Garage Service Entrance

[1stYearElectrican]

Folks, I need a lil help in a question if you be so kind. I feel I know the answer BUT according to journeyman it was labeled it ok, Here is the case:

Installing a sub panel in a garage from the main panel in house. The conductors supplying the sub are thru PVC underground. The sub-panel is 100A and the main panel in house is a 200 amp service.

Here is what I believe is wrong, the conductors running thru the PVC and powering the sub panel are #4 AWG XPLE ALUMIMUM 300V. According to the tables this conductor is rated at 80-90 AMPS and will be supplying a 100A panel. These conductors can not handle 100A. Am I correct in this??

A friend of my Brothers from the power company gave him several hundred feet of #4 AWG XPLE ALUMIMUM 300V and assured him that it was ok to use it to supply a 100A panel. And on top of that an electrician also gave him the ok to use it. Is this really ok??

What i figured is that a #3 COpper awg would suffice or a bigger awg ALUM conductor to supply a 100A panel.

Is the power company guy and electrician right or do I need to do more deeper reading in the code?


The Panel will supply 8 floricent(spell?) lights, a 50 AMP welder and a oil/wood burner furance, 10 recepticles, 3 outdoor lights and a garage door opener.


Thanks

~FyE~

 

[stickboy1375]

Here is what I believe is wrong, the conductors running thru the PVC and powering the sub panel are #4 AWG XPLE ALUMIMUM 300V. According to the tables this conductor is rated at 80-90 AMPS and will be supplying a 100A panel. These conductors can not handle 100A. Am I correct in this??

Your conductors do not have to be able to handle 100amps, they do have to be able to handle the calculated load though. And where did you get the capacity of 80-90 amps for #4 AL? and which is it, 80 or 90?

 

[peter d]

A friend of my Brothers from the power company gave him several hundred feet of #4 AWG XPLE ALUMIMUM 300V and assured him that it was ok to use it to supply a 100A panel. And on top of that an electrician also gave him the ok to use it. Is this really ok??

It's OK for the Poco to use whatever size wire they choose because they are not under the NEC.

However, if you are using this under the NEC it is too small. And seeing that it's a poco product, it likely isn't marked, rated or otherwise allowed to be used under NEC applications.

 

[1stYearElectrican]

Maybe I misread the table, I do not have my code book at home to verify. What do you see for the amp rating of #4 XLPE alum?

I told my Bro the same thing, the POCO can do what they want they only got 1 boss and they are it.

Personally I would not use that size of wire to feed a 100A sub panel. Just needed to confirm if I what I told him was correct.

I stated that he would have to use alot of tools in the garage at the same time to cause the 100A breaker to pop, but the #4 alum wire jacket would melt first before poping breaker. The 100A panel is ample enough to run the garage but I'm afraid the feeders are not protected by the 100A breaker but under protected.


~FyE~

 

[Dennis Alwon]

I don't even see XLPE listed as a legal wiring method. Is it a valid install?

 

[peter d]

I don't even see XLPE listed as a legal wiring method. Is it a valid install?

Which is exactly why I said this above: And seeing that it's a poco product, it likely isn't marked, rated or otherwise allowed to be used under NEC applications.

 

[Dennis Alwon]

Which is exactly why I said this above: And seeing that it's a poco product, it likely isn't marked, rated or otherwise allowed to be used under NEC applications.

I guess I should have read all the responses first. :smile:

 

[Dennis Alwon]

A friend of my Brothers from the power company gave him several hundred feet of #4 AWG XPLE ALUMIMUM 300V

Let me put this in perspective-- The friend of your brother STOLE this wire from the power company and gave it to your brother.

Now-- because the panel is rated 100 amps it does not mean that it must be fed with a 100 amp feeder. I can feed the panel with a #6 if I like as long as I protect the panel accordingly.

I can only guess that XLPE is rated 90 C so at the 75C col. it is only good for 65 amps. As long as the load is less than that then you can protect the panel at 70amps.

 

[ElectricianJeff]

Installing a sub panel in a garage from the main panel in house. The conductors supplying the sub are thru PVC underground. The sub-panel is 100A and the main panel in house is a 200 amp service.


QUOTE]

Is this wire rated for damp locations?

 

[infinity]

You seem to have a few problems with this installation. First you'll need a conductor listed for wet locations. Second, you need a conductor that is rated for 100 amps in table 310.16 (assuming you wanted a 100 amp feeder). You may be able to use a smaller feeder to this panel if your calculated load is smaller than 100 amps. Bottom line is your current installation is no good. And for the record this is not a garage service entrance but a feeder.

 

[iwire]

A friend of my Brothers from the power company gave him several hundred feet of #4 AWG XPLE ALUMIMUM 300V

First problem.

XPLE is not listed in Table 310.13 so unless that cable has a dual listing it is a NEC violation to use that cable for any amount of current.

