Easy electrical question

[George Lohnes]

I have a 3hp 240v saw that I plug into an outlet that is connected wired to two 20amp breakers ... does that make it 20 amp or does that make it 40 amp?

[George Lohnes]

Just figured out my own question... it is two pole 20 amp (whatever the heck that means!!)

So.... how difficult is it to swap out that (or add) a 30amp breaker to the panel then?

[Fred Jones]

George,
Does the saw trip the breakers when you use it? If not you shouldn't need to change it to 30 amps. (Note -- I'm not an electrician-- I'm sure there are a few on SMC who could answer your question)

[David Christopher]

it is still 20 amps

[Tom Veatch]

I have a 3hp 240v saw that I plug into an outlet that is connected wired to two 20amp breakers ... does that make it 20 amp or does that make it 40 amp?

IF the two 20amp breakers, single pole, I assume, are connected to opposite legs of the service, then you have a single 240v, 20 amp circuit although it is probably not in compliance with code. Code requires that each hot wire in a 240v circuit be protected by a separate breaker, but the breakers must be common trip. I.e., if one trips, it forces the other to trip also. That is typically handled by a single, double pole breaker. If the trip handles of the two breakers are connected so that one breaker can't trip without causing the other to trip also, that meets the intent of the code. If not, the installation is non compliant.

If the two breakers are connected to the same leg of the service, then you don't have a circuit. The potential difference between the two wires will be zero instead of 240v. A quick test with a voltmeter at the outlet will tell you which case you have.

Direct answer to your direct question is that it will be a 20 amp circuit.

Edit: Just saw your followup post. No need for a 30 amp breaker. A 20 amp circuit will service a 240v 3HP load without any problem. BUT, if you must swap out the breaker, it's a simple matter to pull that breaker and replace it with a 30amp breaker OF THE SAME TYPE. But, you'll also need 10ga wire and 30amp plug and receptacles. That means that if the existing wire is 12 ga, which it probably is if the breaker is 20amp, that wire will have to be abandoned and a new 10ga wire run installed along with the 30 amp devices. I'd leave it alone unless there's something else that you've not mentioned that is driving the desire for a 30amp circuit.

[David Christopher]

Just figured out my own question... it is two pole 20 amp (whatever the heck that means!!)

So.... how difficult is it to swap out that (or add) a 30amp breaker to the panel then?

take the panel face off disconnect the wires then it will clip out.... it moves from the middle outwards

[George Lohnes]

Tom

I strongly suspect that I have a single, double pole breaker which due to my ignorance of all things electrical, originally looked to me to be two breakers. Now that I have read your post and have spent the requisite 5 minutes on google , I think I understand the difference and have the one that meets code.

For clarification to those above, I need to increase to 30 amp (and I believe 10 gauge wire ) since my new (used) saw is now 5hp instead of 3hp.

I am checking all this out in preparation of moving my saw to the basement (from storage in the garage for the past week) tomorrow. Someone from the Creek here who I don't know but reached out to me via PM has volunteered to help with the electrical... but I am trying to make sure I have what he/we will need.

It is a HUGE help to me to get this info here and also to get the help in person. Last time, and I am not kidding, I tried to get an electrician to wire my basement shop (so not a real small job) I called 11 electricians, 3 of whom returned my call and one of which showed up!

Thanks again... off to the basement to check the circuit breaker again and to see if I have 10 or 12 gauge wire

[Rod Sheridan]

Hi George, it is very unlikely that you will ever run a 5 HP saw in a home application, that will prevent it from running properly on a 20 ampere circuit.

That's why my 3 HP shaper and tablesaw run perfectly on a 15 ampere circuit.

The duty ccle and load profile your saw will be so far below continuous rating that the 20 ampere circuit will be fine, unless your motor has abnormally high starting currents.

I suggest that you try the 20 ampere circuit before you replace it with a 30 ampere circuit.

Regards, Rod.

[Ken Higginbotham]

Hi George, it is very unlikely that you will ever run a 5 HP saw in a home application, that will prevent it from running properly on a 20 ampere circuit.

That's why my 3 HP shaper and tablesaw run perfectly on a 15 ampere circuit.

The duty ccle and load profile your saw will be so far below continuous rating that the 20 ampere circuit will be fine, unless your motor has abnormally high starting currents.

I suggest that you try the 20 ampere circuit before you replace it with a 30 ampere circuit.

Regards, Rod.

So you're saying it's not likely he will ever put a load on it that will bog it down to pull more than 20 amps ? And if he did the circuit would pop and be the indicator needed to put it a heavier circuit?

[Rod Sheridan]

Hi, the motor full load rating will be about 20 amperes.

So if you run at 20 amperes for a minute or so (Which I have a hard time believeing owning a 3HP saw), the circuit will be just fine.

The breaker would need substantially more than 20 amperes for a reasonable length of time (Minutes to tens of minutes) before it would trip.

If the breaker will handle the starting current, it will handle any forseable use a saw in a home shop will ever experience.

When I made hardwood flooring for my dining room, I used my 3 HP saw with a power feeder set at 37 feet per minute (fastest speed on my feeder). Ripping 4/4 oak at 37 FPM the saw ran at 8 amperes for a couple of hours.

What could you ever do at home that would require 16 amperes for hours on end? (The contnuous rating of a 20A circuit).

Regards, Rod.

[Sonny Edmonds]

Sounds like you figured out your confusion about the CB. There are different configurations, but what you have is the most common for late model panels.
Marvelous, not why I am posting.
Why I am posting is about your 5 HP saw and the 30 amp circuit for it. I too, run a 5 HP Unisaw in my shop and feed it with a dedicated 30 amp, 240 volt circuit, wired with #10 wire.
It's for the starting current these powerful motors thirst for to jump to life from a dead stand still. And to alleviate the voltage drop during that start up.
And in reality, the CB is there to protect the wiring, not whatever is connected to the wiring. The overload protection built into most motors in use today in single phase use, is the motors protection.
So do run the 30 amp circuit for your newer saw. And enjoy it's capabilities for the rest of your shop's life.
The 30 amp will snap in right where the 20 amp is removed from.

Always shut off the power to your panel when dabbling in there. Especially since you are learning about this and probably working on it alone. You need to be extra careful!

And congrats on your newer saw! May you never want for more power in your saw cuts, I know I don't.

[George Lohnes]

thanks for the input everyone

I think I confused the issue by mentioning my current saw (at 3hp) vs the saw that I have coming in (at 5hp 21.5Amps).

To answer the obvious, no I don't need a 5hp saw but there was a used Sawstop I was able to pick up at just over a couple of grand hence the larger motor. I barely need the 3hp I already had

So THAT is why I need to go to 30 amp and 10 gauge wire.

Just wanted to clarify.

[Tom Veatch]

thanks for the input everyone

I think I confused the issue by mentioning my current saw (at 3hp) vs the saw that I have coming in (at 5hp 21.5Amps).

To answer the obvious, no I don't need a 5hp saw but there was a used Sawstop I was able to pick up at just over a couple of grand hence the larger motor. I barely need the 3hp I already had

So THAT is why I need to go to 30 amp and 10 gauge wire.

Just wanted to clarify.

As others have mentioned, a 20amp circuit will probably feed your 5HP saw running at full power for as long as you'd need that power output, but you would be marginal with the circuit. The possibility of nuisance trips under sustained heavy usage can't be completely discounted. Although the 20amp circuit would probably work for you almost all the time, I'm going to agree with Sonny that the 30amp circuit would be a better match to the 5HP saw.

However, since that will definitely require new plugs, receptacles, and circuit breaker and most likely new 10ga wire, I'm going to suggest that you add a new 30amp circuit instead of replacing the existing 20amp circuit. If you can't come up with a couple of unused slots for the 30amp breaker, the decision is made, but if you can, the expense would be the same in either case and you might find down the road that a 240/20 circuit comes in handy.

[Roger Frazee]

I'm not sure I can add much to the previous posts but I have wired a few 5 hp saws single and 3 phase. You mention cord and plug for your old saw but it is my guess the manufacturer for your 5 hp saw will say no to this. It likely will be required to be permanently wired to the electrical supply. Might even need a motor starter if it isn't part of the machine. Just some things to check. I did a delta 5 horse once that required 40 amp time lag fusing. Just some things to look at. Maybe the owners manual will say??

[Rob Russell]

Roger - cord + plug is fine. My 7.5HP machinery came that way.