I will be placing a sub-panel in the outbuilding and taking 100 amps from my main panel to feed it. Main panel is 400 amps. My electrician told me to get 1 1/2" conduit and 3 runs of #2 Al. Do stores sell 2-2-2-4 wire all in one or is it cheaper to buy them in separate runs? Hoping to save money I will be doing all the work myself and the licensed electrician will look things over and hook the wiring into the main panel for me ($60). Once I price the wire I might change my mind and let him do everything. At the time $950 seemed like a lot, but I really don't know if I would really be saving that much. I would still have to supply the conduit and dig the trench, but he would supply everything else and install.
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100 amp service to outbuilding
- Thread starter Nissan197
- Start date
Hogan's Hero
Well-known member
that wire is readily available...at least it was for me.
sberry
Banned
Best deal I found on it was from Home Depot as a quad, Lowes had it but had a smaller neutral and was more expensive. I needed a long piece last time so for about 100$ more I bought whole spool. This wire is tailor made for this, can be direct buried or will go thru 1 1/2 but if I had more than 2 turns would run 2 inch. Get a minimum of 5 extra ft. Bury 24 inches deep.Do stores sell 2-2-2-4 wire all in one
Gary S
Well-known member
I ran #2 copper in a 2" conduit to my 100a panel. A larger conduit makes life easier when you get to pulling in the wire.
I rented a walk-behind trencher and got most of the trench done. The soil was still a little damp and I will have to clean it up tomorrow. Went to the local Home Depot and they did have 2-2-2-4 Al, however they did not have enough. It was priced at 1.49, which surprised me. I was thinking it would be at least 2.50+. I have at least five Home Depot's close so one of them should have it. Also bought some 1 1/2" conduit. I will be feeding the wire through the conduit as I go so it should make it easier than having to pull through the whole 90 - 100 ft.
I forgot to say originally what a great site. It was recommended on the TractorbyNet site. Thanks for all the responses.
I forgot to say originally what a great site. It was recommended on the TractorbyNet site. Thanks for all the responses.
I rented a walk-behind trencher and got most of the trench done. The soil was still a little damp and I will have to clean it up tomorrow. Went to the local Home Depot and they did have 2-2-2-4 Al, however they did not have enough. It was priced at 1.49, which surprised me. I was thinking it would be at least 2.50+. I have at least five Home Depot's close so one of them should have it. Also bought some 1 1/2" conduit. I will be feeding the wire through the conduit as I go so it should make it easier than having to pull through the whole 90 - 100 ft.
I forgot to say originally what a great site. It was recommended on the TractorbyNet site. Thanks for all the responses.
As said earlier, #2 AL is not allowed for 100A to a outbuilding AKA "Code Violation" It is another code violation to pull wire into a conduit before the complete conduit run is completed.
jafi
Member
Excuse my ignorance, but why is it against code to pull the wire into conduit before the run is completed?
It is another code violation to pull wire into a conduit before the complete conduit run is completed.
True but its done all the time
Excuse my ignorance, but why is it against code to pull the wire into conduit before the run is completed?
Assumption here but the adhesive for pvc will eat through the insulation of the wire. Or it may adhere the wire to the conduit making replacement a problem for the next poor sob who has to pull it out
lg
no neat sig line
Last edited:
Aceman
Well-known member
True but its done all the time
Not for 90-100 ft runs. I'll admit I leave the 90's off the end sometimes when I do 1000+ foot pulls, but not a short run over to a garage.
As said earlier, #2 AL is not allowed for 100A to a outbuilding AKA "Code Violation" It is another code violation to pull wire into a conduit before the complete conduit run is completed.
I was going off what my electrician was telling me, but I now see the numbers on an ampacity chart when I looked it up. I know the county I live in uses the 2005 NEC.....would that be different than the 2008 NEC regarding wire size? I didn't notice any #1 AL at Home Depot. I guess I could go with 90amp service to the outbuilding or see how much #3 copper wire is.
rhdave
Member
The ampacity rating of conductors wouldn't change in a matter of a few years. As previously mentioned, #3 CU or #2 AL would be good to handle 100A at a reasonable distance (ratings would be in the code book).
