How to pull wire over ceiling

Use cuts of THHN or XHHW, or something along those lines.

Really, this is the kind of stuff you should already know to do a job like this. I'm all for homeowners being able to do their own work, but this isn't the right place for questions this basic. There's a lot in the NEC, all of it is important. Maybe make a free account at up.codes & read up on it before you start.

You need a licensed electrician for this. This is NOT, emphatically NOT, DIY territory. You started off with how to pull a wire — but you are really looking at what is the capacity of the main panel? Is it feed-through or how does this sub panel tie in? Does the sub panel have a master breaker? Where? Why? Grounding? What gets bonded to what?

for 80 Amps

yea

3 conduits

that would only be legal with nonmetallic conduit. with metallic enclosures all of the current carrying conductors need to be in the same conduit so that the magnetic fields cancel out and don't induce current in the enclosure.

Assuming 60° terminations, table 310.16 says #3 is good for 85A, table 250.122 says #8 is good for a 100A (that covers 80A) breaker, so 3x #3 & 1x #8: Annex C table C.1 says 1¼ is good for 6 #3s, so about 1½ OD. You may be able to go smaller if you can use the 75°, you might be able to squeak the #8s the conductors into 1" EMT (1⅜ OD) (it's good for 3x #3s, but you'd have to do the full calcs to see if the #8 will fit) but it'd be tight.

NP: it's been about 15 years since I did this, DOUBLE CHECK. There's been several code revisions since then, & I was never the smartest guy I know.

you can’t add an 80 amp sub panel to a 100 amp main.
please contract a licensed and insured contractor!

I forgot I had an app on my phone. It says 3#3 & 1#8 THHN is 38% fill of 1" EMT, so doable but tight, like I guessed. You'd have to take your time feeding it in, to make sure it doesn't get crossed over itself, maybe use a little smurf juice.

@ratio

That would be very tight I found that out the hard way years ago on a short run it wasn't worth the trouble. I should have run 1 1/4"

The code is the minimum standard. Certainly, when it comes to raceway sizing for wires if you at the max your usually in trouble unless it is a short straight run. Especially when you work by yourself as I usually did. Can't push and pull at the same time (although I have done that with a long rope and a pully) you need someone to keep the wire straight going in the pipe and taping the wires and leaving it taped inside the pipe is not allowed.

I’d run pvc conduit or raceway and pull #4 THHN (2 hot + neutral plus ground)

Conduit can be run across the ceiling or is this a living space?

I don’t recall if conduit carrying power can be buried directly under drywall.

The OP's question was, "I can open a series of openings to get the string through. But then how to repair these holes?"

@mattmia2 is right you need to check the welder's duty cycle and read the code book. You can get away with less than 80 amps but it doesn't change things much. Still have to get power over there.

I dont think the OP has any clue on how to do this!

Looks right to me.

I might add — there's a reason most farms are 200 amp services, and often 400. — and 400 to 600 amp three phase connections aren't unheard of You've just found the reason.

If you overload the main breaker it trips. Next time, don't run the welder, the stove, the dryer and the ac at the same time. Turn off the AC and the dryer, reset the breaker and continue welding.

People tend to overestimate house loads. You can definitely turn on a bunch of devices at the same time and trip but it just doesn't happen in the real world under regular usage.

I have a power meter on my all electric home and I have seen about 15kW (~60A) peak use. That is with a 20a feed for a welder (surprising what you can weld with a 20A inverter one).

The main concern here is wiring this up properly and that is not something you can guess.

I would also recommend 20A GFCI plugs for power hand tools. Much harder to trip when you are going to town on something.

There are other reasons for three phase… and yes, breakers will hold on an overload… unfortunately…

Trust me, @mattmia2 , we ag people may have s**t on our boots, grease on our hands and hay in our hair, but we do know what we are doing and why.

there is a procedure in the code to calculate the load. there will be lines in your calculation for general usage per square foot, major appliances, and small appliance circuits counted at if i remember 80% of the capacity of the circuit and further derating if there are over a certain number of small appliance circuits.

there should be a table that gives the input power to that welder but the table you have is showing the output power. depending on what the input power is, you could potentially use a lower current twistlock or conventional plug and receptacle instead of a range receptacle. does that welder require a neutral, is it 120/240v or is it 240v only? If it is 240v only you could use a 6 series plug and receptacle instead of a 14 series.