Steel vs Aluminum RMC

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mshields

mshields

Senior Member
Location
Boston, MA
I speced Rigid Galvanized conduit for an outdoor application. Contractor wants to substitute Aluminum RMC. Aside from the obvious metalurgical difference, what is the practical difference. I've never used it before nor been asked to make this substitute before?

Thanks,

Mike
 
infinity

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Given the difference in weight is one consideration when bending and installing it especially with larger size conduits. Also it won't rust.
 
C

charlie k.

Senior Member
Location
Baltimore, Md.
The downside is precautions should be taken where it is in contact with concrete or earth. We do a lot of Waste Water plants and use a lot of Aluminum conduit.

Charlie
 
G

G._S._Ohm

Senior Member
Location
DC area
And,

"The conduit may be coated to prevent corrosion by incidental contact with concrete. The extra cost of aluminum is somewhat offset by the lower labor cost to install, since a length of aluminum conduit will have about one-third the weight of an equally-sized rigid steel conduit."

I couldn't readily find a direct comparison between both types that goes into any detail. Here's an overview of several types:
http://en.wikipedia.org/wiki/Electrical_conduit
There's a footnote in this link that cites RS Means so you can closely estimate the difference in labor costs.

I'd think induction heating with aluminum conduit would be almost zero.
 
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R

realolman

Senior Member
Aluminum is waaayyyy nicer to use. Shinier too. I'd say it might be a little harder to pull the wires.... but it's still a lot easier to install.
 
don_resqcapt19

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
I use a higher labor rate for aluminum than I do for steel. It is much harder to work with in terms of threading and bending in my opinion.
 
M

muskrat

Member
Location
St. Louis, MO
mshields said:
I speced Rigid Galvanized conduit for an outdoor application. Contractor wants to substitute Aluminum RMC. Aside from the obvious metalurgical difference, what is the practical difference. I've never used it before nor been asked to make this substitute before?

Thanks,

Mike
Click to expand...

Lighter than galv. steel...to keep it from falling from the roof of the tunnel????
 
tkb

tkb

Senior Member
Location
MA
If you approve it, make sure they use Nolox or Penatrox on all of the threaded connections at couplings and terminations.
It will help with screwing together the sections and help prevent gauling of the threads.
 
K8MHZ

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
mshields said:
Is there a down side?
Click to expand...

1) Al is very expensive.

2) It takes some practice to bend properly. I was trained on it and the worst thing about it is that the spring back is different on each piece. Invest in a Chicago bender. The scrap generated from a hand bender or a sloppy 555 will be very costly.

3) It's much softer than steel and it doesn't take much to bend it after it's been installed.

4) Some specs require AL not to touch concrete so back straps have to be used.

For the folks doing the actual installation, if they can run AL well, it's great because it's light and takes less manual energy to bend. If they can't run it well they will hate it, take loads of time to put it in and generate lots of scrap.
 
K8MHZ

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
tkb said:
If you approve it, make sure they use Nolox or Penatrox on all of the threaded connections at couplings and terminations.
It will help with screwing together the sections and help prevent gauling of the threads.
Click to expand...

If this is in a food grade installation specs may require food grade thread lube. In the baby formula plant I worked in the lube was actually edible.
 
kwired

kwired

Electron manager
Location
NE Nebraska
infinity said:
Although this may be true, how is it related to using aluminum versus steel conduit?
Click to expand...


Maybe some places used aluminum gas pipe?

That is second time I seen an obviously unrelated post like that in a short time maybe something is not working quite right with the forum.
 
weressl

weressl

Esteemed Member
Location
Texas by the Gulf, geat crab, great shrimp
K8MHZ said:
1) Al is very expensive.

2) It takes some practice to bend properly. I was trained on it and the worst thing about it is that the spring back is different on each piece. Invest in a Chicago bender. The scrap generated from a hand bender or a sloppy 555 will be very costly.

3) It's much softer than steel and it doesn't take much to bend it after it's been installed.

4) Some specs require AL not to touch concrete so back straps have to be used.

For the folks doing the actual installation, if they can run AL well, it's great because it's light and takes less manual energy to bend. If they can't run it well they will hate it, take loads of time to put it in and generate lots of scrap.
Click to expand...

It is only expensive in areas that do not stock it otherwise.
Your thread cutter will last a lot longer than cutting steel.
 
ohmhead

ohmhead

Senior Member
Location
ORLANDO FLA
If you have a automatic oiler on your threaden mule you will need this cutting stuff called Blue its for alu conduit only it looks like windex its clean never any mess on pipe or your hands and it cools better then oil .

Regular cutting oil makes it look bad dirty and hand marks on conduit .

Get ready to change you pipe vise grips on you threader head vise if you have lots of alu conduit they make special ones just for alu conduit so it doesnt cut up the nice finish .

All the alu conduit ive seen is dull finish by the master bundle we by in bulk.


And they make yellow looking dope for you threads when you screw the lengths together dont use anything else or it will look like a mess they sell the correct alu pipe threading dope its yellow .

I dont buy this stuff my company does so sorry i can not give you a name .

We bend alu with 881 and a 555 bender no problem if you have alu shoes you bend alu with alu shoes not your regular rigid shoes thats why most folks have issues with big pipe .

If you have the proper tools you can make it look good and theres a few more tricks .

You can bend rigid alu 3/4 and 1 inch on a 50 gallon drum for long radi you can bend it around a tank it gives easy .

And it is safe it will dent but as far as acids and chemicals its a good application in a plant .

Now if you dont dope the threads it will not screw in correctly .

If you force it together it doesnt come apart ever .

Invest in a nylon band wrench lots of them no channel locks !

Good luck take care !
 
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