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  • #46
    Originally posted by Sberry View Post
    He ain't hurting anyone here.
    I agree. I would kill this and one other thread.

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    • #47
      OP here with more contribution
      aametalmaster figured out the intent of the thread.
      Take a barn find TB AC\DC and restore it and rewire it for maximum current output for the fun of it.
      Rules of modification: NONE

      checked out a red box k1170 & k1297 225AC unit power cord, 12\3 flat , 300VAC, same as Miller 225AC TB.
      checked out the new Vulcan\Harbor Freight , 225 AC\DC unit power labeled , 8\3, round, 600VAC .

      know that NEC applies to fixed installations and not portable welding machines,but
      NEC 630 & table 630.11C is only reference found so far that actually addresses derating wiring for arch welding machines.
      Table 630.11C allows for a maximum of 50% duty cycle with a corresponding 71% factor applied to maximum input current.
      TB spec is 47.5A maximum input current, corresponding to 225AC maximum output, so, .71 x 47.5A = 33.7A design continuous current.

      based on McMaster-Carr catalog data for insulated 3 conductor rubber covered portable cable
      rated at 86F ambient air temperature, wires are EPDM, jacket is neoprene by Southwire mfg.
      12 gage. 25 ampacity
      10 gage. 30 ampacity
      8 gage. 40 ampacity
      6 gage. 55 ampacity

      Have no capacity data for the flat 12 gage vinyl insulation cable used as OEM on the 225A TB
      based on 50% duty cycle required wire size would be 8 gage, same as Vulcan 225A unit.

      however, the unit duty cycle spec is 20% based on maximum current demand.
      by taking manufacturers license as a basis for power cord sizing and using linear extrapolation of 50% duty cycle criterion, design current would be 13.5A, in which case, the 12 gage wire size is adequate.

      The 93 TB Miller manual states that a maximum 66 ft long , 8 gage extension is acceptable.

      The conductor size for the primary is 0.148" diameter, which corresponds to 7 gage wire.
      12 gage wire is .0808" diameter, so the primary conductor has almost 3.5X the cross section area compared to the 12 gage power cord supplied with the unit.

      I know the transformer TB was designed as an economy unit.

      This thread must a form of intertainment, look at the number of reviews.

      Very new to this forum,but have been quite active on various forum for twelve years.
      always attempt to contribute positive stuff to the topic.
      Last edited by Almond farmer; 01-03-2018, 10:39 PM. Reason: More

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      • #48
        Interesting the Vulcan has a big cord.

        www.facebook.com/outbackaluminumwelding
        Miller Dynasty 700...OH YEA BABY!!
        MM 350P...PULSE SPRAYIN' MONSTER
        Miller Dynasty 280 with AC independent expansion card
        Miller Dynasty 200 DX "Blue Lightning"

        Miller Bobcat 225 NT (what I began my present Biz with!)
        Miller 30-A Spoolgun
        Miller WC-115-A
        Miller Spectrum 300
        Miller 225 Thunderbolt (my first machine bought new 1980)
        Miller Digital Elite Titanium 9400

        Comment


        • #49
          Originally posted by Almond farmer View Post
          looking the inlet power cord, it's a 12/3 yes a 12/3.
          OMG!

          Originally posted by Almond farmer View Post
          the 12 gage wire size is adequate..
          Golly. A welding machine manufacturer that would actually employ an electrical engineer (or college intern) who could do some simple algebra and thereby save the company from bankruptcy caused by liability lawsuits.

          Who would have thunk it???
          Last edited by Helios; 01-04-2018, 06:56 AM.

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          • #50
            The 1993 Miller manual which corresponds to my TB, states the two power cord wires sizes and and ground wire size are 10 gage in accordance with 1990 NEC.

            however, the actual power cord size furnished with the unit is 12 gage imprinted in the insulation.

            using NEC 630.11c table for a maximum allowable duty cycle = 50% and maximum input current of 47.5A, determines the continous design current equal 28.5A.

            Typically, 12 gage insulated three conductor cord wire is rated at 25A @ 86F & 10 gage cord wire is rated @ 30A, 8 gage @ 40A.

            Therefore, 10 gage is the correct power cord three conductor wire size in strict accordance with NEC.

            For some reason Miller decided to manufacture the unit with 12 gage.
            Miller can use any wire gage power cord and do not have to comply with rules that able to find.
            there is an alliance organization between welding machine manufactures and AWS but can find no rules.

            Replacing the original 12\3 gage power cord with SOOW 8\3, same as the new Vulcan\Harbor Freight Tools power cord.

            Maybe the designers at Valcun used there own design judgement and went with 8\3 power cord.

            It insulated cable engineers association publishes current ratings on various wire cable.

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            • #51
              Looking at the Vulcan unit, input voltage is 59 amps at rated output vs. 47.5 amps for the T-bolt, which may explain why the Vulcan has a larger power cord. If you look at the electrical requirements of the T-bolt, it references the 1993 NEC, stating that a 12ga. input cord is acceptable for a 230V input model. If Miller wasn't 150% sure their product was a quality product and perfectly safe, they wouldn't send them out the door. I appreciate the effort and research you're putting in here, but I can't help but think that you're polishing a turd. Figuratively speaking, of course. T-bolts are good machines. I wish I still had mine. Put your 8ga. cord on it and call it good. Life is too short!

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              • #52
                Epic.

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                • #53
                  Grossly insufficient post for a peer review. Not very engineer-like. What is the exact wording of where your manual says you should have a #10 cord factory-installed?

                  Thunderbolt's duty cycle is 20%, not 50%. I'll stop there.

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                  • #54
                    ...and the beatings continue...

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                    • #55
                      Originally posted by Almond farmer View Post
                      For some reason Miller decided to manufacture the unit with 12 gage.
                      Miller can use any wire gage power cord and do not have to comply with rules that able to find.
                      there is an alliance organization between welding machine manufactures and AWS but can find no rules.
                      Let me get this straight.

                      You actually believe that Miller Electric (who would know better) would knowingly, deliberately use a power cord that – (according to you) is undersize and therefore a fire hazard that could burn down buildings, kill people and expose Miller to potentially-bankrupting liability lawsuits ... all so they could save 16 cents on the cost of the cheaper power cord?

                      Really?


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                      • #56
                        Well, poop. Don't I feel inadequate. I just pulled a couple cases of gunpowder off the top of my old Lincoln AC/DC Tombstone so I could get to the cord. It's a #12. It's a conspiracy, I tell you. I'd probably be embarrassed to let anyone see the terminal connections inside.

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                        • #57
                          Originally posted by MAC702 View Post
                          Well, poop. Don't I feel inadequate. I just pulled a couple cases of gunpowder off the top of my old Lincoln AC/DC Tombstone so I could get to the cord. It's a #12. It's a conspiracy, I tell you. I'd probably be embarrassed to let anyone see the terminal connections inside.
                          https://media.giphy.com/media/erK0wF9pWSokU/giphy.gif
                          Last edited by Helios; 01-08-2018, 12:49 PM.

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