600A 1P Service

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Dansos

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Hey All!!! Just looked at a service that needs to be replaced. Owner wants (2) 200A panels for 1st floor unit and 100A panels for 2nd and 3rd floor units (2 total)

So, I’m figuring for an overhead single phase 600A Service with (1) 320A meter and (2) 100A meters. Without doing too much research, I doubt I’m going to find a meter stack with those specs without paying lots.

I was thinking to run my service mast (3”IMC) into a 10x10x48 Wireway, hit a PDB in there and then run to my 3 meters underneath it. PoCo ok’ed my plan so now I just have to figure out the specs.

parallel 300MCM Cu feeders would give me 512A with derating so that would be good for 600A??? Or go up to 350’s???

Is this a spot where I can use the “next size breaker” rule and go with 300’s?

If 350’s are needed, I’d prob go up to 3.5 or 4” pipe but I’d rather not unless I have to. What do you guys think?

Thanks in Advance!!!
 
petersonra said:
Load calculations required.

Curious where you are getting 512A from. Two 300s is good for 285A * 2 (570 Amps) using 75 Deg C conductors. Derating for 6 current carrying conductors gets you to 456 Amps.

If you are using the wire way as a gutter no derating would appear to be necessary inside the gutter.
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Why would I have to use the 75° column and not 90°??
And the IMC is the part that would need me to derate the wires.... right?
 
Dansos said:
Why would I have to use the 75° column and not 90°??
And the IMC is the part that would need me to derate the wires.... right?
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We are running THHN for the mains.... sorry I didn’t specify on my original post.
 
petersonra said:
Load calculations required.
Click to expand...
No one has spec’ed out load calcs for it. It’s 3 resi units. PoCo did not require them and Township only resulted them for commercial units.

at what “size” or point do load calcs need to be done??? Just asking when and if it becomes required by code?

we’ve only ever had them on prints for commercial units or large multi family projects.
 
Due to derating in the conduit, your 512 would be correct.
Code says the conductors need to be sized to carry the load so using 300s might prompt the inspector to ask for a load calculation.
You could use two separate risers (2") and increase your ampacity to 570.
 
Typically you don't just add up the the rating of all the panels and use that as the main service rating - just like how if you add up all the breakers in a panel, you get a lot more than the rating of the panel. For exaole I just did a 4 plus house meter service (5 100 A panels) and the load calculation was about 250 Amps. I used a 288 amp riser which was parallel 4/0 in the same raceway. you can certainly put in a 600 amp service it's a free country but someone's going to be spending a lot of money that doesn't need to be spent
 
electrofelon said:
Typically you don't just add up the the rating of all the panels and use that as the main service rating - just like how if you add up all the breakers in a panel, you get a lot more than the rating of the panel. For exaole I just did a 4 plus house meter service (5 100 A panels) and the load calculation was about 250 Amps. I used a 288 amp riser which was parallel 4/0 in the same raceway. you can certainly put in a 600 amp service it's a free country but someone's going to be spending a lot of money that doesn't need to be spent
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Ok thank you for explaining that. So maybe by doing a load calc we can actually run smaller wires IF we do what?? Can I just show him the math or does it need to come in the form of prints from engineer?
 
augie47 said:
Due to derating in the conduit, your 512 would be correct.
Code says the conductors need to be sized to carry the load so using 300s might prompt the inspector to ask for a load calculation.
You could use two separate risers (2") and increase your ampacity to 570.
Click to expand...
PoCo said only 1 mast and 1 point of attachment on our end so there in lies one of my dilemmas. If we could run 2 masts (like it was) I would feel a lot better about what I was doing.
 
It's really up the AHJ if/when they want to see load calcs. I think our host here has a good easy excel spreadsheet for doing calcs. Or if the guy doesn't care about money just run a full 690 amps I guess.

I think your plan in the OP is fine. Google "bussed gutter" though, may be more convenient than wireway and splices
 
electrofelon said:
It's really up the AHJ if/when they want to see load calcs. I think our host here has a good easy excel spreadsheet for doing calcs. Or if the guy doesn't care about money just run a full 690 amps I guess.

I think your plan in the OP is fine. Google "bussed gutter" though, may be more convenient than wireway and splices
Click to expand...
Thank you. I didn’t know what that was called but knew I saw it before. That’s gonna make life a lot easier!!!!
 
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