Is aluminum illegal if copper is spec'd?

[George Stolz]

Suppose a soft start for a heap'um big'um (or so the nameplate says) 3? motor is specified to be fed with a single run of 500 MCM CU conductors.

If the installer used two parallel runs of 350 MCM AL instead (seperate conduits), would that constitute a violation of the installation instructions?

If the soft-start folks said that the aluminum conductors were the cause of a damaged soft-start, is there any truth to their claim?

Assume all terminations were made up correctly, tight, etc.

I would assume they're off their rocker, but I'm no authority on this matter. Unfortunately, some people expect a lot from me. So y'all are gonna need to fill in the gaps. I appreciate all replies, thanks.

 

[bdarnell]

Re: Is aluminum illegal if copper is spec'd?

If the installer used two parallel runs of 350 MCM AL instead (seperate conduits), would that constitute a violation of the installation instructions?

I'd say yes. If 500 kCMIL CU was specified in the instructions and the installer used 350 AL instead, he didn't install it per the manufacturer's instructions.

If the soft-start folks said that the aluminum conductors were the cause of a damaged soft-start, is there any truth to their claim?

All things being equal, I see no reason how anyone could claim that aluminum conductors by virtue of their composition or current carrying ability were the cause of any damage. That's assuming all connections were made correctly and the terminations were rated for AL.

 

[charlie b]

If the installer used two parallel runs of 350 MCM AL instead (separate conduits), would that constitute a violation of the installation instructions?

No. But that isn't the question you intended to ask. It isn't an issue of installation instructions. But it would be a violation of the specifications. That is a contractual issue, and a matter of dollars to be discussed between the owner and the contractor.

If the soft-start folks said that the aluminum conductors were the cause of a damaged soft-start, is there any truth to their claim?

None whatsoever. They are shooting blindly, hoping to hit something, hoping to get someone else to pay for the repairs.

There are only two ways in which aluminum conductors would impact the operation of the system differently than would copper conductors.

One has to do with their respective ampacity. Looking at Table 310.16, it is clear that 500 MCM copper has a lower ampacity than a pair of 350 MCM aluminum. So the aluminum is better, from that perspective.

The other has to do with their respective impedance. This is a bit trickier. First look at Table 8. The DC resistance of 500 MCM copper (.0258 ohms/kFT) is lower than that of a pair of 350 MCM aluminum (half of .0605, or .0303 ohms/kFT). So it may seem that the aluminum would give a worse voltage drop, resulting in a lower voltage available to the motor, and perhaps having an adverse impact on the starter.

However, this is a motor, and a big motor at that. You need to include the total impedance of the conductors. So we look at Table 9. The "effective Z" of 500 MCM copper (.043 ohms/kFT in PVC, for example) is higher than that of a pair of 350 MCM aluminum (half of .073, or .0365 ohms/kFT).

Overall, this set of aluminum conductors does a better job of supplying current to the motor than the specified conductors would have done (i.e., it has a lower value for voltage drop along the conductors).

 

[haskindm]

The manufacturer gives you installation instructions which must be followed in order for them to cover the item under warranty. This is probably not an NEC issue. The NEC says that you must follow the instructions "included with the listing and labelling". You must find out if the item was UL listed (or other testing agency) only for the use of copper conductors. If so, you are in violation of the NEC. If not , then you did not follow the manufacturers installation and they MAY deny warranty coverage because of it. I agree that the AL conductors are PROBABLY not responsible for the failure, but it is a loophole that the manufacturer can and will use. The installer took a gamble and decided to save a few bucks by using AL conductors. In this case it was a bad gamble because manufacturer can base denying warranty because of it. In other words, the installer is left holding the bag. You are better off following the instructions.

 

[charlie b]

. . . (the installer) did not follow the manufacturers installation and they MAY deny warranty coverage because of it.

Good point.

I believe the use of aluminum could not have caused the damage. But that may prove to be, in the words of a wise former boss, "true, but irrelevant."

 

[steve66]

If the terminations for the motor wern't listed for 2 sets of 350KCM alumnium wire, than I think you are out of luck. I think alumnium has a higher "contact resistance" than copper. So where you terminated the wires, it would get hotter than if you used the 500KCM copper. This is a whole separate issue than the wire size or the ampacity of the wire.

Also, if the terminations weren't listed for two sets of wire, you may have a similar problem with less surface area or less contact pressure than necessary on the wire.

If the terminations were right on the drive, I could see it causing more heat and being a real problem.

Steve

 

[marinesgt0411]

also were the terminations listed for AL or CU or both

 

[George Stolz]

But it would be a violation of the specifications. That is a contractual issue, and a matter of dollars to be discussed between the owner and the contractor.

In this case, as outrageous as this may sound, the spec's (to my knowledge) started with a one-line sketched out on a 8.5x11 sheet of paper, and didn't progress much beyond that, I don't believe. Just a guess on my part.

