15A or 20A circuit?

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  • 15A or 20A circuit?

    I've been looking through some of the past discussions and someone mentioned one of the quirks of the BT3100 is that it performs best when it's on a dedicated 20 amp circuit. Is this true, and how critical is it? I only have a 15 amp circuit in my garage. I've run a 15 amp circ saw without any problems before. I've been looking at this saw for a while, and, have the wife's ok to buy it. But, I wonder about this circuit question. Thanks.

    John

  • #2
    John it really depends on a lot of different factors. Does your garage have a subpanel? Is there only one 15amp circuit for the whole garage? The BT3 saws have a universal motor which by the way they are built require a big jolt of juice when the switch is thrown on and less when it is spinning freely. The saw will work on a smaller rated circuit, maybe. It most likely will not run at peak performance unless you are supplying it with a wired to code 20 amp circuit.

    IMHO rewiring your garage for this machine will be a good thing. It may add value to the property. You will get peak performance from the saw. Plus maybe the most important reason it might not be as expense as you would think. Since you are already considering buying a swa that would be a great value at twice the price!

    marK in WA and Ryobi Fanatic Association State President
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    marK in WA and Ryobi Fanatic Association State President

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    • #3
      No subpanel, just a single 15 amp circuit. The main panel in the house doesn't have any spots open for a new circuit. Does that mean I would need to redo the main panel, also? Is a universal motor the same type used on circ saws? I have a 15 amp circ saw that I've used in the garage without any problems.

      John

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      • #4
        One word of caution. I, too, had a single 15-amp circuit in my garage. When we started hooking up Christmas lights to the outside plug by the front door, we discovered that all four outside plugs and three bathrooms were on the same GFCI circuit from the garage. You may want to see what all is on that circuit. All it takes is one hair dryer to pop it.

        John Gleason
        "Of all of the things I've ever lost, I miss my mind the most"
        John Gleason
        I'm 62 - Halfway to 124. That makes me Middle-Aged!

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        • #5
          Okay let me qualify my advice to you first. I hold a master electricians ticket in Ohio and CT.

          First to fix you problem about the lack of circuits in you panel. Your first concern is that you do not overload your panel. If you have alot of 15amp outlet and lighting circuits this is probably not an issue but it is something you have to consider. I would go out and purchase a 2 circuit 15 amp space saving breaker and I would and take the two most lightly loaded lighting and/or outlet circuits and move them to this new breaker. This will give you a free single pole space in the panel.

          Then install a new single pole 20 amp breaker there.

          Then run your new cable to the location you wish your outlets to be in the garage. The wiring will need to be at least 12/2 NMB. You will then want to make sure that you buy outlets that rated at 20 amps (the standard outlet is rated at 15 amps.

          Now if this was my installation I would run 10/2 NMB. This will allow for future expansion to a 30 amp circuit in the future without having to run the cable. That way if you decide to purchase more equipment and turn your garage into a complete workshop you will have the wiring to meet you need. (also pulling wire is the least fun part of the job so better to do it once)

          I would also purchase hospital rated outlets as the are very durable and will serve you much better in a workshop enviroment.

          The other thing that is also nice especially if you have a few pieces of bench equipment is a disconnect switch. You a switch type rated for 60 amps at HD for $12. It is invaluable in emergencies and comes in handy to disconnect the power when you do maitenance. Also if you have children the switch cover is lockable so you can insure that they don't accidently turn on a peice of equipment and injure themselves.

          Whatever you decide to do be careful. I would hate to see you do the 60Hz shuffle (electricians Humor)
          Don Hart

          You live and learn. At any rate you live.

          www.hartwoodcrafts.com



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          • #6
            Don, thanks for the thorough advice! That one's going in my file.

            --------------------
            jethro.
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            --------------------
            jethro.
            <font size=\"1\">Never attempt to teach a pig to sing; it wastes your time and annoys the pig. -- <i>Heinlein</i>
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            • #7
              Don, can this be done by a complete novice armed with a home wiring book? In other words, is this something I can learn to do or do I need a pro?

