3 phase power

[Hoff907]

Well I finally got a lot to build a shop on, and there is 3 phase power to it. Right now I am working out the details to compare the two but it looks like I may spend the money up front and bring 3 phase 208 into the shop.

The disadvantage is I don’t get 240 single phase, and installation costs are larger (but cheaper that changing later)

The upside is I can buy oilfield surplus at auction and use it, and i should get better efficiency out of what I use.

I really think it is an asset to have in a shop, any counter arguments?



Oh, high leg delta with 208 & 240 is not available from the power company,

[jeffrey.penfield]

Unless you are really really close to 3 phase (4 overhead lines) the cost is very high and power companies don’t like giving non commercial shops the service with three transformers. How much are they charging?


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[Sberry]

What kind of shop? You want used industrial equipment? A reason to use oilfield surplus? What they have a guy might want?

[ronsii]

If the power co's around there are anything like here they will charge you quite a bit more per KW for the 'commercial' power and I'm guessing a hefty service charge too.

[idacal]

I had 3 phase put in my shop but it is only 2 transformers and its 240 with a wild leg i love having it. I also can have 220 single phase this way. i have a few pieces a three phase equipment my power bill is shocking sometimes tho especially if im running some of my 10 horse motors. Or big welders. Im in prime charges all the time. It costed about 3 grand to put it in thats why i did it if i was looking at much more than that or so to put it in for minor usage i woud buy a generator to fire up when i needed it probably would be cheaper to run. For a couple times a week then just run a dedicated circuit and plug the gerator in when needed

[Hoff907]

To answer a couple questions

If I stay below a 200 amp service it costs and extra 10 dollars a month and .2 cents a kW and hour more, install is free under 275 amps to my pole with a deposit they will refund when service is started .

At the auctions they sell welding machines, brakes, iron workers, shears, rolls, plasma cutters, lathes, mills, presses and more here that are 3 phase so They go a lot cheaper, and I may want to have some of that stuff just because I can or want to

The power pole is on the lot, right smack dab in front with 4 wires

[jeffrey.penfield]

If you are that close, go for three phase. One fellow was charged $1000 for 500 feet of line to his shop. He ended up with 3 phase power for a lathe and had 230volt and 115 volt for standard stuff. Another guy was quoted $30,000 because his house was so far from a 4 line pole. Once he paid that his neighbors could get it for only $500 per install since the lines would be there.


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[ronsii]

To answer a couple questions

If I stay below a 200 amp service it costs and extra 10 dollars a month and .2 cents a kW and hour more, install is free under 275 amps to my pole with a deposit they will refund when service is started .

At the auctions they sell welding machines, brakes, iron workers, shears, rolls, plasma cutters, lathes, mills, presses and more here that are 3 phase so They go a lot cheaper, and I may want to have some of that stuff just because I can or want to

The power pole is on the lot, right smack dab in front with 4 wires

Wow!! that sounds like a pretty good deal definitely worth doing just for the simplicity of being able to use lots of 3ph stuff with out a bunch of converters.

[Willie B]

Here the power company tries to give 208/120 Wye. They argue you don't have to balance load. That is BS! Load balance is not complicated. Much of your load will still be single phase, and 240 is a better power supply than 208. Motors do not perform as well at 208. Motor manufacturers voluntarily build motors to tolerate 10% + or -. A 230 volt motor will function at 207 through 253 volts. Fact is at 208 it gives far less torque, and more internal heat.

480 WYE is a fine power supply. 208 wye is a PITA. Fight for delta 240/208/120 (1 winding center tapped, grounded.

[Sberry]

If you are building a machine and fab shop its a no brainer.

[Hoff907]

Thank you guys. I have been talking to the power company, and they are really willing to work with me and help. My co-worker is the electrical administrator for the company I am the mechanical admin for and he is willing to do the paperwork so I am going to go for it.

Regarding 240/208/120. The power company doesn’t off this deal under the center tapped 240 service, it makes it very expensive fast with demand charges and industrial costs and all


Another factor here, this lot is in a semi industrial area, and a shop in this area with 3 phase has a good resale or rental value

[ferrret3238]

If you have the option of 480/277 I would go that route and buy a transformer. 480 is lots more power and most all machines you will find are 240 or 480 volt 3 phase. 480 to 240 transformers are fairly common, not like 208 to 240 transformers. Most VFD's are 480 volts too if you want to run a motor load like a blower or compressor. I lucked out and got 240 delta where I'm at and is so much nicer than trying to find a transformer or praying 208 doesn't smoke your machine tool. I previously had 3ph through MidAmerican and it was only $2500 with most being my panels. The lines were right in front of my farm house and they placed 2 transformers on the pole, a 25kva and a 15kva I believe. Where I'm at now is a commercial lot and the local utility charged me nothing, all I had was replacing my panels and wiring which was about $1500. Alliant energy in the country around here won't give a delta high leg service. Only Y's.

