conduit size?
- Thread starter jpcjguy
- Start date
wyliesdiesels
Well-known member
something wrong with that calculator.
i entered 250KCmil, 200a, and 250' and it gave me:
voltage drop: 3.6v
voltage drop: 1.5%
it is way off.
Try doing the calcs by hand instead of relying on questionable calculators that give answers that are way off
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mike93lx
ALLIANCE MEMBER
Besides the Calc difference, the inspector's "opinion" doesn't matter.
So based on TTMotorsports usage - looking way more than mine - I think I will be fine with 125A rated wire. (This will be aluminum - copper is too much $$$)
I think I need 2" conduit for that, correct? What wire size would that be?
IF I were to go with 2.5" conduit for the run, can I support 200A (aluminum wire) in that conduit? Thought being that a) it will be an easier pull for the 125A rated wire and b) god forbid I ever never more, I don't have to dig!!
Thanks!
4/0 Al for 125A. 2" is the "correct" size conduit but 2 1/2" will pull a lot easier.
One other thing to check before you run pipe is whether your 125A breaker lugs will accept 4/0. You may need a box near your main panel to splice down to a size the breaker will accept.
IF I were to go with 2.5" conduit for the run, can I support 200A (aluminum wire) in that conduit? Thought being that a) it will be an easier pull for the 125A rated wire and b) god forbid I ever never more, I don't have to dig!!
Again 2 1/2" is correct for 350MCM but 3" would be better. And 350 could be a problem with lug sizes in both panels. Working with wire that large in residential panels wouldn't be easy even if it fit the lugs.....................
Your other option for a 200A upgrade would be 4/0 copper. Wire would cost more but would be easier than trying to deal with 350 Al.
Ok - so 2.5" for the aluminum wire for 125A. If I need more power, I should switch to copper to keep size down - can 4/0 copper be run for that distance in the 2.5" conduit? (My thought is if I need 200A, I need to **** it up and do the copper - if I need that kind of juice, apparently I have $$$)
Oh - and I do plan on having a box near my house panel that I can do a splice. I assume I would need one on both ends then?
wyliesdiesels
Well-known member
correct.
the inspector can give his opinion all day long. In the end, what matters is that the calcs were done correctly.
mike93lx
ALLIANCE MEMBER
Ok - so 2.5" for the aluminum wire for 125A. If I need more power, I should switch to copper to keep size down - can 4/0 copper be run for that distance in the 2.5" conduit? (My thought is if I need 200A, I need to **** it up and do the copper - if I need that kind of juice, apparently I have $$$)
Oh - and I do plan on having a box near my house panel that I can do a splice. I assume I would need one on both ends then?
You only need a splice box if you have to change size or wire type.
The box size is impacted by the conduit size. Bigger the pipe, bigger the box.
You could have that box indoors if the wire is rated for indoor use. Xhhw would cover that.
125A is a ton of power. My entire house is 100a....electric dryer, two fridges, a freezer, well, 2 ton a/c, a furnace, lights, outlets, plus a welder and many power tools in the attached garage.
Similar here. 100A goes a long ways.
The plan is to go with 125A wire - that is the largest breaker that fits in my existing 200A panel. Would 4/0 wire connect to the breaker or am I looking at a splice box either way?
The next question is 2" vs 2.5" conduit. I am willing to spend the little extra for the larger if it makes the pull easier and could allow for an upgrade in wire....
The next question is 2" vs 2.5" conduit. I am willing to spend the little extra for the larger if it makes the pull easier and could allow for an upgrade in wire....
Ok - so 2.5" for the aluminum wire for 125A. If I need more power, I should switch to copper to keep size down - can 4/0 copper be run for that distance in the 2.5" conduit? (My thought is if I need 200A, I need to **** it up and do the copper - if I need that kind of juice, apparently I have $$$)
4/0 copper should be a drop in replacement for the 4/0 aluminum. And yeah if you can afford that much power you can afford copper
I guess you're going to put a 200A panel in the shop right away. That should accept 4/0 no problem so you'd only need to splice that end if you need to change from outdoor to indoor wire like Mike mentioned. It's unlikely you'll need to do that since you're using conduit.
You'll need to look up the specs for that particular breaker. IIRC Square D are 2/0 max but yours may be different.............
mike93lx
ALLIANCE MEMBER
And don't trim away some of the strands to make it fit.
No question 2.5" will make it easier, of course it would. As would 3".
Go as big as you want to pay for and look at. I know I wouldn't want a huge conduit on the side of my house.
No question 2.5" will make it easier, of course it would. As would 3".
Go as big as you want to pay for and look at. I know I wouldn't want a huge conduit on the side of my house.
grumpyvette
New member
check local building codes ,
many areas require the conduit to be 2" PVC and at least 24" below ground surface
many areas require the conduit to be 2" PVC and at least 24" below ground surface
mike93lx
ALLIANCE MEMBER
Why does that matter? There is no discussion on going below 2"
Besides, never heard that requirement, which really doesn't make sense anyway. Any proof?
wyliesdiesels
Well-known member
At 200+ feet and let’s assume (2) 90’s sweeps to get into and out of ground, and you can bow the run so there are not any more sweeps in it. I would use 2” pvc. (3) 4/0 AL, (1)#6 AL will fit and pull through it. You stated that a 125 amp is what you wanted originally. The 4/0 AL will carry up to 200 Amps. But at the distance you stated voltage drop will be no issue. This setup basically covers what you want and gives you the ability to upsize in the future easily.
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mike93lx
ALLIANCE MEMBER
4/0 AL is not good for 200a except in a service entrance application (feeding an entire residential structure) or when looking at a 90*C column, neither of which apply here.
In this application, 180A is best-case before considering voltage drop.
So I had a quick call with my local inspector and told him I was running 2.5" conduit and he was fine with that and I mentioned going with 4/0 aluminum and he said if I am running off a 125A in my house panel that 2/0 is fine. He mentioned something about "80% of the breaker", "save some money", etc. He also said to use XHHW wire......
mike93lx
ALLIANCE MEMBER
XHHW is fine, that's right.
Follow code and calculations, not the inspector's opinion.
If you want 125a,at an acceptable voltage drop, 4/0 is the answer. If you really don't need 125a,then downsize.
2/0 looks fine at 100a
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Just so you know. Most thermal- magnetic breakers. ( the type most residential panels use). Should be able when working properly carry 80% of the amps they are rated for continuously. They can also take amperage up to the 100% capacity for shorter time spans.
What this means is for example: A 15A breaker should be able to carry 12 Amps all day long 365 days without having false tripping issues.
Just take the amperage listed for the breaker and multiply by .8 to give you this 80% rating.
So for a 100 amp breaker you shouldn’t load it down over 80 amps. If you don’t want false tripping issues.
If you go over the 80% rule but not 100%. The breaker may hold now while it new. But just give it time and it will start tripping out. I have seen were it takes a year or 2, because the breaker was at 85-90 % loaded.
Hope that helps.
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What this means is for example: A 15A breaker should be able to carry 12 Amps all day long 365 days without having false tripping issues.
Just take the amperage listed for the breaker and multiply by .8 to give you this 80% rating.
So for a 100 amp breaker you shouldn’t load it down over 80 amps. If you don’t want false tripping issues.
If you go over the 80% rule but not 100%. The breaker may hold now while it new. But just give it time and it will start tripping out. I have seen were it takes a year or 2, because the breaker was at 85-90 % loaded.
Hope that helps.
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wyliesdiesels
Well-known member
No youre not making any sense here.
2/0 AL is good for 135a and 4/0 AL is good for 180a NOT factoring voltage drop.
Please go look at table 310.15(B)(16)
A breaker will hold up to its rated value for x number of secs...
The 80% rule applies to the wire.
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mike93lx
ALLIANCE MEMBER
If you want 125a service, use a 125a breaker and 4/0. Simple as that
mike93lx
ALLIANCE MEMBER
Like many things in life, a friend and lots of lube will help
Innovate1
Well-known member
Large radius bends will help. Just found out the utility wants 24" radius bends on the incoming power conduit here for 200A service.