Breaker size

Reply

  #1  
Old 08-30-06, 11:09 PM
Member
Thread Starter
Join Date: Aug 2006
Posts: 3
Breaker size

What is the maximum size breaker I can safely run in a subpanel in my garage that is wired with about a 100 ft. run of 8 awg copper wire 220 circut........for a welder,thanks.
 
Sponsored Links
  #2  
Old 08-30-06, 11:18 PM
Member
Join Date: Aug 2005
Location: USA
Posts: 995
At least 50A. What is the welder's make/model?
 
  #3  
Old 08-30-06, 11:23 PM
Member
Thread Starter
Join Date: Aug 2006
Posts: 3
I haven't got it yet but I'm looking at a used Lincoln AC/DC 225.
 
  #4  
Old 08-31-06, 07:36 AM
Member
Join Date: Jun 2006
Location: usa
Posts: 274
Smile

Voltage drop (about 6 volts) shouldn't be a problem. #8 copper @75C is good for 50 amps (NEC Table 310.16).
Most breakers and lugs are rated 75C (temperature), although your's may vary. Also, your wire needs to be rated at 75C or more to use a 50A breaker. If it's 60C you will have to use a 40A breaker.
I've got a Lincoln AC/DC 225 on a 30A circuit and I've never had a problem. If you're welding using big rods or doing hard plating you will have to turn the amperage up. I've never run mine on the highest settings, so I don't know how much juice that it will pull at the highest setting
That Lincoln 225 is a good welder for a workshop.
steve
 

Last edited by DIYaddict; 08-31-06 at 07:44 AM. Reason: Removed unnecessary quote
  #5  
Old 08-31-06, 09:05 AM
Member
Join Date: Apr 2006
Location: New Bern, NC
Posts: 1,623
Originally Posted by MAC702
At least 50A. What is the welder's make/model?
At most 50 and it depends on what else is on the circuit.

What else is there? What size breaker is the wire on at the house?
 
  #6  
Old 08-31-06, 09:45 AM
Member
Join Date: Aug 2005
Location: USA
Posts: 995
Originally Posted by jwhite
At most 50 ....
A dedicated receptacle for a welder with a small duty cycle can use smaller wire and a larger breaker, based on calculations in the NEC Article 630. It is not often recommended for residential applications, and should always be appropriately labeled, but to say it doesn't exist is wrong.

His machine has a 20% duty cycle at its rated output and an even smaller duty cycle at its maximum output. The good news is that it will provide full output with a 50A breaker, and if this receptacle is dedicated to this welder, and appropriately labeled, he can actually use #10 wire if he wants to, though it's not a significant expense here to do it with #8.
 
  #7  
Old 08-31-06, 09:51 AM
Member
Join Date: Apr 2006
Location: New Bern, NC
Posts: 1,623
thanks mac but what we have here is a sub panel feed from the house. the sub panel, not the welder is feed with number 8.

The op did not ask about the wire size from the panel to the welder. He asked how big a welder he can buy.
 
  #8  
Old 08-31-06, 09:58 AM
Member
Join Date: Aug 2005
Location: USA
Posts: 995
Thanks jwhite. I did get carried away on the welder bit. So yes, at most a 50A breaker protecting the subpanel, and the welder can be wired to the subpanel with another 50A breaker and at least #10 wire.
 
  #9  
Old 08-31-06, 10:15 AM
Member
Join Date: Apr 2006
Location: New Bern, NC
Posts: 1,623
This still all depends on what else is installed in the garage. The OP may not have that much capacity. But, you are right, he could calculate the addition of that welder at much less than the breaker rating.

Even some electricians cant understand that you cannnot add breaker values to determine anything. The number you get is meaningless.
 

Last edited by DIYaddict; 08-31-06 at 11:48 AM. Reason: Removed quote as it's unnecessary
  #10  
Old 08-31-06, 10:19 AM
Member
Thread Starter
Join Date: Aug 2006
Posts: 3
Thanks everyone.....I was planning on running a dedicated outlet for the welder from the panel of no more than 6 ft. with #10 or #8 wire and the only other thing that will be running on the circut while using the welder are probably some light bulbs.
 
  #11  
Old 08-31-06, 10:35 AM
Member
Join Date: Apr 2006
Location: New Bern, NC
Posts: 1,623
evo, It is great that you understand about the possibility of overloading a circuit. You still need to consider the future. You may not always be the one using this garage. It is best to do a good load calculation to be sure that whatever you do will pass the test of time.

Take the actual wattage of all the lights in the garage. Multiply that times 1.25. Then add 150 for each duplex rec in the garage. If there is anything else out there that uses electricity it needs to be added as well. Get the total VA currently calculated for the garage. All of this needs to be considered when deciding if you can add more to that panel.
 

Last edited by DIYaddict; 08-31-06 at 11:49 AM. Reason: Removed unnecessary quote
  #12  
Old 08-31-06, 11:56 AM
Member
Join Date: Aug 2004
Location: NA
Posts: 1,065
I would agree that a load calculation is important. My addition to what has already been said is that, for example, you decide 60 amps is enough for the garage and welder. Now what happens when you go get that 60 amp sub panel? It normally has two spaces for branch circuits. 4 circuits if you use single pole tandems, 2 circuits in full size single poles or one 240 volt double pole. I would suppose you could on some panels install quad breakers that would give you 2 single pole circuits and one double pole. There are some makers that have quad breakers that are handle tied to provide 2 double pole circuits.

I only bring this up so that the limitation of 40 to 70 amp subs is understood.

My preference is to install 100 amp 6/12 circuit panels (not much cost difference) run the feeder size in accordance with my load calc. and always in conduit big enough to pull in higher amperage wire if needed...not exceeding the panel rating of course. In my experience most handy homeowners have a 120 or 240 volt welder, 120 volt air compressor and 120 volt tools. So generally 60 amps is going to take care of 90% of the handy people out there IMO.

Roger
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes