Running Parallels easier in one conduit or two?

[SillyMe]

Taking 200A service 675 feet from Meter main to sub panel. This requires 750 mcm in 2 parallel sets. Any advice on whether its easier to run both sets in one 5" PVC or use two runs of 4". Its a pretty straight shot down a hill side from the panel to the meter.

Also the calculation for 600 mcm is around 667 feet (really close), so if the load demand is less than 200A could the wire be downsized to 600 mcm?

 

[Fulthrotl]

Taking 200A service 675 feet from Meter main to sub panel. This requires 750 mcm in 2 parallel sets. Any advice on whether its easier to run both sets in one 5" PVC or use two runs of 4". Its a pretty straight shot down a hill side from the panel to the meter.

Also the calculation for 600 mcm is around 667 feet (really close), so if the load demand is less than 200A could the wire be downsized to 600 mcm?

your connected load should not exceed 80% of the service limit.

however, based on 200 amps..... assuming this is 240v 3w service?
120 to neutral is killing you. bump it up to 480, and then back down.
the wire cost for parallel 750 aluminum is far more than the transformers.

two 4/0's and a ground will get you there with 2.44% voltage drop.
it'll legally fit in a 1 1/2" conduit, but you'd be crazy to use less than 2".

a 120/240 ~ 480 dry type transformer of 75 kva will do nicely. you need 48 kva.
$1650

4,200 ft 750 mcm aluminum $10,920

700' 2" pvc
1400' 4" pvc.

you get the idea.

i've pulled 500mcm aluminum thru 4". 750mcm, you can put 3 and a 250 gnd in 3 1/2.
most folks use 5" for something like 750, which most people won't pull. they will use 500's in parallel.

pulling 6 750 mcm and two grounds in a 5" pipe comes out to 36% fill.
you'd be nuts to try that in a single pipe, in my experience.
but... were you to try it, i'd love to bring popcorn and watch....

 

[electrofelon]

What type of load will this be serving? My first thought is you are going way crazy on your wire size. Except for a few exceptions such as using 220.87 or all resistive loads, you can pretty much figure you NEC calc will be twice or more the actual demand. I would think 2 sets of 250 AL would do it.

 

[infinity]

In answer to your question I would use two conduits to make pulling easier given the length of the run.

 

[electrofelon]

In answer to your question I would use two conduits to make pulling easier given the length of the run.

Yes definitely concur

 

[petersonra]

Taking 200A service 675 feet from Meter main to sub panel. This requires 750 mcm in 2 parallel sets. Any advice on whether its easier to run both sets in one 5" PVC or use two runs of 4". Its a pretty straight shot down a hill side from the panel to the meter.

Also the calculation for 600 mcm is around 667 feet (really close), so if the load demand is less than 200A could the wire be downsized to 600 mcm?

600 mcm is good for way more than 200 Amps so no matter what your calculation for VD at 200 Amps shows it would be code legal.

Even if your load calculation came out to something close to 200 Amps, chances are the real load will only rarely exceed 50% of that load calculation, so likely VD just won't be much of an issue.

Personally, I like the transformer and much smaller wire idea. Transform it up to 600 V. You only need 2 wires and a ground. 200 Amps at 240 V is only 48 kVA which is only 80 Amps at 600 V. You could run (2) #1 AL wires and a ground. A lot easier to pull. maybe a 2" conduit to make it even easier. You could even use a couple #4 wires in copper which might be easier to pull and would reduce the conduit size. Might even be the most cost effective solution.

 

[Cow]

I would determine the calculated load, then determine what size of Cablecon to use.

I bet parallel 250mcm AL Cablecon would be close after the calculated load was determined.

 

[Knightryder12]

Energy code

Energy code

I know most of you are saying that he can install smaller wires and be OK even if the voltage drop is high. Problem is is that the OP is in Cali and Cali like Florida has a strict energy code. In Florida are energy code (our inspectors will ding you on this) dictates that the total voltage drop from service to last point in circuit be no more then 5%. However it does dictate the 3%, 2% rule. It just says 5%. So he could be as much as 4% on the service side as long as all the branch circuits don't exceed 1%.

 

[Knightryder12]

After a quick calc, the OP can get away with 2 sets of 300 AL and still be under 3% VD, 2.67% to be exact.

 

[electrofelon]

I know most of you are saying that he can install smaller wires and be OK even if the voltage drop is high. Problem is is that the OP is in Cali and Cali like Florida has a strict energy code. In Florida are energy code (our inspectors will ding you on this) dictates that the total voltage drop from service to last point in circuit be no more then 5%. However it does dictate the 3%, 2% rule. It just says 5%. So he could be as much as 4% on the service side as long as all the branch circuits don't exceed 1%.

But are you required to figure the full feeder (or service) capacity for your VD calc? That would be dumb.

 

[petersonra]

But are you required to figure the full feeder (or service) capacity for your VD calc? That would be dumb.

it is. the guy needs to do a load calculation.

 

[junkhound]

.... like the transformer and much smaller wire idea. Transform it up to 600 V. You only need 2 wires and a ground. .

good for large continuous loads, but transforming up for a 200A residence , the core losses of 2 transformers will be close to 500 watts, or 24hrs*30days*0.5kW *10 cents kW-hr = $36/month.

with residential loads averaged over 24/7 is only 3-4 kW: 3% IR loss with no xfmrs at 3 kW is only $7 or so a month.

 

[Fulthrotl]

I know most of you are saying that he can install smaller wires and be OK even if the voltage drop is high. Problem is is that the OP is in Cali and Cali like Florida has a strict energy code. In Florida are energy code (our inspectors will ding you on this) dictates that the total voltage drop from service to last point in circuit be no more then 5%. However it does dictate the 3%, 2% rule. It just says 5%. So he could be as much as 4% on the service side as long as all the branch circuits don't exceed 1%.

calif used to be like that.... 5% combined. now, feeders are 2% max.
120v ~ N just kills you for this.