Need some wire size advice

[Diabolic]

I have a small 22/x24' detateched garage that I recently built. I just had the panel in my house upgraded from an old Federal Pacific to a new 200A panel. I would like to install a 100amp panel in the garage about 25' away. My electrician is helping me out by letting me buy all the parts and materials myself to save some $$. I'm pretty ignorant whenit comes to anything other than basic home wiring. He said to purchase 1.5" conduit, and 10-4 wire. What is 3-4 wire and is it large enough to feed a 100 amp panel with 3 220 outlets, and 16 110 outlets? I tried looking up 3-4wire, but not sure I'm looking at the correct thing. Is 3-4 correct?

 

[wyliesdiesels]

I have a small 22/x24' detateched garage that I recently built. I just had the panel in my house upgraded from an old Federal Pacific to a new 200A panel. I would like to install a 100amp panel in the garage about 25' away. My electrician is helping me out by letting me buy all the parts and materials myself to save some $$. I'm pretty ignorant whenit comes to anything other than basic home wiring. He said to purchase 1.5" conduit, and 10-4 wire. What is 10-4 wire and is it large enough to feed a 100 amp panel with 3 220 outlets, and 16 110 outlets? I tried looking up 3-4wire, but not sure I'm looking at the correct thing. Is 3-4 correct?

10-4 wire? Huh? Are u sure u heard him right? :Headscrat A 4 conductor cable listed like that is gonna be flexible cord and capable of handling no more than 30a! And not suitable for a service entrance or feeder!

The number of outlets doesn't matter but rather the EQUIPMENT you will be using AND number of people working in garage at the same time- eg. Will this be a one man shop?

 

[sands35]

Google "ampacity"

http://www.cerrowire.com/ampacity-charts

Maybe your electrician intended 1/0-1/0-1/0-1 (?) - which can be misinterpreted at 10-4.

Assuming your conduit is buried, you need THWN rated wire. (W for Wet)

Depends on if you can get 90*C or 75*C rated wire.

Alternatively, you can direct bury service entry wire if you use conduit boxes at the house and garage, then use interior rated wire inside the house (or THHN into conduit) to the two breaker boxes.

You will also need to run 4 wires to the subpanel. L1, L2, Neutral and Ground. Neutral and Ground are to be bonded only at the main house panel (typically) and you will need appropriate grounds at the garage.

 

[theoldwizard1]

If you drop down to 90A on the breaker in main you can use aluminum 2/0, 2/0, 2/0 Mobile Home Feeder (MHF) cable and save yourself a lot of money.


Edit : Wong size ! Charles has it correct below 2-2-2-4 !

 

[wyliesdiesels]

Google "ampacity"

http://www.cerrowire.com/ampacity-charts

Maybe your electrician intended 1/0-1/0-1/0-1 (?) - which can be misinterpreted at 10-4.

Assuming your conduit is buried, you need THWN rated wire. (W for Wet)

Depends on if you can get 90*C or 75*C rated wire.

Alternatively, you can direct bury service entry wire if you use conduit boxes at the house and garage, then use interior rated wire inside the house (or THHN into conduit) to the two breaker boxes.

You will also need to run 4 wires to the subpanel. L1, L2, Neutral and Ground. Neutral and Ground are to be bonded only at the main house panel (typically) and you will need appropriate grounds at the garage.

I thought the same thing that he may have confused 1/0 4 conductor with 10-4.

90* c ampacities are ONLY for derating purposes AND shouldnt be used for breaker sizing....

 

[Diabolic]

Ha ha ha! Yes I menat 3-4. I found some Romex 2-3 with ground that is $5.50 a foot or some 3 gauge individual that is .88 cent s a foot plus a single 6 gauge ground for .44 cents a foot. Would that route work? It's going inside 1.5" conduit in the ground. 18" depth sound correct?

 

[zmaxmotorsports]

Depending on how many bends you have between the 2 points I prefer to use 2" pvc myself,lot easier to pull wire through.

