Sub-panel question

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Old 01-02-19, 12:43 PM
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Sub-panel question

So I ran 4/3AWG 110í to a shed in to a sub-panel. In the s-panel, I installed a single 20A and dual 40A breakers. All breakers read 120v and each outlet wired reads 120v so I think Iím good BUT I plug in a drill or chop saw and very little juice is getting to them. They run but not at the rate they should. Iím not sure where I went wrong. My buddy says that i shouldnít have the common and ground on the same bar but my house has them on the same bar and everything runs fine there. I isolated the ground on the sub-panel to see if that was the case but no, it did not help the situation. My common and ground are on the same bar at the service to this run so Iím not sure what would be causing the short flow. Any info on similar situations would really help. Thanks in advanced!
 
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Old 01-02-19, 12:50 PM
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It's true the ground and neutral should be separated in the subpanel. That is an important safety issue, but would not be the cause of the symptoms you described. See Ray's pictures and thread for information on that: https://www.doityourself.com/forum/e...-diagrams.html



It sounds like you might have something wired in series instead of parallel. Can you measure the voltages under load? Plug in something like a halogen work light or a space heater and take the voltage measurements again while the light is on. Measure between hot-neutral, neutral-ground, and ground-neutral.
 
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Old 01-02-19, 03:38 PM
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The drawing is good. The neutral and ground should NOT be bonded in a sub panel.
Could be a loose connection that creates a voltage drop when current flows.

What voltage do you get across the two hots?
What voltage do you get when the power tools are being used?
 
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Old 01-02-19, 05:45 PM
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So I ran 4/3AWG 110’ to a shed in to a sub-panel
I hope you did not run standard NM-b cable outside, but used UF or some other cable designed for outdoor use.

I agree with the series assessment from IBPooks
 
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Old 01-04-19, 01:08 PM
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The 4/3 is THWN ran through 1-1/4 conduit 24Ē below grade. Iíve isolated the ground with another bar but am still finding the same result. Super weird cause I have a 240v welder powered through the same sub-panel and have absolutely no drop in power in that line when in use. The voltage drops down to 25v when my chop saw is triggered. Found that the other 120v line rises to 235v when I try to power on saw... Swapped breaker but nope, that didnít work either. 109v is the reading when the shop light is on.


 

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Old 01-04-19, 01:26 PM
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The voltage drops down to 25v when my chop saw is triggered. Found that the other 120v line rises to 235v when I try to power on saw
This is a critical finding. One of your neutral wires is loose, broken or connected wrong somewhere between this panel and the power company transformer. You'll have to take measurements further up the chain until you identify a point where both legs stay at roughly 120V under load which tells you the neutral wire is intact.

If this problem can be reproduced at the house, there's a good chance you need to call the power company to have them come inspect the incoming service.
 
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Old 01-04-19, 01:41 PM
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Iím drawing from an irrigation pump panel. It has 3 lines, 120v - 120v - 215v and a ground coming from the power company. Iíve tapped into the two 120v lines in to a dual 60A breaker that feeds the sub-panel. I have no common line coming to my box from power company, could that be the issue?
 
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Old 01-04-19, 01:47 PM
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. I have no common line coming to my box from power company, could that be the issue?
Yes, that is your issue. You do not have a neutral.
 
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Old 01-04-19, 01:52 PM
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Dang it... Well alrighty then... Guess Iíll just not use heavy duty power tools on that 120 line and just my welder at 240. Thank yíall for the help!! I really appreciate it...
 
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Old 01-04-19, 02:10 PM
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But I have a separate 120v line that goes through a single 15A breaker that works just fine without the neutral, coming from the same irrigation pump panel. The neutral on that run is tied just to the ground bar in the panel.
 
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Old 01-04-19, 02:40 PM
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120v line that goes through a single 15A breaker that works just fine without the neutral, coming from the same irrigation pump panel.
Will it work? Yes.
Is it safe? No.

Ground and neutral is tied at the main panel only, so that there is no current carried in equipment ground conductor.
If any fault occurs with neutral wire, it will become hot. When that is connected ground wire, now all grounded chassis becomes hot.
 
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Old 01-04-19, 06:51 PM
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You have a few more issues then not having a neutral (although that is a big one). I should have also mentioned that your irrigation pump panel is 240 volts only You have two hots and a ground, no neutral. Yes, the voltage between one hot and ground is 120 volts, but using the ground to carry current can cause current to be carried by any grounded metal parts. This is a dangerous thing, as Lambition posted. The difference between a ground wire and the neutral wire is the neutral is designed to normally carry current, the ground is not.

You also may only have one feed to a separate building.
 
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