Swap a 30A breaker to 50A for welder

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Old 10-14-19, 10:02 AM
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Swap a 30A breaker to 50A for welder

Figured that would raise an eyebrow.

First, I did not wire this and I am trying to correct this from the master electrician that did and signed off on it. :/

Anyway, I have a shop on my farm that has been wired up a while ago. The power comes from the house 150 feet away or so. The supply to the shop is a 30A breaker at the house. This goes to a subpanel at the shop that splits THAT circuit to a 20A and a 50A for a welder. Obviously, a 30A at the house will not allow a 50A welder to work downstream.

However, the wiring that goes to the shop with the 30A double pole breaker is AWG 6. Since the shop is wired completely with LED lights on a 20A circuit and they are rarely used, is there ANY safe way to swap out the 30A breaker on AWG6 wire to a 50A for welding?

Sketch Attached, but here's a bigger pic. Not sure the attachment works right.

https://bit.ly/31gdJXc
 
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  #2  
Old 10-14-19, 10:08 AM
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THHN or NMb AWG6 supports a 60A breaker. If its very old (TW), then I don't think so.
 
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Old 10-14-19, 12:03 PM
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See sketch. The barn is old. The wire is less than 7 years old. THWN 6 gauge.
 
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Old 10-14-19, 12:12 PM
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At 150', very close to a 3% voltage drop limit for a subpanel. I would be putting in a 60A dp.
 
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Old 10-14-19, 12:49 PM
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60A on 150í 6ga THWN? Thatís cool?
 
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Old 10-14-19, 01:15 PM
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if THWN; that gets you 65A ampacity in conduit.

just did the V drop calculator; 3% at 135' and 60A. If that is a problem, then its a 50A breaker.
 
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Old 10-14-19, 03:14 PM
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60A on 150’ 6ga THWN? That’s cool?
Yes.... that is within code specs.
 
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Old 10-14-19, 06:12 PM
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Thanks for the info, both of you.

If I understand correctly, I COULD put a 60A breaker on that, but if I ever pull close to 60A..or really any more than 55A, then I would see more than 3% voltage drop and that's not great for motors. I have zero inkling of how I could possibly pull more than 50A, so I think that is what I will go with for the breaker size. Even the arc welder full bore won't pull more than about 45A.
 
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Old 10-14-19, 07:05 PM
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if THWN; that gets you 65A ampacity in conduit.
You can actually put #6 THWN on a 70 amp breaker/fuse. (240.4(B))

Also, voltage drop will depend on the actual load, not the rating of the breaker/fuse.
 
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Old 10-15-19, 10:01 AM
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OK, guys. Help me with this calculation:

I'm trying to validate existing wiring.

So, with the current setup, 220V 50A on 6ga THWN for 140'. I have that.

What if I now need to go from the end of that run another 200'? That additional circuit would only need to handle 110V lights at my pens and another barn and a few outlets for rare use. It's a hay barn and storage. How do I calculate wire size for that additional run?
 
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Old 10-15-19, 11:57 AM
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https://www.calculator.net/voltage-drop-calculator.html

Here ya go; I'll let you decide the max current; the formula does the rest.
 
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Old 10-15-19, 08:00 PM
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https://photos.app.goo.gl/MQky1em2MLhbwEreA


WAIT WAIT WAIT.....I think I have a problem here. Someone help me out, this doesn't look right. Everything seems to work fine, and the outlets seem to check out ok.

This WAS done by a local licensed electrician in 2013, but this doesn't look right.

I have a main panel, subpanel, and then another subpanel.

main panel with DP Breaker -> Subpanel on side of house which has 50A and 40A breakers (240V for both) -> subpanel at barn with 20A breaker 110V and 50A 240V AND a ground wire that goes outside the box to a rod driven into the ground.

NONE OF THESE SUBPANELS HAVE A BARE GROUND. I have three and only three sheathed wires between all of these.

This doesn't feel right. IS it right? If not, can I correct it easily? Photos in link above, with annotations.

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Last edited by PJmax; 10-15-19 at 09:01 PM. Reason: added 2 pics from link
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Old 10-15-19, 08:53 PM
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This WAS done by a local licensed electrician in 2013, but this doesn't look right.
I'm guessing no inspections as you are correct...... there should have been four wires to all sub panel locations. The neutral and the grounds WERE supposed to have been connected separately.
 
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Old 10-15-19, 08:56 PM
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How do I FIX it as painlessly as possible while maintaining code compliance? There are THREE panels like this outside, one of which serves a small residence, and multiple subpanels IN my home that I have not checked. I'm terrified to open them. Anyway, let's focus on this one. How do I fix it?
 
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Old 10-15-19, 09:00 PM
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There isn't an easy way to fix it. You'd need to pull a fourth wire. Pretty tough on a long pull.
 
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Old 10-15-19, 09:24 PM
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What about a new separate conduit with another conductor in it to act as ground back to panel 1 and then another conduit doing the same to the main?

Or hell, direct bury as far as Iím concerned.

Is there an issue with either of these options?
 
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Old 10-15-19, 09:40 PM
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By code.... all the conductors feeding the panel must be in the same conduit.,
 
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Old 10-15-19, 10:13 PM
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Ok. So if this were installed in 1995, how were three wire feeds to panels installed on detached structures to meet the 2005 NEC??

i know how to fix this for current code, but Iím curious how to make sure this is at least compliant to OLD code in the interim. Having done more research on the farm, the outbuilding power was installed well before the new stuff and all sub panels and wiring were in place
 

Last edited by agdodge4x4; 10-16-19 at 12:05 AM.
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Old 10-17-19, 04:00 PM
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Confirmed. 2006 install. I have a ground bonded to neutral at the sub and a ground rod at the outbuilding. Not sure if thatís right per old code but hopefully.
 
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Old 10-17-19, 04:18 PM
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The NEC changed in 2008 to require in all cases a grounding wire for power to separate buildings (but the NEC is enacted into state law with various lags, so it could have been legal even after 2008).
 
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