 

[wyliesdiesels]

Ha ha ha! Yes I menat 3-4. I found some Romex 2-3 with ground that is $5.50 a foot or some 3 gauge individual that is .88 cent s a foot plus a single 6 gauge ground for .44 cents a foot. Would that route work? It's going inside 1.5" conduit in the ground. 18" depth sound correct?

What type of wire is the 3/4? If its Romex, it cant be run underground! So no the 2/3 Romex wont work either. What type of wire is the single conductor #3? THHN; cu, al, etc.?

If youre a one man shop with sml and medium load equipment, just go with 2-2-2-4 AL MHF but u will need bigger conduit! CU @ $5.50/ft IS very expensive! AL is way cheaper, unless u want to blow money on cu!

 

[zmaxmotorsports]

What type of wire is the 3/4? If its Romex, it cant be run underground! So no the 2/3 Romex wont work either. What type of wire is the single conductor #3? THHN; cu, al, etc.?

If youre a one man shop with sml and medium load equipment, just go with 2-2-2-4 AL MHF but u will need bigger conduit! CU @ $5.50/ft IS very expensive! AL is way cheaper, unless u want to blow money on cu!

I spent 30 years in the trades and Im drawing a blank on 3-4 and 2/3 also.

 

[wyliesdiesels]

I spent 30 years in the trades and Im drawing a blank on 3-4 and 2/3 also.

I'm not sure what 3-4 is either. Perhaps hes mixing the numbers up again and is actually referring to NM-B 4/3....

http://www.wesbellwireandcable.com/Romex/Romexnmb4-3.html

NM-B 2/3 below, commonly referred to as Romex(though Romex is a brand)

http://www.wesbellwireandcable.com/Romex/Romexnmb2-3.html

 

[theoldwizard1]

...NM-B 2/3 below, commonly referred to as Romex(though Romex is a brand)

I just found out recently that the Romex brand was owned by Southwire. I thought it was dead.

 

[nehog]

Ha ha ha! Yes I menat 3-4. I found some Romex 2-3 with ground that is $5.50 a foot or some 3 gauge individual that is .88 cent s a foot plus a single 6 gauge ground for .44 cents a foot. Would that route work? It's going inside 1.5" conduit in the ground. 18" depth sound correct?

We all need to differentiate between copper wire and aluminum wire when talking current carrying capacities. There is a difference between the two that can't be ignored.

You will need four conductors, two hot, neutral and ground. I would not want to pull four wires of 4 AWG in a 1 1/2 conduit myself. I'd go with 2 inch.

 

[sands35]

Pipe fill matters. need to check with your local inspector if you need schedule 40 or 80 for the riser. The difference hinges on how much mechanical damage is possible for the installation location. If you can run into it with a car, lawn mower or snow blower or something, likely 80 is needed.

http://www.williamsnashville.com/Technical_Data/Conduit_Fill_Table_PVC_80.html

2" schedule 80 is fine for 4 conductors of 4 AWG. (but if you want 100 amps, you need 3 AWG, not 4). You only need schedule 80 to 18" down in the trench, then you can go to schedule 40 for the lateral run.

 

[wyliesdiesels]

I just found out recently that the Romex brand was owned by Southwire. I thought it was dead.

What gave u the idea that the Romex brand of NM-B was dead?

We all need to differentiate between copper wire and aluminum wire when talking current carrying capacities. There is a difference between the two that can't be ignored.

You will need four conductors, two hot, neutral and ground. I would not want to pull four wires of 4 AWG in a 1 1/2 conduit myself. I'd go with 2 inch.

Exactly why i said what i did in #8 above... "what type of wire- thhn, cu, al, etc.?"

The challenege on this thread is that the OP keeps giving us little bits of information, not enough to give a straight forward answer....

 

[Diabolic]

This is my personal home garage. By 3-4 I meant 4 3gauge wires in a single sheath. I'm discovering there is no such thing. Now I'm looking at individual strands. Three 3gauge strands and one 6gauge strand for the ground. It will be buried 18" under the soil. Does that help or clear things up? I appreciate all the help.

