Not the usual table saw wiring question

[Jarcese]

So I just inherited a Unisaw that can be wired for 120 or 240. My house is 120/208. I would like to run the saw on 208, but is it a good idea? What about future tools that I might buy that are only wired for 240. I know it's not going to hurt the motor in the short term, but am I losing the advantage of a quick start up?

Should I play it safe and keep it at 120? Also, I'm adding a strip of outlets in conduit across a 20' wall and it won't be hard to reconfigure.

I was planning on having two of the outlets be 240(208) and maybe 4 20 amp 120 receptacles. I have plenty of room for whatever I like in the panel. What would you do?

 

[BFBOB]

I'd like to know too! As I understand it, in single phase wiring, the higher voltage is always twice the lower voltage. Your house should be 120/240 (or 110/220, etc.) Maybe that could work if your house is somehow getting two legs of a three phase circuit. I'm not sure that's even possible. Have you checked the voltage with a meter at the breaker box? - Phase 1 to ground, phase 2 to ground, and phase1 to phase 2. Let's hope a REAL electrician chimes in to enlighten us (pun intended). I'm really intrigued.

 

[Jarcese]

Should have given more info. I live in a condo complex and they dropped in one three phase pad mount transformer to feed three buildings. No building has more than two legs and a neutral going to it. So I basically have two phase power, not single phase.

 

[pattenp]

You have single phase or split phase, not two phase. Use the saw on 120V, there is no overwhelming advantage to go to 240V.

 

[Jarcese]

Well I know calling something two phase isn't really a term, but I'm getting 208 from two phases on a three phase transformer, not one.

Either way, I guess I'll just play it safe. I'm more curious about future tools that I may purchase that can only be wired for 240. My dryer is starting to have a hard time starting up after being connected to 208 for three years. I don't want the same thing to happen to my new tools.

 

[pattenp]

There is such a thing as two phase but if you are talking residential service it should be single phase. I'm not familiar with the services in Boston and if you say the service is three phase for the 208 then you may have two phase for the 120. Are you in an old converted commercial building that's gone to condos?

 

[Jarcese]

Nope brand new. It's fairly common with newer condos and/or apartments around here. It's usually up to the developer how they want it built. It's cheaper for one transformer than for three. Some of Boston is still old 120/208 that they never upgraded. I work for the power company so I know for sure I have a 120/208 three phase pad feeding my building. I might have used the wrong terminology when I said phase instead of high side or hot leg. So I have a three phase transformer but I only have two legs available feeding the building, therefore I have 120/208 not 120/240.

 

[Norcal]

Nope brand new. It's fairly common with newer condos and/or apartments around here. It's usually up to the developer how they want it built. It's cheaper for one transformer than for three. Some of Boston is still old 120/208 that they never upgraded. I work for the power company so I know for sure I have a 120/208 three phase pad feeding my building. I might have used the wrong terminology when I said phase instead of high side or hot leg. So I have a three phase transformer but I only have two legs available feeding the building, therefore I have 120/208 not 120/240.

208/120V is quite common for multi-family dwellings, & is not obsolete in anyway, if a condo or apt. complex is large enough there is no way it would be 120/240V 1Ø.

 

[240sxguy]

I also have an old unisaw, my experience is that it doesn't matter as long as your 120v circuit can handle it. It also allows you more freedom to plug in wherever you want, which I miss. I run mine on 220v because it was constantly tripping the 120v breaker on startup. I wasn't aware that there was a breaker designed for high initial loads like that, or I would have just done a breaker swap.

Good luck with the saw, I love mine!

 

[Rookie2]

for home use i think either voltage is fine.

 

[sands35]

120 will work fine.

Although... the nice thing about 240 is that the motor will draw fewer amps and run a bit cooler. It will also start better when cold (think winter in unheated garage).

 

[Rookie2]

ON 208 from 3 phase the legs are 120 deg apart . 240 single phase is 180 deg. the 120/240 motors are not wound for 120 deg. they will work but not as designed. just sayin.

 

[Zeke]

Curious, how do other appliances work on this system? I suppose things like resistance heat are not affected that much? But what happens when you want to use a 240v air conditioner?

 

[rabidsquirrel]

Curious, how do other appliances work on this system? I suppose things like resistance heat are not affected that much? But what happens when you want to use a 240v air conditioner?

I just googled real quick Home Depot 208v appliances, and the first thing that popped up is a 230v/208v room air conditioner. I guess manufacturers and making more and more things multi-voltage so they don't lose any market share.

 

[Norcal]

Curious, how do other appliances work on this system? I suppose things like resistance heat are not affected that much? But what happens when you want to use a 240v air conditioner?

Check the data plates of air conditioning equipment,ranges,dryers,& other appliances, most have a 208/230V or 208/240V rating, w/ packaged heating/cooling equipment rated 208/230V all one needs to do to run it on 208V is change the tap on the control transformer, it used to be many eons ago that they had to be ordered either 208 or 230V.


Please note that the BTU rating of A/C equip. & the KW rating of ranges & such will be lower.

Edit: Just for the heck of it took a look at my freestanding range, it is rated 12.5 KW @120/240V & 9.5 KW @ 120/208V.

 

[Jarcese]

My dryer works fine on 208 and it says 240v only except it makes some weird noises starting up recently. My oven says 208 or 240v.

I'm pretty sure I'm the only person out of fifteen units that knows that the voltage is not usual. The ovens came with the house but everyone had to buy their own dryer. Nobody has had a problem yet with their dryers that I know of.

It's not really common for a town house to have 120/208. Apartments and high rises are really common for three phase, but I can't think of a town house complex besides mine that has three phase and I've worked in every complex in the 20 towns that I work in.

I figured I would pop this question on here since I've never seen any body with the same situation. I probably will only buy dual wired tools wired to 120 until I leave this place.

 

[Rookie2]

clothes dryers use a 240v heating element and a 120v motor ,heating elements don't care if they see 208v it just makes a little less heat. I'm sure all residential appliances that are rated for 240 volts is also rated for 208 volts (A/C etc.) by design to prevent warranty problems.

 

[zkling]

3 questions

1.) What motor is on the unisaw, specific please?

2.) What voltage are you actually getting out of your different outlets? (Put an RMS meter on them).

3.) What amperage of breakers do you have avaiable on each voltage?

Depending on your actual line voltage you could end up loosing power (toque) from the motor if you under volt it. The speed will be the same unloaded, but once loaded you could bog down the motor, over heat it and cause issues down the road. Unless you are running production with your table saw this isn't likely to happen.

You have single phase or split phase, not two phase. Use the saw on 120V, there is no overwhelming advantage to go to 240V.

If the motor has any good size to it, and a unisaw motor should. Switching to 240 will drastically reduce the amps needed (by half) as well as the inrush current needed to star the motor.

 

[Jarcese]

1. 1980's 1.5hp not sure of specific model.

2. Exactly 120-120/208 with average to low load.

3. I have no breakers as of yet. I only have one 15 amp circuit in the garage. That's why I was curious if I should even bother adding a couple 240v circuits if the actual voltage is 208. I don't even have the saw running because I don't have a circuit that can handle it. I never had any use for more circuits since I was only using one tool at a time and my other contractor saw was small enough to use on the circuit I already have.

I will keep the motor at 120v, but should I bother thinking about bigger future 240v tools while I'm running wire for the 120v? Or keep everything at 120v and just assume I'm moving out in a few years.

The only deciding factor is the 208v scenario. If I had 240v I would be using it for sure.

 

[Norcal]

W/ a 1.5 HP it is on the borderline for 120V vs 240V (or in the OP's case, 208V), a 2 HP will trip a 20A breaker all the time if 120V, before I got my unisaw, my saw was a Delta contractors saw w/ a 1.5 HP motor & when ripping a lot it would trip the breaker my solution was to just plug it into another circuit, I was going to change over to 240V but never did, the Unisaw came w/ a 2 HP 3Ø motor that was wired for 480V, & the plan was to use a VFD but due to issues w/ that motor,ordered a 3 HP 1Ø motor for it.

To use a 230V rated motor on 208V, the solution is simple just add a buck / boost X-former to buck the voltage down. To the OP did the Uni come with the LVC, Low Voltage Control option?

 

[Jarcese]

No it didn't. I didn't think about adding a transformer, but unfortunately I need a mobile base and blade guard so I'm already up to around $500 in upgrades for a free saw.

The saw was my father-in-law's. He actually had two with a router table in between all bolted together with a 52' unfence. Pretty nice, but I couldn't fit the older 1940's saw in the SUV so I sold it. Regretting that decision pretty bad right now.

He had all of that on one 20 amp circuit and obviously no two things were running at the same time.

I'm thinking my best option is two 120v 20 amp circuits with 4 sets of outlets. The only two things that will run at the same time are mitre saw and dust collector or table saw and DC. I will keep them on separate circuits. I'm not a serious wood worker but it would be nice to be able to make more powerful cuts when needed.

 

[James-W]

I have a Craftsman table saw that came with a 1 hp motor on it. I eventually replaced the motor with a 3 hp motor because the 1 hp motor just couldn't handle what I wanted the saw to do. I bought a longer power cord and I am running it on 220 volts. Initially I ran it on 110 volts but the breaker kept tripping, so I decided to run the motor on 220 volts instead. It works wonderful now and I have no problems with it.