View Full Version : Aluminum wire and plastic conduit or copper and metal?
leejosepho
10-22-2008, 04:50 PM
I have purchased a new subpanel for my attached workshop, and now I need to decide about 100-amp wire and conduit. I can either run three strands of #3 copper in metal conduit for the ground or I can run a 2-2-2-4 aluminum twist in larger plastic. The subpanel will be 50' from my main panel, and I will have four 90* turns along the way. The copper wire would cost me a little over $150.00, and the aluminum would cost about $50.00 less ... but then the plastic conduit for the aluminum would have to be larger than the metal for the copper ...
Also, I presently have a new and fine-for-now 60-amp breaker that might accept the #3 copper going to the subpanel, but I would have to buy a 100-amp breaker if I use the #2 aluminum wire.
Which way should I go?
jar546
10-29-2008, 06:49 PM
Which way should I go?
Pull an electrical permit with hour municipality, then hire an electrician.
leejosepho
10-30-2008, 03:19 AM
... hire an electrician.
... and just who would be paying?!
I decided to use 1" EMT and #4 copper, and changing the path a bit now means I will only have three 90s instead of four.
leejosepho
10-30-2008, 03:39 AM
As long as you pull a permit and get it inspected as your project is being built then I don't care who does the work.
Whew! Thank you.
jar546
10-30-2008, 05:22 AM
How do you plan on running the EMT, underground, overhead, along a wall? This is important because there are many ways that you cannot run EMT.
What type of wire are you pulling and how many conductors? RHW, THHN, THWN, SEU, etc.
What is the conductor fill capacity for 1" EMT and type of wire you are pulling?
What code cycle is your municipality in?
After you answer all of these questions you may get a little farther into understanding exactly what you need to do and why what you have planned so far will not work.
leejosepho
10-30-2008, 05:10 PM
... what you have planned so far will not work.
I can guarantee you that what I have planned will definitely work, but I am nevertheless interested in hearing why you say it will not.
220/221
10-30-2008, 05:44 PM
#4's will not do a full 100 amps.
If you try to stuff #2's in 1" conduit, you will regret it.
No one around here has #3 wire.
Above ground = EMT
Underground = PVC
jar546
10-30-2008, 06:22 PM
Listen to 220/221
Again, what code cycle are you on?
This had direct bearing on grounding requirements.
You will pulling 4 conductors I can only assume or at least hope so. This means that you can only fill 40% of the conduit cross sectional area.
If you plan on 1" EMT which is wrong because it should be PVC then at the most you can get will be not enough so don't plan on using 1". Reason #1, it is too small for the size wires and if you still plan on doing it, I will fly down to video your attempt. It simply won't work and you will make America's Funniest Videos. Especially with 360 degrees of bends between pull points.
If you are going to run 4awg XHHW aluminum then you will need to pull it through at least 1-1/4" conduit and that will be tough. Don't even think about pulling SE cable through because it will not work and it is a code violation.
I am trying to help to save you a headache.
leejosepho
10-31-2008, 03:25 AM
#4's will not do a full 100 amps.
Understood. I was hoping for 100, but I had to settle for the wire I could afford. So, and unless the #4 wire will not clamp into it, I will be using the 60-amp breaker I had already purchased for this project quite some time ago.
Above ground = EMT
Underground = PVC
Yes, I know. I used PVC to go out to a subpanel in my detached garage where we used to live, and now I will be using EMT to run inside along the wall to my attached workshop.
Again, what code cycle are you on?
This had direct bearing on grounding requirements.
I have no idea.
You will pulling 4 conductors I can only assume or at least hope so. This means that you can only fill 40% of the conduit cross sectional area.
It is my understanding that I only need three conductors since the EMT is a mechanical ground. But, I do have enough wire for four if necessary and I believe four will fit into 1".
jar546
10-31-2008, 04:03 AM
EMT is not a mechanical ground if it is not continuous and since you are feeding a separate structure you will need an equipment ground. Again, without knowing what code cycle you are in there are other issues.
You will have to use PVC so eliminate the EMT thought as far as a ground.
It sounds like you are going to do whatever you want anyway because you already purchased the material so what is the point of asking?
You may get it to "work" but that does not mean it is right or safe.
These rules are written in blood because of incidences that have happened over the years causing loss of life, health or property. They are MINIMUM standards.
Will you be taking the 2/2/2/4 back because yo can't run it through conduit or using it anyway? Sounds like SE cable to me.
If you are resigned to using the 60 amp breakers, why would you stay with the 100 amp wires, given the additional cost for the larger conductors?
mattbee24
10-31-2008, 10:46 AM
From what I understand, the sub panel is in an attatched building, and he is running emt along the wall all the way to the sub panel. He is using #4 copper to feed the sub panel. Around here, #4 copper is acceptable for 100a service in a residential home, and #3 for commercial. (he is using a 60a breaker so that point is mute anyway)
As far as using the conduit as the ground, I didn't think you could do that, but I could be wrong.
