30AMP service enough for my garage

kook04 · May 20, 2009

I'm having a buddy who's an electrician install a subpanel in my detached garage. His recommendation to me was to put a 30amp breaker in my main (200amp) panel in my house, and have 30amp service in the garage. He says this will be plenty for what I want to do out there. Which is:

- (12) 2 bulb 4' flourescent lights (~.6 amps each fixture I think)

- (6) Exterior lamps

- (12) standard outlets

The outlets will handle 2 garage door openers, and any tools I use. No welding here, just shop-vac, drill battery charger, circular saw, pancake air compressor, etc... Also, I have a mini-fridge I will probably put out there.

I know nothing about electrical, so I'm just looking for some advice. Do you think 30amp service will be sufficient for me? Thanks in advance for you help.

MXtras · May 20, 2009

Sounds a little on the skinny side to me.

I would go for at least 50 Amp. Figgure if you have the lights on and run the shop vac when your compressor comes on you are in the dark.

Scott

35mastr · May 20, 2009

I would even go as far as 60-100. You will only expand your power tools in the future not deplete them. Just my .02.

If you just decide to upgrade your compressor .You will already be too short on amps to begin with.

Just go as big as your wallet can handle and you will be much happier in the future.

His200HerScout · May 20, 2009

how far is your garage from the house?

30 seems weak for what you're doing. especially if you ever want to do anything else out there (power tools, etc). i have no plans to do anything in my garage in the near future, but i am still going to run 100 amps out there so that i only do the job once.

Charles (in GA) · May 20, 2009

Run at least 60 amp. Crazy not to.

Charles

kook04 · May 20, 2009

Thank you to everyone for your input. You have convinced me that 60amp is the way to go.

So, as I see it, I will need a 60amp breaker in the main panel rather than a 30, but will the wire that runs from the house to the garage need to change? Assuming the 30 amp feed, he had spec'd "10/3 UF direct burial cable".

Now that I will be going with the 60 amp service, what cable should will I be looking at, and does anyone have rough estimate of what it goes for per foot?

Thanks again guys.

His200HerScout · May 20, 2009

kook04 said:
Thank you to everyone for your input. You have convinced me that 60amp is the way to go.

So, as I see it, I will need a 60amp breaker in the main panel rather than a 30, but will the wire that runs from the house to the garage need to change? Assuming the 30 amp feed, he had spec'd "10/3 UF direct burial cable".

Now that I will be going with the 60 amp service, what cable should will I be looking at, and does anyone have rough estimate of what it goes for per foot?

Thanks again guys.

We'd need to know how far the wire will need to run -- how many feet? There is a concept called de-rating that applies to long runs, and that is where you must use a bigger wire than what a Google search might indicate.

As for a rough estimate, look for a local electrical supply warehouse. I went into Home Depot last week and found that a particular type of wire was more than double the price that another local supplier was charging. The HD guy frowned and muttered something about sticker prices not being updated often enough to reflect copper market downturns.

Aceman · May 20, 2009

kook04 said:
Assuming the 30 amp feed, he had spec'd "10/3 UF direct burial cable".

Now that I will be going with the 60 amp service, what cable should will I be looking at, and does anyone have rough estimate of what it goes for per foot?

Thanks again guys.

Man I hate UF cable. Just sayin'. I never understood why people want to direct bury short little runs to their garage when pvc is so cheap? It doesn't make sense. 1.25" pvc, 60 amp breaker and #6 THWN and be done with it. This is about the smallest subpanel I'll install unless I'm lighting a sign for example, where I know the load will never grow.

Stuart in MN · May 20, 2009

Depends on what you're doing out there. I've had a 30 amp subpanel in my garage for a decade and it works fine for me, but I don't have any large loads like a welder or air compressor. That said, if I were to do it over again I'd go larger just in case.

kook04 · May 21, 2009

His200HerScout said:
We'd need to know how far the wire will need to run -- how many feet? There is a concept called de-rating that applies to long runs, and that is where you must use a bigger wire than what a Google search might indicate.

The garage is very close to the house, but by my calculations, it will be about 70' of cable from panel to panel.

nadogail · May 21, 2009

kook04 said:
Thank you to everyone for your input. You have convinced me that 60amp is the way to go.

So, as I see it, I will need a 60amp breaker in the main panel rather than a 30, but will the wire that runs from the house to the garage need to change? Assuming the 30 amp feed, he had spec'd "10/3 UF direct burial cable".

Now that I will be going with the 60 amp service, what cable should will I be looking at, and does anyone have rough estimate of what it goes for per foot?

Thanks again guys.

If you use the 60 Amp breaker, you must use 60 Amp wire. The breaker is to protect the wire from being overloaded.

