1 awd vs 1/0 al

[Kaizen]

Trying to decide on wire and conduit. Was going with a 1 awd aluminum for 100 amp panel but now thinking 1/0 for a little more money. I'd use 125 amp breakers instead of 100. I have a 7.5 hp compressor and a 220 welder along with lights and potentially ac at the same time so the 100 amp panel might be cutting it close? At startup the compressor was 60 amps i believe. any downside to the 1/0? will it fit in 125 breaker fine? Does the 1/0 step up to 2.5 inch conduit or a 3?

 

[Norcal]

Before you go too far need to check if your panel will support a 125A breaker and if it is even needed.

 

[pattenp]

I assume you are looking at XHHW-2. #1/0 Al will fit in 2" conduit just fine and also fits in a 125A breaker.

 

[Kaizen]

I assume you are looking at XHHW-2. #1/0 Al will fit in 2" conduit just fine and also fits in a 125A breaker.

Correct. Shows at .44 each. so probably have half inch to spare in a 2 inch pipe. With two 90s it looked tight.

 

[Kaizen]

I assume you are looking at XHHW-2. #1/0 Al will fit in 2" conduit just fine and also fits in a 125A breaker.

Main panel is 200amps. Physically it will fit. Didnt think there was a limit on main panel amps. thought sub could be up to main panel amps theoretically? Do i need to have 125 amps free in main?

 

[pattenp]

Correct. Shows at .44 each. so probably have half inch to spare in a 2 inch pipe. With two 90s it looked tight.

I don't know how you are estimating the fill coming up with a 1/2" to spare. The NEC tables shows 2" conduit taking up to seven #1/0 conductors, so three #1/0 Al plus a #4 Al ground is not a problem.

 

[pattenp]

Main panel is 200amps. Physically it will fit. Didnt think there was a limit on main panel amps. thought sub could be up to main panel amps theoretically? Do i need to have 125 amps free in main?

You need to look at the stab ratings for branch circuits to see if 125A is allowed. Some panels have a max of 100A for any single branch circuit.

 

[mm08822]

OP, you need to provide the details of your main panel equipment - Mfr and series. Even part #'s would be more definitive.

Distance to sub panel, located in attached or detached bldg?

Why are you planning on 2"C? XHHW will fly through 2"c.

 

[Kaizen]

I don't know how you are estimating the fill coming up with a 1/2" to spare. The NEC tables shows 2" conduit taking up to seven #1/0 conductors, so three #1/0 Al plus a #4 Al ground is not a problem.

ahhh i was thinking .44 x4 but forgot that is just stacked.

Where do i find stab ratings? On my panel?

 

[mm08822]

Where do i find stab ratings? On my panel?

Look on your panel label. Post a legible pic of the label.

 

[Kaizen]

OP, you need to provide the details of your main panel equipment - Mfr and series. Even part #'s would be more definitive.

Distance to sub panel, located in attached or detached bldg?

Why are you planning on 2"C? XHHW will fly through 2"c.

I'll double check later but i believe this is my main panel. sub is a detached garage through 75 feet of conduit. I'd rather do the 2" to give more room for the pull.

 

[pattenp]

There's nothing wrong with using 2" conduit for the 1/0 conductors. It will be easier to pull and there is very little cost savings dropping down to 1.5"

 

[wyliesdiesels]

Trying to decide on wire and conduit. Was going with a 1 awd aluminum for 100 amp panel but now thinking 1/0 for a little more money. I'd use 125 amp breakers instead of 100. I have a 7.5 hp compressor and a 220 welder along with lights and potentially ac at the same time so the 100 amp panel might be cutting it close? At startup the compressor was 60 amps i believe. any downside to the 1/0? will it fit in 125 breaker fine? Does the 1/0 step up to 2.5 inch conduit or a 3?

before sizing wire, you could do a load calc to know what size service you will need.

If this is a one man shop then you can only use a welder and AC at the most at the same time. The compressor would only kick on if using air tools as long as you have no leaks.

Point being 100a is more than enough for a 1 man shop.

a 7.5HP motor would be less than 40a running load.

Startup current would be in the hundreds of amps for 100ms-200ms, NOT 60amps. in-rush current is 4x-8x nameplate FLA. If you measured startup current with a clamp meter that is not specifically designed to meter in-rush current, then any measurements you get will be inaccurate.

Also, some PoCos have limits on motor HP size so you should check with them.

Another thing to look at is the house loads.

 

[Kaizen]

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[Kaizen]

before sizing wire, you could do a load calc to know what size service you will need.

If this is a one man shop then you can only use a welder and AC at the most at the same time. The compressor would only kick on if using air tools as long as you have no leaks.

Point being 100a is more than enough for a 1 man shop.

a 7.5HP motor would be less than 40a running load.

Startup current would be in the hundreds of amps for 100ms-200ms, NOT 60amps. in-rush current is 4x-8x nameplate FLA. If you measured startup current with a clamp meter that is not specifically designed to meter in-rush current, then any measurements you get will be inaccurate.

Also, some PoCos have limits on motor HP size so you should check with them.

Another thing to look at is the house loads.

I could have two people in the shop where the ac/welder/compressor/and other high draw tools like large table saw would be used. My thinking is I don’t want to go through all of this to find I’m tripping the main. House panel probably should be load Calc. Since it’s just me not much will be running in the house if I’m in the garage


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[sberry]

100 will run it.

