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forresth 10-03-2011 10:09 PM

Making a power distribution center
 
I was thinking of just getting a 100' 50 amp extension cord to run a welder instead of putting in a sub panel in my garage. If I have that much money into a monstrous extension cord, I might as well upgrade from a 6/3 to a 6/4 cord (or some RV cords) and get a power distribution center of some kind.

The power distribution center I see for sale seam way over priced and lack a 6-50r receptacle for a welder.

I am thinking all I really need is a box with an appliance cord with plug, a welder receptacle and a pair of outlets (maybe GFCI, but I hear they don't like heavy motor loads); or a source for power DC that doesn't cost more than I budgeted for the whole project.

mpoulton 10-03-2011 10:57 PM

You need GFCI protection for the 120V receptacles, since this will be used outdoors or in a garage. It would really be foolish not to. GFCIs do not have any problems with any specific type of load - if it's tripping, it's doing its job. They're used on all construction sites and have been for many years now.

You will also need 20A circuit breakers or fuses, since the receptacles can't just be connected to the 50A feeder. What you're ultimately trying to produce is something like this:
http://www.google.com/products/catal...ed=0CHIQ8wIwAA

For $370, it might be worth just buying it instead of making it. The end result will be much more durable and well packaged.

forresth 10-03-2011 11:36 PM

I was under the impression the reason garbage disposals were exempted from GFCI requirements was at least partially to the number of false trips.

dmxtothemax 10-04-2011 12:52 AM

If you are tring to do it on the cheap,
Have a scrounge around and see what you can come up with,
A gfci on the source outlet is recommended,
When you have found the appropriate outlets/plugs/etc
then we can advise the best and safest way to assemable it.

You will need,
A plug rated at minimum 50a.
Cable rated at 50a min, ( a little larger helps ).
A 50a recepticule,
A heavy duty pvc box to assemble it all.

Jim Port 10-04-2011 08:29 AM

Quote:

Originally Posted by forresth (Post 741746)
I was under the impression the reason garbage disposals were exempted from GFCI requirements was at least partially to the number of false trips.

You received the wrong information. As was said above, if the GFI is tripping there is a problem with the wiring or the appliance.

mpoulton 10-04-2011 08:41 AM

Quote:

Originally Posted by dmxtothemax (Post 741791)
A gfci on the source outlet is recommended

That is actually a pretty good way to do this. You can use a 50A double-pole GFCI (spa breaker) in the main panel. That way the 240V receptacles and the main cable are protected, too. I did this in a garage at a house I lived in awhile ago. The only disadvantage is that tripping the GFCI shuts off power to everything plugged into the breakout box - which might include your lights if you're working at night. Got plunged into darkness a couple times. That's still better than getting electrocuted by the wet extension cord connections that tripped the GFCI.

forresth 10-07-2011 10:46 PM

A GFCI for the big plug wouldn't be a bad idea anyways. I looked into a 50 amp GFCI breaker, and they look like they are $100. Am I looking at the right thing?:huh: is it that much more involved to trip a ground fault for 50 amps than 20 amps? I know. I am being a huge tightwad, but that just seams steep for what it is.

ps. I have a sub-panel at the folks pool for a heatpump (40 amps) and the pump motor (240v 20 amps). My initial thinking is these might not be bad to install there, but would they even work seeing as everything (even the water) there is bonded and grounded separately? per pool electrical regs. My thinking is through the breaker ground would not be the path of least resistance when there are other ground wires running in parallel, and of a larger gauge I believe.

mpoulton 10-08-2011 05:27 PM

My responses in red.

Quote:

Originally Posted by forresth (Post 744165)
A GFCI for the big plug wouldn't be a bad idea anyways. I looked into a 50 amp GFCI breaker, and they look like they are $100. Am I looking at the right thing?:huh:

Yes, that's it. You can usually get a 50A 2P GFCI breaker in a single-breaker box intended as a spa disconnect for about $70 at HD or Lowes.

is it that much more involved to trip a ground fault for 50 amps than 20 amps? I know. I am being a huge tightwad, but that just seams steep for what it is.

It's not that much more complicated (hardly at all, actually), but many fewer of them are made so the economy of scale isn't there. They also charge more because they can - where a 2P GFCI is required, it's required. People have to buy them.

ps. I have a sub-panel at the folks pool for a heatpump (40 amps) and the pump motor (240v 20 amps). My initial thinking is these might not be bad to install there, but would they even work seeing as everything (even the water) there is bonded and grounded separately? per pool electrical regs. My thinking is through the breaker ground would not be the path of least resistance when there are other ground wires running in parallel, and of a larger gauge I believe.

I don't know exactly what you mean here. Are you suggesting installing 2P GFCI breakers on the pool equipment? If so, you can certainly do that. It adds an extra margin of safety. The redundant bonding on the pool equipment makes no difference to the GFCI. GFCI's do not require a ground connection to operate, and have nothing to do with the grounding connection at all. They sense the difference in current between the hot an neutral conductors, and assume that any missing current must be leaking to ground.


Missouri Bound 10-08-2011 06:20 PM

So....after you buy all the parts to create this distribution center is it cheaper than putting in a sub-panel? Sems like the sub-panel will definetely be more work, but the end result may just be a better setup. I would think you could run wire and conduit for less than the cost of that "monster cable"

forresth 10-08-2011 08:14 PM

Quote:

Originally Posted by Missouri Bound (Post 744603)
So....after you buy all the parts to create this distribution center is it cheaper than putting in a sub-panel? Sems like the sub-panel will definetely be more work, but the end result may just be a better setup. I would think you could run wire and conduit for less than the cost of that "monster cable"

the monster cable can be quite a bit shorter than the buried wire would be; plus any parts for the DC box would have to be replicated in the garage wiring, and then some.

forresth 10-08-2011 08:18 PM

ps. I have a sub-panel at the folks pool for a heatpump (40 amps) and the pump motor (240v 20 amps). My initial thinking is these might not be bad to install there, but would they even work seeing as everything (even the water) there is bonded and grounded separately? per pool electrical regs. My thinking is through the breaker ground would not be the path of least resistance when there are other ground wires running in parallel, and of a larger gauge I believe.
Quote:

Originally Posted by mpoulton (Post 744551)
I don't know exactly what you mean here. Are you suggesting installing 2P GFCI breakers on the pool equipment? If so, you can certainly do that. It adds an extra margin of safety. The redundant bonding on the pool equipment makes no difference to the GFCI. GFCI's do not require a ground connection to operate, and have nothing to do with the grounding connection at all. They sense the difference in current between the hot an neutral conductors, and assume that any missing current must be leaking to ground.

there is no neutral; they would compare the 2 hots then?
I had assumed a GFCI looked for current in the ground, and the multiple grounding paths would bypass the GFCI.

mpoulton 10-08-2011 10:51 PM

Quote:

Originally Posted by forresth (Post 744716)
there is no neutral; they would compare the 2 hots then?
I had assumed a GFCI looked for current in the ground, and the multiple grounding paths would bypass the GFCI.

Both hots and the neutral all run through a current transformer together. Thus, the transformer senses only the net difference in current between all three wires. If the neutral is not used, then it is irrelevant. All that matters is whether all the current that leaves the breaker also returns through the breaker.


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