100amp service in garage?

[2000pstrokeblue]

So im new member to the site but have been lurking for awhile. Just got the approval to build my new 36x40 garage. My plan is to run between 80- 100amps for 220 service and lights etc. to a panel in the garage. Im no electrician but im not really worried about doing the work. I have been reading in here and I hear people talking about aluminum wire, and I don't know much about it and cheaper is always a plus. It's a total of 100 ft run from the house panel the the garage panel, with 60ft of it being run in conduit under ground. Was planning on running 2-#3 copper, #4 neutral #6 ground. A. does that sound right for copper? B. what would be my other cost effective options? keeping in mind I want it at least buried the 60ft in conduit?

 

[2000pstrokeblue]

will this be sufficient?
http://www.lowes.com/pd_70262-295-28...ome&facetInfo=

 

[Charles (in GA)]

The old standby. 2-2-2-4 mobile home feeder. Aluminum. OK for direct bury or conduit. Must be in conduit above ground and inside the building. Other option is to splice it at a junction box on outside to another type of cable that does not need to be in conduit, but conduit is cheap and splices cause future problems.

Charles

 

[pattenp]

Another vote for the 2-2-2-4 AL MHF. Use a 90A breaker on it. 100ft is no problem.

 

[EdT]

When I built my separate garage I ran it off a branch circuit off my main power panel. At the time ( 20+ years ago) a 60 amp branch circuit was the largest that they would allow me to run. Different times, different place, maybe a different answer. I'd want to be sure that the building dept would allow a 100 amp branch before they made me take it all out. I don't know if a mobile home power supply is different from a "branch" circuit. Could be. Don't forget to use ALOX or something like it on the aluminum wire terminations.

 

[pattenp]

Mobile Home Feeder is just the name of the cable. Its use is not limited as a service feed to a Mobile Home. In this case it is being used as a branch feeder to an out building. There very well could be a local code limit for the branch size to an out building.

When I built my separate garage I ran it off a branch circuit off my main power panel. At the time ( 20+ years ago) a 60 amp branch circuit was the largest that they would allow me to run. Different times, different place, maybe a different answer. I'd want to be sure that the building dept would allow a 100 amp branch before they made me take it all out. I don't know if a mobile home power supply is different from a "branch" circuit. Could be. Don't forget to use ALOX or something like it on the aluminum wire terminations.

 

[2000pstrokeblue]

edt, I don't know what you mean by ALOX, im assuming that it is some kind od coating? on that note is it ok to terminate in aluminum to the box in the garage and run copper from the box to all receptacles? I was told going from aluminum to copper might be an issue?

 

[pattenp]

I think he meant Noalox which is an aluminum antioxidant paste you put on at the terminals/lugs. It's fine to run aluminum for the feed to the panel and then have copper for the branch circuits. The terminals/lugs in the panel are made to handle either aluminum or copper. The thing is you shouldn't connect/splice copper directly to aluminum you need to have a splicer that is rated for both copper and aluminum that keeps the 2 different metals separate.

 

[2000pstrokeblue]

thanks pattenp

 

[SALIV8]

Personally I would never use aluminum wire. But yes it is a bit cheaper than copper.

Do it right and never worry about any issue in the future (copper). The small savings isn't worth the potential fire from the aluminum ****.

 

[pattenp]

So, what experience and knowledge do you have with modern aluminum wire causing fires?

Personally I would never use aluminum wire. But yes it is a bit cheaper than copper.

Do it right and never worry about any issue in the future (copper). The small savings isn't worth the potential fire from the aluminum ****.

 

[Bib Overalls]

Personally I would never use aluminum wire. But yes it is a bit cheaper than copper.

Do it right and never worry about any issue in the future (copper). The small savings isn't worth the potential fire from the aluminum ****.

Aluminum wire is an excellent conductor and it is well suited for supplying power between the service entry, the main panel, and sub-panels.

During the Korean War, when copper was scarce, the building industry tried wiring homes with aluminum wire Romex. It did not work. The expansion and contraction of the aluminum wire loosened terminals and broke wire.

Note: If you are thinking about buying a house built in the late 40s to middle 50s inspect for aluminum wire in outlet and lighting circuits.

This is not a problem with multi-stranded wire that terminates in lugs, such as found in electric meters, electric panels/sub-panels, high amperage circuit breakers, welding outlets, and the like.

