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-   -   Out of Ground slots (http://www.houserepairtalk.com/f9/out-ground-slots-14938/)

donald73d 10-20-2012 12:05 PM

Out of Ground slots
 
I have a 40 circuit 200 AMP box where I am out of neutral/ground slots and cannot seem to find any to double up on. Yet I have empty slots for circuit breakers and I would like to add a 50 amp welding circuit.

Wuzzat? 10-20-2012 12:22 PM

Please post what the welder nameplate says.
Values to look for are
I1eff, the RMS value of current the welder draws
I1max, the max current the welder draws
Duty cycle, which depends on the two values above.

donald73d 10-20-2012 03:37 PM

Ok, my first problem is I am out of screws to connect a ground wire.

The welder is a Lincoln 275VS Invertec. It says use a super lag fuse or time delay circuit breaker. It says a 100Amp fuse. On max output it draws 67Amps @ 230V, 35% duty cycle. But will I ever use full power?

Wuzzat? 10-20-2012 06:10 PM

Quote:

Originally Posted by donald73d (Post 78730)
Ok, my first problem is I am out of screws to connect a ground wire.
The welder is a Lincoln 275VS Invertec. It says use a super lag fuse or time delay circuit breaker. It says a 100Amp fuse. On max output it draws 67Amps @ 230V, 35% duty cycle. But will I ever use full power?

My bad. The nameplate info is more useful to sizing breakers and wire lengths.

A small search I did showed that the answer to your question is controversial, and this usually means more detail is required. I have also seen a photo somewhere of a Y shaped device that converts one busbar hole into two.

JoeD 10-20-2012 09:31 PM

You can usually buy additional ground and neutral bars to add to a panel.

donald73d 10-21-2012 06:03 AM

Quote:

Originally Posted by JoeD (Post 78744)
You can usually buy additional ground and neutral bars to add to a panel.

Do you mount them or just tuck them on the side?

notmrjohn 10-21-2012 08:20 AM

The new bars have to be mounted securely inside to panel. You need to connect new bars to original bars with a jumper. If box is getting crowded with wires consider sub panel, even if you have empty breakers.

This is good time to check your ground. It is not unknown for houses using plumbing lines as ground to have lost protection due to repairs, replacing a section of copper line with PVC for example. Possibly install, main GFI and/or surge protector, drive a ground rod into earth. You may need non GFI circuits for refrigerators and AC units.

Wuzzat? 10-21-2012 09:51 AM

Thanks for the info.
I'd like to compare your proposed setup with the rules for Article 630 from my '99 copy of the NEC. The rules in this article are pretty basic so they may not have changed over several code cycles.
http://freenec.com/T513.html

Along those lines, what length will you be using for your #6 input wire? Usually you want less than a 5% voltage from load center to device. Here's one formula for figuring this
http://books.google.com/books?id=UvmE_6XsszcC&pg=PA110&lpg=PA110&dq=mullin +K+cma+electrical+residential&source=bl&ots=4eJvlS jwdr&sig=8OELhLvPI41xLDKTl2o4uYYxl10&hl=en&sa=X&ei =D_aCUO_jHIS-0AHGoIHoDw&ved=0CDEQ6AEwAQ#v=onepage&q=mullin%20K% 20cma%20electrical%20residential&f=false
but deciding what welder current to use for this may be tricky.

For ground checking I guess you could check the ohms between your house ground and a sanded-clean spot on the upstream metal pipe of your water meter.

Footnote: Using your 67A @ 35% duty cycle, 150W idle current and the formula from art 630, the current your welder will draw while the arc is struck is 113A.
Using copper #6 AWG, 26,300 CM at a 5% voltage drop from the 230V you can have up to 112' of cable, so says my spreadsheet.

If the NEC permits you to go smaller on the cable due to insulation temp ratings for a 67A RMS current, I'd do it but you'd also need to go shorter on the length to keep the 5% voltage drop guideline.

With this much current the voltage at your load center may drop 3V or so (more if your house is far from the pole transformer) so with incand. bulbs in your house you may see lights blinking.


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