Having said that, I've never seen a 90A breaker before. I've seen 60 and 100A, and 70A in some older panels. IMO it'd be worth the extra few bucks to get the proper size wire for your original 100A subpanel plan.
You should also check out pricing at any electrical wholesalers in your area, they often sell cable cheaper than hardware stores because they sell so much volume.
Having said that, I've never seen a 90A breaker before. I've seen 60 and 100A, and 70A in some older panels. IMO it'd be worth the extra few bucks to get the proper size wire for your original 100A subpanel plan.
You should also check out pricing at any electrical wholesalers in your area, they often sell cable cheaper than hardware stores because they sell so much volume.
kool55
Well-known member
I just ran 230 ft. of 2 inch. Lowes was 4.20 a stick. The electric supply house was 5.88. Bought from them before and asked for their best price. After that I got everything from Lowes.
nate379
Banned
Lowe's has 90 amp breakers in the Siemens line for sure. It wasn't cheap though, something like $40 vs $30 for a 100 amp one.
The ampacity rating of conductors wouldn't change in a matter of a few years. As previously mentioned, #3 CU or #2 AL would be good to handle 100A at a reasonable distance (ratings would be in the code book).
Having said that, I've never seen a 90A breaker before. I've seen 60 and 100A, and 70A in some older panels. IMO it'd be worth the extra few bucks to get the proper size wire for your original 100A subpanel plan.
You should also check out pricing at any electrical wholesalers in your area, they often sell cable cheaper than hardware stores because they sell so much volume.
The ONLY way 2 AWG aluminum is suitable for 100 amperes is for service entrance conductors and/or a panel that handles the entire load of a dwelling, a feed to a subpanel or a outbuilding does not meet the criteria in the NEC allowing someone to UNDERSIZE the conductors.
The OP needs to find a competent electrician to get advice from, 'cause that one probably does not even own a copy of the NEC or has not bothered to open it.
sberry
Banned
I wonder what the reasoning was behind the code change with the 2 wire? I can see not using it where continuous load of 100 might be a factor but just out of curiosity wonder why they limit it for sub panel style installations, especially detached buildings?
I wonder what the reasoning was behind the code change with the 2 wire? I can see not using it where continuous load of 100 might be a factor but just out of curiosity wonder why they limit it for sub panel style installations, especially detached buildings?
You almost figured it out. Sub panels are more often done on the cheap and tend to be loaded more with less over head then the main service.
You almost figured it out. Sub panels are more often done on the cheap and tend to be loaded more with less over head then the main service.
thats not it at all. the table that allows wire to be undersized for a dwelling unit's service is based on load diversity found in a residential dwelling unit and nowhere else.
sberry
Banned
You figure a garage to be different?
You figure a garage to be different?
we can do all the figuring we want, but the code says what it says.
sberry
Banned
I am not debating the code, just wondered the reasoning behind it.
I am not debating the code, just wondered the reasoning behind it.
The reason one is allowed to undersize SE conductors for a dwelling is the load diversity means it's not likely to be overloaded, the NEC code committees have chosen not to include subpanels & outbuildings under the same rules.
rhdave
Member
The reason one is allowed to undersize SE conductors for a dwelling is the load diversity means it's not likely to be overloaded, the NEC code committees have chosen not to include subpanels & outbuildings under the same rules.
Ah, that's one of the differences between the NEC and the CEC. I've never come across any restrictions for subpanel feeder conductors, nor have the inspectors ever brought up anything related to this.
Ah, that's one of the differences between the NEC and the CEC. I've never come across any restrictions for subpanel feeder conductors, nor have the inspectors ever brought up anything related to this.
It's not a restriction on subfeeds, they are subject to normal rules it's only for dwelling SE conductors that are allowed to be undersized when it meets the criteria in the NEC.
For normal uses #2 AWG AL is rated for 90 amperes.
gatchel
Well-known member
I amamazed at how many times this thread or topic comes up here. It really should be stickied as people seem to not use the search feature.
Anyway, regardless of what the code says, around our area, there are several electricians that I have spoken to and several underwriters. They all seem to think is is acceptable to use #2 AL berakered at 100 A for a sub panel. The inspector who inspected my garage panel even allowed 2-2-2-4 AL service entrance cable to be pulled in conduit (2") as the sub feeder. I asked him before completing the work. Is it right. No. But why do so many "trained and knowledgable" seem to think it is alright?