The wire can be bigger than the breaker, but the breaker can not be bigger than the wire

MXtras · May 21, 2009

Without looking at the code (you need to) - I suggest using at least #4 wire for a 60 amp run of less than 75'. Larger wire will not hurt - except your wallet. You might look into using aluminum if your run is distant, just make sure your breakers and lugs can accept aluminum wire.

Charles is the resident electrical expert and always gives solid advise.

Scott

ripsnortMN · May 21, 2009

Hell I only have a 100amp main in the house and then there is a 100amp subpanel from that going to the garage. I have never popped a breaker in either building.

sberry · May 22, 2009

Agreed, the labor is the same essentially, it would be a minimum of 60 for me too.

FlameOut · May 22, 2009

ripsnortMN said:
Hell I only have a 100amp main in the house and then there is a 100amp subpanel from that going to the garage. I have never popped a breaker in either building.

I always thought you could only have a subpanel that was a percentage of your main. Something like 30%?? I don't know where I heard this, but I sure hope I am wrong and you are right. I have a 150 amp main, and thought most I could run to my detached garage was 50 amp. I'd love to run a 100 amp out to it.

nate379 · May 22, 2009

THWN/THHN is more expensive than UF here.

Aceman said:
Man I hate UF cable. Just sayin'. I never understood why people want to direct bury short little runs to their garage when pvc is so cheap? It doesn't make sense. 1.25" pvc, 60 amp breaker and #6 THWN and be done with it. This is about the smallest subpanel I'll install unless I'm lighting a sign for example, where I know the load will never grow.

nate379 · May 22, 2009

Tell that to the electrician that wired my welder plug.

I threw it in the house offer so it was done. Got too looking and for a 50 amp plug and breaker he ran 10/3. I ripped it all out and did it right with 6/2.

nadogail said:
If you use the 60 Amp breaker, you must use 60 Amp wire. The breaker is to protect the wire from being overloaded.

The wire can be bigger than the breaker, but the breaker can not be bigger than the wire

roygrady · May 24, 2009

Yea go with the 60amp at least, always good to future proof

Stuart in MN · May 24, 2009

nate379 said:
Tell that to the electrician that wired my welder plug.

I threw it in the house offer so it was done. Got too looking and for a 50 amp plug and breaker he ran 10/3. I ripped it all out and did it right with 6/2.

Without knowing the details, your electrician may have been looking at article 630 of the NEC, which under some conditions allows the conductors to be downsized depending on the duty cycle of the welder.

metal1313 · May 29, 2009

im looking to do the same, prob 50 amps. but i do have a few questions. im wondering how i can have one 50 plug, possibly one or two 30amp outlets, and a 4 bank of 20 amps. never running the 50 amp welder with anything else, and never multiple 30 amp machines. i have a tiny garage and so far one extention cord has suited all my needs, but i do want a larger compressor, and a new 230 mig gun.

i cant have a larger braker in the main box, with out having to take out the 20 slot panel and add a larger one. old houses equal really pricey electrical work

nate379 · May 29, 2009

I spec'd a 50 amp 240v circuit run to the garage.

Now to me that means a receptacle and wiring capable of handling 50 amps. Plus putting a 50 amp breaker on 10 guage wiring isn't very safe... or to code!

Stuart in MN said:
Without knowing the details, your electrician may have been looking at article 630 of the NEC, which under some conditions allows the conductors to be downsized depending on the duty cycle of the welder.

Aceman · May 29, 2009

nate379 said:
Plus putting a 50 amp breaker on 10 guage wiring isn't very safe... or to code!

You're mistaken. Stuart is correct, welders/motors don't follow standard procedures, they have different rules. Folks seem to get it drilled in their head that:
#14=15 amps
#12=20 amps
#10=30 amps
etc.

That is not always the case. I'll give you a couple code references since you seem to think it's not to code:
630.32(A)&(B)

To sum those articles up, overcurrent protection can be sized at up to 300% of the conductor rating in some cases. For #10 Thhn, that is 105 amps. Of course you still need to follow the welder manufacturers guidelines for breaker sizing, but this is what the NEC allows.

nate379 · May 29, 2009

So if a welder draws near 50 amps at full load I can run 10 gauge still because it's ok to 105 amps on a welder? This is the first time I hear of this.

sberry · May 29, 2009

You can run a 10 to 60 for most machines in the class found here, millions of legal 10/50 circuits were wired in the day of the buzzbox.
Aceman is much more knowledgeable than I am with specifics so I defer to him,,, but for most cases here with special equipment, corded equipment and some specific, 12 wire, max 50A, 10/60 and 8 up to 100A. These are not for feeders to a garage or a panel but certain types of equipment.

30AMP service enough for my garage

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