Are there any PROBLEMS with using compact ALUMINUM FEEDERS for MOTOR LOADS?

[mike abbott]

I am wiring a new school that allows for compact-stranded aluminum alloy wiring for feeders.

However, the engineer is arguing that aluminum cannot be used for any feeders that have motor loads attached.

Has anyone ever heard of a reason why this would cause problems?

Thanks

 

[chris kennedy]

What is the EE's argument.? Al is used for feeders with motor loads all the time.

Edit:: This is a school, check the specs.

 

[skeshesh]

The only downside I can think of is that the terminals for most devices are made of copper and terminating AL may effect the lifetime adversly but I dont think this is a big issue at all. I don't know of any specific issues with motors though the prior statement is pretty general.

 

[BJ Conner]

Aluminum cables are stiffer and engineers sometime don't know to order motors with extra larger peckerheads.

 

[TOOL_5150]

Aluminum cables are stiffer and engineers sometime don't know to order motors with extra larger peckerheads.

I have always known copper to be much more rigid and difficult to deal with. Especially the larger sizes.

~Matt

 

[hurk27]

I don't know if this would be a reason, but with starting current much higher then other types of load might play into early failure with the temporary over loading while a motor starts up maybe stressing the connections from heat?

Just a WAG but the only thing I can think of?

 

[nakulak]

I would bet that the engineer has experienced motors that vibrated the alum connections loose prematurely.

 

[steve66]

All valid concerns. But IMO, if the drawings and specs allowed alumnium feeders, you should be entitled to a change order for substituting copper.

 

[haskindm]

The OP states that aluminum is going to used for FEEDERS. The individual motor branch circuits will probably be copper, so the vibration and motor termination arguments PROBABLY do not apply. Unless there is something in the specification that prohibit the use of aluminum conductors for feeders, the engineer is blowing smoke. I once had an engineer complain that there had not been "enough wires" installed in his building. After much inquiry we found out that he did not feel that he had enough grounded conductors. I explained that most of his branch circuits were installed as multi-wire circuits so he only had one grounded (neutral) conductor for every three "hot" conductors. He did not know what a multi-wire circuit was and swore it was a code violation. I had to copy the appropriate sections of the code to prove that it was code compliant. Many engineers (and electricians, for that matter) THINK they know what the code says and are surprised to learn what it really says!

 

[skeshesh]

The OP states that aluminum is going to used for FEEDERS. The individual motor branch circuits will probably be copper, so the vibration and motor termination arguments PROBABLY do not apply. Unless there is something in the specification that prohibit the use of aluminum conductors for feeders, the engineer is blowing smoke. I once had an engineer complain that there had not been "enough wires" installed in his building. After much inquiry we found out that he did not feel that he had enough grounded conductors. I explained that most of his branch circuits were installed as multi-wire circuits so he only had one grounded (neutral) conductor for every three "hot" conductors. He did not know what a multi-wire circuit was and swore it was a code violation. I had to copy the appropriate sections of the code to prove that it was code compliant. Many engineers (and electricians, for that matter) THINK they know what the code says and are surprised to learn what it really says!

Good point about the OP referring to feeders. I also agree completely with your other statement. I certainly try to keep an open mind when anyone (eng, techies, contractors, whoever really) tells me something I haven't heard of before. In any case back to the topic: so where does that leave us as far as the engineer's concern? The only possible reason I can think of to care about the material of a feeder that has motor loads somewhere down the distribution line is concerns about short circuit and transient effects. I don't know of any reason why AL would be a worse choice than Cu in that regard - would be great if anyone could confirm or elaborate.

 

[jdsmith]

How are the motor feeders going to be terminated in the makeup box at the motor? If you hypress crimp a lug onto the cable then bolt, vulcowrap, and 33 tape you should be fine, assuming you have the right crimp lug for aluminum and prepare the conductor properly.

 

[wireguy8169]

It almost sounds like the job was bid with AL conductors and now the EE is saying no go for motor loads? If its spec'ed the way he is saying then you really can't just charge for copper because you priced it on AL, now if it was not spec'd for CU. on the motor loads and you bid it with AL you should be able to use what your bid included and if they now say "oh we do not want AL on the motor loads" then a change order should be submitted....

Good luck with that...

 

[mayanees]

I think the safest way to handle Aluminum for motor circuits is to run it to a tapbox at the motor, or to a local disconnect, then continue to the motor in Copper.
The argument against aluminum for usage on motor circuits has to do with termination at the motor.
John M

 

[short circuit faulted]

Are the motor loads HVAC?

Are the motor loads HVAC?

We have had incidents not caused by the engineer but the HVAC folks saying they would not warranty units connectec to AL. In a school the only motor loads I can think of would be recirculating pumps on water heaters with circuits normally too small to apply OR heating and cooling units. If it is the later and the bid documents allowed compact aluminum conductors for those circuits (nomally the line is drawn at # 4 AWG here). Someone needs to clarify why you are not being allowed to use and if they continue pressing the issue without providing documentation as to why you cannot, then in my humble opinion you follow the advice given previously in regards to AL on line side of disconnect and copper on the load side - priced and accepted as a change order, provided you are in the clear with AHJ / EE

Have a great day all!