Paralleling Size

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mbrooke said:
You know, that might be it. In addition to the fact colored conductors are easier to get in small sizes.
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Don't think so, before I retired I could order thousands of feet of 500 in assorted colors and have it within a couple of days if not the next day. I dealt with a number of suppliers that would bring it in overnight if needed.

Roger
 
mbrooke said:
Are smaller parellel sets more efficient?
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Smaller conductors can carry more current per circular mil but when you increase the number of raceways required you also increase the number of pulls required. Depending on your labor rate one conduit with larger conductors may be much cheaper than multiple raceways with smaller conductors.
 
infinity said:
Smaller conductors can carry more current per circular mil but when you increase the number of raceways required you also increase the number of pulls required. Depending on your labor rate one conduit with larger conductors may be much cheaper than multiple raceways with smaller conductors.
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What about two sets in a single raceway vs one set? I know I'm splitting hairs- just want other opinions.
 
roger said:
Don't think so, before I retired I could order thousands of feet of 500 in assorted colors and have it within a couple of days if not the next day. I dealt with a number of suppliers that would bring it in overnight if needed.

Roger
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They had it already in stock though, right?
 
mbrooke said:
What about two sets in a single raceway vs one set? I know I'm splitting hairs- just want other opinions.
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Now you have to factor in derating which may or may not be a deal breaker.

Roger
 
mbrooke said:
What about two sets in a single raceway vs one set? I know I'm splitting hairs- just want other opinions.
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As Roger stated then derating would apply not to mention you have to run the larger raceway for the multiple sets of small conductors.
 
infinity said:
As Roger stated then derating would apply not to mention you have to run the larger raceway for the multiple sets of small conductors.
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Two sets of 4/0 in 2-1/2 inch conduit vs one set of 500MCM in 3-1/2 inch conduit.

416 vs 380 amps- calculated load is at 380, 400 amp OCPD.
 
mbrooke said:
Regarding the EGC, do you ignore table 250.122 and just size it to half of the mm2 area of the phase conductors?

For example if I have 3/0 CU per phase I'll multiply 85.01 by two getting 42.5mm2 which brings me to a #1 equipment ground.
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My understanding of parallel installations is that each parallel set requires a full size EGC.

-Jon
 
mbrooke said:
Two sets of 4/0 in 2-1/2 inch conduit vs one set of 500MCM in 3-1/2 inch conduit.
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The first one will probably cost more money. Unless the run is very short pulling 10 conductors in a 2.5" raceway isn't as easy as pulling 4-500 kcmil in a 3.5". Also I don't know how it's estimated but if the installation somehow factors in the number of feet of conductor to be installed that would also add to the labor cost. For me I would rather pull 600 kcmil in that 3.5" raceway instead of trying to pull 10 conductors in a 2.5". Lastly now you have 10 extra terminations to make which also increases your labor costs.
 
infinity said:
The first one will probably cost more money. Unless the run is very short pulling 10 conductors in a 2.5" raceway isn't as easy as pulling 4-500 kcmil in a 3.5". Also I don't know how it's estimated but if the installation somehow factors in the number of feet of conductor to be installed that would also add to the labor cost. For me I would rather pull 600 kcmil in that 3.5" raceway instead of trying to pull 10 conductors in a 2.5". Lastly now you have 10 extra terminations to make which also increases your labor costs.
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I like how you think.

Would you make 500MCM or 750MCM your cut off point?
 
mbrooke said:
I like how you think.

Would you make 500MCM or 750MCM your cut off point?
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I have decades of experience with large conduits and wire so i can see it both ways.

We regularly install up to 750 kcmil copper. I would design for 600 kcmil max with some circumstances using the 750's.
 
infinity said:
I have decades of experience with large conduits and wire so i can see it both ways.

We regularly install up to 750 kcmil copper. I would design for 600 kcmil max with some circumstances using the 750's.
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What would those circumstances be? why specifically stop at 600kcmil?
 
There are lots of variables but say you needed an 1200 amp feeder (3 runs of 4" EMT and 600 kcmil Copper conductors) but you also want to provide VD compensation so you just upsize to 750's. Raceways stay the same, number of conductors stays the same, wire pulling/terminations relatively the same, etc.

For us our labor cost is very high so spending more on larger conductors and less terminations usually saves money in the long run.
 
infinity said:
There are lots of variables but say you needed an 1200 amp feeder (3 runs of 4" EMT and 600 kcmil Copper conductors) but you also want to provide VD compensation so you just upsize to 750's. Raceways stay the same, number of conductors stays the same, wire pulling/terminations relatively the same, etc.

For us our labor cost is very high so spending more on larger conductors and less terminations usually saves money in the long run.
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Makes sense. Though I'm still tempted to use 750 for a 500 amp OCPD.
 
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