Blank slate, what would you do for electrical service?

[Frank Pratt]

Again, what John said. You'd best not be taking advice from your electrician buddy if that's his understanding of power.

[Julie Moriarty]

Is your problem not enough breaker space or are you anticipating tripping the main breaker or larger branch breakers on your existing panels when you're running to expected capacity?

If you have a 600A/208V service I'm guessing you are in a commercial zone. Do you have a fused distribution panel feeding breaker panels?

Before you decide on what size service you should ideally have, you should get all the loads from all current and future equipment and lighting. It's hard to imagine you ever needing a 1000A/480V service, based on what you said in your first post.

[Anthony Whitesell]

Point blank he's wrong. A watt is a watt. The revenue meter is going to see the same load for the same size boiler regardless of input voltage. Putting in a 1000 amp 480 volt service for a 5 man cabinet shop is just plain ridiculous. I would suggest you work with an engineer or a competent industrial electrician before you throw your money away on this.

Could the electrician be referring to the heater itself and not to the electric meter?

[John Lanciani]

Could the electrician be referring to the heater itself and not to the electric meter?

It still doesn't matter. Electric resistance heaters are 100% efficient in turning electricity into heat. Even if you tried to argue that at a lower voltage there is higher line loss due to the increased current those (inconsequentially minor) losses still end up as heat in the space. (and there is no way that he needs 200 amps worth of heat pumps to cool +/- 6000sf so it has to be resistance heating)

To put this class of service in perspective, a service this size will support well over 600 hp worth of motors all running at full load at the same time.


ETA, There is a sawmill in our service area that runs, among other things, a 50hp head saw, 50 hp gang rip, and a 200hp hog (chipper) simultaneously on an 800 amp 208/120 volt service with no issues.

[Phillip Gregory]

So my current shop had 600 amps of 208V coming into it when I moved in almost 5 years ago, and last year I spent almost $5k bringing another 200amp service into the building that I won't get back, (I lease my space). I don't want to have to do that again. The boiler for the infloor heat draws almost 200amps on its own. The original 3 phase panels are all full, and that's with some things being the same circuit. I had to add a 100 amp sub panel to make enough room to get my panel saw hooked up.

There's pro's and cons all around to upping the voltage if I were to build a new shop. I think all of my 3 phase equipment can be wired for 480V and they will certainly run more efficiently on 480. Some of the single phase stuff will run on 240V, and I know I'll have to have a step down transformer for lighting, 120V outlets, and the rest of the single phase equipment that won't run on 240V.

If I build, I'm thinking about bringing in 1000 amps of 480V. I shouldn't have to bring more juice in for a very long time, if ever. Also it should make the eventual resale of the building more appealing if the perspective buyer won't have to spend big money bringing more juice in. I'd also be able to run a 480V boiler for the in floor heat, which will lower the operating cost of that a bit. Wire is a smaller gauge since the amperage will be essentially halved as well. So that saves some money on wire, and conduit. Downsides are the breakers and panels are more expensive. Plus the added expense of a step down transformer. There will be some expense in swapping some stuff over to the higher voltage, but I think the largest will be the widebelt, and that will involve getting a new VFD for the conveyor, not a huge deal. Also the 480V service will cost a bit more up front to bring into the building.


So I'm torn, and I don't really know what the correct answer is. Input appreciated.

277/480Y would be a big benefit for you. You can run lighting off of the 277 V single phase as most "commercial" HID/fluorescent ballasts are 120/208/240/277 multi-voltage units as are "commercial" light switches. Cheap residential stuff is 120 volt only though, so you'd need to look carefully at your equipment. Standard Romex is good for 300 volts as well. 277 volts is extremely commonly used for lighting in places that have 277/480Y 3-phase for other loads.

Most 3-phase motors are 208-240/480 so you can certainly change their voltage by rewiring them. You will need to adust the magnetic starter amperage though, if not replace the starters entirely with 480 volt starters. Most of the cabinet shop kinds of equipment I've seen that have been 3 phase often require a different magnetic starter for 208-240 vs 480 volt operation due to the amperage range being significantly different. The older starters simply needed different heaters installed while newer electronic ones required being replaced with a different amperage unit.

You can run some 240 volt single-phase equipment on two legs of 208 volt 3-phase but you need to look at it carefully. Anything resistive like an oven or dryer will do fine on this arrangement and most of it is rated for either 208Y three phase or 240 volt single-phase. Most 240 volt single-phase motors tend not to run well on 208 and aren't rated for it; you'd do better to try to wire them to 120 volt if you can or replace them with a 3-phase motor.

Dealing with 120 volt loads will require you to get a 277/480Y-to-120/208Y transformer or have separate 120/208Y service. I've seen both used with generally the larger the building, the more likely they are to have a dedicated utility-to-120/208Y transformer with its own independent entrance panel rather than stepping down 277/480Y to 120/208Y on premises. Some of the places I've worked have even had 2300/4160Y medium voltage which meant they had at least three transformers feeding independent entrance panels.

[Rollie Meyers]

A 1000 ampere or larger 480Y/277V service will be required to have GFP, ground fault protection on the main, very costly upgrade & everything will need to be coordinated otherwise a fault on a 20A 277V circuit could trip the main breaker, happened to a friend of mine where that fault occurred & took out power to 7 courtrooms. The engineering required to coordinate protection will not come cheap, as a cost saving measure some specify multiple 800A mains just to avoid GFP. If the load justifies it then 480 volts is the way to go, but everything will be more costly plus needs to be installed by & maintained by qualified people.

GFP requirement is in NEC art. 230.95, 240.13.