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  • Voltage drop

    I have a RIDGID 6800b generator that I want to connect to a transfer switch during power outages. The genny runs at 6800 watts. It is 75' from the house. I will probably put the 50' well pump, stove,microwave, sump pumps, AC and (gas) furnace with some lights on the switch. What gauge cable should I run from the genny to the transfer switch?

  • #2
    Re: Voltage drop

    chances are the generator cord set is wired in 10 gauge. which is adequate for the 3400 watts a side.

    i would run 8 gauge for the transfer switch. but you need a cord set to plug into the generator panel.

    rick.
    phoebe it is

    Comment


    • #3
      Re: Voltage drop

      Lol... I am going to start giving plumbing advice. I have an E-1 license, so I am qualified. Forget the stove you don't have enough horsepower for that and run anything else at the same time. Lights, refrigeration, well pump and microwave. Give us the amp draw on each appliance you want to run and we can determine the wire size.

      Comment


      • #4
        Re: Voltage drop

        Each of the items you mention ,round numbers , could be near 1500 watts ( that assumes the stove is gas). You have about 9KW there. A gas stove powering just the ingniters would only 750 to 1000 watts, then add some assorted lighting.

        Comment


        • #5
          Re: Voltage drop

          Originally posted by lovetheUSA View Post
          Each of the items you mention ,round numbers , could be near 1500 watts ( that assumes the stove is gas). You have about 9KW there. A gas stove powering just the ingniters would only 750 to 1000 watts, then add some assorted lighting.
          Why does ANY of this matter. It is the size of the genny that matters.

          Also, a gas range will hardly pull 750-1k watts.

          Comment


          • #6
            Re: Voltage drop

            If it is 6800 running watts then #10 is fine. You shouldn't run a genny at 100% for any length of time so you are perfectly safe and within spec with #10. Anyway, if you draw too much the breaker on the genny will trip.

            Comment


            • #7
              Re: Voltage drop

              Originally posted by killavolt View Post
              Lol... I am going to start giving plumbing advice. I have an E-1 license, so I am qualified. Forget the stove you don't have enough horsepower for that and run anything else at the same time. Lights, refrigeration, well pump and microwave. Give us the amp draw on each appliance you want to run and we can determine the wire size.
              the numbers are all in the post. 6800 watts is 3400 watts a side. 30 amps is = 3600 watts. 10 gauge is maxed out at 30 amps for the most part. 8 gauge is a better choice. i rather doubt the generator has anything bigger than 10 gauge feeding the 25' generator line set.

              the question was the wire size from the generator to the transfer switch 75' away.

              maybe you should give up the license and get a library card.

              rick.
              phoebe it is

              Comment


              • #8
                Re: Voltage drop

                Originally posted by PLUMBER RICK View Post
                the numbers are all in the post. 6800 watts is 3400 watts a side. 30 amps is = 3600 watts. 10 gauge is maxed out at 30 amps for the most part. 8 gauge is a better choice. i rather doubt the generator has anything bigger than 10 gauge feeding the 25' generator line set.

                the question was the wire size from the generator to the transfer switch 75' away.

                maybe you should give up the license and get a library card.

                rick.
                OK Rick, then what do you base your answers on?
                Is it what you've always heard? Bigger is always better, right?

                Maybe plumbers should stick to giving advice on plumbing. You don't see me over in the plumbing forum, do you?

                Comment


                • #9
                  Re: Voltage drop

                  Originally posted by Speedy Petey View Post
                  OK Rick, then what do you base your answers on?
                  Is it what you've always heard? Bigger is always better, right?

                  Maybe plumbers should stick to giving advice on plumbing. You don't see me over in the plumbing forum, do you?
                  you're all over thinking the question.

                  the question is the wire size from the generator to the transfer switch 75' away.

                  the max output on the generator is 6800 watts. that's 3400 watts a side. 3400 watts / 120 volts = 28.33 amps.

                  regular 10 gauge thhn is rated for 30 amps.

                  8 gauge is rated 40. of course depending if it's in conduit or open air will fudge the numbers.

                  but remember the question was the size from the generator to the transfer switch . not the transfer switch to the load center/ panel.

                  maybe i should spend more time on the electrical forum as you guys are really over thinking a very basic question.

                  3400 watts is the limiting numbers and the generator is also limited by it's own breakers too along with it's cordset.

                  show me where i'm way off

                  rick.
                  phoebe it is

                  Comment


                  • #10
                    Re: Voltage drop

                    Originally posted by Scratcher View Post
                    I have a RIDGID 6800b generator that I want to connect to a transfer switch during power outages. The genny runs at 6800 watts. It is 75' from the house. I will probably put the 50' well pump, stove,microwave, sump pumps, AC and (gas) furnace with some lights on the switch. What gauge cable should I run from the genny to the transfer switch?
                    here is the question that was asked.

                    rick.
                    phoebe it is

                    Comment


                    • #11
                      Re: Voltage drop

                      Originally posted by PLUMBER RICK View Post
                      you're all over thinking the question.

                      the question is the wire size from the generator to the transfer switch 75' away.

                      the max output on the generator is 6800 watts. that's 3400 watts a side. 3400 watts / 120 volts = 28.33 amps.

                      regular 10 gauge thhn is rated for 30 amps.

                      8 gauge is rated 40. of course depending if it's in conduit or open air will fudge the numbers.

                      but remember the question was the size from the generator to the transfer switch . not the transfer switch to the load center/ panel.

                      maybe i should spend more time on the electrical forum as you guys are really over thinking a very basic question.

