Feed wire sizing to my garage

I haven't read every post word for word,,,, but what size of the entrance to your house? 200Amp? Do you have room for an additional 2 pole breaker in you main CB box? It is exactly like everyone says.................. size up.

steve

Potential altitude is of no value.
 
I ran #2 THHN copper in conduit and protected it with a 125A breaker. #2 is good for 115A, but due to the next size up rule you can protect it with a 125A.

#2 is small enough it is still pretty easy to work with.
 
2/2/2/4 and 100 amp here as well. 70' you can hand trench quite easily in most soils, match electric code requirements for depth, wire size, etc.

In your 1/2" EMT you can run 4 #10 wires for 30 AMP 220. If that can meet your needs. Otherwise, you have to run new wire anyway. 12/3 with ground only gets you 20 amps. One circuit.

How you're getting EMT to hold up underground beats me.

Jeff
 
Hi all, I'm looking for some advice. I'm looking to add power to my detached garage ...the run will be 70', it will power some lights (>2amps), a little old radio, and 1... a 1 HP vfd to power both my mill and lathe (240 3ph, 3/4 and 1/2 Hp respectively) I will also install 8 outlets.
.

If you want it up to code, it'll take a subpanel in the outbuilding with its own breakers. Your lights and
outlets will have 120V breakers, and the VFD a 240V breaker, so a stalled motor doesn't leave
you in the dark... Maybe there's already a breaker box there?

General guidelines: for a farm outbuilding, #8 wire for up to 50 feet, #6 wire minimum for anything
farther. Specifically, there's worksheets for totaling up loads (get _Wiring_Simplified_, H. P. Richter,
from the library if you want to see details), but probably the smallest subpanel (60A) and #6 wire
are going to be required.
 
I've read most of the comments and you've gotten some good info. There's a couple of points I will make. Safety is a factor when you attempt to stretch electricity beyond the laws that govern it. One comment I read from ewkearns had flashing red lights. You electrical service from which you will be pulling to your shop is the key. If you only have 100A then you may be stretching it. The electrical code dosen't say it's okay to it wire it like this, ________ (insert reason)? I know you stated you would be working when everything in the house is idle but on the occassion when it may be different? The second item is the 1 hp vfd. It would be good to look at the full load amps (FLA) of what you are running vs looking at HP. When electric motors run at less than or more than how they are rated it reduced their life, and this includes speed. Slowing a motor down or speeding it up by less than or more than 20% is detrimental.

With funds being a factor, my recommendation on pulling the wire would be to pull the correct size required. There's plenty of info on the net in regard to wire size, amperage, voltage drop, etc. You can use an undersized circuit breaker on the correctly sized wire, safely, but not an oversized breaker on incorrect wire size. I was taught to alway respect water, fire and electricity.
 
Run 2" pvc conduit out there and pull in wire for your present load. PVC conduit is cheap and digging is expensive. The 2" conduit could accommodate a 200 amp circuit in the future,should your needs increase.
 
One item that is never talked about in these thread is you voltage drop requirements. First I agree that the larger the wire the better, but better equals more expensive.
The original problem was the garage is approximately 70 feet. So assume a 100 foot run. The load requirements are lite, but allowing for future expansion lets assume 120 V @ 20 amps and 240 volt @ 30 amps. That amount of power will run most equipment. We can also assume a continuous load of 15 amps for lights and other small items. That mean a 120 V @ 35 amps. The National Electric code (NEC) recommends 3% voltage drop.

2017-03-14_10-28-13.jpg 2017-03-14_10-21-41.jpg

Doing a quick calculation, the recommended wire size is #8 for the 240V requirements but is #6 for the 120V needs. Note the multiplier show is incorrect, but calculations are correct.

Here are he calculations. Please note that the spread sheet isn't mine.

2017-03-14_10-34-40.jpg
 
One item that is never talked about in these thread is you voltage drop requirements. First I agree that the larger the wire the better, but better equals more expensive.
The original problem was the garage is approximately 70 feet. So assume a 100 foot run. The load requirements are lite, but allowing for future expansion lets assume 120 V @ 20 amps and 240 volt @ 30 amps. That amount of power will run most equipment. We can also assume a continuous load of 15 amps for lights and other small items. That mean a 120 V @ 35 amps. The National Electric code (NEC) recommends 3% voltage drop.

Voltage drop is an important consideration, but I am not sure I agree with your calculations. Assuming the OP has a standard 120/240 split phase service, then only the unbalanced current between the hot legs ends up travelling back on the neutral.

Using your example above, with 20A of 120V for receptacles and another 15A for lighting, assuming that the single pole breakers are connected to different poles in the panel (and any panel should have its 120V breakers balanced!) then you only have a 5A delta between the legs, and the neutral will end up carrying that 5A.

In other words, you would end up with 15A of 240V and only 5A of 120V in that example. Add in the 240V loads and you have a total of 45 amps of 220V and only 5A of 120V.

In most cases the feeds to outbuildings end up carrying very little current over the neutral. In big installs, it is allowed to undersize the neutral compared to ungrounded conductors for this reason.
 
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Voltage drop is an important consideration, but I am not sure I agree with your calculations. Assuming the OP has a standard 120/240 split phase service, then only the unbalanced current between the hot legs ends up travelling back on the neutral.

Using your example above, with 20A of 120V for receptacles and another 15A for lighting, assuming that the single pole breakers are connected to different poles in the panel (and any panel should have its 120V breakers balanced!) then you only have a 5A delta between the legs, and the neutral will end up carrying that 5A.

In other words, you would end up with 15A of 240V and only 5A of 120V in that example. Add in the 240V loads and you have a total of 45 amps of 220V and only 5A of 120V.

In most cases the feeds to outbuildings end up carrying very little current over the neutral. In big installs, it is allowed to undersize the neutral compared to ungrounded conductors for this reason.

Wondering what you mean by split phase service? I agree with you if this is 3 phase but I'm pretty sure I read single phase in the question being presented along with the need for the VFD.
 
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