electricmonk
spending too much on rocks
Member since August 2011
Posts: 281
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Post by electricmonk on Oct 21, 2011 21:37:07 GMT -5
Anyone know roughly speaking how many 1/3 - 1/2 HP motors one could run, under load, on a 15 Amp household circuit? I figure 3 slab saws, a 20, 14 and 10" as well as 1 maybe two arbors all at the same time. That would be maximum usage. I have to run some new circuits into the panel and want to limit how much I am adding due to cost and the fact that I rent. Not concerned about the work itself, I have done some electrical and know the principles/safe practices to ensure I don't get zapped or burn the place down. On a side note, I have a compressor with a blown out tank that I was going to salvage the motor off of. It is a 3.5 HP, not sure the speed. Assuming it is running 1725 RPM (typical) would that be overkill for a 20" saw? I figured I might was well use it if it isn't unreasonable. If it is a high speed motor then I am going to turn it into a high speed sander project so, go me
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rockhound97058
freely admits to licking rocks
Thundereggs - Oregons Official State Rock!
Member since January 2006
Posts: 760
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Post by rockhound97058 on Oct 21, 2011 22:42:09 GMT -5
Afraid I don't know how many you can run on one circuit - however my main problem is start-up of the motors. It usually takes a heavier load during start-up than when they are running - so keep that in mind. I know my 20" saw has a 1 or 2hp motor on it and when I hit the power switch my lights dim for a second.
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Post by parfive on Oct 21, 2011 22:45:59 GMT -5
If you’re running a couple of new circuits, why mess around w/15@ circuits. Run a 12/3 home run and be done with it.
And if you’re doing this in the garage, GFI receptacles are required.
Two 1/3 hp motors (~6@ each) “should be” the max for a 15@ circuit – 80% of the circuit rating.
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Post by parfive on Oct 21, 2011 22:54:47 GMT -5
And forget about that 3.5 horse motor – wiring it will blow your budget, running it will blow your electric bill. ;D
(Covington’s 36” slab saw only has a 2 horse motor.)
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Post by jakesrocks on Oct 21, 2011 22:58:00 GMT -5
Just to add to what has already been said, that 3.5 HP motor will be way overkill for just about any lapidary equipment you'll be likely to have in your shop, unless you're planning on building a huge drag saw.
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electricmonk
spending too much on rocks
Member since August 2011
Posts: 281
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Post by electricmonk on Oct 21, 2011 22:58:49 GMT -5
If you’re running a couple of new circuits, why mess around w/15@ circuits. Run a 12/3 home run and be done with it. And if you’re doing this in the garage, GFI receptacles are required. Two 1/3 hp motors (~6@ each) “should be” the max for a 15@ circuit – 80% of the circuit rating. Basically because I have 250' of 14/2 ROMEX already, not to mention almost all of the receptacles already. I used to build houses and did a lot of remodel work and I want to use what I already have. Basically I have to go buy a half dozen single gang boxes and a breaker and I am good. I have a GFCI receptacle in the garage that I have two other receptacles chained off of (downstream, series connection). I am going to run another two circuits with a GFCI outlet as the first upstream receptacle. I appreciate the input as far as draw goes, I honestly figured someone here would know. So the plan is, 1 circuit for the saws, 1 for the arbors/buffer, and another for the fridge and deep freeze (already being used). Going to chain all of my shop lights off of the lighting circuit that is already in the ceiling. There is a single gang box in the ceiling for an (unused) garage door opener. Will run a single pole light switch and 3 outlets downstream of that for the shop lights. I was just wanting to get a feel for how much ladder work I need to do, it won't be too bad. That and I only want to have to kill main power to the house once when I get into the panel to wire the new breaker(s). I don't relish having to get in the panel but I know electrical safety well enough to not tough what I shouldn't and test voltages before doing anything. Thanks for the input folks! Erik
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electricmonk
spending too much on rocks
Member since August 2011
Posts: 281
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Post by electricmonk on Oct 21, 2011 23:01:14 GMT -5
Thanks for the input regarding the 3.5 HP motor, might try to trade the whole compressor for a motor that I can use. Someone is likely to have a tank already and the desire to rebuild it on the cheap...I hope
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Post by johnjsgems on Oct 22, 2011 6:42:47 GMT -5
About 6 amps per should be right. Usually 3 times that for the start 2-3 seconds. Check the breaker for the garage opener. If it is 20 amps it should be 12 ga wiring. I think most tract homes use 15 for lighting and 20 for receptacles. You can tell by the breaker. In CA anyway it is 6 outlets on a 20 amp circuit and 6 light fixtures on a 15. If your furnace is in the garage like most CA homes it is likely on a separate breaker too.
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Post by rocklicker on Oct 26, 2011 18:25:16 GMT -5
I usually plug everything into the socket for the washing machine because it's a 20 amp plug. Now and then I was running a 1/3HP motor on a tumbler, a 1/2HP motor on a slab saw, and a 1/4HP motor on a cabber. I avoided that setup because the extension cord and plug got pretty warm. Best practice was to turn off the tumbler.
When I can afford an electrician again, I am hoping to get a couple dedicated rock curcuits set up in the garage. Steve
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