                      3400 watts is the limiting numbers and the generator is also limited by it's own breakers too along with it's cordset.

                      show me where i'm way off

                      rick.
                      What the hell are you talking about?? Really???

                      First off, it is 6800 watts divided by 240v. You DON'T call it 3400 watts "per side".

                      Yes, #10cu is typically rated for 30A. Are you aware that this limitation to 30A is WAY under rated? Are you familiar with 240.4(D) in the NEC? Are you also aware that for derating purposes we use the appropriate column in 310.16 (or Table 310.15(B)(16) in the 2011 NEC)?? Which is 30A for NM cable, and 40A for THHN in conduit.

                      Yes, the question is what wire from the transfer to the genny. The genny will never put out more than 6800 watts, or 28.33 amps @ 240v. it is in the documentation for almost every genny I have seen to keep the load to around 75-80% for extended periods.

                      HOW in the world is this "over thinking" things???

                      I'll ask again, HOW do you figure #8 is that much better.

                      Comment


                      • #12
                        Re: Voltage drop

                        Originally posted by PLUMBER RICK View Post
                        here is the question that was asked.

                        rick.
                        Once again, NO ONE is disputing this.

                        Comment


                        • #13
                          Re: Voltage drop

                          Originally posted by Speedy Petey View Post
                          What the hell are you talking about?? Really???

                          First off, it is 6800 watts divided by 240v. You DON'T call it 3400 watts "per side".

                          Yes, #10cu is typically rated for 30A. Are you aware that this limitation to 30A is WAY under rated? Are you familiar with 240.4(D) in the NEC? Are you also aware that for derating purposes we use the appropriate column in 310.16 (or Table 310.15(B)(16) in the 2011 NEC)?? Which is 30A for NM cable, and 40A for THHN in conduit.

                          Yes, the question is what wire from the transfer to the genny. The genny will never put out more than 6800 watts, or 28.33 amps @ 240v. it is in the documentation for almost every genny I have seen to keep the load to around 75-80% for extended periods.

                          HOW in the world is this "over thinking" things???

                          I'll ask again, HOW do you figure #8 is that much better.
                          go ahead and tell ridgid that they're wrong while you're at it.

                          keep in mind i didn't need to look this up in the owners manual. but now i will post the link and you can argue all you want with ridgid.

                          not bad for winging it off the top of my head with no cheating from any site.

                          http://www.ridgid.com/ASSETS/9840704...0Generator.pdf

                          see page 7 for their formula.

                          also keep in mind that the 30 amp 240 outlet is only accessible when the control panel is not removed from the generator. otherwise it's a 20 amp twistlock outlet.

                          also remember that it takes a plumber to pipe a generator to the fuel source. i've bailed out an electrician from getting back charged $50,000 when he came begging for help with the 100kw he installed at a private home.

                          stop overthinking such a simple question.

                          so what size would you run based on his 6800 watts at 75' distance?

                          rick.
                          phoebe it is

                          Comment


                          • #14
                            Re: Voltage drop

                            Originally posted by PLUMBER RICK View Post
                            go ahead and tell ridgid that they're wrong while you're at it.

                            keep in mind i didn't need to look this up in the owners manual. but now i will post the link and you can argue all you want with ridgid.

                            not bad for winging it off the top of my head with no cheating from any site.

                            http://www.ridgid.com/ASSETS/9840704...0Generator.pdf

                            see page 7 for their formula.
                            Who's "cheating"?
                            That chart is fine, and @75' #10 is FINE also since the load will NOT be 30A for any extended period of time. Besides, the genset is only rated for 28A output, not even 30.



                            Originally posted by PLUMBER RICK View Post
                            also keep in mind that the 30 amp 240 outlet is only accessible when the control panel is not removed from the generator. otherwise it's a 20 amp twistlock outlet.
                            OK, SO WHAT.
                            This is one of those removable panel gensets. You cannot use the 30A receptacle when the panel is removed. That is because the "jumper cable" they provide is only 20A. THAT is why the receptacle behind the panel is 20A.



                            Originally posted by PLUMBER RICK View Post
                            also remember that it takes a plumber to pipe a generator to the fuel source. i've bailed out an electrician from getting back charged $50,000 when he came begging for help with the 100kw he installed at a private home.
                            Once again, WHAT'S your point???




                            Originally posted by PLUMBER RICK View Post
                            stop overthinking such a simple question.
                            Once again, WHO is over thinking this???? If anyone it's you.


                            Originally posted by PLUMBER RICK View Post
                            so what size would you run based on his 6800 watts at 75' distance?
                            Like I have stated quite a few times in this thread. #10 is FINE.


                            I have to say, you are one strange man, you know that?

                            Comment


                            • #15
                              Re: Voltage drop

                              Well I never thought that my first post on the RIDGID forums would generate more heat than light.

                              I'm leaning more toward #8 since I'm an overkill kind of guy who believes its better to have it and not need it rather than need it and not have it. I will be connecting the circuits I mentioned earlier but Im aware that I cannot run everything simultaneously. So when we need clothes dried we will shut down the well pump and when we want water refilled we will shut down everything else until we are finished with the pump etc etc etc etc.
                              I'm also considering the fact that my wife and kids are probably not going to remember that we cant run too many things together so the #8 will provide some margin for error hopefully

                              Thanks to all who took time to reply. Your help is appreciated although I have to admit that I cant help thinking how interesting the experience would be If you were all on the same job at the same time trying to work together.
                              Last edited by Scratcher; 12-15-2011, 09:35 AM.

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