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New shop electrical service

MotoX

Cast Iron
Joined
Nov 14, 2011
Location
Enid, Oklahoma
I'm going to build a new shop soon at the house. Local utility company says i can have my choice of any electrical service up to 400 amps at no charge(I'm right next to the pole).
I'm leaning towards 208v 3phase. The building will be approx 2250 sqft.

If you were building a shop and could have any service you wanted, what would you choose and why?

Current equipment is
  • 240v Knee mill
  • 240/480v 22x120 gap bed lathe
  • single phase 240v 13x36 lathe
  • 240v single phase IGBT multiprocess welder (tig,stick, plasma)

Once the building is up, i will add a turning center, a small surface grinder and a VMC.

I'm trying to avoid any regrets, but also save some money if i can. The electrical equipment can get pricey in the 480v range, which i doubt can be justified in wire size difference in such a small building. But i'm no electrician.


So overall what will be the best choice for economy considering cost of equipment(transformers, breakers, disconnects etc..)?

i would like to hear any opinions you may have.

Also im wondering how i could power a single phase 240v welder with three phase? I would assume just using two legs of the 3phase, but I'm unsure.
I was taught that single phase is 180* out of phase and 3 is 120* out. I'm not sure if this matters or not.
 
All your 240 vac equipment will run just fine on 208. It's actually the voltage I prefer, as there is no hi leg to worry about. You can just use one leg of it to power up 110 vac stuff. Try to keep the loads balanced a little bit if you can. ( don't run all your 110 off just 1 leg)
 
All your 240 vac equipment will run just fine on 208.

I wouldn't go that far. Three-phase 240V motors will run on 208V, but they will draw a bit more current and run hotter. If the nameplate says 230/208, then the motor designer built in enough extra capacity to deal with that. If the nameplate says 230V, then running continuously loaded at full load on 208V would probably make the motor overheat. But machine tool motors aren't continuously loaded at their full rating, in fact they spend a fair bit of time running nearly unloaded and a lot of time running at less than half load. So you will probably get away with it. That covers motors.

You also mentioned welders. Again, check the nameplate. If it says 240/208, then you are good to go. If it says 240, it _might_ work at 208, and you _might_ get full rating from it. But no guarantee. Especially with modern inverter welders. And if something blows up, you might get in a pissing contest regarding warranty if the manufacturer finds out you ran it on 208V.


It's actually the voltage I prefer, as there is no hi leg to worry about. You can just use one leg of it to power up 110 vac stuff. Try to keep the loads balanced a little bit if you can. ( don't run all your 110 off just 1 leg)

If MOST of your load (including mundane stuff like lights, computer, furnace blower, angle grinders, hand tools, and other random appliances) is either 120V single phase or dual-rated 240/208 on the nameplate, then 208Y/120 is the way to go. But you need to be aware that anything that is nameplated for 230 or 240 only (single- or three-phase) may not be happy and you may void warranties on anything you buy new. I'd be particularly worried about the VMC.

If MOST of your load is 240V (single- or three-phase), then "high-leg delta" is the right choice. You get genuine 240V from any phase to any other phase. You also get a limited amount of single-phase 120V from two of the three phases to neutral. The third phase is the "high leg" and should only be used for 240V loads, so you need to keep track of which phase is which. The problem here is the limited amount of 120V available. I don't have the data at my fingertips, but I think only something between 10-20% of the total power is available at 120V.
 
If MOST of your load (including mundane stuff like lights, computer, furnace blower, angle grinders, hand tools, and other random appliances) is either 120V single phase or dual-rated 240/208 on the nameplate, then 208Y/120 is the way to go. But you need to be aware that anything that is nameplated for 230 or 240 only (single- or three-phase) may not be happy and you may void warranties on anything you buy new. I'd be particularly worried about the VMC.

Pretty sure i am going with the 208Y. Anyone know of any downsides to this?

The lathe and the mill are plated 230/460 iirc. I can buy a small boost transformer for these.

The welder specs from the manufacturers website is 220v±10%.

Also the engineer from the utility company said that typical line voltage is in the higher range for the 208 system. He said i can expect voltages to be in the 205-218range or so. My house voltage is this way also. I typically am at 245 250 from line to line single phase.

Any turning center or vmc will have a small transformer if needed.
 
I just had this choice and decided to go Delta rather than Wye. With the 120/240 Delta I get true 240 volt 3ph (just like my American Rotary RPC) and also 120 volt single phase from the same setup. I have lots of old motors, stuff with 240 volt coils etc, this was no brainier for me as I only have one motor marked 208 only. The only negative is you can't use the "B" phase aka 'high leg' for single phase loads with a neutral, you can however use that high leg in combination with any other leg for any pure 240 single phase load (no neutral). Long term plan will probably include a 240 to 480 transformer to be able to run 480 only loads.

Wye is the preferred power for modern office buildings and stores because there is no high leg so you can get 120 single phase from all three wires and balance the load better. At least assuming you do it right, I know of a location that tried to cook a phase from load imbalance.


