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Old 04-29-2006, 02:01 PM
Spencer Spencer is offline
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Default Fusing down a 50-amp circuit to 30-amps

I have an existing 240-volt, 50-amp circuit in my shop that I would like to be able to plug a 240-volt, 30-amp device into. Simply putting a 50-amp plug on the 30-amp device would work, but it would not give me any over-current protection. I still want to be able to plug 50-amp devices into the 50-amp receptacle so downsizing the breaker on the circuit is not an option.

So what I would like to do is make an adapter that would plug into the 50-amp receptacle and have some sort of in-line 30-amp fuse with a 30-amp receptacle on the other end.

I would also like to make a similar adapter to use on my engine driven welder. I would like that adapter to plug into the 50-amp receptacle and give me a 30-amp 120-volt circuit.

Any ideas would be appreciated.
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Old 04-29-2006, 02:07 PM
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The breakers are there to protect the wire in the wall not really the load/device. Most (good; blue, red, yellow...) welders have internal protection so really IMO you are worrying about nothing.
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Old 04-29-2006, 02:52 PM
Spencer Spencer is offline
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Quote:
Originally Posted by Shade Tree Welder
The breakers are there to protect the wire in the wall not really the load/device. Most (good; blue, red, yellow...) welders have internal protection so really IMO you are worrying about nothing.
That's good to know about the welder, but I still want to be able to pull 30-amps of 120 off of my engine driven welders 50-amp receptacle. This is for a Milwaukee core drill rig with a vacuum base.
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Old 04-29-2006, 05:12 PM
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..."The breakers are there to protect the wire in the wall not really the load/device."
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Old 04-29-2006, 07:14 PM
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Quote:
Originally Posted by Spencer
That's good to know about the welder, but I still want to be able to pull 30-amps of 120 off of my engine driven welders 50-amp receptacle. This is for a Milwaukee core drill rig with a vacuum base.
What engine drive do you have?
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Old 04-29-2006, 07:22 PM
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Is it a NEMA 14-50R receptacle, like found on Miller Bobcats and Trailblazers and many other machines?

Get a NEMA 14-50P plug and a convenient length of 10/3 SO cord. You'll only need to install one of the hot prongs and the neutral prong and the grounding prong on the big plug. The other hot doesn't even need to be there, which also makes plugging it in and taking it out a little easier anyway.

The other end of the SO cord goes to the appropriate 30A receptacle cord cap for your machine. As mentioned, I wouldn't hesitate to run it just like that with no further overcurrent protection. If a serious short develops, it'll trigger the magnetic trip on the 50A breaker anyway.
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Old 04-29-2006, 08:09 PM
Spencer Spencer is offline
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Quote:
Originally Posted by Shade Tree Welder
What engine drive do you have?
Nothing to get excited over. I just happened to be in a Home Depot on a business trip down in Clarksville Tennessee when I came across a Lincoln on clearance.

Here is a link to the thread I made that day while trying to decide if it was a good enough deal to buy or if I should pass it up.

Price Check - Lincoln Ranger 10,000
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Old 04-29-2006, 08:11 PM
Spencer Spencer is offline
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Thanks everyone, I guess I have nothing to worry about.
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Old 04-29-2006, 09:49 PM
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What is it you want to plug into a 30A 120V circuit? Is it the Miluakee? What about the 30A 240 shop load?
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Old 04-30-2006, 08:58 PM
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Quote:
Originally Posted by Sberry27
What is it you want to plug into a 30A 120V circuit? Is it the Miluakee? What about the 30A 240 shop load?
Yes, my Milwaukee core drill rig with the vacuum base is what I may need to plug into my Lincoln Ranger 10,000. I use a 100 foot 10 gauge 3-wire extension cord for the core drill rig. It has a standard 125-volt 15-amp plug on the one end and a twist-lock receptacle on the other end for the core drill rig to plug into. I went ahead and made up an adapter for it tonight. I just took one of those heavy 2-foot long 12-gauge 3-way adapters and cut it in half. Then I wired up the 3-way adapter to a new 14-50 plug that I bought today.

The 30-amp shop load is for the Millermatic 35s mig welder that my Dad gave me last month. The machine is probably over 20 years old, but I doubt it has seen a full spool of wire through it. What wire it has seen has been used by his neighbors borrowing it. My Dad likes the tig process best and I don't blame him. I messed around with some stick welding last week and I got the mig welder going tonight. I really want to learn both of those processes, but starting out with tig like I did will make it harder. Tig is so quiet and clean compared to mig and stick, but I'm not telling you guys anything new. Anyway, I just put a 14-50 plug on the mig machine like you guys suggested and pluggeg it in. The tip that came with it was pretty buggered up already and my first bead didn't make it any better. I'll have to get down to the welding shop and see if I can still get tips for this ancient Bernard gun.
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