Simple (I Hope) 240V AC Electrical Code Question

[Andy Shearon]

Hi,

Background
I have had the good fortune to be able to purchase a Laguna 14SUV band saw, and I have a question regarding how to connect the machine to power.

Here's the issue. The saw has a 3HP 220V 1 phase motor. The saw is pre-wired with a 20A AC Plug (NEMA 6-20P, to be precise). The manual, however states the following:

"All machines require the minimum of a 30-amp circuit breaker."

In my garage, I have a 240VAC 30 amp circuit, with the corresponding 10 gauge wire going to a box with a NEMA 6-30R receptacle.

Question: Can I remove the 6-30R receptacle and replace it with a 6-20R receptacle and still have the circuit be code compliant, or must I remove the molded in plug and replace it with a 6-30 plug? My preference is to leave the cord alone.


Andy

[Mike Cutler]

Andy

Yes you can change the receptacle. What you can't do is provide the protection of a 30 amp receptacle with a 20 amp breaker and wire.

You could also just make, or buy, a pigtail adapter cord (6-30P to 6-20R) if you don't feel comfortable.

[Andrew Fleck]

I wonder why they would say that and provide a 20 amp plug. I would call Laguna and have them explain it to you. I suspect that 3hp motor draws under 20 amps. It might be a typo with Laguna. Or maybe it's not and they will send you the right plug.

Andrew

[Alan Trout]

That motor should not draw anywhere near 30amps. I agree to call Laguna before you do anything. Sounds like a typo to me.

Alan

[Jason Roehl]

Ever look at the plug and wire on a lamp cord? They're not rated for anything close to 15A, yet they get plugged into 15A (and 20A) 120V circuits exclusively. Breakers are sized according to the wire gauge of the circuit too keep it from overheating and causing a fire. Receptacle size, and what's plugged into it doesn't really matter (with a few minor exceptions).

[Ole Anderson]

A 3 hp saw ought to be able to run fine on a 20 amp circuit, my Grizz TS does as does my Kazoo chop saw. I would probably follow Mike's suggestion of making up a short pigtail adaptor using some 12 ga extension cord wire. And I wouldn't be surprised if the wire on the Laguna cord is 14 ga.

[Joseph Tarantino]

Hi,

Background
I have had the good fortune to be able to purchase a Laguna 14SUV band saw, and I have a question regarding how to connect the machine to power.

Here's the issue. The saw has a 3HP 220V 1 phase motor. The saw is pre-wired with a 20A AC Plug (NEMA 6-20P, to be precise). The manual, however states the following:

"All machines require the minimum of a 30-amp circuit breaker."

In my garage, I have a 240VAC 30 amp circuit, with the corresponding 10 gauge wire going to a box with a NEMA 6-30R receptacle.

Question: Can I remove the 6-30R receptacle and replace it with a 6-20R receptacle and still have the circuit be code compliant, or must I remove the molded in plug and replace it with a 6-30 plug? My preference is to leave the cord alone.


Andy

post a pic of the motor's data plate. that will show FLA rating, which will drive circuit size and attendant requirements.

[Wade Lippman]

Ever look at the plug and wire on a lamp cord? They're not rated for anything close to 15A, yet they get plugged into 15A (and 20A) 120V circuits exclusively. Breakers are sized according to the wire gauge of the circuit too keep it from overheating and causing a fire. Receptacle size, and what's plugged into it doesn't really matter (with a few minor exceptions).

But the outlet is part of the circuit. Unless the outlet is rated for 30a, it is a code violation. Probably not dangerous, but still....
I looked at the manual. It says it comes with a cord but no plug.
And it doesn't say how much current it draws. My guess is that it draws 18a and a few 20a breakers will trip on that, so the call for a 30a breaker just so they don't get complaints. But that doesn't really help the OP.
If you had nothing, i would says that 20a would do; but since you already have 30a, cut off the wrong plug and put a new one on.

[Howard Acheson]

>>>> and it doesn't say how much current it draws.

But, it must state the amperage on the the plate on the motor...

[Andy Shearon]

To answer a couple of questions in the thread:

1) The motor plate reads 12.8 FLA, so I'm a little bamboozled as to why they recommend a 30A breaker

2) Although the manual states there is no plug, it came with one (The cord is 14 AWG, too)


I think I'll try calling Laguna. I was hoping to find an off-duty electrician in the crowd on the receptacle swap... :-)

[Leo Graywacz]

Plug it into your 20 amp circuit and enjoy your saw. I have several 3HP single phase motors on 20 amp circuits and I run them every day.

