Sub panel feed transition from alum to copper.

[Donttouchthat]

Hi All,

I have a detached structure that I plan on feeding 2/0 aluminum (2/0-2/0-2/0-1). It's a 100A subpanel from a 200A main (single phase). This is for a small in-law apt. I calculated just under 100A load. Would like to run copper from my main till it exits my basement foundation. Have about 70 LF in the basement then another 130LF in conduit/trench then enter the detached structure and into new subpanel. From a previous post here I gather I need 2 grounding rods there.

Since I am trying to avoid running conduit in my basement, which means I need to transition to copper sheathed cable. How do I go about determine the specs/wire size for this 70 lf basement run to my main panel? Do you calculate for the full 200 lf run? I plan on getting a terminal junction box with maybe Polaris type connectors to connect the al/cu together. But don't know what type of cu cable I need. This is being done under a permit that I will be filing. Thanks!

 

[u2slow]

Have you checked your 100A breaker for what size the lugs can accept?

#2 or #1 copper gets you similarly oversized for 100A as the #2/0 alum.

Are you in Canada or usa? Here we would do the whole run in ACWU (alum) which eliminates the extra cost for copper, conduit, and the splice box.

 

[Donttouchthat]

In the usa. I have a ge goldmark main panel. I have not researched yet the 100a double pole breaker. Just figured they make them for this purpose?? Running conduit (in my basement) would be more of a PIA then transition stuff. Thanks

 

[u2slow]

I have no GE equipment to compare. 100a lugs may top out at #1/0 or #2/0. Check the markings.

When i last used #2/0 alum, i ran into this lug size issue.

 

[Donttouchthat]

OK thx for the heads up.

 

[pattenp]

Why copper? Use aluminium SER cable in the house.

 

[PCustoms]

Since I am trying to avoid running conduit in my basement, which means I need to transition to copper sheathed cable.

Huh?

 

[Donttouchthat]

Why copper? Use aluminium SER cable in the house.

I think i'm a bit mixed up on Alum. Orignally someone suggested MHF cable to save money over copper but you had to run in in conduit indoors. I made the assumsion that all alum need to be run in conduit lol. I am worthy of my user name. So I plan on running about 115 lf of 2" conduit underground. Whats the most cost effective way for wire? Should I run 4 wire individually? Aluminum? or a sheathed MHF cable or something similar? Then I have to run about 70ft in my basement to my main panel box and I dont want conduit. It's obvious that i'm not abreast of some wire terminology i.e. SER etc. Thanks!

 

[Donttouchthat]

Huh?

I take that's similar to WTF? see my latest post. Thx

 

[mike93lx]

AL Sear indoors, transition to conduit outdoors and if you are running conduit the whole rest of the way, use AL Xhhw.

Copper will be 3-5x more expensive for no benefit other than a smaller cable

 

[Donttouchthat]

Thanks. So if I need about 500 lf of 2/0 AL XHHW wire (135 ft run x 3 wires ( 2 hot and 1 neutral)) Would you get like a 500 ft spool of the same wire? Specifically what lingo (non layman) would you ask for at the counter to accomplish this? And what specifically would I be asking for, forthe basement 70ft portion? Would it be

2/0-2/0-2/0-1 3E AL SERVICE ENTRANCE TYPE SER PVC JACKET?? Thanks man.​

Thanks

 

[pattenp]

Correct on the service entrance cable. But you'll need 4 wires of the XHHW-2, 2 hots, 1 neutral and 1 ground. Obviously the ground doesn't need to be 2/0.

 

[wyliesdiesels]

Hi All,

I have a detached structure that I plan on feeding 2/0 aluminum (2/0-2/0-2/0-1). It's a 100A subpanel from a 200A main (single phase). This is for a small in-law apt. I calculated just under 100A load. Would like to run copper from my main till it exits my basement foundation. Have about 70 LF in the basement then another 130LF in conduit/trench then enter the detached structure and into new subpanel. From a previous post here I gather I need 2 grounding rods there.

Since I am trying to avoid running conduit in my basement, which means I need to transition to copper sheathed cable. How do I go about determine the specs/wire size for this 70 lf basement run to my main panel? Do you calculate for the full 200 lf run? I plan on getting a terminal junction box with maybe Polaris type connectors to connect the al/cu together. But don't know what type of cu cable I need. This is being done under a permit that I will be filing. Thanks!

how did you come up with 2/0 AL? 1/0 should be fine.

why would you need to change to copper sheathed cable? whats wrong with aluminum sheathed cable?

