webzter wrote:I hope this is the right forum to ask this question. I am planning to wire in a dedicated circuit for my Mark V 500 using a circuit breaker and am a little confused on the proper amperage to use. In the manual it states that a 15 amp circuit is required but if you can use "wire and receptacles rated to handle 20 or 25 amp will give you an even bigger safety margin" and then in the next paragraph it says not to use a circuit breaker over 15 amp. I have purchased the matarial to wire in a 20 amp breaker but I don't want to proceed any further until I get this clarified. Any help would sure be appreciated.
First let me clear up a serious misconception. Increasing the amperage of a circuit (done corrctly of course) does not mean the device plugged in will get more amperage. It simply means the circuit can handle more amperage.
A device (properly functioning) will only draw as much current as it needs and is designed for. Problems occur when the device can't get enough current and trips the breaker or if circuit is marginal and device experiences a lower voltage which will increase it's amperage demands.
Second the breaker in the circuit box is not there to protect the device plugged into the circuit but it there to protect the circuit. A 15 circuit breaker means it will only allow 15 amps to be drawn on that circuit. If you have a device that for some reason draws more the breaker will trip thus protecting the circuit not necessarily the device. It is possible that a malfunction in the device could cause an current draw that would destroy the device but never trip the breaker. Example you have a device that is built to draw 3 amps, for some reason a component fails and the draw jumps to 10 amps, everything in the device can be fried and it can in fact catch fire but would never trip the breaker. I believe more than one house has burnt down because a heating blanket malfunctioned shorted but not enough to exceed the breaker rating and caught fire.
Shopsmith says their machine operates on 115volt at 15 amps or less and this is verified by the UL approval. (UL will not approve any 115 volt device that draws more than 15 amps I believe). However what Shopsmith doesn't say is if the line voltage at the machine is too low it will draw more current and a breaker is liable to trip.
By upgrading your circuit to 20 amps circuit you will have to upgrade the wiring from a 14 gauge to 12 gauge that one factor has a positive effect. A 12 gauge wire will have less voltage drop than a 14 gauge wire for the same lenght run. That means the voltage the device sees will be closer to it's exact need and therefore it's amp draw will be lower. Also while the inside components of the SS are only rated at 15 amps the safety margin built into them will probably keep them from self destructing should a short occur (your wiring insulation wore through and your wire touched bare metal).
I have my SS on a total 20 amp circuit, 20 amp breaker, 12gauge wire, 20 amp connections. I even changed the line cord from the stock 14 gauge to a 12 gauge and I attribute that change for making a marked improvement in the realized power of my SS. I have no impericial data to support that claim but to me my SS seems to work better.