What amperage breaker do I need?
dovetail97128
| Posted in Tools for Home Building on
What amp. breaker do I need for this motor?
230 Volts 1 Phase 20.8 FLA (Full Load Amps)
Currently have 2-twin 30 amp circuits for table saw, jointer and planer ( all have 2 hp. motors) and one twin 50( originally set up for a welder).
Shop is set up with one twin 30 circuit down each side already so planer/jointer and saw are on different circuits.
This motor would be for a dust collector.
They can’t get your Goat if you don’t tell them where it is hidden.
Replies
Sounds like a 30 to me.
30. is there room?
Like everbody else, sounds like 30A breaker to me.
Thought:
If the old 50A line is unused, and the cable terminates in a convenient location for your dust collector - you could change the 50A breaker to a 30A, and the receptacle to a 30A style and utilize the existing (#6?) cable to feed it.
This plan assumes the #6 cable will connect properly to the 30A receptacle and breaker - a quick read on the devices will confirm or deny. Might need a magnifier........
Saves a little on cable and labor and will function just fine.
Jim
"This plan assumes the #6 cable will connect properly to the 30A receptacle and breaker"Accessible junction, probably right inside the panel.
OK 30 amp breaker it is. I forgot to ask an important question however.
Does that mean that the breaker for the dust collector is a dedicated circuit or can it be shared with one of the 2 hp. units and have them operate simultaneously? I can swap out the 50 amp breaker and outlet easily enough if I need to.
They can't get your Goat if you don't tell them where it is hidden.
"Does that mean that the breaker for the dust collector is a dedicated circuit or can it be shared with one of the 2 hp. units and have them operate simultaneously?"Depends on what they're pulling and what the code allows (if at all) for stacking & looping onto a 220 line.
You don't want that circuit to trip every time you turn those machines on.
Accessibility at either end was not my concern.
My primary concern was the maximum, approved, wire size rating for the new 30A receptacle.
The breaker wire size rating should be fine, just warned him to check ---- jus' tryin' ta stay legal!
JimNever underestimate the value of a sharp pencil or good light.
Understood and appreciated.
They can't get your Goat if you don't tell them where it is hidden.
"wire size rating for the new 30A receptacle."I believe it's 10 guage for 30
8 guage for 40 and so onAny junctions to a wire gauge change are ok so long as the gauge of any wire used is code with the amp breaker size. Maybe the code has changed on that though, I'm sure Bill would know. All junctions must be accessible.
You missed my point re: maximum approved wire size - AKA listed wire size.
dovetail (OP) got it.
Many / most devices have a maximum wire gauge which can be safely connected to them --- that maximum size is known as the "listed" maximum.
It has to do with the physical space available and configuration of the device's connection points. Screws, clamps, back-stab holes, whatever.
For example, many 15A duplex outlets are listed for #14 or #12 ga wire - they are "listed" for connection to these wire gauges regardless of the breaker installed on the circuit.
It would be a no-no to attempt to connect #8 wire to these devices even though you had installed a 15 or 20A breaker on the circuit.
I was merely pointing out that I was unsure of the maximum listed wire gauge for dovetail's new 30A receptacle - if he chose to go the "trade out breaker and receptacle" route to power his dust collector.
Breakers are typically also typically listed as to maximum wire size (minimum also sometimes).
You are correct in that a 30A circuit would "normally" be wired with #10 ga wire, and his new 30A receptacle would certainly accept, and be listed for use with, #10 wire.
However, my suggestion was to leave the existing #6 wire in place (from the unused 50A arc welder circuit); change out the old 50A breaker to a 30A, and the existing receptacle to a 30A.
Therefore, I was suggesting for him to be using the existing #6 wire in a 30A circuit. It was declared a 30A circuit by changing the breaker from a 50A to a 30A.
#6 is two gauges larger than the "normal" #10 wire for this circuit rating.
I was most concerned with the maximum wire size rating for his new receptacle(nothing to do with amperage or breaker sizing).
Less concerned with the breaker as they are typically listed for use with wire gauges in excess of their "normal" amperage rating's wire gauge.
This wire size listing information is usually supplied on the packages, or by stickers on the device, or molded directly into the device's body, or stamped into the metal of the device's yoke.
Likewise, most devices (all?) carry a listing for wire type - "Cu only" or "Copper Conductors Only", or "Al/Cu" - either aluminum or copper. Have never consciously seen an "Al only" listing - but they might exist.
I also understand that wire gauge changes are acceptable (but not my preference) within the circuit - i.e., he could pigtail #10 onto the existing #6 within the receptacle box if he needed to (assuming he had changed the breaker to 30A).
