Rewiring for 240V...

[SteveColes]

..... Again, this situation with the Nova lathe is vastly different than the question of improved power on a standard dual voltage induction motor.

Chuck

Agreed, but to just clarify my point. The blanket statement that re-wiring a 110 to 220 motor WILL NOT increase output is what I am objecting to. The current/voltage should be looked at least. Then there are other factors such as how long is the wire run. Is the motor more efficient at one voltage rather than the other? And so on.

 

[Mike Davis]

So, my Rikon band saw is advertised as being wired 220 but I didn't see that and plugged it into 110. It seems to work fine. Am I ruining the motor running it on 110?

 

[pslamp32]

You can't plug a 240 plug into a 120 receptacle can you? Maybe someone converted it to 120 already.

 

[Gofor]

You should not have been able to plug a 220 plug (factory supplied) into a 110 outlet, or vice versa, so I would say your saw was wired for 110 or the outlet is not "code". If the saw was wired for 220 and the circuit has GFCI protection, it would immediately trip.
Go

 

[scsmith42]

Don / Chuck: What about the benefit that comes from balancing the current draw onto both legs of your power service?

Wont rewiring to 240 tend to balance the amp draw across both legs, instead of just one?

The reason that I bring this up is that in years past I've measured 5 - 6 volt differentials across the different power legs in shops that had a lot of 120V equipment. Presumably this is not a good thing?

Scott

 

[junquecol]

This story is a marketing ploy by Delta. Look at the amps used at 120, and 240. If the motor was rated at 2.0 HP at 120, they couldn't put a 15 amp plug on it. But if they down rated it, they could. Similar thing in the 120 volt, 1.5 HP Uni saws. Run the numbers and you see that motor is actually capable of about 2.5 HP. I know, as I have one of the 120 V Unisaws. My Delta CS has a 2.0 HP motor on it, but it isn't the stock motor. and I do run it on 120 V. At max load, motor draws 19.6 amps at 120 V. Only a couple times have I ever tripped the breaker. There are also two shop lights on the same circuit.

 

[Makinsawdust]

PSLamp32 and Gofor you are right if the machine came with a power cord. Sometimes 220V machines come without a power cord and are to be direct wired according to the manual. Seems like my 17" bandsaw had a cord but I had to put a plug on it. If this was the case and Mike added his own cord and/or 110V plug it's possible. I have no experience with such a case. If a motor wired this way will run I would think with the voltage being out of the required range would damage the motor in time. Someone with more knowledge and Mike will have to get to the bottom of this one.
Rob

 

[Mike Davis]

My saw came with a standard 110 plug already on it. That's why i never thought anything about it until I read on some web site that they came wired for 220.

I guess the web site was wrong because it starts and runs fine.

I also have a 2 HP motor that came with my lathe, I have been running with a 1/4 HP motor because I didn't want to run the extra wire. It hasn't bothered me being underpowered. I guess I'll leave it alone until I get ready to mount a 200 pound bowl blank.

 

[Don Sorensen]

Scott,
That's a good point, but depends on the use of the TS. If you'll be running it under load, often, it might be worth it. Balancing the load would be more important for a dust collector, imho, since you tend to leave that running.
The "advantage" that I'd see from wiring the TS to 240 is not dimming the lights every time I start it up. Start up draws the biggest load to get the motor turning - after that the current draw is relatively low until you start pushing wood through it. Then it depends on your blade and the wood and how hard you're pushing.

And there's also the concept of "reflected power" that is actually power you pay for, but don't get to use. This happens at sites where there are large, uncompensated inductive loads (lots of motors). Again, if you're running the motors all the time, it would be good to use the higher voltage/lower current winding. But for temporary loads it's hardly worth the effort, and the savings would be negligible.

 

[cpowell]

Don / Chuck: What about the benefit that comes from balancing the current draw onto both legs of your power service?

Wont rewiring to 240 tend to balance the amp draw across both legs, instead of just one? Yes.

The reason that I bring this up is that in years past I've measured 5 - 6 volt differentials across the different power legs in shops that had a lot of 120V equipment. Presumably this is not a good thing? The only way to balance the current on both 120V lines in a 240/120V elect dist pnl is to move around 120V loads. So, if you have 2/3 load on Line1, and 1/3 load on Line2, you could move single pole ckts from Line1 to Line2.


Scott

Chuck

 

[cpowell]

My saw came with a standard 110 plug already on it. That's why i never thought anything about it until I read on some web site that they came wired for 220.

I guess the web site was wrong because it starts and runs fine.

I also have a 2 HP motor that came with my lathe, I have been running with a 1/4 HP motor because I didn't want to run the extra wire. It hasn't bothered me being underpowered. I guess I'll leave it alone until I get ready to mount a 200 pound bowl blank.

Mike, it would be interesting to open the wiring box and check the motor wiring to see if wired for 120V or 240V. Rikon's website states the 10-325 Deluxe Bandsaws are pre-wired for 120V. Page 16 of the manual here http://www.rikontools.com/images/Manuals/10325.pdf I can't remember which model you have. :eusa_thin

Here's a link to some good, general info on single phase induction motor types with some performance data. There are a lot of options depending on application and load characteristics. http://net.grundfos.com/doc/webnet/professional_profile/pdf/2_Single_phase_motors.pdf

In Section 2.8 they have a simple diagram showing a typical split winding 120/240 arrangement with permanent run capacitor. If the BS motor in question was wired for 240V operation but fed with 120V, then I believe that this motor might run (but at 1/2 rated torque and HP) ...unless the load exceeded the torque capability of the derated motor. I would expect startup ramp times to be very long on a high inertia load. Now, if the motor was wired for 120V operation and fed with 240V, you would exceed the torque capabilities, resulting in motor overload.

Regarding Steve Cole's comments:
Thank you for making the point. After reading your comments I have spent a great deal of time searching online for manufacturer's or professional forums, looking at various single phase motor designs and operating characteristics. I have actually learned a lot about single phase motors.

My answer is no different as it applies to the question of 33 percent HP increase at 240V versus 120V operation. However, I realize I steered the discussion toward a battle of opinions of HP, efficiency, line loss , etc. In that regard, a different response would have been more helpful to Peter.

A better initial approach to the pslamp32's question might be to ask:

1. What is the motor full load amps at 120V and 240V?
2. Is there a dedicated 20 amp ckt available to feed the new TS?
3. If not, what circuits are available and what machines or loads are already on that circuit?. Please include wire size from breaker to outlet and breaker size.
4. How far is the machine from the outlet to be used?
5. How many unused spaces are available in your distribution panel?

The answers to those questions would eventually lead to a solid recommendation.

I am very familiar with 460V, 60 Hz, 3-phase motors and have quite a bit of experience with medium voltage (2300V, 3-phase) motors up to 1000HP. Much of what I share on discussions of motors/controls, etc is based on my work experience. Admittedly, I just don't have much experience with single phase motors. I do have a solid foundation in the theory behind motor operation and control.

I am not anti 240 Volt. The 240V loads in my shop are TS, jointer, BS, DC. In each case a 240V feed allowed me to use smaller wire and breakers compared with 120V feed.

I enjoy the fact that we can have such open discussions here. It is interesting to read the different pieces of information and different perspectives on technical topics. This topic has pushed me to learn a little bit more than I thought I knew.


Chuck

 

[pslamp32]

1. What is the motor full load amps at 120V and 240V? The motor says 15 / 7.5
2. Is there a dedicated 20 amp ckt available to feed the new TS? Yes
3. If not, what circuits are available and what machines or loads are already on that circuit?. Please include wire size from breaker to outlet and breaker size.
4. How far is the machine from the outlet to be used? ~2 ft. It's overhead.
5. How many unused spaces are available in your distribution panel? I just had a new 200A panel installed in the basement where my 'shop' is. I've got many spaces available. The panel is no more than ~10-20 ft at the furthest from where any power tool would be used.

Thanks!

 

[cpowell]

Peter,

There are a lot of different options for the feed from overhead. For 240V feed, I like to come out of a J-box with 12/3 SJOW cord (use a cord grip fitting for strain relief where the cord leaves the box). I get enough cord to reach from ceiling to floor plus 6 feet to allow me to wheel the saw anywhere. SJOW is very flexible.

I used a 6-20R plug for the TS. The plug is rated 250V/20A.

Pic - box/cord grip

Pic - 6-20R Plug

You'll need a 2-pole, 240V, 20A breaker for 240V feed, and a few wire nuts to make joints in the wiring box.

The wiring box (I think it's called a handi-box, 6 inch), box cover, breaker, plug, SJOW cord and cord grip fitting should be at the BORG -that's where I got mine. Don't get SO cord, it has 600V insulation and the diameter is too large to use easily.

Make sure you put the cord grip threads against the box to make sure the knockouts match the thread...they should. Also verify the grip portion fits around the cord.

It may be cheaper to use premade 12AWG extension cord. It was a wash when I priced several years ago. I don't like the stiff cord but some of the made up cord are SJOW style and would be fine.

PM if unsure about 240V wiring and I'll shoot you my cell phone number.


Chuck