Another what power wire to run to garage thread

[ixlr8]

I am looking for the collective wisdom here to come up with an answer. Here is my situation, I am building a detached garage/shop, it is 85 ft from my house. I plan on putting in 2 pvc conduits between garage and house. A 2" one for power, and a 1-1/2" one for phone, internet, etc. I have talked with 2 electricians, they both recommend putting in 100 amp service to the garage based on my planned uses and possible future uses. I have a 200 amp panel in the house with 7- 20amp breakers I am removing as they are for the electric baseboard heat I am removing. One says to use SER cable, the other says that is illegal and I need to use something else, I forgot what he said. The wire run is, 58' in the house, 85' between house and garage, 5' in the garage to the panel, so about 150' total. I talked with our code enforcement officer, he said that I could use whatever works, no permits or inspections required. I don't want any short cuts, I want to do this the best possible way so I have no issues in the future.
What do you folks recommend for size and type of cable?

Thank you,

 

[mrb]

cant put SER in the ground. You should use THWN in the conduit, I would just pipe it the whole way. Alternately you could transistion from pipe to cable in the house, but it will be costly to make the splices -not worth it. You need 4 wires to the garage and keep the neutral and ground seperate in your subpanel. The ground can be reduced size (#8cu for 100 amp feeder), but if you increase your conductor size you need to increase the ground as well. For example if you do this in copper you could use 3x #2 and 1x #8. You need to install two ground rods at the garage.

 

[Professur]

Best no shortcut option? Have a new second service entrance run from the pole to the garage. It probably won't cost a whole lot more in wire, and you'll have the advantage of being able to monitor exactly your garage power usage. More importantly, when your 15A compressor kicks on, it would be sending power spikes through your home stereo system.

 

[bondsman]

I ran 115' of aluminum 2-2-2-4 from Lowe's in conduit from box to box. It is rated at 100 amps but I only have a 60amp breaker feeding it from the house. It was the least expensive way. If you run the single wire (you are gonna need 4) thhn/thhw it will be very expensive.
Two ground rods 6' apart with one continuous wire #6 as mentioned above and also your neutral and ground buss bars need to be seperate and the neutral cannot be grounded to the box (that is in your garage panel).

 

[mrb]

cant use #2 AL at 100 amps, have to breaker it at 90

as far as putting in a second service with its own meter at the garage, IF the power company will even do it (many areas you can only have one meter per legal dwelling unit) its not worth it here as the monthly fix cost of having the meter will cost more in the long run.

 

[ixlr8]

as far as putting in a second service with its own meter at the garage, IF the power company will even do it (many areas you can only have one meter per legal dwelling unit) its not worth it here as the monthly fix cost of having the meter will cost more in the long run.

They will allow it, but the monthly fixed cost is prohibitive.. as well as the 400 ft trench to go around my house to get to my shop. My house is directly in line with the nearest pole and shop, and at about the mid point between them.

 

[ixlr8]

cant put SER in the ground. You should use THWN in the conduit, I would just pipe it the whole way.

I know SER is not rated for direct burial, one electrician said it was okay to put in a conduit underground.
That is going to be fun to pull the THWN, 58' of conduit in house, with 5-90's between breaker box and fitting to go outside. It is a straight line from house to the shop.

 

[mrb]

I know SER is not rated for direct burial, one electrician said it was okay to put in a conduit underground.
That is going to be fun to pull the THWN, 58' of conduit in house, with 5-90's between breaker box and fitting to go outside. It is a straight line from house to the shop.

shouldnt be too bad to pull. one person pushing and one person pulling and you'll get it in. 5 90s is not ok though. You will need a pullbox (I like to use an appropriate length section of gutter) somewhere in there.

you cannot put SER in conduit underground. Underground conduit is a wet location and the wire in it has to be listed as such.

 

[bondsman]

cant use #2 AL at 100 amps, have to breaker it at 90

Correct. While I was doing my research and picking everybody's brain as well as scouring the NEC, runs over 100' would require the next larger size of wire if you wanted the 100amp service. There are some wire calcs on the net somewhere.
That is alot of pull/pushing to get the wire into the house though. I would try and find an alternative. It was a pain running my straight shot with 2 sweeping 90's to come out of the ground then to the elbow to run into the house.
I have mine breakered at 60. Should I need more amperage, I guess I can go up to 90.
I am by no means an electrician, this has been just my experience. Best thing to do would be to have an electrician come out and give you some options. Ask hime about the different types of wire that your code will allow. Then go from there.

 

[ixlr8]

I am by no means an electrician, this has been just my experience. Best thing to do would be to have an electrician come out and give you some options. Ask hime about the different types of wire that your code will allow. Then go from there.

That is part of my problem.. I have had 3 electricians give me 3 conflicting "how-to's".

 

[Aceman]

That is part of my problem.. I have had 3 electricians give me 3 conflicting "how-to's".

If I was looking at your job and cost was an issue, I'd most likely be recommending 1/0 Aluminum USE for your 100 amp feeder. I don't know how you're up to 5-90's in a run to a garage. I usually have two...maybe three total. I usually LB out of the back of the house panel, sch. 80 down into the ground. Run over to the shed/garage and 90 up through the slab, etc. Or if it's already poured, I do it just like the house and run sch. 80 up the outside and LB through the wall.

I like to bow pvc in the ground rather than use actual 90 sweeps if at all possible.

Any electrician that wants to pull SER underground is a bonehead. It's not legal and most importantly, large multiconductor cables **** to pull into conduit compared to individual conductors. Go to HD and grab a piece of SER and try it yourself. It doesn't bend very well, then imagine having to pull it through 4-90's at the same time!!

 

[nate379]

I was just wondering, why are sub panels under a different set of rules then a main?

#2 AL would be fine for a main, but not for a sub panel. Why?

 

[mrb]

I was just wondering, why are sub panels under a different set of rules then a main?

#2 AL would be fine for a main, but not for a sub panel. Why?

the 75deg ampacity of #2 AL is 90 amps. There is a code section which allows a reduced wire size when the wire is carrying the entire load of a dwelling unit. Their basis on this is load diversity in a dwelling unit, which doesnt exist to the same extent on a subpanel.

 

[nate379]

I thought it was main panel, doesn't matter to what?

I'm too lazy to go dig out my books, but I'm going off table 310.15(B)(6) for the main panel feed.

If #2 wire is fine to feed the main panel, I don't see how it couldn't be fine to feed a sub panel.

What is #10 wire rated for in a subpanel? I ran that out to where my shed will be built and will have it setup for 30 amp 240v service.

 

[mrb]

I thought it was main panel, doesn't matter to what?

I'm too lazy to go dig out my books, but I'm going off table 310.15(B)(6) for the main panel feed.

If #2 wire is fine to feed the main panel, I don't see how it couldn't be fine to feed a sub panel.

What is #10 wire rated for in a subpanel? I ran that out to where my shed will be built and will have it setup for 30 amp 240v service.

right 310.15 B 6 is for conductors carrying the ENTIRE LOAD of a dwelling unit. The subpanel isnt carrying the entire load of a dwelling unit so that table cannot be used.

 

[nate379]

I understand that, but what I don't understand is why if it's ok for the main panel it's not fine for a sub panel.

 

[mrb]

I understand that, but what I don't understand is why if it's ok for the main panel it's not fine for a sub panel.

because you dont have the load diversity on a subpanel that you have on the main panel.

 

[bondsman]

Wow, this is getting deep and very confusing.

Check with your inspection office. If they say you can run Al wire, run it. It is cheaper when compared to copper.
I would do what Aceman said above. The only difference in your house panel and your new garage load center would be that in the garage load center, the neutral and ground bars have to be seperated and remove the screw in the neutral bar that grounds it to the panel. you will have to run grounding rods at least 6' apart with a continuous #6 bare copper wire from the panel ground bar to the rods. If you definitely need 100amp service the 1/0 AL would be the way to go. Run it all in conduit from house to garage.

I ran the 2-2-2-4 AL from my house panel on a 60amp breaker out to the 200amp load center (the 200amp main on that load center will never pop so it is basically a shut off switch and the 60amp breaker in the house is the actual protective breaker). I never figured I would need anymore than 60amps in a one person garage with light air compressor work, occassional welding, and just normal stuff... There will be a lift going in soon and it will require a 30amp breaker, but I will never be welding with the air compressor running, operating the lift and running all sorts of electric stuff that would test the 60amp breaker.

 

[Norcal]

I understand that, but what I don't understand is why if it's ok for the main panel it's not fine for a sub panel.

Realize that #2 AWG is UNDERSIZED for 100 amperes, the NEC only allows it to be used for 100A for the main service*,or a panel carrying the entire load.


*Residential ONLY....

 

[bondsman]

Try this link out.... It is an older version but you will get the basics...

http://www.selfhelpandmore.com/home-wiring-usa/accessory-structures-to-dwellings/wiring-a-detached-garage-2002.php

 

[hidollartoys]

I understand that, but what I don't understand is why if it's ok for the main panel it's not fine for a sub panel.

The engineering fundimental to support this is based on the "Lighting Load Demand Factor"(table220.42, 2005 NEC). The service entrance conductors are rated based on the "Demand Factor" that derates the actual calculated service load.

