Wire calculation help needed

[Red88Carrera]

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[wdfifteen]

Originally Posted by Rusty Heap

you didn't list much any requirements in your OP.....you asked us to do your budget and design for you...go to your electrician then, go to your county code and kneel and swallow before your inspector, fullfill your mistakes, you didn't list much in your OP...........grins........whiner.

enjoy your 95 VAC line voltage running 12 gauge romex out to the end of the 200 foot run.

"The power requirements at a max will be to run some lights and an air compressor (240 volt 100amp at startup 20 amp cont.) " Seems pretty concise to me. I asked for suggestions so I could get a ballpark on the cost of the project as defined, I didn't ask for a total redesign of the project. Some people here were very helpful in that regard. Thank you.

[john70t]

Here's some more.
Ohm's Law Calculators has a calculator for figuring out total power requirements. I don't know what the "% over peak" standard is(mabye 20%)? Bigger is always better for future needs.

American Wire Gauge table and AWG Electrical Current Load Limits with skin depth frequencies has some info on resistance drop over distance.

There is a difference between interior-rated and exteriour-rated wiring. Some can be directly buried and some are required to be enclosed in a conduit. For safety, I'd recommend the conduit anyways.
Better double-check wire type and burying depth with the city before buying anything.

+1 on telephone/cable or leaving a sacrificial pull-wire for later needs.

[billybek]

Originally Posted by milt

The man breaker should not touch any AL. It's the lugs that touch the AL. Branch circuit breakers will have a wire connected to them.

Yup, your right. The main breaker snaps into the buss for the supply and the feed to the breakers.
I did run Al. into the house from the breaker in the garage too. Used a 100 amp breaker at the main panel and for the main breaker in the house.
I did separate grounds at both buildings.
Anyway, it looks like the OP has an electrician and he should be OK.
What were we talking about anyway?

[DanielDudley]

Originally Posted by wdfifteen

Which wire needs to be upsized? The one from the transformer to the house, or the proposed one from the house to the garage? I am concerned that if the wire from the transformer to the house was sized for the 200 amp house panel, adding another 100 amps of draw to the garage would overheat it.
A possibility is dropping the service to the garage to as low as 60 amps. It's a long shot that I will ever move my welder or my big air compressor to this shop, so it may never have anything bigger than a 1 hp air compressor and lights in it.

You cannot over draw a wire if the breaker is sized correctly. At most you would blow the main breaker, and that is highly unlikely.

[john70t]

Good point on the breaker. You don't want a 20amp breaker when the wire and outlet are rated for 15amp.