Second problem

At best and assuming the cable was dual listed the NEC rates 4 AL at 65 amps, you could use a 70 amp breaker.

This feeder does not qualify to use Table 310.15(B)(6)

and assured him that it was ok to use it to supply a 100A panel.

The power company guy could use that cable to supply a 100 amp service. He can do that as he is not working on a premises wiring system and the NEC does not apply to the power company.

What i figured is that a #3 COpper awg would suffice or a bigger awg ALUM conductor to supply a 100A panel.

In order to use a 100 amp breaker for this feeder at a minimum the NEC requires 3 AWG copper or 1 AWG aluminum

 

[1stYearElectrican]

Tell ya the truth this whole thing got me bugged!! I warned my Bro that I was sure that this #4 AWG Alum (XLPE) will not hold up to past 70Amps. I also was unable to find a listing for the ampacity of that conductor and found various ampere (55-90) on several Different types of #4 alum conductors.

BTW the conductor is marked or laser etched and that how I know what the size and type is.

Is this rated for Underground, Someone asked? Hell If I know for it is non existent in the code. Maybe it is in an older code book and that specific conductor is no longer used nor listed. Guess that why the PoCo uses, they bought it all up at rock bottom price ((FREE)) lol

Going to get my Bro to use a ladder and scope out the conductors that supplies his 200A service and see if they are the same size wire as he gonna use for the sub panel.

Oh btw, he had the old temp service still in his basement from when the house was being built so I open up the service box to see what size the breaker was, and behold a 100a breaker. The Poco attached the same #4 awg alum XLPE to his temp service. Kinda Hard to convince my bro that I am right when other long time professionals say it ok when it is not. Make me doubt myself since alot more cause I am new to the trade. Hope this is not a " I told ya so" case. Thx for all your comments and help.


Here is a list of what is being supplied in the garage:

12 Fluorescent ceiling lights (1260 Watt total)
2 baseboard heaters (5000W) Only use as back up
wood\oil furnace ( 15 A for blower)
50 A welder
8 reg recepticles( one celing recept will serve as the power for the garage Door opener
3 t-slot receptiles (work bench)

A 70A breaker is not enought if he uses the welder, Electric heat, and lights at the same time. Dont know what else to tell him for not to use that #4 alum.



~FyE~

 

[wireguru]

is this #4 wire you got single conductors? or is it triplex (2 black and a bare neutral)

 

[1stYearElectrican]

3 Single conductors run in PVC. If I wanted to I could remove any one of the 150 ft lenghts from the PVC.
2 are all black and the other conductor marked with a white stripe representing the Neutral.

Although he label it triplex


~FyE~

 

[JohnJ0906]

Going to get my Bro to use a ladder and scope out the conductors that supplies his 200A service and see if they are the same size wire as he gonna use for the sub panel.

What the POCO uses to supply a service has nothing to do with what we must use for the same service. We follow the NEC, POCOs do not.

 

[Dennis Alwon]

Here is another issue. If you are under the 2008 NEC then you need a 4 wire cable. You may also need a 4 wire under the 2005 if certain conditions exist. Read art. 250.32

 

[charlie]

1. #4 AWG XLPE ALUMINUM 300V. According to the tables this conductor is rated at 80-90 AMPS and will be supplying a 100A panel. These conductors can not handle 100A. Am I correct in this??
2. A friend of my Brothers from the power company gave him several hundred feet of #4 AWG XPLE ALUMINUM 300V and assured him that it was OK to use it to supply a 100A panel. And on top of that an electrician also gave him the OK to use it. Is this really OK??
3. Is the power company guy and electrician right or do I need to do more deeper reading in the code?

1. XLPE (cross linked polyethylene) is not a listed material and the electric utilities are still buying it for UG (underground) use. If it were used for OH (overhead), it would just be PE (polyethylene) and we would use it for 100 ampere services as triplex service drops. My utility does not use anything smaller the 2/0 Al. for UG. However, we size according to the expected load and will replace the cable if it is the wrong size even 25 years later (how is that for a guarantee?).
2. Generally speaking, power company guys (normally linemen) are not electricians and electricians are not linemen. Generally, power company guys are not familiar with the NEC and can not be trusted to give you a straight answer concerning the NEC requirements. There are exceptions in both directions.
3. NO! Pay attention to what you are being told here. These guys are correct.

 

[billsnuff]

Not for sale in US

Not for sale in US

http://www.generalcable.com/NR/rdonlyres/2041323E-135E-47AE-A9D8-3FDC5924C29F/0/SPEC_5550.pdf

Is this what you have?

 

[wireguru]

Here is another issue. If you are under the 2008 NEC then you need a 4 wire cable. You may also need a 4 wire under the 2005 if certain conditions exist. Read art. 250.32

i guess you saw where i was going with that :grin: