Copper vs aluminum on large jobs

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When the time comes to actually place the order, it is worth double checking the prices of alternative materials, especially the weird stuff that you know will be more expensive.

I was once about to press go on some 12/3 NM, and on a lark check the price of 12/3 MC. Yup, more expensive. Then 12/3 MC stranded. _Cheaper_ then the NM. I prefer MC, I prefer stranded. Guess what ended up getting used :)
 
infinity said:
Aluminum conductors still suffer from the stigma of being less reliable than copper. If you tell the designers I want the best possible materials regardless of cost then copper wins every time. In my experience most of the failures with aluminum stem from the terminations. If you can mitigate those failures with crimp terminals, anti-ox paste and proper torqueing then aluminum is certainly better in large conductor sizes if you want to save money.
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Crimp on terminals as opposed to terminating on a lug?
 
One thing to keep in mind is the potential impact on the duct sizes if there is a lot of underground duct bank. I've only been peripherally involved with duct banks so I have no idea how sensitive their cost might be to conductor size.
 
electrofelon said:
Is that pretty common to submit a bid, but with it say something like, "I can install aluminum conductors instead and it will be $10,000 less...."?

Just curious about all this, I do all my own design, fortunately, and rarely have to install someone else's.
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Or if you are in similar situation as I am often in, the so called "bidding" isn't in accordance to a specific electrical plan, but rather based on a general floor plan and maybe a general listing of some major items that are known that might have a significant impact on the electrical construction, still with a lot of minor details being unspecified though. In those situations you do need to include wording to tell them exactly what your price includes and what might be options but possibly will change the price. Many these people don't know what they want until a suggestion is made to them or maybe know some of what they want but don't realize what options all can go with it.
 
Little Bill said:
Not my job, but one of my friends was pricing for a job and found he could get #6/3 NM CU cheaper than #4 SER.
My take on this is everyone was jumping off the copper band wagon and buying Al. Now the Al industry has adjusted their price to near copper since the demand is there. I don't know of, or heard of, any reason for Al to have made such a jump. I think it is just "because they can"!
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The plastics used in insulation for both have jumped in price as well
 
infinity said:
For the past 35 years for us it has always been copper first. In the past 3 years we're starting to see designs where aluminum is being substituted for copper. IMO larger aluminum conductors like 600 and 750 kcmil with crimp on terminals are better than copper even when the copper uses less labor intensive mechanical lugs because it's so much easier to work with.
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Why would AL use crimp on and CU use mech?
 
infinity said:
Aluminum has a much higher expansion rate than copper so the quality of the terminations become more critical. By crimping on a lug filled with anti-ox there is almost no chance that the connection between the lug and the terminal will fail.
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Would crimp on lugs be attached to bus already or you would crimp it then attach to bus?
 
No they're removed before being crimped. The procedure goes like this: the lug is installed on the bus, the conductor is inserted and a mark is made to note the orientation. The bolts are removed , it's crimped and then reinstalled.
 
infinity said:
No they're removed before being crimped. The procedure goes like this: the lug is installed on the bus, the conductor is inserted and a mark is made to note the orientation. The bolts are removed , it's crimped and then reinstalled.
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Some lugs come already installed on the bus I believe.
so the lug is removed ….crimped when removed then reinstalled. Why would you want the lug already in the bus? Just another step to remove.
 
Alwayslearningelec said:
Some lugs come already installed on the bus I believe.
so the lug is removed ….crimped when removed then reinstalled. Why would you want the lug already in the bus? Just another step to remove.
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The lugs are installed for transport. Also on larger equipment/larger projects the lugs will get placed in the correct section of gear. Also ideally will be coordinated with a one line diagram so the proper number of sets and size wire used is accurate. I have been in a job where the GC purchased all service and distribution panels. Few of the lugs both crimp and mechanical were correct.
 
Alwayslearningelec said:
Some lugs come already installed on the bus I believe.
so the lug is removed ….crimped when removed then reinstalled. Why would you want the lug already in the bus? Just another step to remove.
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Typically because of the spacing between the lugs you cannot get the crimper head around the barrel to crimp it without first removing it. Take a look at the photo:

IMG_20170426_135232.jpg
 
As a design build contractor, I always start with copper to open the door for VE item of AL feeders. I will never offer up a AL feeder if I feel the customer is in the industrial setting or a building that is going to have a lot of motors and high loads at intermittent times. The reason being in my head with my knowledge, I love the idea of the cost savings (which isn't much anymore), but the conductor properties of AL vs CU in the heating and contraction of the wire. I know it isn't much, but with these customers that are looking at investments of buildings over 15-30 years I want to make sure that feeders are going to withstand that longevity. I know they all will, but a customer that is budget conscious and looking at bottom dollar I give them the options, pros and cons, and let them make the decisions. Then its off my chest and I can sleep better. Ultimately if it is strictly a load consisting of lights, HVAC, computers, etc....I'll always offer the AL as a cost savings and typically it is accepted. I save this for an avenue of the customer knowing we are working for them and we going to be extremely diligent in getting within their budget as needed. BRANCH CIRCUITING #1 AND SMALLER IS ALWAYS CU, just the way I run my shop.
 
infinity said:
Typically because of the spacing between the lugs you cannot get the crimper head around the barrel to crimp it without first removing it. Take a look at the ph
infinity said:
Typically because of the spacing between the lugs you cannot get the crimper head around the barrel to crimp it without first removing it. Take a look at the photo:

View attachment 2563964
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Very clean and nice install! Great work!
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electrofelon said:
Is it a government project or large corporate entity where they don't care?
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The government has its own design standards called "Unified Design Criteria." UFC 3-520-01, "Interior Electrical Systems," requires CU for AWG #6 or smaller, and allows AL (of equivalent ampacity) for #4 and larger. Nevertheless, some military installations publish their own criteria, and some of those forbid AL.

The UFCs are public domain and can be found at WBDG.ORG (i.e., Whole Building Design Guide).
 
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