Riser Diagram ALU Equivalent

[electriciansnet]

Hey everyone. I got to trim a little fat and have permission to supplement feeders with ALU.



I feel a little dumb for asking this but since I'm not using a tap box and I'm going straight from the LL disconnect to the new Panel 'A', is there any reason why I cant use 2 sets of 4/0 and, (1) #2 ALU THHN in the 3" EMT or do I need to stay at 75 degree and use #250 (I can have up to 13).
Is the deration factor of more than 3 CCCs prohibitive of either of these factors?

Note:
The job is 5 hours away in Miami and I have not seen the LL equipment so I'm not sure if rejection clips are applicable so I have to assume that I have to full rate the feeders at 400

 

[Smart $]

This appears to be an engineered project. While the NEC may permit what you are asking, you'll still likely have to coordinate with the engineer of record.

 

[electriciansnet]

Fair enough but which option makes the most sense? Value and application?

 

[Smart $]

Fair enough but which option makes the most sense? Value and application?

While aluminum conductors may "trim some fat" on the front end, the higher number increases pull set up and serving difficulty, plus distance and number of bends will factor into how much harder the pull will be. I'm not an estimator, but I can see possibly no end gain.

 

[electriciansnet]

Except for approximately 1/3 the cost of copper.

I'm going with ALU because I'm able to qualify it so ultimately the question is:

>Am I legally allowed to dual parallel 4/0 aluminum THHN in a 3" EMT with more than 3 current carrying conductors from this existing 350A source?
>Am I legally allowed to dual parallel 250 aluminum XHHW in a 3" EMT with more than 3 current carrying conductors from this existing 350A source?
> IF yes to both, which is better?

 

[iceworm]

Except for approximately 1/3 the cost of copper.

I'm going with ALU because I'm able to qualify it so ultimately the question is:

>Am I legally allowed to dual parallel 4/0 aluminum THHN in a 3" EMT with more than 3 current carrying conductors from this existing 350A source?
>Am I legally allowed to dual parallel 250 aluminum XHHW in a 3" EMT with more than 3 current carrying conductors from this existing 350A source?
> IF yes to both, which is better?

Just curious - what does "qualify it" mean.

As for your questions, the applicable code section is 310.15.3.a. You will also need to check for conduit fill (whoops you already did this)

Second edit to add: Also following S$ comments: Considering 9 conductors in the conduit, you may wish to perform an pull tension calculation. Be poor to rip the conduit off the wall, or damage the insulation - that would likely ruin your savings.

edit to add: Which option makes the most sense? Well, I would go with what Smart$ said.

ice

 

[pjholguin]

I concur with iceworm, have you done a cost comparison between cooper and Alu manhours not just material cost? What I have seen quite a
few times people only see what the material costs and the extra labor needed to complete the job...JMHO

Just curious - what does "qualify it" mean.

As for your questions, the applicable code section is 310.15.3.a. You will also need to check for conduit fill (whoops you already did this)

Second edit to add: Also following S$ comments: Considering 9 conductors in the conduit, you may wish to perform an pull tension calculation. Be poor to rip the conduit off the wall, or damage the insulation - that would likely ruin your savings.

edit to add: Which option makes the most sense? Well, I would go with what Smart$ said.

ice

 

[electriciansnet]

Qualify it meaning to stipulate it as a condition in our proposal and follow it up with an engineered letter if necessary. AKA cover our backs

Both quotes (actually line-items as part of a master quote) contain an extra 1000 in expenses just for clarity.

Quote 1: Furnish and install 150' 3" EMT w/ (4)#400 CU, (1) #3 CU $9327.29
$5466.46 material, 56 man hours labor
Quote 2: Furnish and install 150' 3" EMT w/ (8)#4/0 ALU, (1) #2 ALU $5279.77
$2458.21 material $47.68 man hours

I apologize if I misrepresented my question but come on guys- its kind of a no-brainer that if the contractor can get by with using aluminum the job cost is usually lower... profit higher. Additionally, aluminum conductors are about 25% of the weight their copper equivalent.

The question is: "Am I legally allowed to parallel x2 4/0 ALU with more than 3 current carrying conductors in the same raceway to obtain my 400A (350A) service? "

 

[Smart $]

$47.68 man hours

I fail to see how you come up with less man hours to install a greater number of conductors (assuming the "$" was a typo). Weight has very little to do with actual installation man hours.

The question is: "Am I legally allowed to parallel x2 4/0 ALU with more than 3 current carrying conductors in the same raceway to obtain my 400A (350A) service? "

You will derate your conductors to at least 80%, perhaps even 70% if the neutral is to be counted as a CCC.

Based on diagram, 400kcmil CU has an ampacity of 335A@75?C without adjustment and correction. To get the same or greater ampacity with paralleled aluminum, your looking at at least 335A/80%/2=209A....or at least (8) 300kcmil AL, 230A ea.@75?C. which will not fit the 40% area of 3" EMT.

