fbhwt
Electrical Systems Inspector
- Location
- Spotsylvania,Virginia
- Occupation
- Electrical Systems Inspector
Why is aluminum conduit used? I have good idea, but would like a more knowledgeable answer.
High frequency wiring
- Thread starter fbhwt
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brian john
Senior Member
- Location
- Leesburg, VA
when 400 HZ was the main frame standard I knew this off the top of my head...Brain and Brian are aging I think/know.
I believe it is because ferrous conduit with it magnetizing properties can have thermal issues due to inductance.
I believe it is because ferrous conduit with it magnetizing properties can have thermal issues due to inductance.
Weight, cost, ratings
Weight, cost, ratings
The above is true. Hysteris losses in steel, increasing conductor heating slightly.
Aluminum conduit is approximately 1/3 the weight of steel, likely easier to install. Better thermal conductivity and heat dissipation (I believe)? Aluminum might be better suited than steel in certain corrosive atmospheres. However less strength per volume. Though I don't know how it forms, you might have to be more careful with bends.
Weight, cost, ratings
The above is true. Hysteris losses in steel, increasing conductor heating slightly.
Aluminum conduit is approximately 1/3 the weight of steel, likely easier to install. Better thermal conductivity and heat dissipation (I believe)? Aluminum might be better suited than steel in certain corrosive atmospheres. However less strength per volume. Though I don't know how it forms, you might have to be more careful with bends.
I agree with Brian and dinkelja. If you do the "advanced level" voltage drop formula, it proves this out. Below is from an earlier post...
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In regard to voltage drop, at a reasonable PF (85%) we can use the following information -
Standard chart usage (tables 8 and 9) will get you the following formula -
Q as a Multiplier
For ac dircuits, the dc Resistance Constant (K) must be adjusted for the effects of eddy current and skin effect. The Q-Factor multiplier is calculated by dividing the ac resistance (chapter9 table 9) by the dc resistance (chapter9 table 8.) as listed in the NECode. Eddy currents and skin effect are insignificant for conductors No. 1/0 and smaller and their effects can be ignored.
Here is a q factor table -
Size COPPER ALUMINUM
AVG ... PVC.......AL.......STEEL... PVC.......AL..... STEEL
MCM - Conduit Conduit Conduit Conduit Conduit Conduit
2/0 -- 1.0341 1.0341 1.0341... 1.0062 1.0062 1.0062
3/0 -- 1.0052 1.0704 1.0313... 1.0317 1.0317 1.0317
4/0 -- 1.0197 1.1019 1.0362... 1.0000 1.0000 1.0000
250 -- 1.0097 1.1068 1.0485... 1.0035 1.0626 1.0153
300 -- 1.0256 1.1422 1.0489... 1.0042 1.0749 1.0184
350 -- 1.0354 1.1717 1.0627... 1.0083 1.0909 1.0413
400 -- 1.0280 1.1838 1.0903... 1.0201 1.1153 1.0397
500 -- 1.0465 1.2403 1.1240... 1.0142 1.1321 1.0613
600 -- 1.0748 1.3084 1.1682... 1.0198 1.1615 1.0765
--------------------------------------------------------------------------------
In regard to voltage drop, at a reasonable PF (85%) we can use the following information -
Standard chart usage (tables 8 and 9) will get you the following formula -
VD=Q x K x I x D
CM
CM
Q as a Multiplier
For ac dircuits, the dc Resistance Constant (K) must be adjusted for the effects of eddy current and skin effect. The Q-Factor multiplier is calculated by dividing the ac resistance (chapter9 table 9) by the dc resistance (chapter9 table 8.) as listed in the NECode. Eddy currents and skin effect are insignificant for conductors No. 1/0 and smaller and their effects can be ignored.
Here is a q factor table -
Size COPPER ALUMINUM
AVG ... PVC.......AL.......STEEL... PVC.......AL..... STEEL
MCM - Conduit Conduit Conduit Conduit Conduit Conduit
2/0 -- 1.0341 1.0341 1.0341... 1.0062 1.0062 1.0062
3/0 -- 1.0052 1.0704 1.0313... 1.0317 1.0317 1.0317
4/0 -- 1.0197 1.1019 1.0362... 1.0000 1.0000 1.0000
250 -- 1.0097 1.1068 1.0485... 1.0035 1.0626 1.0153
300 -- 1.0256 1.1422 1.0489... 1.0042 1.0749 1.0184
350 -- 1.0354 1.1717 1.0627... 1.0083 1.0909 1.0413
400 -- 1.0280 1.1838 1.0903... 1.0201 1.1153 1.0397
500 -- 1.0465 1.2403 1.1240... 1.0142 1.1321 1.0613
600 -- 1.0748 1.3084 1.1682... 1.0198 1.1615 1.0765
tallgirl
Senior Member
- Location
- Glendale, WI
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- Controls Systems firmware engineer
Aluminum's lower strength means you have to be more careful with bends of all sorts. Aluminum is great stuff when you need the lighter weight, but it's a pain to work and weld, even if it's a lot easier to cut into pieces and carry around.
Mike Holt had a newsletter out recently on this...
Aluminum is the most abundant of all metals and is extracted from bauxite. Technical discussions and articles about the use of aluminum vs. copper have been published in the electrical industry for many years. The objective of the following document is to provide the reader with information by which they are able to make a more informed decision given a choice between the two materials in electrical equipment.
Click here to read the paper titled Aluminum ? The Other Conductor, written by Bob Yanniello with Eaton Electrical Inc....
Misconceptions - What are the Facts?
The following misconceptions have led to the perspective that aluminum is an inferior conductor to copper:
Misconception #1 - Many electrical equipment manufacturers have completely eliminated AL conductor options from some of their offerings, which is evidence that AL is an inappropriate conductor for some electrical work.
Misconception #2 - It is common knowledge that AL is a poorer conductor of electric current because it has higher resistance than CU.
Misconception #3 - The public is aware that of the problems that resulted during the late 60's and early 70's when the industry introduced AL residential wiring, thus AL must be inferior since it was replaced by CU.
Misconception #4 - The public knows that AL is less expensive than CU, thus CU must be better.
Be an urban legend destroyer...read the article!
The comments in the commentary section are good too.
Aluminum is the most abundant of all metals and is extracted from bauxite. Technical discussions and articles about the use of aluminum vs. copper have been published in the electrical industry for many years. The objective of the following document is to provide the reader with information by which they are able to make a more informed decision given a choice between the two materials in electrical equipment.
Click here to read the paper titled Aluminum ? The Other Conductor, written by Bob Yanniello with Eaton Electrical Inc....
Misconceptions - What are the Facts?
The following misconceptions have led to the perspective that aluminum is an inferior conductor to copper:
Misconception #1 - Many electrical equipment manufacturers have completely eliminated AL conductor options from some of their offerings, which is evidence that AL is an inappropriate conductor for some electrical work.
Misconception #2 - It is common knowledge that AL is a poorer conductor of electric current because it has higher resistance than CU.
Misconception #3 - The public is aware that of the problems that resulted during the late 60's and early 70's when the industry introduced AL residential wiring, thus AL must be inferior since it was replaced by CU.
Misconception #4 - The public knows that AL is less expensive than CU, thus CU must be better.
Be an urban legend destroyer...read the article!
The comments in the commentary section are good too.
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