Anyway, regardless of what the code says, around our area, there are several electricians that I have spoken to and several underwriters. They all seem to think is is acceptable to use #2 AL berakered at 100 A for a sub panel. The inspector who inspected my garage panel even allowed 2-2-2-4 AL service entrance cable to be pulled in conduit (2") as the sub feeder. I asked him before completing the work. Is it right. No. But why do so many "trained and knowledgable" seem to think it is alright?
. But why do so many "trained and knowledgable" seem to think it is alright?
I'd have to question whether they are knowledgeable. This isn't something new
gatchel
Well-known member
I'd have to question whether they are knowledgeable. This isn't something new
I get it. It just seems that there are others that are doing the same types of panel adds and allowed to do it the "wrong way" with out any issue. The reality is that in my situation I will never pull 100A from in the garage. If I ever come close to needing this wil will look into another service at 200A, that's how I like to do things. If the wire is cut into I don't think a 90A braker as compared to a 100A breaker will make much difference. But that's my amateur, home owner opinion.
sberry
Banned
Its not about being cut into, its about continious loading. If its cut, shorted, a fault it will be hundreds of amps. I think the guys said, this changed in 2008 code?
nate379
Banned
Sometimes the pros screw up as well.
When I bought my house I found that the wire from my meter panel to my load center was #4 AL XHHW-2
The main breaker on the meter panel was 125 amp. That #4 Al is only rated to 75 amps.
They had to come in and rewire after I talked to the electrician and showed them 310.16 out of the NEC.
When I bought my house I found that the wire from my meter panel to my load center was #4 AL XHHW-2
The main breaker on the meter panel was 125 amp. That #4 Al is only rated to 75 amps.
They had to come in and rewire after I talked to the electrician and showed them 310.16 out of the NEC.
Its not about being cut into, its about continious loading. If its cut, shorted, a fault it will be hundreds of amps. I think the guys said, this changed in 2008 code?
SER changed in 08 code, unless you're in Maine. You can still breaker #2 SER in Maine to 90a, otherwise its 75a
EdT
Well-known member
What's often most important in these situations is not what the code says, or what the electrician says, or what the customer thinks is what he wants; it's what the inspector thinks he wants to see. So, before I went to all the trouble of putting all the stuff in a ditch three feet deep (or whatever) I think it would be easy to just ask the inspector if what you're planning to do id OK with him. If you put it all in and ask for an inspection, you're doing the same thing and betting that he'll agree with you. If he doesn't, it's a mess.
SuperSocket
Well-known member
I amamazed at how many times this thread or topic comes up here. It really should be stickied as people seem to not use the search feature.
Anyway, regardless of what the code says, around our area, there are several electricians that I have spoken to and several underwriters. They all seem to think is is acceptable to use #2 AL berakered at 100 A for a sub panel. The inspector who inspected my garage panel even allowed 2-2-2-4 AL service entrance cable to be pulled in conduit (2") as the sub feeder. I asked him before completing the work. Is it right. No. But why do so many "trained and knowledgable" seem to think it is alright?
Two wrongs do not make a right. If you can get away with it, then go for it, but I'd say play it safe and toss in a 90a breaker... since you are not going to go near those loads anyways according to you.
Just breaker it at 90 and solve two problems one shot. I find that sometimes inspectors have changed their minds before or realize that they mis-spoke... or simply woke up on the wrong side of the bed the next day.
What's often most important in these situations is not what the code says, or what the electrician says, or what the customer thinks is what he wants; it's what the inspector thinks he wants to see. So, before I went to all the trouble of putting all the stuff in a ditch three feet deep (or whatever) I think it would be easy to just ask the inspector if what you're planning to do id OK with him. If you put it all in and ask for an inspection, you're doing the same thing and betting that he'll agree with you. If he doesn't, it's a mess.
A inspector has no effing right to make up rules, they are required enforce the code as adopted w/ any local amendment if any were adopted. If a inspector does make up a rule they need to be called on it......