200A Aluminun Feeder

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hillbilly

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I've got a question and want to get the opinion of the learned members of this forum.

I'm getting ready to tun a 200A feed from a outside main to a inside MLO panel. I can get a good deal on some 4/0 aluminun quad plex but I have a few questions.
The cable has two 4/0, one 2/0 and one #4 for the equipment grounding conductor. The conductors are rated USE/RHH/RHW. The feeder will be 28 feet long. Ordinarily I would use a bigger grounding conductor although 250.122 allows #4 aluminum for 200 amps.
Would you use it? If not, why not.
I normally use copper inside a home, but you know how it is with prices these days.
steve
 
If these are individual conductors requiring conduit, I would think that SER would be more economical.
 
Hillbilly , aluminum is all that some peolpe use for feeders unless spec'ed otherwise. Your combination for a 200 amp service in a residential application seems good also.
Don't forget the de-ox or penatrox at the terninations though.
 
LarryFine said:
If these are individual conductors requiring conduit, I would think that SER would be more economical.
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Yes it would, but I'm commited to conduit (2" pvc).
I'ts just that I normally use a bigger grounding conductor. I'm curious if if will affect the fault clearing time of the larger (Main and 60A) circuits. I don't want to comprise quality and safety for a few bucks....but...if I don't need it (a larger ground), I don't want to buy it.
steve
 
hillbilly said:
I'm curious if if will affect the fault clearing time of the larger (Main and 60A) circuits. I don't want to comprise quality and safety for a few bucks....but...if I don't need it (a larger ground), I don't want to buy it.
steve
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Since the circuit is only 28 ft, the impedance of #4 AL = 0.0128 ohms. The impedance of 1/0 is 0.0056 ohms. The numbers are so small a larger conductor would not make any difference.
 
I'm also showing Z = 0.014 for that #4 al EGC, with a GF ASCC of 8403A, over 42x the 200A main OCD --more than enough to instantly trip the breaker --.

Also see a #6 al GEC requirement for that panel, if aluminum is OK for GEC's? Bare aluminum can't contact the soil, can it?

Perhaps the biggest issue is getting CU/AL rated terminals between the SVC & panel?
 
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hillbilly said:
Would you use it?
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The 2 AWG AL will be fine for the EGC.

hillbilly said:
I'm curious if if will affect the fault clearing time of the larger (Main and 60A) circuits.
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The fault clearing times of the 60 and 100s are likely to be faster than the 15 and 20s. The larger circuits use larger circuit conductors and will provide higher fault current levels tripping the breaker faster.

A ground fault typically trips the instantaneous portion of the breaker.

The instantaneous trip setting is pretty much the same on breakers 15 through 100.

drg said:
Don't forget the de-ox or penatrox at the terninations though
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Good idea but keep in mind it is not a NEC requirement unless the manufacture requires it.

ramsy said:
Perhaps the biggest issue is getting CU/AL rated terminals between the SVC & panel?
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That should not be an issue, any of that equipment will be shipped with AL/CU terminals.
 
drg said:
Don't forget the de-ox or penatrox at the terninations though.
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Why?
iwire said:
Good idea but keep in mind it is not a NEC requirement unless the manufacture requires it.
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I agree

I have not used the junk for over twenty years. Read closely 110.14 then look up the third party listing of the terminal.
 
In the interest of keeping an open mind, I guess it is possible that deox on AL conductors is an exercise in futility but I do'nt think so.

How many of us have opened a panel to see the aluminum conductors caked with white powder caused by oxidation where no oxide inhibitor was used.

The Ilsco company claims their product prevents the formation of oxides by sealing out air. I am not a chemist but there maybe something to this.

I would have to agree with Bob on this one. No code requirement but its use is a good idea.
 
Mike you asked why?

Probaly the main reason is , that's what I was taught .

I have read 110.14 and see what your getting at, never gave it much thought before .

Well in the mean time it looks like Im stuck using it everytime we use aluminum for feeders and i don't really see a problem with putting it on anyways , besides the guy who signs my paycheck insists on it.

Thanks for your thoughts though.

John
 
buck33k said:
In the interest of keeping an open mind, I guess it is possible that deox on AL conductors is an exercise in futility but I do'nt think so.

How many of us have opened a panel to see the aluminum conductors caked with white powder caused by oxidation where no oxide inhibitor was used.

The Ilsco company claims their product prevents the formation of oxides by sealing out air. I am not a chemist but there maybe something to this.

I would have to agree with Bob on this one. No code requirement but its use is a good idea.
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Out here on the left coast some jurisdictions (usually on the coast) have local ammendments requiring anti-oxidant compound on AL connections. One that I know of even requires stainless steel ground rods (expensive). Back in the days when AL conductors used very soft alloy there were all kinds of problems due to under/over torquing, corrosion etc. The newer alloys are almost as forgiving as CU conductors. Also if you do use the inhibitors the NEC requires you to follow the manufacturers instructions which may involve cleaning and wire brushing the conductor before you apply the compound. Most installations I have seen recently just have the compound slopped on the conductor which is probably a violation of the NEC.
 
I use anti-oxidant on every connection on the service copper or aluminum.
I also remove the set-screws and apply it to the threads.
I had a ear break off a meter one time while I was trying to loosen a (corroded) set screw to change out a service entry cable. It was a real problem and required changing out the meter, which involved cutting the service loose, which involved calling the POCO, which wound up taking about 10 hours to get the power back on. The customer was ill.
If I can save someone else that headache, I will.
steve
 
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