              Is it legal for me to do something like this or does it need to be inspected by licensed pro to meet code?

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              • #8
                To answer your question about code. This varies from state to state. Each state has it own interpretations of the code. Most follow the NEC (national electric code) fairly closely but some do not. In fact in some states the code varies by city or county.

                Now most states allow homeowners to make minor upgrades and repairs without a permit and inspection and do major work with minimal cost homeowners permit.

                For something like this I would not be too concerned. It is a simple 3 wire connection and with a little common sense and a good reference it can be done by a novice.

                If you are going to do this take your time and do a neat job.

                Pointers (If you already know some of this I apologize)

                1. Black is hot

                2. white is neutral

                3. Bare copper is ground

                4. drill the holes for your wires through the center of beams and studs.

                5. Be sure to leave pleant of slack on both ends (1 would leave at least 15 inches in the outlet box and 36 in the panel)

                6. Remember unless you have the utility company come and pull the meter base there is always areas of you breaker box that are hot. so be aware of the areas and use caution.

                7. connect your wires starting at the outlet end and work your way back to the breaker box.

                8. your last connection should be the black wire to the breaker.

                All in all it is a fairly easy operation.

                Plan it out and if you have any questions just ask.
                Don Hart

                You live and learn. At any rate you live.

                www.hartwoodcrafts.com



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                • #9
                  quote:Originally posted by don_hart

                  Okay let me qualify my advice to you first. I hold a master electricians ticket in Ohio and CT.
                  Don, I'm afraid you've just become the expert electrician on this forum![^]

                  Question for you-I've recommended to friends to "double up" on a circuit with one of those "space saver" breakers in order to free up a slot. What if you had one open slot, freed up another, then put in a 60A double-pole breaker to feed a subpanel? Or even put in two space saver breakers to free up two poles for the same purpose? What, if any, limitation is there on a main panel feeding a sub-panel, or the number of total amps of circuit breakers that you can stuff into one?

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                  • #10
                    Well the limiting factor is the size of your service. Most homes biult in the recent past have at least 200 amp service and most have 250 amp service. If your house is large it may have 300 amp or higher.

                    The simplest way to tell what service you have is to check the rating on the main breaker on your panel.

                    The quick way to see if you have room on your sevice is to add up the ratings of all of the circuits you have on your panel as each circuit could theoretically draw that much load. If the total is less than the rating of your main breaker then you have at least that much room on your service. now if you have added it all up and you find you have no room don't despair.

                    In real life most circuits are not loaded to anywhere near thier limit. Now to get a true idea of your real world load you would need to take ammeter readings over a period of time and record the readings. Of course most people are not equipped to do this so there is another way.

                    The biggest loads on your system will be things such as your stove electric dryer, air conditioning, electric heat, well pump, dishwasher, refriderator ect. Over the last serveral years this equipment has become more energy efficient and runs at a much lower amp load than they used to. You can go around to each of these items and look at the rated current draw and see how much your circuit is oversized. By adding up the slack you have in the ratings of the breaker as compared to real current usage you can get a good idea of what you can install in the way of a subpanel.

                    Now if you come up a little short on what you would like to put in for a sub panel I would not worry as most of your lighting and outlet circits are probably not loaded to anything over 50% load.

                    when you decide what rating of breaker you can put into the main panel get a subpanel main breaker one size smaller. For example if you have installed a 60 amp breaker in the main panel install a 50 amp as the main breaker in the subpanel. This is done to insure that the breaker closer to the load trips before a breaker farther away. This provide the maximum protection in case of a dead short.

                    When you purchase the wire for your subpanel leg purchase wire one size larger than is required to handle the full load of the subpanel. This will reduce heating at times of high current draw and help prevent thermal expansion of your connections. Thermal expansion can cause connection to losen creating high resistance connections that can cause voltage drops. Running ac motors at lower voltages will create greater wear on the motor and possibly damage. Not to mention the havoc this can cause with electronic equipment.