If the calculated load is less than 2 x 205 (410) x 80% = 328A and no further decreasing adjustment and correction to ampacity, and neutral is not a CCC, you could drop to 250kcmil AL, which will barely fit in 3" EMT... so again you're looking at excess pull tension depending on number of bends.

 

[electriciansnet]

Yes $ was a typo and I didn't come up with the hours- my estimating software did.

The second part of your post does cover my answer and thank you very much!

 

[iceworm]

Qualify it meaning to stipulate it as a condition in our proposal and follow it up with an engineered letter if necessary. AKA cover our backs

Both quotes (actually line-items as part of a master quote) contain an extra 1000 in expenses just for clarity.

Quote 1: Furnish and install 150' 3" EMT w/ (4)#400 CU, (1) #3 CU $9327.29
$5466.46 material, 56 man hours labor
Quote 2: Furnish and install 150' 3" EMT w/ (8)#4/0 ALU, (1) #2 ALU $5279.77
$2458.21 material $47.68 man hours

I apologize if I misrepresented my question but come on guys- its kind of a no-brainer that if the contractor can get by with using aluminum the job cost is usually lower... profit higher. Additionally, aluminum conductors are about 25% of the weight their copper equivalent.

The question is: "Am I legally allowed to parallel x2 4/0 ALU with more than 3 current carrying conductors in the same raceway to obtain my 400A (350A) service? "

Yes - got your question - the first time.

And I am completely baffled by why you are not asking your engineer. What is going on with that. If you don't like him why would you think our unpaid advise, following an unseen set of specs, is better. It isn't - infact likely worth less.

Another curiosity question: Who are you going to get to supply this "engineered letter"? You?

Deleted: (rant about the evils of "Value Engineering unto Project Death)

We helped you get started with the code sections. You want to be the engineer of record - then you need to be able to figure this out. How else would you know the ghost engineering is correct?

ice

ps: I need to come up with an AFLA - "VEPD " just doesn't have any impact

 

[electriciansnet]

But Smart- If I go with 250 THHN ALU parallel x2?

 

[electriciansnet]

Just cool your jet iceworm! I came here to ask a legit question without getting a bunch of cocky arrogant flack!

 

[Smart $]

But Smart- If I go with 250 THHN ALU parallel x2?

You have to make sure the calculated load is not greater than the ampacity. You have to remember you're automatically facing at least an 80% reduction in ampacity due to the number of conductors in the raceway. Also leaves little room for additional loads in the future.

 

[electriciansnet]

Understood. Thanks!

 

[iceworm]

Just cool your jet iceworm! I came here to ask a legit question without getting a bunch of cocky arrogant flack!

jets cooled

However, in a non-adversarial, non-cocky, non-arrogant, respectful manner, I am still curious about why you are dodging the question about why you don't want to talk to the engineer of record.

just a worm (today only I hope)

 

[electriciansnet]

Hello Ice.
I had walked away from this and just now saw it.

In this case its like this:
I needed to get my quote down to a certain number and the awarded GC, who I have history with, gave his blessing to use Aluminum.
The relationship with the engineer of record in this case is between the GC/owner and that engineer.
Once the GC that has hired me say"Go Aluminum" I'm covered a practical sense because I qualified it in my quote by stipulating aluminum feeders only- per this GC.

I realize that this opens the door for much conversation about all sorts of things related to responsibility but the most likely result will be the application of aluminum feeders without any further discussion.

As for the application:
I had emailed my electrical engineer friend at the same time as posting the question and here was his response:

" If you are going to use the 350A disconnect (assuming the panel is M-LUG with 400A Bus), the calculated load is under 350A, and voltage drop is not an issue, then you can use the parallel 4/0 AL conductors with the #2 GRND(total 360A).

If you are going to put in a 400A Disconnect, then use the parallel #250 AL conductors with the 1/0 AL GRND(Total 410A).
"

 

[Smart $]

...
I had emailed my electrical engineer friend at the same time as posting the question and here was his response:

" If you are going to use the 350A disconnect (assuming the panel is M-LUG with 400A Bus), the calculated load is under 350A, and voltage drop is not an issue, then you can use the parallel 4/0 AL conductors with the #2 GRND(total 360A).

If you are going to put in a 400A Disconnect, then use the parallel #250 AL conductors with the 1/0 AL GRND(Total 410A).
"

I have to assume you did not mention to your engineer friend that your parallel conductors were in the same conduit, as it appears he made no consideration for derating of more than three current-carrying conductors in a raceway.

The matter regarding the engineer of record has to do with plan review, approval with his stamp on it, and review's approval for construction. Whomever installs the electrical is obligated to do so within plan and project specifications, or otherwise seek and get a deviation through the engineer and/or approved-for-construction revision through plan review. It is not simply a matter of whether the deviation from plan is NEC compliant or not.

 

[iceworm]

Hello Ice.
I had walked away from this and just now saw it.

...the most likely result will be the application of aluminum feeders without any further discussion. ...

Yes, that was my guess.

ice