 

[wyliesdiesels]

I think i'm a bit mixed up on Alum. Orignally someone suggested MHF cable to save money over copper but you had to run in in conduit indoors. I made the assumption that all alum need to be run in conduit lol. I am worthy of my user name. So I plan on running about 115 lf of 2" conduit underground. Whats the most cost effective way for wire? Should I run 4 wire individually? Aluminum? or a sheathed MHF cable or something similar? Then I have to run about 70ft in my basement to my main panel box and I dont want conduit. It's obvious that i'm not abreast of some wire terminology i.e. SER etc. Thanks!

all loose/non-sheathed conductors need to be in conduit. doesnt matter if its cu or al....

most cost effective way to do this would be with MHF, running it in conduit inside. If you transition from one cable to another, you will have added costs for splice connectors, junction box etc.

 

[wyliesdiesels]

Thanks. So if I need about 500 lf of 2/0 AL XHHW wire (135 ft run x 3 wires ( 2 hot and 1 neutral)) Would you get like a 500 ft spool of the same wire? Specifically what lingo (non layman) would you ask for at the counter to accomplish this? And what specifically would I be asking for, forthe basement 70ft portion? Would it be

2/0-2/0-2/0-1 3E AL SERVICE ENTRANCE TYPE SER PVC JACKET?? Thanks man.​

Thanks

just keep in mind that SER CANNOT go underground regardless of conduit

 

[Donttouchthat]

Correct on the service entrance cable. But you'll need 4 wires of the XHHW-2, 2 hots, 1 neutral and 1 ground. Obviously the ground doesn't need to be 2/0.

OK. If you ordered this would you use the same black hot wire for the neutral (with some white tape designating) i.e. 135 ft x3(wires) or would you ask for 135 ft white 2/0 wire for neutral? and then the ground of course. Thx

 

[Donttouchthat]

how did you come up with 2/0 AL? 1/0 should be fine.

why would you need to change to copper sheathed cable? whats wrong with aluminum sheathed cable?

Hey WD, how are you? pls read my above post re" "I think I'm a bit mixed up on Alum"... RE 2/0. I went to a wire size calc. Aluminum wire-single phase-240v-100a-200ft and it says 2/0

 

[u2slow]

I went to a wire size calc. Aluminum wire-single phase-240v-100a-200ft and it says 2/0

Every calculation is qualified with a % voltage drop. What % did you specify?

Also, its been pointed out before some online calculators arent accurate.

 

[wyliesdiesels]

Hey WD, how are you? pls read my above post re" "I think I'm a bit mixed up on Alum"... RE 2/0. I went to a wire size calc. Aluminum wire-single phase-240v-100a-200ft and it says 2/0

i did the calcs myself. 1/0 al will get you 3.3% VD @ 100a full load which i doubt a small apt unit would ever be able to pull.... 2/0 is overkill here... online calculators often oversize the wire... just the reason why i posted the VD formula in the FAQ sticky

 

[Donttouchthat]

i did the calcs myself. 1/0 al will get you 3.3% VD @ 100a full load which i doubt a small apt unit would ever be able to pull.... 2/0 is overkill here... online calculators often oversize the wire... just the reason why i posted the VD formula in the FAQ sticky

Specified 3%. See pic for my load calc (did my best). I think all the 220 electric heaters are driving it up perhaps. But I have them and cheapest way (right now) to provide heat. I may be selling in near future. This is a page in my plan I submitted to the building inspector and have received my building permit. But now I need to submit the individual mechanical permits i.e. plumbing, heating/AC and Electrical (which asks for wire size etc) Thanks

 

[Donttouchthat]

i did the calcs myself. 1/0 al will get you 3.3% VD @ 100a full load which i doubt a small apt unit would ever be able to pull.... 2/0 is overkill here... online calculators often oversize the wire... just the reason why i posted the VD formula in the FAQ sticky

FYI, I don't have any clue what a 3% vs 10% loss would mean in regards to code, building inspector/permit and practical functionality

 

[pattenp]

OK. If you ordered this would you use the same black hot wire for the neutral (with some white tape designating) i.e. 135 ft x3(wires) or would you ask for 135 ft white 2/0 wire for neutral? and then the ground of course. Thx

With conductors larger than #6 you can re-identify with tape on the ends. So using all black wire being taped white for neutral and green for ground will be okay. I suggest getting the ground in green if available.

 

[wyliesdiesels]

FYI, I don't have any clue what a 3% vs 10% loss would mean in regards to code, building inspector/permit and practical functionality

there is actually no maximum % for VD requirement in the NEC code. 3% for feeders and 5% for branch circuits is RECOMMENDED.

i highly doubt the unit will be pulling anywhere close to 100a. even if it did, it would be 3.3% with 1/0 AL....

 

[Donttouchthat]

With conductors larger than #6 you can re-identify with tape on the ends. So using all black wire being taped white for neutral and green for ground will be okay. I suggest getting the ground in green if available.

OK, Thanks again.

 

[Donttouchthat]

there is actually no maximum % for VD requirement in the NEC code. 3% for feeders and 5% for branch circuits is RECOMMENDED.

i highly doubt the unit will be pulling anywhere close to 100a. even if it did, it would be 3.3% with 1/0 AL....

Then I'm going to propose 1/0 wire. An see what happens with approvals. Thanks WD

 

[Innovate1]

XHHW individual strands is what I did. More choices on sizes than MHF. I got mine from wireandcableyourway.com based on recommendations from others here. They will put it on separate spools of whatever length you want. From pricing on that site it will be cheaper than MHF - I used 2/0 wire for comparison because they didn't have 1/0 MHF. And what they list has reduced neutral which isn't allowed some places.

 

[Donttouchthat]

XHHW individual strands is what I did. More choices on sizes than MHF. I got mine from wireandcableyourway.com based on recommendations from others here. They will put it on separate spools of whatever length you want. From pricing on that site it will be cheaper than MHF. And what they list has reduced neutral which isn't allowed some places.

Thanks. Good to know about separate spools. I am confused with RHH, RHW-2 vs XHHW terminology. Are they the same?

 

[mike93lx]

Thanks. Good to know about separate spools. I am confused with RHH, RHW-2 vs XHHW terminology. Are they the same?

Netceed

www.multicominc.com

Focus on xhhw. You have to be careful as some insulation types are not allowable indoors at all (not even inches) due to the smoke they make in a fire. URD is one such wire type.

 

[Donttouchthat]

Netceed

www.multicominc.com

Focus on xhhw. You have to be careful as some insulation types are not allowable indoors at all (not even inches) due to the smoke they make in a fire. URD is one such wire type.

OK. That helped. Thanks

 

[Donttouchthat]

XHHW individual strands is what I did. More choices on sizes than MHF. I got mine from wireandcableyourway.com based on recommendations from others here. They will put it on separate spools of whatever length you want. From pricing on that site it will be cheaper than MHF - I used 2/0 wire for comparison because they didn't have 1/0 MHF. And what they list has reduced neutral which isn't allowed some places.

For my 3-individual 1/0 xhhw-2 Aluminum run, would a #2 awg xhhw-2 wire be good (vs 1/0) for the ground portion? Thx

 

[mike93lx]

For my 3-individual 1/0 xhhw-2 Aluminum run, would a #2 awg xhhw-2 wire be good (vs 1/0) for the ground portion? Thx

#6 AL is acceptable

 

[mike93lx]

You need copper #6 for the ground rods though. All the rest can be AL

 

[Donttouchthat]

#6 AL is acceptable

Got it. Thx

 

[Innovate1]

For my 3-individual 1/0 xhhw-2 Aluminum run, would a #2 awg xhhw-2 wire be good (vs 1/0) for the ground portion? Thx

The run between buildings needs to be 4 wire.

 

[Donttouchthat]

You need copper #6 for the ground rods though. All the rest can be AL

Thanks

The run between buildings needs to be 4 wire.

Thx man

 

[mike93lx]

The run between buildings needs to be 4 wire.

I count 4 in his list

 

[Donttouchthat]

The run between buildings needs to be 4 wire.

Yes, 3-1/0's (2 hot, 1 N) then ground (#6 awg) make 4.

 

[wyliesdiesels]

For my 3-individual 1/0 xhhw-2 Aluminum run, would a #2 awg xhhw-2 wire be good (vs 1/0) for the ground portion? Thx

since you increased the ungrounded conductors in size from #1 al to 1/0 al, you need to also increase the size of the grounding conductor, proportionately the same as ungrounded conductors increase in size.

so you need #4 AL

#6 AL is acceptable

nope. too small since he increased the size of the ungrounded conductors.

Yes, 3-1/0's (2 hot, 1 N) then ground (#6 awg) make 4.

you need 1/0-1/0-1/0-4

 

[wyliesdiesels]

You need copper #6 for the ground rods though. All the rest can be AL

he could use AL for the GEC as well but solid CU is best for this

 

[mike93lx]

nope. too small since he increased the size of the ungrounded conductors.

I believe this is different for 2020, correct? That may not apply here, just confirming though