 

[Charles (in GA)]

Go with the 2" conduit, it is very little money more than the 1½" and much easier to pull in. Also go with Aluminum Mobile home feeder quadplex, 2-2-2-4. Its four wires all twisted together but no jacket, rated for direct burial but also can be pulled in conduit. If dual rated as USE-2 AND RHH AND RHW (see the pic) You can carry this wire from the 90 amp breaker to the new panel uninterrupted. You will need it in conduit in the walls, crawl space, etc, but this is a minor issue generally. This wire is made by Southwire and is available at Home Depot and supply houses. DO NOT get a USE-2 wire that does not have the other ratings stamped on it. This wire is less than $2 a foot and can be protected by a 90 amp breaker at the house panel, IT doesn't matter than you are using a 100 amp panel in the shop, it could be a 200 amp panel, doesn't matter, its protected by that 90 amp breaker.

This is the best deal going for powering a shop. All legal, all easy to work with.

Charles

 

[theoldwizard1]

Only slightly off topic.

Why does MHF need to be in a conduit in walls, crawl spaces, etc ?

Southwire says RHH/RHW/USE cable is "High-Heat, Moisture, and Sunlight Resistant". How does an outer sheath give more protection in an interior space ?

 

[pattenp]

MHF needs to be in conduit inside the structure because it is individual conductors that are not encased by an outer jacket. As an example, SER and NM cable have an outer jacket, so no conduit is needed for other than protection from physical damage..

Only slightly off topic.

Why does MHF need to be in a conduit in walls, crawl spaces, etc ?

Southwire says RHH/RHW/USE cable is "High-Heat, Moisture, and Sunlight Resistant". How does an outer sheath give more protection in an interior space ?

 

[Diabolic]

Bringing this back from the dead. It's go time for the purchase. I want to list what I'm buying and make sure it is correct.

Wire
65' of 3AWG( I will need 3 65' strands of this)
65' of 6AWG(single strand for the ground)

Box, Conduit, and Breaker
2" plastic conduit schedule 80 and 40
12/24 single phase, 125 amp, main lug box(this goes in the detatched garage)
100 AMP 2 pole square D Home Line Breaker(this will go in the 200 amp home panel)

Does all this sound correct? I was confused because I was asked if I wanted 3AWG or 3/0 wire. I'm not sure what the difference is but AWG is far less $$$ per linear foot.

 

[VHF]

#3 CU (copper) wire is what you want for 100A service to your detached garage (not 3/0 which is much heavier.) Make sure you are right on the length, because you can always cut it shorter but you can't cut it longer!

However, I don't think you want a main lug panel for the garage. If you have more than 6 breakers, NEC requires a main disconnect in the detached structure. Go with a 20-position 100A main breaker Square D HomeLine pannel--these are readily available for under $60. The main breaker serves as your disconnect.

The 100A breaker to go in your house panel is correct. I've seen these for $35 at the farm supply store, but some people have reported paying a lot more for them.

You'll also need two ground rods with clamps and enough #6 bare copper to run from the ground rods (6' apart) into the panel.

 

[VHF]

You'll also need PVC cement for the conduit, and some pulling lube will make the job of getting the wires through the conduit much easier.

 

[VHF]

BTW, did you check with your electrician that 2" conduit is OK? It certainly makes pulling the wires easier, but you need to make sure there is an available 2" knock-out on your 200A house panel for it to connect to. 1.5" PVC conduit is adequate for three #3 + one #6 THHN/THWN wires if that is a better fit for your situation.

Also, think about how you want to route your ground wire from the panel to the ground... it is common to just run it exposed tucked behind the 2" conduit on the outside of your garage wall, but you can use a length of schedule 80 1/2" PVC conduit and an a 1/2" LB for neatness and to protect the wire until it is under ground.

Ground rods are usually driven until the top is a few inches below the surface, that way the clamps and the wire are safely buried. Put one next to the building, and one out in the yard 6' away. The ground wire must be continuous from one rod to the other to the panel.

That reminds me, one more item for your shopping list: a ground bus (or two) for your garage panel. These are not included with the panel. I like to have one on each side to be able to land the ground on the same side of the panel as the hot and neutral.

 

[Diabolic]

Well after reading the replies I may be returning some stuff. I completely did a 180 and bought

100 Amp 2 pole home line breaker for the house box

8/16 Square D box for the garage, but its not the home line

75' of the Southwire 2-2-2-4 AL Direct bury cable. Now I won't need counduit. I dug the trnch 22" deep.

Did I just screw up? Sorry I didn't wait for the reply's but I had to get it on my lunch break. Got the wire for $1.20 per ft.

 

[pattenp]

You can only use a max of a 90A breaker on Al 2-2-2-4. How did you come up with the 100A was okay? And the 2-2-2-4 will need to be in conduit where exposed above ground and inside the house and garage.

Well after reading the replies I may be returning some stuff. I completely did a 180 and bought

100 Amp 2 pole home line breaker for the house box

8/16 Square D box for the garage, but its not the home line

75' of the Southwire 2-2-2-4 AL Direct bury cable. Now I won't need counduit. I dug the trnch 22" deep.

Did I just screw up? Sorry I didn't wait for the reply's but I had to get it on my lunch break. Got the wire for $1.20 per ft.

 

[VHF]

Exchange your 100A breaker for a 90A and you'll be good to go with the AL 2-2-2-4 wire. As already mentioned, you'll still need a couple LBs and enough schedule 80 conduit to get you underground on each end, plus a 90 degree sweep elbow on each end down in the trench. Direct bury wire needs to be 24" below the surface, so your trench should be at least 25" deep. Make sure to bury a red "buried wire" tape (not yellow "caution" tape) about 12" above your burried wire.

Sounds like you might have gotten a Square D QO box for your garage, which is better quality than the HomeLine, but at a higher price. Once again you either need a main breaker (disconnect) in the garage or you need to limit yourself to no more than six breakers (no more than six handle flips to turn off all power in the building.)

It is OK to have a 100A main breaker in the garage fed from a 90A breaker in the house. The breaker in the garage is just there to serve as the disconnect; the breaker in the hosue provide overcurrent protection for the wires feeding the garage.

When using AL wire you need anti-oxidizing compound ("Nolox") on the connections.

 

[pattenp]

Good catch VHF on the required depth for direct bury. Diabolic, for the little cost of PVC conduit I'd put it in conduit before having to dig that trench another 3- 4 inches deep. Plus I think in conduit is the best way to do it.

 

[Diabolic]

Exchange your 100A breaker for a 90A and you'll be good to go with the AL 2-2-2-4 wire. As already mentioned, you'll still need a couple LBs and enough schedule 80 conduit to get you underground on each end, plus a 90 degree sweep elbow on each end down in the trench. Direct bury wire needs to be 24" below the surface, so your trench should be at least 25" deep. Make sure to bury a red "buried wire" tape (not yellow "caution" tape) about 12" above your burried wire.

Sounds like you might have gotten a Square D QO box for your garage, which is better quality than the HomeLine, but at a higher price. Once again you either need a main breaker (disconnect) in the garage or you need to limit yourself to no more than six breakers (no more than six handle flips to turn off all power in the building.)

It is OK to have a 100A main breaker in the garage fed from a 90A breaker in the house. The breaker in the garage is just there to serve as the disconnect; the breaker in the hosue provide overcurrent protection for the wires feeding the garage.

When using AL wire you need anti-oxidizing compound ("Nolox") on the connections.

So do they make a box for the garage that has a built in 100A breaker or do I just add that? I will swap the 100A Home line for a 90 AMP. I'm going to un the wire under the concrete footer of the house(Pier and Beam) and then up the base plate right into the bottom of the 200Amp home box. Since it will be under a sealed foundarion and through a wall will I still need Conduit for that portion?

 

[pattenp]

Use a 100A main breaker panel for the garage, it has a buillt-in 100A main breaker disconnect.
And the feeder you have needs to be in conduit when inside of the structure. Doesn't matter if it's in the wall. If it's like this....

