120 to 220 bandsaw conversion?

[Rick Christopherson]

In regards to the switch for 120 V vs 240 V. It is a matter if both legs of the 240 V need to be disconnected. For 120 V, only one leg is hot. Certainly, disconnecting one leg will stop the current but the other leg is still hot.

For safety, I believe both hot legs for 240 V should be disconnected so a double-pole switch should be used.

Amen, Brother.

I'd never put a single pole switch on a 240V tool. One day, you'll forget to unplug the tool before you work on it. Or you'll sell it and the person who bought it will think it has a two pole switch.

Mike

What happens if you forget to unplug the tool before working on the switch? Both conductors on the upstream side of the switch are hot. There is obviously nothing wrong with opening both conductors, but I have always felt this was a poor reason to worry about it, because there will always be live conductors present in virtually every system once you open a secured cover without disabling power. The neutral is still a current carrying conductor too. Anyone foolish enough to open the peckerhead of a motor without cutting power deserves to have his widow selling his tools to the rest of us on eBay.

I am not saying it is a bad idea or anything, but simply that people should be told that it is their option if they want to replace a single-pole switch with a double-pole switch when they make this conversion. It is not mandatory that they use a 2-pole switch on a 240 volt motor. (I just read this within the last 24 hours, but I cannot remember which article, but I am sure it was within NEC 430.)

Oh, I found it!

Article 430.84 Need Not Open All Conductors. The controller shall not be required to open all conductors to the motor.
Exception: Where the controller serves also as a disconnecting means, it shall open all ungrounded conductors to the motor as provided in 430.111.

[Mike Henderson]

Rick - you and I have had this discussion before. You're right, there's no code requirement to break both hot connectors but I prefer to do so on my equipment. I'll also recommend it to anyone who asks me.

We may disagree on this, but I feel it's safer to have a switch that breaks all the hot lines.

Mike

[Mike Lipke]

Mike, the current carrying capacity of a conductor is not affected by the voltage.

14 AWG wire is rated at 15 amperes, it doesn't change from 120 volts to 240 volts.


Regards, Rod.

You are correct. I meant to say wattage doubles when you go to 220 volts. As I did say, correctly, that 14 g wire carries 15 amps, by code, whether 110 or 220 volts.

[Rick Christopherson]

No Mike, we don't actually disagree. I just feel that it is important that people know what their options are so that they can make that choice for themselves, especially when specific circumstances favor one over the other.

The standard advice gets repeated so much that most people do not know that it is their choice to make, and I am simply balancing that advice.

[Mike Henderson]

No Mike, we don't actually disagree. I just feel that it is important that people know what their options are so that they can make that choice for themselves, especially when specific circumstances favor one over the other.

The standard advice gets repeated so much that most people do not know that it is their choice to make, and I am simply balancing that advice.

I understand and appreciate your knowledge and advice.

One thing I remind people of occasionally is that "code" is actually the minimum acceptable. It's okay (and may be desirable) to exceed code in certain situations.

Mike

[Tom Veatch]

...
Article 430.84 Need Not Open All Conductors. The controller shall not be required to open all conductors to the motor....

I'd never put a single pole switch on a 240V tool. ...

I've got a question, and I'm not sure how to ask it without ruffling somebody's feathers which I've no intent to do.

Rick says, and cites the NEC to the effect, and Mike agrees, that there is no code requirement for a DP switch on a 240v (two hot wires) motor. But, my question is, "Is the NEC even applicable?"

The original discussion involved a bandsaw being converted from 120 to 240 volts and the question was asked whether the switch would need to be replaced also. There's no question that the NEC, or at least the local jurisdiction's implementation of the NEC, is applicable to the permanent wiring up to, and including, the wall socket. But the bandsaw in question is a "plug and cord" device, not permanently hardwired into the circuit.

So, do code requirements extend past the wall socket into the device plugged into that socket? If it does, how are they enforced? You're certainly not required or expected to pull a permit and schedule a visit by the electrical inspector to plug something into the wall socket in your living room.