None whatsoever. They are shooting blindly, hoping to hit something, hoping to get someone else to pay for the repairs.

That's what I was thinking.

The installer took a gamble and decided to save a few bucks by using AL conductors. In this case it was a bad gamble because manufacturer can base denying warranty because of it. In other words, the installer is left holding the bag. You are better off following the instructions.

I don't believe it was so much a gamble, as a deliberate decision to use aluminum conductors because the same (or better) quality could be had with aluminum, given the copper prices.

I don't believe the owner was trying to "sneak something past the customer", is what I mean. This job was actually 'cost-plus', which I didn't know was in my boss' vocabulary. :lol: He would have insisted on copper conductors if anyone realized that it was "copper exclusive".

So where you terminated the wires, it would get hotter than if you used the 500KCM copper. This is a whole separate issue than the wire size or the ampacity of the wire.

Can you give more detail on this? I don't understand.

also were the terminations listed for AL or CU or both

I assume they were CU/AL.

Thanks to all for the replies.

 

[iwire]

George I also agree with much of the above responses.

Most of our jobs are specified copper only we would never install AL when the specs say otherwise.

If the equipment instructions ask for copper AL would not even be a passing thought.

We are professionals and we install per the instructions.

If at any point this soft start releases it's factory installed smoke the factory will deny responsibility due to not following the instructions.

I think Charlie summed it up nicely

I believe the use of aluminum could not have caused the damage. But that may prove to be, in the words of a wise former boss, "true, but irrelevant."

Now as a side subject....money.

Do you not make money selling material?

If your mark up is 25% than would you not be better off installing copper?

I am not a money hungry person but we are in business and we are not talking about bilking grandma out of her nest egg.

Any place that needs a soft start of this size has to understand the costs of doing business.

We recently replaced a 400 amp I-Line breaker in a office building, it had a high AIC rating. I believe our cost was above $2000.

Should we have offered to installer a lower rated rated breaker to save them a few bucks?

Should we have sold the breaker at our cost just because it cost a lot?

Making money is not a crime, install copper and make money doing it.

JMO, Bob

 

[petersonra]

Re: Is aluminum illegal if copper is spec'd?

I would suggest a couple of things.

1. There is a difference between a specification and installation instructions. The specification is part of the contractual obligation between the owner and the EC, and may be stricter than the installation instructions.

2. It seems unlikely that the use of AL conductors would damage a soft starter.

3. It is possible the manufacturer of the soft starter used terminals that are not rated for AL.


4. It is possible the assembly is listed under UL508a and the manufacturer has chosen to make a nameplate and instructions up that is more restrictive than necessary so they only have to have one nameplate for field conductors. That is what we do.

Note the difference in the phrasing of (a) below versus (b), (c), and (d).

Clipped from UL508a

54.11 All field-wiring terminals shall be marked with one of the following:
a) "Use Copper Conductors Only" for terminals intended for connection only to copper wire;
b) "Use Aluminum Conductors Only" for terminals evaluated only for connection to aluminum wire;
c) "Use Copper or Aluminum Conductors" or "Use Copper, Copper-Clad Aluminum, or Aluminum Conductors" for terminals evaluated for either copper or aluminum wire; or
d) "Use Copper or Copper-Clad Aluminum Conductors" for terminals evaluated for connection to either copper or copper-clad aluminum wire.

 

[james wuebker]

If your not sure call the manufacture and ask. Have them send you an e-mail verifying it's OK to use. If not, then use the copper.
Jim

 

[George Stolz]

I was thinking about this, let's try another angle at this:

• A 300 HP 3? motor has an FLC of 361 amps.
• We must upsize these conductors by 125%, correct?
• If this is done, no adjustment for continuous duty is necessary, correct?
• So the conductors must be sized for the adjusted 451 amps.
• When sizing the conductors, the engineer errs on the one-line, and calls for conductors for 361 amps. [2 (3 x 250 MCM AL)] at 410A.
• For discussion's sake, the electrician notices the "CU Only" sticker (not the undersized conductors), reviews the contract and diagrams, and installs per plan.
• Some of the smoke escapes from some equipment.
• Equipment supplier refuses warranty, because AL was used, and the conductors were undersized (should have been parallel CU 250 MCM minimum).

Who made the biggest mistake? Who has the greatest culpability?

Do the stamped plans trump the NEC (special ampacity calcs are allowed under engineering supervision that I cannot understand ), so the undersized conductors spec'd by the engineer belong to the engineer? Or should the EC stop work and get an RFI from the designer?

The contract documents likely contained language to prevent the use of copper to increase the price of the installation once under way, since the bill was to be directly related to cost.

Note: This information is not to be used in any proceeding, speak freely. I'm looking at this as a real world experience to learn protocols and procedures from; I spent a grand total of four hours at that job, so I can't be blamed for anything. Therefore, I can say with a (somewhat) clear conscience, I don't really care who foots the bill, I didn't do it.

I'm interested in never getting whipped by a similar predicament myself, someday.