I'm eventually going to need to rewire my shop and was searching the forum for ideas and ran across some statements about making two separate breakers work as one larger one.Here are a couple quotes from 2 different posters:"My stick welder calls for a 50amp breaker but that's only if I'm building a bridge in my garage. Know what I mean so if you only have a 40 laying around that's cool. Or piggyback two 20's." "With power factor correction kit installed amperage draw on 230v goes from 70 amps to I believe 58 or 59 amps.I run mine on a double 40 amp breaker (80 amp breaker) and have never tripped it."I don't plan on doing this, but is this possible? I have always thought that all you could ever get out of two 20amp breakers would only be 20 amp protection, and two 40amp breakers would only protect 40 amp. But I'm not an electrician, so what are your thoughts.
Reply:> I run mine on a double 40 amp breaker (80 amp breaker)What?!? No! A two pole 40A breaker is a 40A breaker.
Reply:Yup- what he said and what you knowEd Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:Yes, what litman and Broccoli said is correct. As you suspected, if you run off of (2) 40A breakers, you have (2) conductors that will be protected at 40A each. All that a breaker or a fuse does is open/disconnect a circuit when the current level reaches the level specified on the breaker. It is equally important that the conductors are sized together with the breaker. If you run too small a conductor for the breaker that it is connected to, the wire can burn up and never trip the breaker.
Reply:Thanks guys. I thought they were wrong, but since they weren't corrected when they made those statements, I thought that maybe I was unaware of some sort of unusual wiring technic that would double the amp protection.
Reply:As stated Two 40 amp breakers does NOT = 80 amps. In a normal residential situation a single breaker is for a 115/120 V circuit. In order to get a 230/240 V circuit, two breakers are needed; however, if you are using two separate breakers for the 240 V circuit, the breakers should have a device tying them together so that an overload on either leg will trip both breakers. In short, double breakers = double the voltage, NOT double the current.
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UOTE "Or piggyback two 20's"this came out of the first post and just sounds VERY WRONG!!!!!!
Reply:if you had a pair of double pole 20 amp breakers and tie them together with the phases matching you would effectively have a 40 amp 2 pole set up. this would however be unsafe and illegal because of the possibility of only shutting off 1 set and leaving the line live while working on it.You didn't build that.'85 Miller AEAD-200LE
Reply:220v is two 110v circuits on each side of the neutral. (Right, 2 breakers connected with a tab?) You would need four breakers connected in 'proper polarity' <- or BIG trouble!! also if ALL breakers do not 'trip' off, you still would have at least 110v in your circuit, which could lead to, , , (ultimatly death) Do it right, GET THE PROPER BREAKERS, electricity is a harsh mistress-corne-
Reply:Ok first disreguard everything you have heard that wasn't spoken by an electrician. Those dudes are miss informed and they are going to get someone killed.I can't tell you whT your machine is going to draw, but mind this!Don't try to do any piggy backing or any of that!Most importantly A 50 amp circuit needs #6 wire minimum. Oversize if its over 50 feet. 40 amp circuit need #8 wire30 amp needs #10 There are two ways to wire a 230 volt plug. With or without a nuetral. If it has 3 prongs its without. 4 prongs is with.If its a circuit with a neutral use a 3 conductor wire (the ground doesn't count as a conductor) hook the white to the nuetral bus, green to the ground bus ( where the green and bare wires mount) and then hook your black and red in each side of the two pole single throw breaker sized for the load.If there is no neutral needed use a 2 conductor wire and use the white as the other hot.It wouldn't hurt to have an electrician look over your work before you throw the breaker on!
Reply:Will it work? YesBut it is wrong!!!If you have room for 2 2 pole breakers to jumper out, dont be a cheap prick. A 2 pole 40 or 50 is well under 20 bucks for most breaker panels.Ron( An electrician for 25 years)Registered Six OffenderHome of the Buzzin Half Dozen
Reply:Originally Posted by eastexan"if you only have a 40 laying around that's cool. Or piggyback two 20's."