The sud-panel is considered a branch circuit and the conductors are rated according to the actual ampacity potential.

 

[ixlr8]

I think I am getting this sorted out, although I have had 2 more licensed electricians tell me to use the SER cable, 2-2-2-4 alum. I am not going to use SER cable, but I do need some guidance on cable size. It is 150' from breaker box to breaker box, sized for 100 amps. I have been told that minimum would be #4 copper but #2 would be better. I have also been told that #2 alum would be fine. Online calculators give me similar variations. Based on what folks here have said, that #2 copper is correct, what size would I need to run in alum? Does ground wire from house to garage need to be CU or can it be AL? I understand that ground wire from shop breaker box to ground post needs to be CU.

TIA

 

[hidollartoys]

If you want to maintain a max 3% voltage drop for the entire 100 amp load, you will need to install 2/0 cu. or 4/0 al.

Since the ground wire will be in a wet location copper will be required. I would use an insulated conductor.

 

[79firebird]

I my self would use teck cable. my buddys work uses it all the time to go from a house to any out door building. heck most places even use it for hottub power for years burry it no prob as long as you are down far enuf and then run it thru the house no splice or any thing needed

 

[Norcal]

I my self would use teck cable. my buddys work uses it all the time to go from a house to any out door building. heck most places even use it for hottub power for years burry it no prob as long as you are down far enuf and then run it thru the house no splice or any thing needed

Teck cable is a Canadian product it's not widely known nor is it used in the US.


Note: The NEC allows a maximum of 360 degrees between pulling points which equals 4-90's. (this is in reply to a prev. poster writing about using 5-90's)

 

[ixlr8]

Teck cable is a Canadian product it's not widely known nor is it used in the US.


Note: The NEC allows a maximum of 360 degrees between pulling points which equals 4-90's. (this is in reply to a prev. poster writing about using 5-90's)

I was going to say.. I have never heard of 'Teck' cable, thanks for the clarification.

If I use THWN, will that need to be run through conduit inside the house? If I don't need to run it in conduit, then getting through the house will be easy. There is just lots of stuff like chimneys, plumbing, duct work between breaker panel in house and other side of house where cable will exit and head to the garage. That is why I was thinking of needing 5-90's, to get around all that stuff.

Thank you,

 

[Norcal]

THHN/THWN must be run in a conduit.

 

[hidollartoys]

THHN/THWN must be run in a conduit.

Where does it say that in the code(2005)?

 

[walrus]

Teck cable is a Canadian product it's not widely known nor is it used in the US.
)

I've used it, its used around here but its expensive. Easy for one guy to lay it in. In fact my feeder to my shop is teck cable

 

[Stuart in MN]

THHN/THWN must be run in a conduit.

Where does it say that in the code(2005)?

I don't have a 2005 edition here at home, but per my 1999 edition I believe it's Article 300-3. Individual conductors have to be in an approved raceway, or part of an approved cable or cord.

 

[JBurgess]

I don't have a 2005 edition here at home, but per my 1999 edition I believe it's Article 300-3. Individual conductors have to be in an approved raceway, or part of an approved cable or cord.

In 2008:

300.3 Conductors.
(A) Single Conductors. Single conductors specified in
Table 310.13(A) shall only be installed where part of a
recognized wiring method of Chapter 3.

Exception: Individual conductors shall be permitted where
installed as separate overhead conductors in accordance
with 225.6.

 

[Aceman]

Since the ground wire will be in a wet location copper will be required. I would use an insulated conductor.

Which ground are you referring too? The one in the conduit or the ground wire to the rods?

 

[79firebird]

dident know it was not used much in the us heres some info on it
http://www.electrocables.com/page76.htm

Its cheaper then running copper most times it was 1/2 the cost for the wire we used at work to go to a new 200amp panel we got put in. What i like about it is no worry about using the wrong kind o cable

 

[hidollartoys]

Thanks to stuart and jburgess for pointing me to the specific sections that clearify the requirement

 

[RossRinSD]

Try this link out.... It is an older version but you will get the basics...

http://www.selfhelpandmore.com/home-wiring-usa/accessory-structures-to-dwellings/wiring-a-detached-garage-2002.php

So, my question didn't really require a new thread...

I'm running power to my detached garage. Its about 60 feet total wire run with a 60A service. I'm planning on using 6 gauge feeders in buried rigid plastic conduit.

After doing a ton of research, I thought I needed to run two hots and a neutral, neutral not bonded to ground in the subpanel, and two ground rods at the garage.

I would like to install water at a later date, for a deep sink and to make cleaning up and washing the cars easier.

Do I need to run a ground from the main panel to the subpanel?