000 Aluminum conductor will limit the voltage drop to 4.64% or less when supplying 320.0 amps for 430 feet on a 240 volt system.
For Engineering Information Only:
445.0 Amps Rated ampacity of selected conductor
0.027 Ohms Resistance (Ohms per 1000 feet)
0.037 Ohms Reactance (Ohms per 1000 feet)
12.0 volts maximum allowable voltage drop at 5%
11.127. Actual voltage drop loss at 4.64% for the circuit
0.9 Power Factor

limiting the VD to 3%
2 conductors per phase utilizing a #750 Aluminum conductor will limit the voltage drop to 2.71% or less when supplying 320.0 amps for 430 feet on a 240 volt system.
For Engineering Information Only:
385.0 Amps Rated ampacity of selected conductor
0.034 Ohms Resistance (Ohms per 1000 feet)
0.038 Ohms Reactance (Ohms per 1000 feet)
7.199999999999999 volts maximum allowable voltage drop at 3%
6.49. Actual voltage drop loss for each cable at 2.71%
12.980633599999999 volts Total maximum allowable parallel voltage drop loss for the circuit
0.9 Power Factor

If you had a specific question we could probably answer it, but just asking for "feedback" is pretty vague.

Is the transformer supplied by the POCO? If so would they be willing to give you 480V single phase instead of 240V? That way you could just add one xfmr near the panel board.

The other thing you could do is have them wire the taps so the voltage at the xfmr is at the high end. Have to be a little careful about that as you don't want a real high voltage at the other end.

I got my calculation from "Southwire"

I am concerned that without using Transformers to step up and down to travel the distance, the calculated #750 kcmil will still create a bit of a drag/load and affect the Greenhouse Ballasts on the other end.

 

[charlie b]

My calculator tells me that parallel 750 MCM aluminum carrying 320 amps (i.e., 160 amps on each of the paralleled conductors) for 430 feet and a 240 volt source will give a voltage drop of 3.9 volts, or about 1.6%. Parallel 500's would give a VD of 5.8 volts, or 2.4%.

 

[charlie b]

I am concerned that . . . the calculated #750 kcmil will still create a bit of a drag/load . . . .

I don't know what that phrase would mean. What is the concern?

 

[petersonra]

I got my calculation from "Southwire"

I am concerned that without using Transformers to step up and down to travel the distance, the calculated #750 kcmil will still create a bit of a drag/load and affect the Greenhouse Ballasts on the other end.

another grow operation?

 

[oldsparky52]

....
2 conductors per phase utilizing a #750 Aluminum conductor will limit the voltage drop to 2.71% or less when supplying 320.0 amps for 430 feet on a 240 volt system.

My calculator tells me that parallel 750 MCM aluminum carrying 320 amps (i.e., 160 amps on each of the paralleled conductors) for 430 feet and a 240 volt source will give a voltage drop of 3.9 volts, or about 1.6%. Parallel 500's would give a VD of 5.8 volts, or 2.4%.

Those 2 %'s are too far apart for science. Are you guys calculating 2 different things, if not, why the difference?

 

[oldsparky52]

another grow operation?

:lol:

I didn't consider THAT, :angel:

 

[charlie b]

Those 2 %'s are too far apart for science. Are you guys calculating 2 different things, if not, why the difference?

I don't know. It is apparent that we are taking different approaches. In one case, you tell the software what you want the maximum VD to be, and it selects the cable size. In the other case (mine), I tell the software the wire size, length, amperage, and voltage, and it calculates the resulting VD. It uses the formula that is commonly used and that has been discussed on this forum many times.

The formula is VD = (2K x L x I) / D, with K being 21.2 for aluminum and 12.9 for copper.

 

[oldsparky52]

This is a little humorous. I used VD=R*I and came up with 1.62%, but since Peter was so much higher and I believe he is more educated than I, I deleted my response.

VD = R * I

VD = ((.430*2)*.0282)*160

VD= 3.88

3.88/240 = 1.6167%, or 1.62%

 

[petersonra]

This is a little humorous. I used VD=R*I and came up with 1.62%, but since Peter was so much higher and I believe he is more educated than I, I deleted my response.

VD = R * I

VD = ((.430*2)*.0282)*160

VD= 3.88

3.88/240 = 1.6167%, or 1.62%

I just used the online calculator. maybe I entered something wrong.

 

[Cow]

I got my calculation from "Southwire"

I am concerned that without using Transformers to step up and down to travel the distance, the calculated #750 kcmil will still create a bit of a drag/load and affect the Greenhouse Ballasts on the other end.

Southwire's calculator always calls out one size larger than necessary from what I've found. I've always attributed to Southwire being in the business to sell wire.

I also don't understand what bearing the wire has on greenhouse ballasts?

Our crew regularly pulls in feeders up to 800-1000' and beyond. The wire affecting ballasts has no bearing on our decisions when sizing wire, other than the wire being able to carry the ballast load.

If we were doing this we would size for the voltage drop for the specific load plus a little fudge factor based on a conversation with the customer over their future plans. If we have no idea, and wanted to cover ourselves we would size for full bore panel rating. But that is rarely the case.

 

[powerplay]

I don't know what that phrase would mean. What is the concern?

an electrician who does this regularly mentioned it would still create a 'drag' on the syatem, and I assume that the length of copper ends up being an "load" like an baseboard heater... that when the equipment runs it becomes an voltage drop and causes the ballasts to not have their intended voltage and output.

 

[powerplay]

another grow operation?

apparently growing tomatoes also makes a lot of money without the stigma attached...

 

[JFletcher]

Due to many large trees being in the Way and cost, Primary power was not sent to the back of a farm to keep Secondary 240 volt supply close to the area needing Electrical Service.

The voltage drop calculation for 160amp on each conductor calls for Parallel #750 kcmil Aluminum for the 430' run. I have looked at Transforming to 600 volts and drop back down to 240 volts at the Load end, but the cable would still need to be 4/0 aluminum and the Transformers are expensive for that single phase voltage that will take time to build and ship to Site. If we used #750 kcmil paralleled to supply an 80% load of 320amps, would there be issues with voltage drop even when using such large cable? At that distance I could see a lot of line loss at 240 volts?

Thanks for your feedback!

Yes, there is some resistance (your "drag/load") of the wiring itself. Larger wire has less resistance.

As others have mentioned, what is the actual load on the panels? What voltage drop is acceptable to you at that load?

480x240V xfmrs are readily available if you want to go that route. You could also lay 2 sets of conduit to avoid eating the derating. or use CU wire. Having the POCO set a 480V 1ph xfmr would work too, then you only need a small xfmr on your end for 120V loads.

 

[electrofelon]

Southwire's calculator always calls out one size larger than necessary from what I've found. I've always attributed to Southwire being in the business to sell wire.

The southwire calculator figures .9 PF whereas other calculators assume 1, nor sure if that fully explains it.

 

[steve66]

Have you tried 4 sets of smaller wire? It may be harder to terminate - you may even need a terminal box at each end to get the wire back to something that will land on the breaker.

But with really large wire (750KCM) the current tends to flow on the outside of the cable, and not in the middle. That means you have a lot of extra copper that isn't helping much.

For example, I think 4 sets of 3/0 is less copper, but only about 70% of the voltage drop.