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	Subject - 3 phase or single phase power acejake I am setting up a wood shop in a 5,000 sq ft warehouse. I will have 7 or 8 machines in the 2 to 5 horsepower range. Perhaps in the future I will have one or two 10 horse machines. I am preparing a list to speak to an electrician. I have one vendor that supplies single phase power on most machines while other give options for singe phase or three phase. The singe phase only vendor is less expensive (for the same size motor) then other manufactures. The questions is, what factors do I consider in regard to if I should go with single phase or three phase motors? What are the advantages? When should one definitely go with three phase? Over 10 horse? Note: This is a start up so cost is a high priority at present. Scott Vickrey Three phase motors are cheaper to replace and operate. The only catch is they require three phase power which is not usually available at a residential location. This means you'll have to purchase a phase converter for each piece of three phase equipment. Single phase motors are often a practical option for use in an area without three phase power. A 10 HP single phase motor is about the size of a 5 gallon bucket. I hope you have 200 amp service. If not you might need to upgrade your service and if you do ask the power company if it's possible to get three phase power. JimmyDee For that many motors and size, go for 3 phase if you can. Smaller 3 phase converters or variable frequency drives have come way down in price and would probably be very cost effective for you. There are many options in 3 phase for you to work with if it is available. Jim iwire My feeling is unless you get a 3 phase service stay away from 3 phase motors. 1)Watts (power) is what spins the electric meter, and this remains unchanged for single phase or 3 phase motor. A given HP takes a given amount of watts. A 3 phase motor draws less current but not less power. 2)The use of a phase converter adds to the operating cost, good ones have about 80% to 90% efficiency, right away 10% to 20% more in electric costs. The only real reason to go with phase converters IMO is that some equipment is not available with single phase motors and often can not be retrofit as the same HP in single phase is physically larger. iwire I went to a motor supplier web site and selected two 5 HP motors as identical as I could find. A single phase 230 volt 5 HP 1740 RPM motor draws 23 amps or 5290 watts. 230 volts x 23 amps = 5290 Watts A three phase 230 volt 5 HP 1755 RPM motor draws 13 amps or 5173 watts. 230 volts x 13 amps = 2990 x 1.73 = 5173 watts In this case the 3 phase shows a slight edge in efficiency of about 2%, which will be blown away with the loss at the phase converter of 10% to 20%. I am not saying phase converters do not have there place but if you can get a 3 phase service in the long run you will be ahead. frenchelectrician if you have true 3 phase electrical service near your area, yes you can do that. or the other option that you can use the phase conveter for time being while you are planning to change over to 3 phase service and i mean new meter box , new loadcenter etc.. but before you get ahead of the game. i really suggest to check the POCO [power company] to see what they can do with 3 phase service if fesible to do it or not depending on the location and type of transmisson line they have near your area. many time they useally upgrade the line and few time they will bring the 3 phase line if they can but as i say check with poco first before you spend money on phase conveter and see where it stand and time window frame how long it will take and so forth .. merci , marc