 

[pattenp]

Based on catalog info for the S4040B1200 the branch circuits are rated to 200A, so a 125A breaker is okay.

 

[Kaizen]

Based on catalog info for the S4040B1200 the branch circuits are rated to 200A, so a 125A breaker is okay.

Thanks for checking. For my own info panels that are not are made differently? Thinner buss bars?

 

[mm08822]

Since your panel label does not include any limitations for buss stabs nor does the catalog, I would say that two 125A cb's could be opposite each other.

125a is the largest QP style cb offered.

 

[Kaizen]

Since your panel label does not include any limitations for buss stabs nor does the catalog, I would say that two 125A cb's could be opposite each other.

125a is the largest QP style cb offered.

Can you elaborate please? You talking putting two opposite of eachother in the panel? wouldnt that be on the same buss?
Do i need to get breakers with buss stabs? My current ones just push onto the center portion.

 

[mm08822]

Can you elaborate please? You talking putting two opposite of eachother in the panel? wouldnt that be on the same buss?
Do i need to get breakers with buss stabs? My current ones just push onto the center portion.

You will be using a 2 pole circuit breaker (Siemens Q2125) that plugs onto two existing adjacent (vertical) stabs that are part of the panel buss. Buying the cb provides everything you need to be able to install it into the panel. There is nothing more for you to buy or be concerned about.

As a side note only, all I was referring to was the buss stab (from an electrical ampacity rating) could probably handle another Q2125 cb plugged in opposite to the one you installed b/c no limitation is indicated. This has no impact on your current situation - please ignore this comment.

 

[earlybirds]

I used I/0 alum. XHHW for the 2 hots and the neutral, #4 for the EGC in 2" PVC conduit for my 165 foot power line to my shop to have 100 amp service.

The run has 2 long sweep 90's and 1 45 degree turn. We used LOTS of wire lube with the wife feeding the wire and me pulling. It was all we could handle, but doable. Definitely us 2" or larger conduit.

I also have a big compressor, welders, plasma cutter, good lighting, etc. Never a problem with 100 amps.

 

[Kaizen]

I used I/0 alum. XHHW for the 2 hots and the neutral, #4 for the EGC in 2" PVC conduit for my 165 foot power line to my shop to have 100 amp service.

The run has 2 long sweep 90's and 1 45 degree turn. We used LOTS of wire lube with the wife feeding the wire and me pulling. It was all we could handle, but doable. Definitely us 2" or larger conduit.

I also have a big compressor, welders, plasma cutter, good lighting, etc. Never a problem with 100 amps.

appreciate your example. Lately I seem to be in the "just go a step up in case" mindset. Still tossing the plan around though.

 

[Kaizen]

You will be using a 2 pole circuit breaker (Siemens Q2125) that plugs onto two existing adjacent (vertical) stabs that are part of the panel buss. Buying the cb provides everything you need to be able to install it into the panel. There is nothing more for you to buy or be concerned about.

As a side note only, all I was referring to was the buss stab (from an electrical ampacity rating) could probably handle another Q2125 cb plugged in opposite to the one you installed b/c no limitation is indicated. This has no impact on your current situation - please ignore this comment.

Thanks for clarifying.

 

[sberry]

I know several setups use 5 hp and 60A,,, a couple 70A on this forum and got lotso ****. You don't got to weld while the comp is on , its as simple as that and even then could a modern welding machine. I am a fan of 5 hp air in residential or hobby unless I got pressing demands. 50% of 60A service and 30 of 100 which is great.
But a 7.5 has a lot of range and do you really need to sandblast steady while stick welding wide open with a 225 buzzer with the air cond going?

 

[sberry]

It gets to be second nature about utilities, I can wait a minute till someone is finshed, etc. So what if I get 5 more psi drop to a sander for a couple minutes etc and one of the benefits in your own shop is the management, I have seen guys be quite proficient fabricators from 30A service.
My helper can live from a 16 cord and 3 way, just does one thing at a time.
I have ran a bunch of stuff a couple times in my career from 100A service, where we rigged hillbilly or start up jobs. I never tripped up 100 and I done a lot of makeshift shate.
I ran a welding shop a winter from a 60A and the air comp, the well, the pressure washer a dwelling from more feeds from 100 but plasma cut and weld from 60 no problem.
I just didn't plasma when someone was welding with a 250 but could with out tack up 180. The air came from another circuit.

 

[Kaizen]

I know several setups use 5 hp and 60A,,, a couple 70A on this forum and got lotso ****. You don't got to weld while the comp is on , its as simple as that and even then could a modern welding machine. I am a fan of 5 hp air in residential or hobby unless I got pressing demands. 50% of 60A service and 30 of 100 which is great.
But a 7.5 has a lot of range and do you really need to sandblast steady while stick welding wide open with a 225 buzzer with the air cond going?

This thread is more about why can't i do a 1/0. Others have answered that i can so for 30 bucks more in wire and some more on breakers i'll do a 125amp.
Can i make do with a 60? Yes. I have for ten years. Can i manage my time due to the amps? Sure. Could i probably never trip 100amp? possibly.
But this is as close to a dream shop as i'm going to get so why not? I've worked off extension cords for so long I have "favorites". Now i'm just ready to go for it.