Print

[hondaracer2oo4]

I am building a 28x40 garage this spring. The garage is detached from house. It will be about 55 feet from the house. I am going to run a sub panel in the garage tapped off my panel in the house. The run from the panel in the house to the sub in the garage will be in the neighborhood of 110-120 feet when you account for turns in the wire Etc. My thought was to run a 60 amp breaker off the main panel and use a main lug panel in the garage.  First my plans are to run a 180 mig welder once in a while and a Lincoln tombstone welder once in a while. Those would be the two highest consuming power items.  Other than that I will put a two post lift in at some point which will be 220. Anyone think that 60 amps isn't enough?  So my real question comes down to someone that is knowledgable about carrying capacity of wire. Is 6/3 with a ground wire going to be sufficient or not over that run? I think I am pushing it with 60 amps at that length with 6/3. Could I run 4/3 in the basement which is about 45 feet into a junction box and then step down to 6/3 for the underground conduit to go out to the garage which will be about 65 feet  if the 110-120 feet is to much?

[willieG]

I think I read that  your 6/3 wire (if copper)  will carry 60 amps to a max of up to 300  feet ( that is the wire manufactures rating I believe, what the electrical code of your area is I don't know) the chance you will have a draw of 60 amps is likely low.  I would ask what your current amp service is now. if it is only 100 amps then you may on occasion blow your main breaker when the house and garage over draw the main breaker (if you have a 200 amp service you will be fine)

I know a fella who wired his tombstone welder to a double pole 40 amp breaker (even though the instructions with the welder called for a 50 amp) and he said he has never blown the breaker. is it right, not likely but it works for him

perhaps a licensed electrician that knows the code in your area would be a good fella to have a chat with

[RSI]

Unless you are using multiple things at the same time, I think it will be ok. I would have to check but I think the shed where I use my welder is close to that distance and I think it is 6 gauge wire. I only ever tripped the breaker once and it was running with the welder turned all the way up and doing a long weld. My mig is an ESAB MM250 which is a max output of 280 amps.

Going half way with the larger wire would help a lot with voltage drop especially if you do run a lot of stuff at the same time.

[hondaracer2oo4]

I don't run a lot of things at the same time. Just a hobby garage with the typical man stuff like welders and car lifts.

[mlappin]

Technically 6 is good for 60 amps. What local code or your insurance company thinks might be a different story.

Also depends on your supply from the road. First place I worked had chronic low voltage problems so we always ran a gauge heavier. Lower voltage equals more amps being pulled.

Lucky here at the farm, I’ve never had a reading lower than 242 volts on each leg for the three phase, never lower than 120 or 240 for the single phase. Although it is a small difference, something running on 120 will pull be less amps than on 110.

Our entire shop used to be run on a 60 amp feed.

Lincoln 225 amp buzz box. Drill presses, lathe, 60 amp plasma cutter. Sometimes you’d see the lights dim when starting the plasma cutter.

Ran a new hundred amp single phase and a new 100 amp three phase to the shop, running the big wire welder, the bridgeport, lathe and plasma cutter off the three phase which leaves a ton of reserve on the single phase.

Easier now to run heavier wire than you need and use a small circuit breaker than it is to replace the wire later if you want more juice.

[mlappin]

Here is a VERY handy app I use all the time when doing electrical work, enter the load, alum or copper and temp range and it will tell you the wire gauge, if distance becomes a factor goto the next heavier. Not quite as handy as a chart I had once that gave copper or alum, temp, distance then gauge but still works very well.


https://itunes.apple.com/us/app/elec-ref/id360723129?mt=8

[RSI]

Technically 6 is good for 60 amps. What local code or your insurance company thinks might be a different story.

Also depends on your supply from the road. First place I worked had chronic low voltage problems so we always ran a gauge heavier. Lower voltage equals more amps being pulled.

Lucky here at the farm, I’ve never had a reading lower than 242 volts on each leg for the three phase, never lower than 120 or 240 for the single phase. Although it is a small difference, something running on 120 will pull be less amps than on 110.

Our entire shop used to be run on a 60 amp feed.

Lincoln 225 amp buzz box. Drill presses, lathe, 60 amp plasma cutter. Sometimes you’d see the lights dim when starting the plasma cutter.

Ran a new hundred amp single phase and a new 100 amp three phase to the shop, running the big wire welder, the bridgeport, lathe and plasma cutter off the three phase which leaves a ton of reserve on the single phase.

Easier now to run heavier wire than you need and use a small circuit breaker than it is to replace the wire later if you want more juice.