Or do the provisions and requirements of the electrical code stop at the permanently wired receptacle? If so, what rules apply to the "plug and cord" device that's plugged into that receptacle? UL listing? If that's the case, maybe the UL listing requirement, if any, that addresses switching 240v devices is more appropriate to the switch question.

The reader is, of course, free to do it however they wish, but I'll continue to use DP switches on 240v loads, either permanent wiring or plug and cord devices, not because of any regulatory requirement, but simply because I'm more comfortable doing it that way.

[Rick Christopherson]

That's a good question Tom, and I am not entirely sure what the answer should be. However, it actually becomes a moot point, because if the NEC doesn't apply, then nothing applies.

UL is not a regulating body and adherence to their requirements is voluntary only if the manufacturer (not the end user) wishes to have the UL label affixed to their product. For example, you will notice than none of the Fein Turbo vacuums have a UL sticker. This is not because they are dangerous, but because a specific UL requirement that does not serve the needs of the end user prevents Fein from obtaining a UL listing for the vac (without great inconvenience to the end user).

UL987 section 19.3 does in fact stipulate that.....oh jeez, do they use crappy wording....if the tool is over 125 volts, then it should have a 2-pole switch (it makes no mention of opening all ungrounded conductors, which is the proper wording for such a directive ).

Anyone that has spent any time reading UL documents knows that they are pretty rediculous. Did you know that the majority of the poor english and typographical errors in owner's manuals were actually mandated by UL 60745? I kid you not! UL 60745 paragraph 8.12.1 states that manuals must contain the safety warnings listed in the subsequent sections, and they "must be verbatim!" Those safety warnings that everyone laughs at were riddled with mistakes and typos that every manufacturer was forced to follow. Only recently did many of these errors get fixed, but there are still a few.

As for the NEC's applicability to this discussion, you can't have it both ways. Either they are or they are not, and there have been many discussions where people (including yourself I believe) that have used the NEC's statements to corroborate information provided on the forum. In this particular case, the NEC states what most people familiar with electrical systems already know--it takes only one break in a circuit to stop the flow.

[Rod Sheridan]

I would like to see a 2 pole switch on 240 volt equipment to disconnect both lines, however as Rick indicated, it's not required.

The one item that hasn't been adressed is that if you only open one line with a single pole switch, the switch will see 240 volts across the open contact, not share the voltage across two open contacts as would happen with a 2P switch.

You would have to check whether the single pole switch is actually rated for 240 volts or not.

Regards, Rod.

P.S. As many have stated, I wouldn't change a 3/4 HP motor to 240V unless as in this case, the person doesn't have enough 120 V circuits to run his vacuum and motor at the same time.

[Rick Christopherson]

I am sorry Rod, but that is a little misleading. It makes no difference whether it is a single pole switch or a double pole switch, it must be rated for the voltage. Because it is virtually impossible for both contacts to make the connection at the same instant in time, one of the two contacts will see the full circuit voltage. They do not necessarily share or split this voltage.

[Roger Frazee]

HI Tom

That is.... a very good question.... and I'm not sure one will ever get consensus on the correct answer.

I think it my be hidden in Article 90 Specifically 90.2 (A) and (B). I'm reasonably sure that for residential or commercial the authority ends at the connection to the supply conductors (utility). As an example if your home has and overhead messenger utility supply to your mast. The NEC would take over where the drip loop of the entrance conductors connect to the overhead supply from the utility. The utility falls under regulation by the NESC.

But that wasn't your question but it gives us a beginning point at least....

Now I think the defintion of branch circuit conductors gets us close to the end for a dwellings premise wiring and associated devices and equipment (Panels etc).

I may not get it perfect but I believe this is pretty close " Branch circuit conductors are those conductors between the Final overcurrent device and the outlet or connected load." So I think that covers the end of NEC regulation as to branch circuits and associated equipment of the premise wiring.