IMHO, it would be a superior method to connect the existing #6 directly to the new receptacle if it was listed to accept #6 wire.
Fewer connections within the circuit, and less junk in the receptacle box - "Ahm toldin ya, them war nuts fer a #6 anna #10 kin get rat big, an thet #6 war ain't too flex-e-bull niether!" :-)
Jim
Never underestimate the value of a sharp pencil or good light.
You missed my point re: maximum approved wire size"No....I didn't. I got it loud & clear before. You answered my question though.
The 30a receptacle for that dust collector will probably take 6ga wire and if it has internal overload protection, like Bill was describing, the 50a breaker is OK.
I thought he was planning on keeping the welder circuit and it would usually be OK if he did. I am sharing my welder circuit with my 5HP pressure cleaner (both 30a 240v) and since I will never be pressure cleaning while I am arc welding I call that non-coincidental loads. I think the same would be true of the dust collector.
Actually if it is a dedicated circuit he can probably keep the 50 amp breaker.But I need to get the code book out and look at the details to find that max breaker size..
William the Geezer, the sequel to Billy the Kid - Shoe
I was hoping you would post a reply here.
Not sure I understand your comment about the dedicated circuit, but here is what I have: 50 amp. dedicated welder circuit.
30 amp, west wall of shop 3 outlets. (220 13 amp planer almost exclusively)
30 amp east wall of shop , 3 outlets (220 15 amp table saw almost exclusively)
30 amp dedicated heater circuit. Now that I typed that out I can answer my own question.. the 30 amp circuits won't handle both the dust collector and the saw or planer at the same time.
Can I switch out one of the 30 amp breakers for a 40 amp?
Wire is romex #10. Maybe better to wire in a sub panel as the main panel is full up on 220 circuits.
They can't get your Goat if you don't tell them where it is hidden.
I think I would put the dust collector on with the welder. They are not going to be used at the same time in a one man shop.
What Bill was talking about is you can use a breaker 250x the FLA of the motor so 50 will work.
Thank You for the clarifications.
They can't get your Goat if you don't tell them where it is hidden.
"Can I switch out one of the 30 amp breakers for a 40 amp?
Wire is romex #10."No, if I understand correctly.First you need to look at if the circuit is dedicated to a know motor load or not.Now you can have receptacles on a dedicated motor circuit if it is needed repositioning or maintaining equipment. But not if you want to plug in different combination of equipment. Then it becomes a general purpose circuit.The whole purpose of the code is to protect the wiring and of course the structure that it is attached to. It is not to protect the load. Motors are suppose to have either starters with motor overload protection or overload protection in the motor. Most motors of this size have internal protection. Typically a button that will pop out. Some applications have self-resting overloads. But for something operating machinery you don't them to restart unknown. So they should have a manual reset.On a general purpose circuit you never know the what combination of loads is going to be. So the breaker must be sized to protect the wiring from long time overloads.For the dedicated circuits the the load is known. And the wire can withstand a large amount of overload for a short period of time. So the breaker can be sized to only protect the wire from a fault, ie short. And for motor overloads the motor overload will trip. So basically the wire is sized for the nominal motor load and the breaker (or fused) is can be much largers. IIRC it can be 1.75 to 2.5 times the nominal motor current depending on the type of breaker or fuse.Now you can have multiple KNOWN motors on a dedicated circuit. But the calculations are more complicated.The classical case is for central AC compressors. They have 2 motors (compressor and fan). But all of the calculations are done for you and the label will have a minimum circuit (wire) rating and a much larger maximum breaker size."Maybe better to wire in a sub panel as the main panel is full up on 220 circuits."Probably the best option. While dedicated motor circuits and be useful and might want to install one for large and hard starting equipment, such as an air compressor, in general they are too trickly to use in an "uncontrolled" situation and you never know in the future what some one will try to plug into those circuits..
William the Geezer, the sequel to Billy the Kid - Shoe
Edited 6/2/2009 12:36 pm by BillHartmann
the rule of thumb that i have gone by is that items like welders, compressors, power feeders should be on their own circuit becuase the are on a constant load. I'm not an electrician, so this opinion will vary. i have been told to size up to 150% of the max load. I have even been told 200%. My understanding that this is a general rule of thumb. Each device must be calculated by an engineer to be legal.
I have been know to run a table saw, shaper and dust collector on the same circuit(20A), but rarely do they run combined and never loaded all at the same time. I have not had a problem.
But, I usually do have dedicated circuits for each piece of equiptment. I also run 3/4' EMT on most walls of the shop/garage with twist lock recepticles so that I never have a problem moving machinery around.