You have single phase and 3 phase as separate services? Usually in commercial buildings I have seen, if there is 3 phase in the building then everything runs off it. They just use 2 of the phases instead of a center tapped single phase transformer. If you have 208v and 120v then it is running off 3 phase.

Not everything draws more amps at lower voltage. Some draws less.

[mlappin]

Have two separate services. One pole has the single phase which was here when grandfather bought the farm, when father expanded the dairy he had the three phase added which is on a separate pole. This is farm service, not commercial. Both are 200 amp services, if we expand the grain drying setup much more then we’ll have to either add a second 200 amp three phase service, replace 700 feet of underground line so we can goto a single 400 amp service or goto 480. I’d much rather do either of the first two than play with 480. If going to 480 then we’d also have to add a lot of step down transformers as we have a lot of definite purpose contractors with 220 volt coils.

The three phase is all Delta, hook your two hots up to a single phase 220 volt motor and ignore the neutral/wild leg and the single phase motors run just fine on 3 phase.

For the most part on all the electric motors I’ve used 220-240 volts pull less than 208 volts and 440-480 pulls less amps than 220-240.

[RSI]

If the contactors are the only problem, wouldn't it be worth replacing the contactors? If the coils could work up to 277v you could just rewire then to run on one phase to neutral instead of 2 phases.

What size are the contactors? I have a pile of new old stock contactors. I would have to check on the coil voltage and contact ratings.

[mlappin]

Would still need step down transformers for all the stir-ators as well. All of have a 220 single phase motor running off two legs of the three. Don’t think they’d like 480 at all.

Then would have several burner units to change out as well or add step downs too. Two use 220 circuit boards and the last one still has the old style looking vacuum tube type controls.

Personally I’d rather not mess with 480 at all. Worked on our own irrigation when we had it, all was 480 three phase, stuff makes me nervous. 240 three phase just stings a little, 480 will kill yah.

We have Delta phase at the farm, two hots and a neutral, single phase 240 breaker boxes pass code, two pole breakers, goto 480 and technically according to our service provider all breaker boxes has to be changed out to three pole breakers for 480.

Given that it’s delta phase and how our transformers are wired on the pole you have 240 from a hot leg to the neutral, you also have 240 from the other hot leg to the neutral, you also have 240 from hot leg to hot leg. So it’s not possible to grab just one leg and the neutral on 480 Delta and end up with 277 or grab a leg on 240 and a neutral and end up with 120.

[mlappin]

If the contactors are the only problem, wouldn't it be worth replacing the contactors? If the coils could work up to 277v you could just rewire then to run on one phase to neutral instead of 2 phases.

What size are the contactors? I have a pile of new old stock contactors. I would have to check on the coil voltage and contact ratings.

Contactors range anywhere from a 1/2 hp up to a 20hp. All different brands as well. The corn dryer has high dollar ones with built in overloads that are adjustable with a dial and a slider. Each grain bin has a minimum of three contactors just for the load outs and sweep, 7 grain bins so 21 coils needed right there. Pneumatic grain mover has 4 contactors in it, grain leg only has two motor starters and a but load of relays, etc etc.

Just much easier to either add another 200 amp service and run the bins south of the drive on the second service or goto 400 amp service.

[BIG AL]

Speaking from personal experience when we built my fathers barn we ran a 60 amp feed from the house over to the barn to a 60 amp main disconnect sub panel. We frequently run a big 325 lincoln tombstone up to about 150-160 amps on a 40 amp breaker no problems also runs the mig fine. We also have a wood shop upstairs and run a 220 planer , joiner , and table saw  with no issues. I guess it would be better with a bigger feed but it wasn't cost effective to up the house service to 200 amps or give the barn a separate service. As long as you don't run everything at once you should have no problems

[oldchenowth]

I have been wiring residential for years, 60 amp should run what you call for without issue.  Don't run different sizes to the barn using a junction box.  Run all one size in one continuous run.  4/3 Cu is better than 6/3 Cu just for heat build up in the wire.  Separate the neutral and ground in the sub panel and put in a ground rod at the sub panel.  It is not code to bring a ground from the main panel to the sub.  Most areas are requiring two ground rods 6 feet apart at a sub panel (Michigan).  If your sub panel is 100 amp, I would put in a 100 amp in the main just as convenient insurance.  #2 is better in longer runs than #4 but #4 will carry 100 amp.  If you go aluminum from the main to the sub, 1/0 is the smallest I would go.  Watch over time for thermal contraction / expansion breaks in it, normally at the breakers and booger it up good with anticorrosion gel anywhere it is bare.  Aluminum sucks but it is more affordable.
Just my penny and a half