1/0cu x 3 gets 320A within 75C column, relying on software load shedding for future expansion.
When I was working as a full time commercial PV system designer, out installation guys asked that I not specify conductors larger than 500kcmil. When I needed more ampacity I went to multiple sets. One reason for that is that most of the time we were adding to systems where we had to work around existing conductors and conduit.I have only used each once. 750 AL isn't horrible, but it does suck. 750 CU is completely awful. I think I am still sore from the having to wrestle that and that was 6 years ago
With existing equipment more sets isn't always the answer. For example if your existing 400 amp circuit breaker has only a single terminal for each phase running mulitple set just makes everything more complicated.
I find equipment lugs to generally be lacking in number of ports. 400A with one terminal is really lame. Like even 1200A stuff usually only has 4 ports. Maybe I am an unusual case because I work alone 99% of the time I tend to go for a more sets and aluminum.
The company I work for doesn't usually go over 600kcmil because of diminishing returns (you'll notice the curve flatten around 600 in ampacity tables) and ease of installation for the contractor.
Be that as it may, I set 500kcmil as the largest conductor as the default; if they wanted something different they told me.
For us 750 kcmil is the largest size we would ever use. And for something like a 400 amp feeder never parallel #3/0's, one set of 600 kcmil. Maybe it's a regional thing but we almost never see parallel condcutors smaller than 250 kcmil.
I only design stuff with parallel 1/0 copper but they are only inside of enclosures so the cost is not as big of a deal. I don't like having a bunch of unused scraps of wire laying around and if I always try to use 1/0 the leftovers will get used up on the next project.
Bean counter mentality right there... I've run into that many times in my career, I still don't get it. I was told once "Well it's the cost of replacement that counts!". But if you have been sitting on it for 5+ years and not had an occasion to NEED it, why on earth would you replace it? In fact, as I kept getting repeatedly told, old inventory was "written off" after some length of time, so from an owned cost perspective, the value is zero and if you don't need to replace it, then why would you care? But that's why I hated accounting...
When I was an estimator for a medium size shop, the owner and I did a bunch of cost analysis and smaller parallel conductors always won out on cost. We would never work with anything over 500, maybe 600, but on services only.
Plus greater ampacity per total conductor area due to better surface area and heat dissipation.
We did it every way possible, including the conduit.
The thing is two smaller wires in parallel with the same ampacity as a larger single conductor will generally fit in the same size conduit and even derated from the 90 degree column for six ccc in the conduit you still typically come out ahead.
I would be skeptical on the "always" part. Although I generally prefer more smaller parallel sets, seems like they're just too many variables to say it's always going to be more cost effective.
You can probably come up with some odd ball case where it isn't. But I bet you cannot come up with a case where aluminum is not cheaper than the same ampacity of copper, where aluminum is an option.
There may have been some (very few) occasions that it didn't win out, but it was definitely more cost affective for multiple smaller wires most of the time.
Thats true, but the smaller everything is the quicker the work can be done. And the materials are less expensive even if you have to buy more. At least thats what I remember. Its been a long time since than. Things may be different now. For the life of me, I don't know how nay of you guys price anything these days the way the price fluctuates every hr on the hr it seems.
Why more conductors equal more pulling or more conduits? There will generally be less copper so the parallel conductors should fit in the same size conduit.