Aluminum wire can be safely used with any terminal that is marked AL/CU.

 

[Falcon67]

Personally I would never use aluminum wire. But yes it is a bit cheaper than copper.

Do it right and never worry about any issue in the future (copper). The small savings isn't worth the potential fire from the aluminum ****.

Have you looked in a meter box lately? Every house done since I can remember has 200A service run with aluminum wire, either dropped from the pole or run underground. Properly terminated, it's as safe as copper.

 

[wyliesdiesels]

O geez. Here we go with another thread debating aluminum wire. People really need to do their homework before insertin their foot in their mouth!

 

[Falcon67]

I had to run aluminum. Its getting really hard to find wire coat hangers these days.

 

[Zeke]

So, what experience and knowledge do you have with modern aluminum wire causing fires?

The only experience he could have is with the 2 common things that can go wrong with AL wires: improper junction connections and panel lugs working loose over time. Or interior problems which can be real.

I had a POCO lineman tell me to tighten the nuts on the lugs after 30 or so days. Personally I never have and have never seen a problem. I have seen the problem with inside AL wires connected directly to devices. I think this is where all AL gets its reputation.

 

[justsam]

Was planning on running 2-#3 copper, #4 neutral #6 ground. A. does that sound right for copper? QUOTE]

Regarding question "A"; NO! Do not undersize the neutral. OK for ground but not neutral for feeder.

Use the 2/2/2/4 as many have recommended. Note all conductors here are same size

, except ground.

 

[JoeFin]

The only experience he could have is with the 2 common things that can go wrong with AL wires: improper junction connections and panel lugs working loose over time. Or interior problems which can be real.

Except for water intrusion on Direct Burial Al. Lines

Went on a service call many years ago. The Boss had installed a splice under ground and about 12" back of it had nicked the wire. Once moisture entered the aluminum wire it accelerated the oxidation process a 1000 fold.

All that was left of the aluminum was a powdery white oxidation substance where the wire once was - took about 2 weeks


Personally - I ran Copper in EMT because I had to run through the existing house to get to my garage. That is about the only circumstance where Copper is warranted above Al.

 

[Norcal]

The proper way is to torque it to manufacturers specs & leave it alone, do not come back & retorque it. By "torquing" it means using a proper torque wrench / screwdriver not a WAG on whether it's tight enough as too tight is as bad as loose.

 

[Zeke]

The proper way is to torque it to manufacturers specs & leave it alone, do not come back & retorque it. By "torquing" it means using a proper torque wrench / screwdriver not a WAG on whether it's tight enough as too tight is as bad as loose.

Generally the electrical contractor or electrician will run the service to the weatherhead so he can do that. When it's a buried cable from the pole, who connects the service lateral to the POCO side of the meter in your area? If it's the linemen from the POCO, do they have a torque wrench?

Remember, I'm just a 'visitor' here because I like the electrical forum. I'll have some questions and I'll have some answers. More questions than answers.

 

[Charles (in GA)]

Aluminum wire is an excellent conductor and it is well suited for supplying power between the service entry, the main panel, and sub-panels.

During the Korean War, when copper was scarce, the building industry tried wiring homes with aluminum wire Romex. It did not work. The expansion and contraction of the aluminum wire loosened terminals and broke wire.

Note: If you are thinking about buying a house built in the late 40s to middle 50s inspect for aluminum wire in outlet and lighting circuits.

Solid strand Aluminum Romex type branch circuit wiring was used in houses up until 1976 when it was banned by the code.

I owned a house in the late '80s that was built in 1970. All of the houses on that street were wired with Anaconda brand NM made of aluminum. I found several burned connections where the wire attached under the screws of receptacles. In one case the wire was badly burned for about a foot up the wire from the receptacle.

During the time I owned the house, there was a mobile home fire in town and an infant was killed in the fire. The family sued Anaconda and Leviton, claiming they were aware of the problems with aluminum branch circuit wiring and its incompatibility with switches and receptacles, and had conspired to conceal the information during the time the products were being manufactured and after the NEC banned the use of solid AL wire for small branch circuits. Sadly (at least for the family of the child) they lost the lawsuit. Clearly there was a problem.

I replaced all of the receptacles with CO/ALR type receptacles and had replaced about half of the wire in the house when I sold it.

Charles

 

[Charles (in GA)]

If it's the linemen from the POCO, do they have a torque wrench?

I think many POCOs use preset torque wrenches to do this. They have two or three different ones for different torques and so there is no setting them, just use them.

Charles

 

[Norcal]

10 & 12 AWG Aluminum is still code compliant, just there is no one manufacturing it. You cannot use NOS, new old stock because the NEC requires NM cable to be rated 90c & in the heyday of AL being used to rope houses it was 60c, BTW, the AL used in the dark ages of the '60's is not the same as the aluminum alloy used in the early '70's it was a much improved product, that being said, I prefer copper, & if was given the AL for free would not use it for branch circuits, but for larger feeds aluminum is a legit way of cutting costs, & the only ban on AL is HUD's ban in trailers ("manufactured homes"), the NEC does allow it.

 

[Zeke]

Aluminum wire is an excellent conductor and it is well suited for supplying power between the service entry, the main panel, and sub-panels.

During the Korean War, when copper was scarce, the building industry tried wiring homes with aluminum wire Romex. It did not work. The expansion and contraction of the aluminum wire loosened terminals and broke wire.

Note: If you are thinking about buying a house built in the late 40s to middle 50s inspect for aluminum wire in outlet and lighting circuits.

This is not a problem with multi-stranded wire that terminates in lugs, such as found in electric meters, electric panels/sub-panels, high amperage circuit breakers, welding outlets, and the like.

Aluminum wire can be safely used with any terminal that is marked AL/CU.

They did this during Viet Nam too. So the industry must have not been yet convinced. I lived in a house built in '68 that was all AL. It was a real problem on outlet circuits wired through the devices as the demands for electricity increased with ever more electronics like computers with CRT monitors and TV recorders, just to name a few. The kitchens were not wired for microwaves, they used a convenience outlet along with any number of other plug in appliances. Over time the outlet lug screws worked loose.

I know backstab outlets are bad news but at least they stayed clamped on the wires. Of course the AL wiring itself became brittle with any heat. I pigtailed mine with stranded copper and Noalox but I suspect some of the homes in that area have never been completely redone. I only saw one burn and my own house almost did as I caught the offending outlet arching one evening. Had it not been twilight I may not have seen it before I left for the evening.

I'll not forget that day in 1985.

I can not tell you if there ever were any backstab outlets that were rated for AL/CU use sold at the time. I'm sure a lot of CU only outlets were installed by various people from owners to handymen.

 

[SALIV8]

I'm just stating my opinion and will stand behind it. No reason some of you guys get your aluminum ******* all wadded up.

Al does not impress me. There are reasons al is not allowed everywhere no matter NEC minimum code. Power lines ran in aluminum is simply a cost saving measure imo period.

If you were given an unlimited supply of copper wiring or aluminum for free, would you still choose aluminum?

The simple fact that aluminum expands/contracts with temp swings, oxidizes ridiculously underground, and with high humidity, etc. is reason enough to stay away imo. Not to mention the special goo you have to use with some connections.

But I don't want to get in a ******* match. Be my guest and use all the aluminum you guys want. I won't, and I have my reasons.

Edit- some good first hand experiences posted above ^^ that I agree with totally. I should have read more responses before posting I guess.

 

[pattenp]

The free wire question is not a reasonable question in regards to using copper over aluminum because it's a cost issue. There is no question that copper is better than aluminum. But when it comes to cost effectiveness for long feeder/service runs, that's where aluminum wins out over copper. The added durability and safety aspects of copper over aluminum are just not great enough to justify the cost difference. This is just my opinion.

I'm just stating my opinion and will stand behind it. No reason some of you guys get your aluminum ******* all wadded up.

Al does not impress me. There are reasons al is not allowed everywhere no matter NEC minimum code. Power lines ran in aluminum is simply a cost saving measure imo period.

If you were given an unlimited supply of copper wiring or aluminum for free, would you still choose aluminum?

The simple fact that aluminum expands/contracts with temp swings, oxidizes ridiculously underground, and with high humidity, etc. is reason enough to stay away imo. Not to mention the special goo you have to use with some connections.

But I don't want to get in a ******* match. Be my guest and use all the aluminum you guys want. I won't, and I have my reasons.

Edit- some good first hand experiences posted above ^^ that I agree with totally. I should have read more responses before posting I guess.

 

[2000pstrokeblue]

ok building is now up and I plan to start the electric very soon and just wanted to clarify a few things. As far as the mobile home feeder you guys are suggesting 2-2-2-4 that is #2 wire not 2/0? for the 100 amp service? and will a 2in pipe be sufficient for the run? I was reading in another post about something about LB size that there is some formula as to what size wire to LB I need to use for code.

 

[pattenp]

The 2-2-2-4 MHF is #2, not #2/0. Depending on the length of run the #2MHF is good up to 90 amps. 2 inch conduit is plenty large enough for the 2-2-2-4 MHF, and 2 inch LB's are plenty big enough as pull points. But, you can't use the LB for any splicing, it's not big enough for that.

Edit: Sorry about the repeat of the amps and distance. I see earlier in your post I stated the max amps and I see you're at about 100ft.

 

[wyliesdiesels]

ok building is now up and I plan to start the electric very soon and just wanted to clarify a few things. As far as the mobile home feeder you guys are suggesting 2-2-2-4 that is #2 wire not 2/0? for the 100 amp service? and will a 2in pipe be sufficient for the run? I was reading in another post about something about LB size that there is some formula as to what size wire to LB I need to use for code.

Can only do 90a with #2 AL as a branch feeder!

 

[James-W]

I am a little confused here. Shouldn't the first question be, "How big is the electric service to your house"? If his house service is only 100 amps then how can he run a 100 amp service from his house breaker panel to another building? Would he not have to increase his house service before he could do this?

 

[pattenp]

I am a little confused here. Shouldn't the first question be, "How big is the electric service to your house"? If his house service is only 100 amps then how can he run a 100 amp service from his house breaker panel to another building? Would he not have to increase his house service before he could do this?

If the main service is 100A it would be advisable to increase the main but not technically required as long as the sub feeder is not larger than the main.

 

[James-W]

If the main service is 100A it would be advisable to increase the main but not technically required as long as the sub feeder is not larger than the main.

I was not aware you could do that, thank you for clearing that up for me. I had thought you needed to have a lesser amount of power delegated for running to the sub-panel.

I can't help but think though, the potential for problems is very real and if he decides to do very much out in the garage that requires large amounts of current (welding and running air-conditioning, etc) he may find the main breaker in the house tripping. Not that a main breaker tripping is a big deal, but it does indicate a problem that should really be addressed. A house can draw quite a bit of power at times, especially if there are a lot of higher energy appliances running at the same time, central air, water heater, clothes dryer, electric stove, refrigeration, dehumidifiers, stuff like that. Anyway, that's just my personal thoughts on the subject.

 

[wyliesdiesels]

I am a little confused here. Shouldn't the first question be, "How big is the electric service to your house"? If his house service is only 100 amps then how can he run a 100 amp service from his house breaker panel to another building? Would he not have to increase his house service before he could do this?

Add up the breakers in your panel. If u have electric appliances such as stove dryer water heater ac etc and u only have 100a service guaranteed your branch breakers will add up to more than 100a and if u have a big house with 200a service almost guaranteed that the breakers add up to to more than 200a!

Also, continuous load circuits are oversized at 125% so while a stove has a 40a or 50a breaker feeding it, most of the time its pulling a fraction of that. For example, i put a clamp meter on one of the hot legs feeding my stove while i was baking a pizza. It read just over 12a despite the breaker having a 50a rating...

 

[James-W]

I understand that the total of all the circuit breakers will exceed the rating of the main breaker. But that doesn’t mean anything because not every circuit is using power all the time. I also understand the central air, even though it is on a 30 amp breaker, may only be drawing 20 amps and the electric water heater on a 30 amp breaker may only be drawing 20 amps as well. But the point is, when several of these higher current draw appliances happen to be running at the same time the load in the house increases dramatically. So if the opening poster starts using equipment in the garage that requires a substantial amount of power to run at the same time the house is drawing a large amount of power, he may very well trip the main breaker.

We have tripped the main breaker is our home back when we had a subpanel out in the old garage feeding off the house breaker panel. That’s one of the reasons we had a separate service run to the new garage when we built it. I am not saying the opening poster WILL have a problem with this, I am just saying the potential is there for it to happen.