[Art Mann]

I am an electrical engineer by trade but I have wired several houses for people and am familiar with most of the common rules. I can tell you right now it is not acceptable (per NEC) to replace the 30A receptacle with a 20A receptacle unless you also replace the 30A breaker with a 20A breaker. It will be no risk to you either way because the saw isn't really a 30A load but it will allow someone in the future to draw 30A through a receptacle that was designed to carry only 20A. If I were you, I would just cut the 20A plug off your saw and and replace it with a 30A plug. That does not break any code rules and doesn't create any additional risk. Also, in the future you may want to operatre a 30A piece of equipment using the same outlet.

[Mike Cutler]

I am an electrical engineer by trade but I have wired several houses for people and am familiar with most of the common rules. I can tell you right now it is not acceptable (per NEC) to replace the 30A receptacle with a 20A receptacle unless you also replace the 30A breaker with a 20A breaker. It will be no risk to you either way because the saw isn't really a 30A load but it will allow someone in the future to draw 30A through a receptacle that was designed to carry only 20A. If I were you, I would just cut the 20A plug off your saw and and replace it with a 30A plug. That does not break any code rules and doesn't create any additional risk. Also, in the future you may want to operatre a 30A piece of equipment using the same outlet.

What would prevent the occurence of what you detailed is that that a 6-30P will not fit into a 6-20R receptacle. They don't match.
The receptacle will carry much more amps that it is installed for. It's the wiring from the breaker to the receptacle that you're trying to protect.
That saw was shipped with a molded plug, and I'm willing to bet there is a UL approval on the cord. I wouldn't modify it on a brand new saw for risk of voiding warranties.
If Andy uses the pigtailed adapter I suggested, all the concerns are gone, and he doesn't have to cut the plug off the saw. Which would personally be my very last resort.

[Wade Lippman]

That saw was shipped with a molded plug, and I'm willing to bet there is a UL approval on the cord. I wouldn't modify it on a brand new saw for risk of voiding warranties.
If Andy uses the pigtailed adapter I suggested, all the concerns are gone, and he doesn't have to cut the plug off the saw. Which would personally be my very last resort.

Are you serious about voiding the warranty? How would they even know? And why would they care? Bear in mind that the manual says it ships without a plug.

[Jim Neeley]

If it ships without a plug, I definitely recommend using a 6-30P, or even an L6-30 (locking), if you're installing both the plug and receptacle.

I too assumed it came with a 6-20P plug, like mine did. Here's my story and what I found.

When I received my Unisaw it had a 6-20P, connecting with #10 wire, for a motor with a nameplate rating of 20 FLA and the Delta users manual recommended a 40A circuit breaker.

Given that the heaviest commercial 6-20R I could find was only rated for up to #10 wire and being a (Registered) Electrical Engineer I investigated the heck out of this issue prior to installing that 6-20R with #10 wire. First I didn't want to fail inspection (yes, I had it inspected) and second I didn't want to take the ribbing I knew I'd get from my buddies if I got written up for a code violation in my own house. This had to flow smooth. Know what I mean?

I downloaded the NRTL listing documents for the saw, talked with several peers, my local inspector and my Intertek (formerly ETL Testing Labs) inspector I work with for work. All said the same thing:

The saw was approved as a system to be connected using a 6-20P. Therefore that part is legit. They did not recommend replacing the plug due to warranty concerns and we discussed how the NEC permits (under tight rules) using a breaker larger than the wire's typical rating for a dedicated motor circuit and this qualified, even with the plug.

Nevertheless I chose to label as dedicated to that service, even though it was not technically necessary.

If someone else reading this considers following my path I recommend contacting your AHJ (inspector) and asking them if they would find a code violation if you install this way. The AHJ woun't tell you that something "meets code" for liability reasons but can tell you if they would write it up. If they're the one that's going to be inspecting it you can at least avoid the potential problem of an AHJ who decides differently.

The AHJ's have a lot of flexibility in their interpretation of the code and, if you can find a 6-20R that will take a #8 wire I'd go with both. What you do not want to do is to insert (or trim) a #8 wire to fit a teminal rated for a max of a #10 wire. That will get you busted.

Just my $0.02.. and experience.. YMMV.

Jim in Alaska