Then of course there are feeders etc.. but trying to summarize I would say the NEC goes from the connection point of the supply and to the connection point of a load or outlet for a load.

Now that seems easy but I don't think it is quite that easy. The NEC spends a lot of ink in several chapters identifing specific loads like motors, motor operated appliances and so on... and how conductors and cords and plugs must be rated in order to connect to the premise distribution outlets and conductors like branch circuits depending of course their intended use for the connection point....is the plug going to be a disconnect.

So it would seem to me the NEC regulates up the connection to the utilization equipment whether that be a plug and cord or hardwire.

If a switch is used for on and off on a piece of equipment that is cord and plug like a table saw IMO does not fall under the NEC. It has already been wired into the tool by the manufacturer. The nec is not a design enforcer. But the manufacturer has his set of rules... And I believe they would have to work to a degree with the NEC and listing laboratories to have some sort of consensus on the minimums required for control and disconnection of any piece of equipment so that an electrician can bring power to the load in compliance with code.... and be able to install the necessary conductors and overload and circuit protection required for safe operation that protects the utilization equipment and for human safety. So I would say it is a hand in hand deal as Rick said with the manufacturers and the NEC and the listing laboratories. But if you have to replace a switch on a saw or an electrical component on a saw I don't think the NEC necessarily regulates how you should wire it but only sets the minimums of how it should be wired.

Just my thoughts

[Rod Sheridan]

I am sorry Rod, but that is a little misleading. It makes no difference whether it is a single pole switch or a double pole switch, it must be rated for the voltage. Because it is virtually impossible for both contacts to make the connection at the same instant in time, one of the two contacts will see the full circuit voltage. They do not necessarily share or split this voltage.

Yes Rick, I did not mean to indicate that the switch didn't need to be rated for the voltage, that was my point regarding checking the switch voltage. I'd hate to see the person use the wrong switch......regards.....Rod.

[Roger Frazee]

Yes Rick, I did not mean to indicate that the switch didn't need to be rated for the voltage, that was my point regarding checking the switch voltage. I'd hate to see the person use the wrong switch......regards.....Rod.

You didn't Rod you were very clear about the switch rating needing to be 240 volts.

However on a 240 volt switch I suppose you won't see full voltage on the contact(s) until they close...You need to be very careful about those nanoseconds between contact closures....

But I certainly don't see anything wrong with your sharing analysis. A double pole switch would share the opposite leg voltages in the open position over 2 contacts ...a single pole the opposite leg voltages over one.
I think it is fine to look at it that way.

[Roger Frazee]

......and more importantly, a 3/4 hp motor is not a good candidate for the argument that it needs to be done due to substandard wiring. A 120 volt 3/4 hp motor is going to draw only about 7 amps at maximum rated load.

Rick I think you have a typo. Should be 230 volts 3/4 hp at about 7 amps. 115 volt at 13.8 amps.

[Mike Henderson]

Rick I think you have a typo. Should be 230 volts 3/4 hp at about 7 amps. 115 volt at 13.8 amps.

I think those numbers are a bit high. A HP is about 750watts (rounded). Let's assume a 3/4 HP motor is only partially efficient and the motor draws about 750watts to produce 3/4 HP out. At 120 volts, that would be about 6.5 amps (rounded).

Mike

[Roger Frazee]

Mike

Depends on what is meant by maximum rated load. If your talking FLC the table rating is as I posted. It doesn't seem right to me that at 3/4 hp the maximum rated load would be 1/2 of the motor table flc??? I would think the rla would not be more than 4 or 5 amps less than table value depending on the type of motor.,I've never seen motor load (amps) (nameplate amps) calculated like you did...but If I misundertood what Rick was saying then I will concede he may have reached that figure as you did....so my apologies. I thought we were talking about this motor on this thread...the maximum rated load or full load rated current as i would view it would not be 7 amps for a 115 volt 3/4 hp single phase ac.