                    IF you are going to do this and you have never done it before be sure to plan it out fully. This is not as simple a job as running a new outlet circuit.

                    One final thing about all of this wiring advice.

                    BE CAREFUL electricity is not your friend and you might survive bieng shocked might you are just as likely to die. It only takes .5 amps of current arcross your torso to ensure death.

                    If you think I am saying this just to scare you you are partially right. If you are scared of electricty you will respect it and be careful when you work with it.

                    So with that said this job is not beyond the abilityies of a novice who plans it out and is careful.



                    You can go around
                    Don Hart

                    You live and learn. At any rate you live.

                    www.hartwoodcrafts.com



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                    • #11
                      I like to work with electricity. So did one of my cousins back when I was a teenager. He knew all there was to know working with electricity and was dead by the time he was 28. He didn't know enough and was killed. I have been afriad enough to have never gotten a shock since.

                      Be smart and remember "If you think that something is not right, it probably isn't".

                      Trust your instincts.

                      The Fat Chef
                      Never trust a skinny chef
                      The Fat Chef
                      Never trust a skinny chef

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                      • #12
                        Very well done Don.

                        Monte
                        Reporting Live from somewhere near Kalamazoo
                        Monte (another darksider)
                        Reporting Live from somewhere near Kalamazoo

                        http://community.webshots.com/user/monte49002

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                        • #13
                          Yeah I worked in the feild for a lot years both residential and industrial before I left and went into computers. The guys who scared me where the ones with no fear. If someone made the statement "Its only 110 volts" I knew they were the ones to be careful around. You would see it alot in industrial electricians. They spend alot of time working with higher voltages and start to lose there respect for 110 volt residential power. I guess that is why 110 kills more people each year than the higher voltages.

                          Well I have some other plans for shop electricity that I will get around to posting here soon so keep your eyes open.
                          Don Hart

                          You live and learn. At any rate you live.

                          www.hartwoodcrafts.com



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                          • #14
                            Hey Don,

                            Welcome to the forum. One question: can you give us any tips on keeping the smoke in our motors? Everyone knows that once the smoke gets let out that they quit working... [}]


                            Sam Conder
                            Sam Conder
                            BT3Central's First Member

                            "I have not failed. I've just found 10,000 ways that won't work." -Thomas A. Edison

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                            • #15
                              Well i always recommend having some canned smoke on hand to add smoke back to the motor as needed.

                              Well one of the common things that could happen is that your motor stalls and overloads itself and the breaker does not open. This can happen if the breaker is oversized for the load. A lot of people run a dedicated 20 amp circuit just for the saw. This is a good idea. The increased wire gauge will provide you with better current flow and will compensate for the starting surge of the motor and for running it under full load. But if the only thing you are running off the circuit is the saw then I would run wire for a 20 amp circuit but install a 15 amp breaker.

                              The reason i suggest this is that the rating of a breaker is what [u]sustained</u> current it can handle. now the key word here is sustained. If you have a 15 amp circuit breaker it will carry 15 amps all day with no problem and will carry surges of up to twice that for very short periods without tripping. They are built this way so that the starting surges of motor will not trip them offline.

                              So you can easily run you 15 amp rated saw on a 15 amp breaker if you wire a size larger. This will give you better overcurrent protection and the breaker will trip earlier hopefully preventing damage to the motor.

                              Now of course if you are running the circuit to handle more than just the saw you would install a 20 amp breaker.

                              The other thing is to make sure that all of your extension cords and bench wiring are in good condition and will make good clean conection. Poor connections create higher resistances in the line and cause voltage drops. this will cause you saw to draw more current.

                              The same things apply to sizing of extension cords. The standard cord is not designed to handle the load of the saw. I make my own extension cords for the higher power equipment I run.
                              Don Hart

                              You live and learn. At any rate you live.

                              www.hartwoodcrafts.com



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