sizing feeder power

[MerlinsBeard]

I'm trying to decide whether 4-4-4-6 XHHW-2 copper is enough to handle my future shed usage as a workshop.

Planning to have

15A lighting circuit branch - 4 LED strip lights, door light, flood light
two 20A 120V outlet branches
decent sized air compressor
small mini-split for 10x16'
possibly wire one 240V 30A outlet as equipment demands it for woodworking

Length from main panel to shed subpanel through conduit is around 110ft.

I feel like 3 AWG would definitely handle it, but I don't want to overspend for no reason.

wireandcableyourway doesn't seem to sell 5 AWG to make 3-3-3-5, so if I went with 3 AWG, would a 6 AWG ground work instead? Can't quite figure it out from the NEC.

 

[wyliesdiesels]

skip the copper, save some dough and use #2 al mobile home feeder. will give you 90a...

 

[MerlinsBeard]

Unfortunately, to save on trench length, there will end up being 70' routed in conduit in the unfinished basement, eventually routing down from basement ceiling joist area vertically down outside wall, through house, then down into trench.

Once outside, there's no 90s other than down and up into the trench. I thought single conductors would make for an easier pull, even if more expensive.

 

[dcg9381]

15A lighting circuit branch - 4 LED strip lights, door light, flood light
two 20A 120V outlet branches
decent sized air compressor
small mini-split for 10x16'
possibly wire one 240V 30A outlet as equipment demands it for woodworking

I think you need 50-60A. My 2 ton ductless units pull under 12A continuous (@240V). 90A is probably the next size up.. In a 20x24 garage, 50A was more than I could use..

 

[wyliesdiesels]

Unfortunately, to save on trench length, there will end up being 70' routed in conduit in the unfinished basement, eventually routing down from basement ceiling joist area vertically down outside wall, through house, then down into trench.

Once outside, there's no 90s other than down and up into the trench. I thought single conductors would make for an easier pull, even if more expensive.

Ok then go with #2 al xhhw with a #4 al EGC

 

[Gto7419]

Copper may be more expensive but it's better. Less.chance of corrosion or loosening of terminals.

 

[Norcal]

Copper may be more expensive but it's better. Less.chance of corrosion or loosening of terminals.

Horse ****! There is no difference when when properly terminated & torqued.

 

[wyliesdiesels]

Copper may be more expensive but it's better. Less.chance of corrosion or loosening of terminals.

less chance of corrosion? umm apparently youve never seen corroded copper?

terminals dont loosen unless they werent torqued to spec

 

[Gto7419]

less chance of corrosion? umm apparently youve never seen corroded copper?

terminals dont loosen unless they werent torqued to spec

Why don't they use copper for residential wiring anymore?

 

[pattenp]

Why don't they use copper for residential wiring anymore?

Huh...what's the meaning of that question? Copper is used for branch wiring where small conductors are used. Feeders of larger sizes are commonly aluminum.

 

[bjcouche]

If in conduit the entire way, you are correct, individual conductors will be much easier to pull than 4 conductors twisted together (mobile home feeder). As stated above 2-2-2-4 aluminum XHHW is a good solid, affordable solution. You might call around to some of your local electrical supply houses too. The ones by me carry single conductor ALUMINUM THWN which could be used instead of the XHHW, and many brands come PRE lubed. There is nothing wrong with modern aluminum wire, heck the lugs on both ends are likely aluminum anyhow.

 

[Gto7419]

Huh...what's the meaning of that question? Copper is used for branch wiring where small conductors are used. Feeders of larger sizes are commonly aluminum.

I'm sorry, I meant aluminum. Not sure what happened there. I don't see much aluminum being used around here though most of my past work was residential.

 

[u2slow]

I don't see much aluminum being used around here though most of my past work was residential.

Aluminum dominates in resi for service wiring and panel feeders. It's low-cost (like everything resi) and today's aluminum wire alloy has no real downside.

 

[grounded-b]

I'm sorry, I meant aluminum. Not sure what happened there. I don't see much aluminum being used around here though most of my past work was residential.

Aluminum is used for residential service conductors and feeders to sub-panels all the time. Your PoCo is using aluminum all the time.

Aluminum in sizes 12 and 10AWG would be used more often ( with the correctly rated devices and wire connections (wirenuts), but it got a bad rap in the 1970's, when it wasn't installed correctly . It is not prohibited by the NEC.

Also, generally, it needs to be one size larger than copper for the same ampacity

Steve

 

[Norcal]

Aluminum is used for residential service conductors and feeders to sub-panels all the time. Your PoCo is using aluminum all the time.

Aluminum in sizes 12 and 10AWG would be used more often ( with the correctly rated devices and wire connections (wirenuts), but it got a bad rap in the 1970's, when it wasn't installed correctly . It is not prohibited by the NEC.

Also, generally, it needs to be one size larger than copper for the same ampacity

Steve

AL conductors got a bad rap from the 1960’s AL conductors, in the early 1970’s it became aluminum alloy conductors to correct the deficiencies of the earlier products.

 

[wyliesdiesels]

Aluminum is used for residential service conductors and feeders to sub-panels all the time. Your PoCo is using aluminum all the time.

Aluminum in sizes 12 and 10AWG would be used more often ( with the correctly rated devices and wire connections (wirenuts), but it got a bad rap in the 1970's, when it wasn't installed correctly . It is not prohibited by the NEC.

Also, generally, it needs to be one size larger than copper for the same ampacity

Steve

it wasnt just because of bad installs. the alloy was actually bad and oxidized easily. the alloys used nowadays do not have this issue

 

[grounded-b]

Yes, the aluminum wire of today is not your father's AL wire. !!

Also, thanks for the date correction. I knew it was before my start date as an apprentice electrician !!

Steve