If he does need to pull a ground, it looks like he should still be able to do that. The chart I have shows you can have up to 4 strands of #4 thhn in 1" emt.
That's just my opinion, I could be wrong.
jar546
10-31-2008, 01:23 PM
He said he already purchased aluminum and your chart is wrong. THHN takes up more space than XHHW. There are two charts and a calculation that you must use in order to decide what can fit in conduit.
jar546
10-31-2008, 01:32 PM
The problem in this situation is that the materials that were already purchased will not work.
This is where the limitations of a DIY come into play.
Something of this magnitude should be done professionally.
Of course we can all keep asking the same questions to enough people so we eventually get the answer that we wanted to hear in the first place.
IMHO
leejosepho
10-31-2008, 04:45 PM
EMT is not a mechanical ground if it is not continuous and since you are feeding a separate structure ...
Something has become all confused here. The EMT will be continuous, the subpanel will be in attached workshop and I have purchased copper wire.
leejosepho
10-31-2008, 04:50 PM
If you are resigned to using the 60 amp breakers, why would you stay with the 100 amp wires, given the additional cost for the larger conductors?
Partly because I got the wire at a good price, but also because I would rather run heavier wire than is actually required anyway.
leejosepho
10-31-2008, 04:59 PM
From what I understand, the sub panel is in an attatched building, and he is running emt along the wall all the way to the sub panel. He is using #4 copper to feed the sub panel. Around here, #4 copper is acceptable for 100a service in a residential home, and #3 for commercial. (he is using a 60a breaker so that point is mute anyway)
As far as using the conduit as the ground, I didn't think you could do that, but I could be wrong.
If he does need to pull a ground, it looks like he should still be able to do that. The chart I have shows you can have up to 4 strands of #4 thhn in 1" emt.
That's just my opinion, I could be wrong.
You definitely have the details of my structure and purchased-so-far supplies correct, and I am not yet absolutely certain about the EMT as the ground ... and if four strands of #4 actually do turn out to be too much for the 1" EMT, I believe I can use a smaller ground wire. The aluminum wire I had merely *thought* about using has a #4 ground running alongside three strands of #2. So, I can imagine #6 copper would be fine as a ground alongside #4 copper lines and a neutral if I must have a fourth wire even with continuous EMT.
I am not yet absolutely certain...
I believe...
I can imagine...
The electrical codes are not items of uncertainty, belief or imagination. They are hard and fast rules and where enacted into law they MUST be followed. There is no place for uncertainty, belief or imagination. Follow the codes or do not do the job.
220/221
10-31-2008, 05:33 PM
Even if you are not yet required to pull a ground, pull a #8 anyway.
Grounding = good.
The charts may say you can fit the wires in but the charts are often unrealistic. Does it still say something like 10 #12's in 1/2 EMT??? :eek:
I recently re pulled 3, 4's + ground into an existing 1" EMT and it was NOT easy. An inexperienced person couldn't have done it without damaging the wire. Wires cannot twist or kink at ALL or they take up too much space.
Run 1.25 or 1.5.
There is no place for uncertainty, belief or imagination.
But there are MANY places for interpretation.
jwelectric
10-31-2008, 05:45 PM
Anyone want to bet that this is what he is installing?
click here (http://www.terrylove.com/forums/showpost.php?p=161226&postcount=4)
leejosepho
11-01-2008, 03:28 AM
The electrical codes are not items of uncertainty, belief or imagination ...
I understand, and I do not proceed until my own uncertainties and unknowns have been resolved.
Even if you are not yet required to pull a ground, pull a #8 anyway.
Grounding = good.
That makes sense to me, and I might just do that. Thank you.
I recently re pulled 3, 4's + ground into an existing 1" EMT and it was NOT easy. An inexperienced person couldn't have done it without damaging the wire. Wires cannot twist or kink at ALL or they take up too much space.
Run 1.25 or 1.5.
I have yet to put the wire and EMT side-by-side, but I will take a good look and do the computations before hanging anything. I only have to go about 20' before my first turn, then another 20' before turning again and then turning up to the subpanel, and I can put that last turn in place after-the-fact, if necessary. Also, this is not my first time pulling wire.
Anyone want to bet that this is what he is installing?
click here (http://www.terrylove.com/forums/showpost.php?p=161226&postcount=4)
No, that stuff was #6, and I have #4.
I greatly appreciate everyone's help here, and I especially thank you, Jar546, for responding to this thread at all after others had either ignored or missed it entirely. I would have preferred to just ask simple questions and get straight answers -- Aluminum and plastic or copper and metal? -- but even antagonists can end up being helpful.
