Weird Electrical Q over 30 amps on a 10ga wire-Duration of danger?

[lobstahmeatwad]

so I have a 10Ga wire strung about 100 feet from the main box
It powers a shed with a 100 amp breaker with 4 20 amp circuits.
I plan to pull perhaps at max 38 amps through at peak load.
It will be a min of 24 amps for about an hour.
I understand a 10ga wire to really max at 30amps and you really want to operate at 80% of load.
Does running the machines on different circuits only protect and or optimize the equipment or does it reduce the potential for too much resistance in the line? I don't think so.
So....its an older 10ga line in the ground. What is my potential fire risk here?
How long does it take to heat up a wire like this at this load?
Will it heat where it meets the breaker in the shed? in the ground or back at the main?
will it heat evenly?

The potential to be running at 38 amps is only a few minutes, But I know I will run at around 24 amps for an hour and then again in a few hours after that.

I don't think I am in danger here, being as though 80% of 30 is 24, just trying to get some speculation from other electricians.

[jongtastic]

you might need this for your "shed"

[doughboyshredder]

Ha ha ha, his shed is for building skis. LOL

If nobody beats me to it, I'll do the calculations tomorrow.
Quick glance tells me you should upsize the wire.

[Crass3000]

I certainly would run a larger guage if I had the choice. Max current on a wire also needs to take into account the length of the wire as well as the guage. FWIW I ran to a second box like you're doing around a similar distance but I used 6/3. Seems like you're pushing it with that distance and your max current. If you want to try it out, keep an eye on how hot the 10 guage wire gets under full load (by touching the plastic coating on the wire. If it starts getting hot you have problems. You basically just don't want things heating up. You will likely have a voltage drop over the span but it probably won't be too bad. You running 10/2 (120V) or 10/3 (120V or 240V capability)?

Edit: Check out the first graph. According to that you should really use 6 guage but could probably get away with 8. I always oversize so I would use 6AWG.

http://www.windsun.com/Hardware/Wire_Table.htm

[Beaver]

Put a little transformer (240/600V, 15KVA, single phase) at the source end protected by an 80A2P breaker, bump the voltage to 600v, put a matching transformer at the other end drop the voltage back to 120/240 and you'll have bags of power through your skinny ass wire, it'll never see more than 25A. A little 100A panel in your shop & you'll be good to do whatever the fuck you want.

You don't want to run motors on what you've got they'll run slow, draw more current than rated and it'll significantly shorten their life expectancy.

[Art Shirk]

[Crass3000]

Put a little transformer (240/600V, 15KVA, single phase) at the source end protected by an 80A2P breaker, bump the voltage to 600v, put a matching transformer at the other end drop the voltage back to 120/240 and you'll have bags of power through your skinny ass wire, it'll never see more than 25A. A little 100A panel in your shop & you'll be good to do whatever the fuck you want.

You don't want to run motors on what you've got they'll run slow, draw more current than rated and it'll significantly shorten their life expectancy.

Never used these transformers but I see no reason this wouldn't work as well. By transforming your voltage higher over a wire the current then needs to be lower to get that same amount of power since Power = voltage x current. When you use the transformer at the recieving end then you would go back to usable voltages but have more current available. This is basically how power is transmitted over the grid. Higher voltages require smaller conductors for the same amount of power. If you did this make sure your wire is rated for the higher voltage. The voltage rating is normally written on the jacket of the wire.

[runethechamp]

Size the main breaker in the subpanel by the wire you have (30 amp breaker I guess). The breaker won't trip instantaneously at overload but will make sure you are safe. If it trips on you all the time, upgrade the wire or do the transformer trick.

[doughboyshredder]

transformers are a good idea, hadn't thought of that.

Either that or put in the 6/3

[jongtastic]

and when your tapping into your neighbors power be inconspicuous,you dont wanna roll over there like "Hey im lobstahmeatwad and I HAVE A HUGE GROW OP in my ski building shed! Thanks for the power!"

what kind of lights are you using? ventilation is key.

[warthog]

Size the main breaker in the subpanel by the wire you have (30 amp breaker I guess). The breaker won't trip instantaneously at overload but will make sure you are safe. If it trips on you all the time, upgrade the wire or do the transformer trick.