If MOST of your load is 240V (single- or three-phase), then "high-leg delta" is the right choice. You get genuine 240V from any phase to any other phase. You also get a limited amount of single-phase 120V from two of the three phases to neutral. The third phase is the "high leg" and should only be used for 240V loads, so you need to keep track of which phase is which. The problem here is the limited amount of 120V available. I don't have the data at my fingertips, but I think only something between 10-20% of the total power is available at 120V.

For my setup I have 3 new matched transformers. It is my understanding that I should be able to pull the full rated capacity on either A and/or C phases regardless of it being a 1 phase or 3 phase load. Not that will ever come close on single phase.

Pretty sure i am going with the 208Y. Anyone know of any downsides to this?

I think we already covered this, 208 is NOT 240. Will most stuff work? Yes, but we can't guarantee everything would work. If its just one device you can use a 208 to 240 boost transformer but that could get expensive/messy for multiple machines.

Let me guess your contacts at the power company and your electricians are all telling you "everyone does WYE these days..."?
 
Wire it for the machine tools you have now 240 volt 3 phase wild leg delta, do not let the power co give you open delta.208 is not 240 volt, motors do not like it...Also go with a 200 amp service without a demand meter if you can....Phil
 
For what's it worth 240 Delta, In my home shop I installed a 400 amp, 3 phase braker panel for all the 3 phase equipment with a 200 amp master braker pulling off the two non stinger legs in that cabinet that is feeding a single phase braker panel for the 120/240 volt single phase equipment. I believe 208 has too many disadvantages, I love the fact I don't have to run transformers. My main shop starts at 2400 volt and transforms down to 480 volt throughout the shops. Then we have far too many step down transformers in multi locations to get 120/240 volt throughout. distance through the shop is a concern for voltage drop that's why all the step down transformers. All that buzzing.
 
I prefer 480v. Have 240v high leg in my shop now. I need big transformers to run a few machines.

Sent from my SM-N960U using Tapatalk
 
If i go with delta, what is the difference in open vs closed?

I did a bit of googling on the subject, but with no clear answer.

Can anyone shed some light?
 
Pretty much what he said. also with a comment of "cleaner better regulated voltage".

I call that BS. Your power company should supply clean stable power now no mater what the service is.

If i go with delta, what is the difference in open vs closed?

Closed Delta has three transformers and is more robust. Open Delta uses just two transformers, and would be better for a larger single phase loads and a smaller three phase load. Not to completely confuse you but the terms Delta/Wye can reference either the primary (utility company) side or the secondary (customer) side of the transformer connection. All you care about is what is on the secondary side. Check out these videos for examples that may help you understand the differences between the services.

Wye: YouTube

Delta: YouTube

Open Delta: YouTube

I hope this helps.
Mike
 
I just went through this recently when I installed a 400amp 480v service on a shop. Like mentioned above I was given 208v by my electrician, because "that is all anyone ever does". In the end I decided it was okay, but in large part because I also have 480 now. I decided that a large percentage of circuits after my step-down would be 120v so it makes sense to go 120/208y if thats going to be the case. I would probably have had a harder time with accepting 208v if I was not doing the 480v since a lot of my equipment I will end up wiring 480v now anyways. If you get a 208v service from the PC there is a chance it could drop on the low side of 208 with no fix, but since I was creating it in my building I knew I could tap my transformer to have a solid 208v if it was an issue. At least that was my thinking, and I am certainly no expert.

I will add that I have not noticed a bit of difference in any of my welding machines or other 208-240v loads since the changeover. Most things are rated for both, but will not run as efficiently I suppose. (mine was previously 240v 1ph service)

Also If you intend to add any very large loads wire cost can add up faster than you would think in a short distance, ask me how I know...
 
Update.

Got a call yesterday from the power company's engineer. I asked about closed vs open delta. He said they only offer open delta nowadays.

Given these options, would you still go with 240 open delta? or 208 wye?

I noticed Phil said to not let them give me open delta, anyone else share his opinion?

Actual voltage in this area is typically high, but i'm only judging from work and home. We have open delta at work, and we have to have a small buck transformer for all the cnc's to bring the voltage closer to 230 nameplate. We tried to skip this on one machine, but after a power supply failure in its first year we put a transformer on it. Typical line voltage on the two low legs is around 257.
 
Open delta is weaker on the third phase, and so more variable in voltage. But you get the 230/240VAC.

The 208 is weaker on ALL phases all the time, due to being lower voltage, and may not suit all motors that are intended for 230/240.

Yuh pays yer money and yuh takes yer choice.
 
Ya the damm power co, cheap, cheap, cheap, Open delta is better than y 208 but vfd,s dont like it, and you will have a voltage/ amp unbalance. It only takes 1 more wire and transformer to give you real 3 phase, I have the same problem at my home shop, It will show its uglys on heavy loaded motors, and your welding power supplies. At my big shop real 240 volt delta, 600 amp, no problems with vfds ...Phil
 








 
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