220V Outlets - necessary?

[JLNorthGA]

Our power to our stage is all 110V single phase. The power to our dimmer rack is 3 phase - but we don't have any plugs coming off of that breaker box.

Is there any reason why I would "need" a 220V outlet convenient to the stage?
We are contemplating getting a saw that requires 220V. It would be easier to "justify" the electrical work (and the expense) if there were other reasons to have a 220V outlet.

Most of the musical acts that come in just need 110V.
I was wondering if any incoming groups might need 220V.

 

[htroberts]

Our power to our stage is all 110V single phase. The power to our dimmer rack is 3 phase - but we don't have any plugs coming off of that breaker box.

Is there any reason why I would "need" a 220V outlet convenient to the stage?
We are contemplating getting a saw that requires 220V. It would be easier to "justify" the electrical work (and the expense) if there were other reasons to have a 220V outlet.

Most of the musical acts that come in just need 110V.
I was wondering if any incoming groups might need 220V.

Is the saw single-phase 240V, or three-phase 208V (I'm assuming you're in the US)?

If the saw is single-phase 240V, it should be inexpensive to run an extra wire in the conduit that feeds an existing receptacle.

If the saw is three-phase 208V and you don't have a 120/208V-3ø panel feeding the area where you want the new outlet, it's probably prohibitively expensive. I wouldn't feed general purpose receptacles from the panel for the dimmers.

 

[Scenemaster60]

If your dimmer rack is fed by 3 phase 120/208 volt Y service, chances are really high that all of the sub-panels in the building that feed convenience and utility outlets are also 120/208 volt three-phase Y. There is also a possibility that there may even be 277/480 volt 3-phase distribution panels and step-down transformers lurking. As htroberts asked, what exactly are the power requirement of the saw in question?

As to your question about usefulness on stage I would say "that depends".

Is your existing dimmer rack and distribution system adequate for your needs? If it's not, then I could see some usefulness for it in being able to connect smaller distributed dimmers either directly or through a fused breakout panel depending on the amperages involved.

Other than making it easier to add additional dimming capacity, I can think of no other use for a 208/240 volt outlet onstage. Anyone else?

 

[porkchop]

A lot of moving lights run on single phase 208VAC. Not really sure if a single outlet would be much help, but if the powers at be wanted to make a capital improvement to add a few 208VAC circuits to be ready to accommodate future needs, then there's no reason there couldn't be plugs that are also convenient for table saw use.

 

[JLNorthGA]

If your dimmer rack is fed by 3 phase 120/208 volt Y service, chances are really high that all of the sub-panels in the building that feed convenience and utility outlets are also 120/208 volt three-phase Y. There is also a possibility that there may even be 277/480 volt 3-phase distribution panels and step-down transformers lurking. As htroberts asked, what exactly are the power requirement of the saw in question?

As to your question about usefulness on stage I would say "that depends".

Is your existing dimmer rack and distribution system adequate for your needs? If it's not, then I could see some usefulness for it in being able to connect smaller distributed dimmers either directly or through a fused breakout panel depending on the amperages involved.

Other than making it easier to add additional dimming capacity, I can think of no other use for a 208/240 volt outlet onstage. Anyone else?

The dimmer rack is fed by 3 phase 208. I suppose the sub panels are the same.
The rack is more than adequate for our needs.

The saw in question is a G0715P from Grizzly. It just says 220V single phase.

I talked with an electrician this morning - we would have to pull it from the box downstairs.

 

[RickR]

Grizzly says it's a 110 or 220V, but comes wired for 220. Naturally the amperage doubles going to 110. Making sure you have a dedicated circuit (20A) and rigging the saw for 110 should be just as good and vastly cheaper than dragging in a 220 line.

You might find that a 3 phase saw is more practical. Motors run better on 3ph and the bigger saws are only 3ph. Getting a 3ph breaker from the existing outlet panel shouldn't be a big deal.

 

[Scenemaster60]

Thanks for the clarification about the saw. I pulled up its spec sheet and RickR is dead on that it would be vastly cheaper to convert this saw to 110 volts. Unless your building was built before about 1960, all of the 110 volt utility outlet circuits in your shop should be 20 amp circuits anyways. You might have to do a little investigation to see how those circuits are wired so that you don't already have an 8 or 10 amp load on the same circuit that could be used simultaneously.

Also, like I said earlier, you may not even be able get single phase 220 volt power from anywhere in the building to begin without installing a separate step-up transformer (MANY $$$$). You would most likely be getting 2 legs (phases) of a 120/208 volt 3-phase Y feed which is technically NOT the same as a single phase 220 volt circuit off of a single phase transformer.

I have no idea how fussy these saw motors are to the difference between the two. It may make no difference at all, but I have a sense that this motor may actually be happier and have more power on a 110 volt single phase circuit than a 208 volt multi-phase circuit.

Another factor to consider is how much this saw will actually be used. If it's going to be used hard ripping 2xs or 3/4" plywood for extended periods of time it will likely run hotter on 110 volts than 220. But if you are mainly ripping 1x stock and luan, it should be just fine.

 

[JLNorthGA]

Thanks for the clarification about the saw. I pulled up its spec sheet and RickR is dead on that it would be vastly cheaper to convert this saw to 110 volts. Unless your building was built before about 1960, all of the 110 volt utility outlet circuits in your shop should be 20 amp circuits anyways. You might have to do a little investigation to see how those circuits are wired so that you don't already have an 8 or 10 amp load on the same circuit that could be used simultaneously.

Also, like I said earlier, you may not even be able get single phase 220 volt power from anywhere in the building to begin without installing a separate step-up transformer (MANY $$$$). You would most likely be getting 2 legs (phases) of a 120/208 volt 3-phase Y feed which is technically NOT the same as a single phase 220 volt circuit off of a single phase transformer.

I have no idea how fussy these saw motors are to the difference between the two. It may make no difference at all, but I have a sense that this motor may actually be happier and have more power on a 110 volt single phase circuit than a 208 volt multi-phase circuit.

Another factor to consider is how much this saw will actually be used. If it's going to be used hard ripping 2xs or 3/4" plywood for extended periods of time it will likely run hotter on 110 volts than 220. But if you are mainly ripping 1x stock and luan, it should be just fine.

The real problem is the max power draw at 110V - current draw (although transitory) will be upwards of 30+ amps.

 

[JD]

The real problem is the max power draw at 110V - current draw (although transitory) will be upwards of 30+ amps.

Well, that kind of settles it. It's got to be a special run either way, so it might as well be a 240 or 208v 20 amp circuit and plug. Cheaper to run [HASHTAG]#12[/HASHTAG] than [HASHTAG]#10[/HASHTAG].

 

[markviml]

Where are you getting 30A? The manual says 16A @110V.

 

[albinotuba]

Is there any reason why I would "need" a 220V outlet convenient to the stage?

Amp racks? The ones I've seen usually have NEMA L14 inputs.

 

[JLNorthGA]

Where are you getting 30A? The manual says 16A @110V.

The inrush current draw for an electrical motor is what it takes to start the motor going. It is the "inrush current".
To quote:
"When an electric motor, DC or AC, is first energised, the rotor is not moving, and a current equivalent to the stalled current will flow, reducing as the motor picks up speed and develops a back EMF to oppose the supply. AC induction motors behave as transformers with a shorted secondary, until the rotor begins to move, while brushed motors present essentially the winding resistance. The duration of the starting transient is less if the mechanical load on the motor is relieved until it has picked up speed."

It can be several times that of the typical peak or load current. A 16 amp motor may have several times the peak current value - so figure on 30-48 amps. It is transitory, typically lasting only a couple hundred milliseconds. The breakers are built to handle the inrush current. Three phase motors don't have this problem - which is why they are used in industrial settings. It ordinarily isn't a problem. But you are really operating at the edge for 16 amps on a 20 amp circuit (with 12 gauge wires). I would rather not be that close to the edge. If I were to use the saw at 110V, I would want to resize the breaker to 30 amps and the wire to 10 gauge. If I am going to that trouble - I might as well get a 220V circuit run. It would cost a similar amount.

The saw would run better at 220V (8 amp draw), I would be able to use 12 gauge wire for the extension cord as opposed to 10 gauge.

 

[Scenemaster60]

My question for you: is 230 volt single phase power even available in your building?
Given what you say about you dimmer racks I would suspect it is not.
You can put a 2-pole breaker in a 3-phase panel, but then you only get 208 volts.

Read this thread about running single-phase motors designed for 230 volt operation on 2-legs of a 208/120 and discuss it in detail with your electrician. You may be just fine, but some motors will not be happy and have reduced HP on 208 volts.

http://forums.mikeholt.com/showthread.php?t=144958

 

[JD]

Unlike Lamps, there is a lot more latitude voltage-wise on motors. Often, the rating is right in the middle (220 or 230 being used for 208 to 240) and there is not too much difference in performance. The reason for that is that induction motors are somewhat self-ballasting. By nature, they want to achieve a certain RPM based on the frequency of the line power and the number of poles in the motor. When they are at that RPM, the current draw is minimal. As they are loaded down and drop below that RPM, the current draw skyrockets. For a 220 motor, 208 is only 5% down, and 240 is only 6% up. Although there is truth that under heavy load, a low line voltage will make a motor run hotter, in the case of a saw the duty is transitory.
Recently, I was involved moving 5 car lifts and two 15hp compressors from one location to another for an auto shop. The old shop was 208 Wye service, the new shop was 240 Delta. The motors on the lifts listed the voltage as 230. I contacted the manufacturer and asked about the lift motors. The reply, "Doesn't matter." The compressor motors had me even more worried. They were name-plated at 200 volts. Again, I put in a call to the manufacturer and asked what voltage could these be used at. I was told 208 to 240 and there would be no problems at either voltage. In the lighting industry, lamp voltages are rather critical. Life plummets as voltage goes up, color temp plummets as voltage goes down. Motors, however, are an inductive device. (Think loudspeaker.) More is based on duty cycle. The closer you are to running 100% 24/7, the more critical line voltage becomes as heat becomes a major factor. Obviously, if you take a 120 volt motor and tie it to 480, it's life will be quite brief. But, a 10% variance is not going to be a big factor on a table saw.