A motor load will constantly trip it. Motors pull a whole lot more at start up than they are rated for.

Never tried the transformer trick. Not sure about that one. I would pull new wire. It is not as tough as it sounds. I am assuming there is conduit leading to the barn.
Worst case, hire an electrician to come out and pull 6 Awg. They have the tools to pull that wire really quickly, and you won't have to do the sucky part of the job.

[lobstahmeatwad]

120V

This is for homemade heat blankets for cooking skis. Growing weed is definitely not profitable or worth my time in montuckistan these days, everyone is doing it.

The heat blankets draw 11.9 amps each and cycle on and off to ramp to temp through a fused controller.
Yeah the conduit is really old and probably corroded in the ground so pulling a new wire was something the electrician didn't want to mess with.
They suspend my main in the air why couldn't I do this with a new 6 ga wire?
Code shmode.
10/2 or 10/3 I do not know.
I though ga was ga.
The lights are task lighting and draw about 1.75 amps when on.
Its really the compressor and the baseboard heater and the blankets that pull all the juice but we can turn everything else off except for the blankets when cooking the skis. My blankets do 1450 watts so I bet top and bottom will cook the skis in 30 min easy. So 24 amps is the max we will pull.
Transformers huh, more than meets the eye.


Again tgr confuses me more than need be....

[doughboyshredder]

Dude, just dig a fucking 18" deep trench and put some direct burial 6/3 in there.
Still try a test pull through the conduit first. Unless they used metallic conduit, it shouldn't be corroded, and even if they did it shouldn't really be corroded. Expose the end of the conduit by the shed, and by the house, see what it looks like.

[warthog]

I would recommend piping it out. You might want to upgrade some day- air compressors, welders, etc.
You never know. PVC conduit laid in the trench- prevents you from hitting it later.

[lobstahmeatwad]

this is a shed built to house a modal A car. the conduit is iron. Its corroded. Built 1920ish.
Its not actually my residence so there's that also.

If I am gonna dig a giant 100ft long trench I'm dropping 220 in there and then I would have to rebuild my blankets to be more efficient.
edit: and the controllers.

[runethechamp]

A motor load will constantly trip it. Motors pull a whole lot more at start up than they are rated for.

Never tried the transformer trick. Not sure about that one. I would pull new wire. It is not as tough as it sounds. I am assuming there is conduit leading to the barn.
Worst case, hire an electrician to come out and pull 6 Awg. They have the tools to pull that wire really quickly, and you won't have to do the sucky part of the job.

Not sure if they exist here, but I'm pretty sure that in Norway you could get "slow" breakers that wouldn't trip during startup of motors. In any case, it wouldn't cost much to switch out the main breaker in the sub panel.

My last option would be to try to run this as-is. The main breaker in the sub panel is not doing its job right now, which is to protect the 10ga wire coming in to the panel.

[doughboyshredder]

this is a shed built to house a modal A car. the conduit is iron. Its corroded. Built 1920ish.
Its not actually my residence so there's that also.

If I am gonna dig a giant 100ft long trench I'm dropping 220 in there and then I would have to rebuild my blankets to be more efficient.
edit: and the controllers.

Pick up a couple mexicans at the home depot and that trench will be done in a few hours for 40 bucks.

Cue up all the attacks...............

Either that, or since it's not your place and you don't care about code just get some 6/3 romex pull it through some pvc conduit and lay it on the ground. Ain't gonna hurt anything.

[lobstahmeatwad]

yeah well we don't really have mexicans here believe it or not, I mean we do but not like everywhere else in america.
kinda like my joke when I moved here I was the mexican, still am.

[doughboyshredder]

ahhh, lol

[Crass3000]

Size the main breaker in the subpanel by the wire you have (30 amp breaker I guess). The breaker won't trip instantaneously at overload but will make sure you are safe. If it trips on you all the time, upgrade the wire or do the transformer trick.

Yah you REALLY don't want a 100A breaker. Breakers are relatively cheap. New conduit with 6/3 is your best bet. The old conduit is rusty and likely undersized since they only ran 10AWG. 6/3 is a thich wire. Roughly the size of a quarter in diameter but probably slightly bigger.

I'm not sure I would say that a 30A breaker on 10AWG of 100ft would keep you safe from fire since it's not rated for that current at that length.