And here's a panel..........
http://www.lowes.com/pd_286858-296-HOM24M100VP_0__

So do they make a box for the garage that has a built in 100A breaker or do I just add that? I will swap the 100A Home line for a 90 AMP. I'm going to un the wire under the concrete footer of the house(Pier and Beam) and then up the base plate right into the bottom of the 200Amp home box. Since it will be under a sealed foundarion and through a wall will I still need Conduit for that portion?

 

[Diabolic]

The wire I have is 2-2-2-4 provided by King Wire and Cable. It's Amp rating is 165 out of conduit or 120 amp inside conduit. Does this mean that the 100 AMP 2 pole I have for the house will work ok? The wire will be coming out of the ground underneath the house. The house has a concrete footer around the perimeter which I will be feeding the wire underneath from the outside to the underside. From there it will come out of the soil and through the wood 2x6 base plate and directly into the bottom of the 200 amp panel box. No wire will be exposed except the 14" where it comes out of the soil and goes into the base plate. Are you saying I need to put 2" conduit inside the wall?

 

[pattenp]

Diabolic, does the wire you have look like what I posted a picture of? If so, then it needs to be in conduit in the wall and under the house. If it's #2 aluminum then it can only be over current protected by a 90A breaker max. This is all by the NEC. I assume you are in the US.

Edit: I'm thinking based on the amp ratings you listed the wire you got is Quadruplex UD or ****. If I'm correct, that cable is not allowed by code to be run to the inside of the structure because the insulation is not fire resistant approved. The wire you need is called Mobile Home Feeder (MHF). It is rated for inside use but does need to be in conduit inside the house.

The **** will have 3 black and 1 black with a white or yellow stripe.
MHF will have 2 black, 1 black with white stripe and 1 green.

*

 

[Diabolic]

Diabolic, does the wire you have look like what I posted a picture of? If so, then it needs to be in conduit in the wall and under the house. If it's #2 aluminum then it can only be over current protected by a 90A breaker max. This is all by the NEC. I assume you are in the US.

Edit: I'm thinking based on the amp ratings you listed the wire you got is Quadruplex UD or ****. If I'm correct, that cable is not allowed by code to be run to the inside of the structure because the insulation is not fire resistant approved. The wire you need is called Mobile Home Feeder (MHF). It is rated for inside use but does need to be in conduit inside the house.

The **** will have 3 black and 1 black with a white or yellow stripe.
MHF will have 2 black, 1 black with white stripe and 1 green.

*

Yes it has a yellow stripe. But once it's cut it's paid for so it's still going in. Not getting inspected anyway and this garage will never, ever be at anywhere near 100amp load. At most it will have a welder and window unit running at the same time. The funds have been cut off so it is what it is. I hate doing things this way, but for a small personal garage I should be ok. It's going to be run in 2" conduit from box to box. Im hooking 3 220 breakers and 3 30 amp breakers into the sub panel for now. This should get me in under the 6 switches to kill the power. I will swap the 100amp for a 90 amp breaker tonight.

 

[pattenp]

Well if that's the way it is then just use the 100A breaker for the feed. One more thing not to code won't matter. You aren't going to find a 90A breaker at any big box store. You'll need to go to an electrical supply to get the 90A breaker.

Oh.. just kidding about using the 100A breaker.

 

[Diabolic]

Ok, I returned the 100, got a 90, got a new box with a built in breaker for the garage. I killed the wiring under the house, ran it all in 2" conduit and went straight through the outside wall directly into the back of the 200amp box.

 

[wyliesdiesels]

Here is some food for thought:

If u ever sell the place and an inspector catches the incorrectly used wire, u may have to correct it in order to sell.

Also, if there is ever a fire, the insurance company could deny a claim based on the wrong(non fire resistant rated) wire being used.

 

[Diabolic]

Just an update......It's all up and running well. 2-2-2-4 cable in 2.5" conduit. I installed a 12/24 Square D QO sub panel with a 100amp 2 pole breaker. The 200 amp home panel now has a 90amp 2 pole breaker. I came right through the wall and into the back of the panel in both the house and the garage. I hope all is well now.