Peace.
jar546
11-01-2008, 07:22 AM
I have yet to put the wire and EMT side-by-side, but I will take a good look and do the computations before hanging anything. I only have to go about 20' before my first turn, then another 20' before turning again and then turning up to the subpanel, and I can put that last turn in place after-the-fact, if necessary. Also, this is not my first time pulling wire.
Still need some clarification for grounding purposes and for all purposes for that matter:
1) What code cycle are you under?
2) Is the garage attached or detached (conflicting posts)?
3) Will the conduit be run underground or above ground?
4) Will the conduit if run above ground be subject to the weather?
5) Are your pull points from beginning and the end only or do you have pull points in between start and finish too (real pull points)?
6) Will the installation get inspected by local authorities during or at completion?
If the job is not going to be inspected then I refuse to assist you with anything further.
Without ALL of those questions answered above, no one can really help you or give you guidance.
Either you want help and realistic, actual guidance or you want people to tell you what you want to hear regardless of the actual situation.
Safety first. People have died doing what your are plannin on doing.
1. originally you were debating aluminum or copper, but the aluminum would have required a larger breaker.
2. Originally you were debating 1" or 1 1/4" conduit.
3. Then you debated whether the copper wire would support 100 amps, which is the same breaker you would have needed for the aluminum wire.
4. Now you are sticking with the 60 amp breaker which does not need the same wire as the 100 amp one would have.
5. Now you say you have the 100 amp wire and the conduit, so why are we still discussing it.
6. Since there is little possibility that you will ever reach the 240 v, 60 amp plateau, why worry about oversizing the wire?
leejosepho
11-01-2008, 05:48 PM
1. originally you were debating aluminum or copper, but the aluminum would have required a larger breaker.
Yes, I believe my 60-amp breaker would not have accepted #2 wire.
2. Originally you were debating 1" or 1 1/4" conduit.
Yes, I was wondering what size conduit I would need after deciding about the wire.
3. Then you debated whether the copper wire would support 100 amps, which is the same breaker you would have needed for the aluminum wire.
Yes, and when I discovered I could not afford 100-amp copper, I settled for the #4 that will easily carry all the current my existing 60-amp breaker will allow through.
4. Now you are sticking with the 60 amp breaker which does not need the same wire as the 100 amp one would have.
Yes.
5. Now you say you have the 100 amp wire and the conduit, so why are we still discussing it.
Other than for the sake of some folk's desire to trash me or whatever, I have absolutely no idea! My questions have all been answered:
Three strands of #4 copper inside 1" EMT as a ground will easily carry 60 amps for 50' to my attached workshop's subpanel and be completely legal here where I happen to live.
6. Since there is little possibility that you will ever reach the 240 v, 60 amp plateau, why worry about oversizing the wire?
I was not actually worrying about that, but at least now I know the wire is quite sufficient.
peteferrell
03-10-2013, 12:57 PM
Dear Sir,
I am a licensed Master Electrician. Funny you are asking this question as I am currently adding a 100 ampere sub-box in my own workshop which is also about 50 feet from my main box. I already had some 2 gauge alum. twisted duplex wire taken down from a power drop. First let me say that if you can afford the copper wire, then that is your best bet. Second, if you can't afford the copper wire in your project budget, then the alum. wire is fine. Just keep in mind the alum. wire does not conduct as well as the copper so we must treat it differently. Since I already have the #2 alum. I'm going to use it myself. When using alum. wire you must remember it will emit more heat at full load than the copper. There fore up size your non-metallic conduit (PVC) on size to allow more room for the wire to "breath." I choose to use 1 1/2 PVC conduit. The number of turns doesn't matter as long as you have wire pull access along the way. Never put more than 270 degrees of turns under a floor or underground as you will not be able to pull wire through it. #2 Alum. is rated at 124 amps of current in a raceway or conduit. When I design and build anything electrical, I always try to design the equipment to never run at more than 80% full load on the amp rating of the materials. In other words, if the wire is rated at 124 amps, then a 100 amp breaker feeding the wire is perfect. Be sure to drive an 8 foot copper ground rod at the new sub-box. You only bond the neutral and ground at the main box. All sub boxes should have the neutral and ground buss bars separate from one another. Just remember the main job of the breakers is to protect the wire and equipment down stream from being over loaded which could cause fire. Never use a larger breaker than the wire or equipment it is feeding is rated at. Even better, don't exceed the 80% load factor and you will never have problems kicking breakers. Also when using alum. wire don't forget the Anti-ox grease in the wire connection points. Alum. expands more than copper when it heats up, the grease will help insure a good non-oxidized connection. I hope this helps!
quote; #2 Alum. is rated at 124 amps of current in a raceway or conduit.
My book says 3 #2 alum in a conduit is limited to 75 amps.