[scsmith42]

Here the power company tries to give 208/120 Wye. They argue you don't have to balance load. That is BS! Load balance is not complicated. Much of your load will still be single phase, and 240 is a better power supply than 208. Motors do not perform as well at 208. Motor manufacturers voluntarily build motors to tolerate 10% + or -. A 230 volt motor will function at 207 through 253 volts. Fact is at 208 it gives far less torque, and more internal heat.

480 WYE is a fine power supply. 208 wye is a PITA. Fight for delta 240/208/120 (1 winding center tapped, grounded.

When Willie B talks electricity, I listen.

I’m in the process of getting bids to bring 480VAC into the farm so that I can retire my generator.

[jeffrey.penfield]

If resale is important, 480 volts sounds best. Maybe you should be asking these questions on an electrician forum or even better, consult your electrician.


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[Willie B]

If resale is important, 480 volts sounds best. Maybe you should be asking these questions on an electrician forum or even better, consult your electrician.


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Most industrial facilities transform power line voltage down to 480/277 WYE, then a number of secondary transformers to bring it to 240/208/120 Delta.

[Willie B]

Another concern is a capacitor bank. Single phase motors often have capacitors in them to correct power factor. Three phase motors I haven't seen with capacitors. That is usually done on a whole facility service.

I work frequently at a facility where they have had two different second hand capacitor banks. A new well engineered bank will correct numerous power quality problems. These aren't built for this facility.

Power ranges from 486/280 on a weekday to over 500/290 on Sunday when load is small.

Multi volt equipment often has max volt rated at 277. The mortality of lighting equipment is high. The power company lost 1 leg of the three phase one day. Magnetic field in the transformer weakened, current spiked, causing 1 phase a voltage surge. Lots of VFDs, and lights died that day!

[danielplace]

Most all your modern 3 phase motors are designed to work fine on 208 and are rated for it.

Scroll through any manufacturers voltage ratings nowadays. Not one motor in 10 different manufacturers lineups that isn't rated for 208

https://www.grainger.com/category/mo...&filters=attrs

[Willie B]

208 is near the bottom end of what wide range tolerant motors need. A motor serving a load on the upper edge of design horsepower will struggle to do its job if voltage is low. On a long group of conductors losing significant voltage, it may not start well.

I see most frequently air conditioning units far from the service equipment. At 240 volts 20 volts could be lost in the circuit, motor still runs fine. Starting with 208, you lose 20 volts, it won't get started.

[scsmith42]

Guys, you are probably not aware of this, but our very own Willie B is a licensed commercial electrician with many, many years of experience. He is an expert in this area and his advice is worth heeding.

Scott

[ronsii]

Most all your modern 3 phase motors are designed to work fine on 208 and are rated for it.

Scroll through any manufacturers voltage ratings nowadays. Not one motor in 10 different manufacturers lineups that isn't rated for 208

https://www.grainger.com/category/mo...&filters=attrs

Yeah, I know what the 'specs' say but have seen it more than once on warehouses we work on.... had one a while back some other outfit had installed a tank and pump for waste water... a month later the pump was not working... yank it out had a little crud on the impeller stalling it so cleaned it up put it back in... week later same thing get there pump the tank yank the motor which is a 3.5 or 5 HP rated for 240+ to 207 on the specs... meter the box sitting at 208 no load... should work right??? So the third time we went back the motor was toasted... but hey!!! it was within spec

[Willie B]

Yeah, I know what the 'specs' say but have seen it more than once on warehouses we work on.... had one a while back some other outfit had installed a tank and pump for waste water... a month later the pump was not working... yank it out had a little crud on the impeller stalling it so cleaned it up put it back in... week later same thing get there pump the tank yank the motor which is a 3.5 or 5 HP rated for 240+ to 207 on the specs... meter the box sitting at 208 no load... should work right??? So the third time we went back the motor was toasted... but hey!!! it was within spec

Been there, done that. It's less fun when it is a sewer pump. I got hepatitis A or B, I can't remember, the kind you get over, and you aren't contagious afterward. I can't prove it was a septic pump, but the timing doesn't disprove it. Be careful with that stuff!

[Willie B]

The best motor book I have I keep close to my desk. It was written many years ago. It gives typical percentages for 230 volt rated motors. The author is an expert in motors. Like me, he is opinionated. He talks of the heat generated inside a motor measured in BTU.

If a motor's cooling system is capable of dissipating a hypothetical 5000 BTU per hour, but the motor produces more than that, it gets hot. A motor designed for 208 volts will have a functional range of 187.2 through 228.8 It'll run all day happy on 190, 18 volts less than intended, but will get hotter than it would at 208.

I see very few motors designed for 208, I'd say they are hard to come by. Most are designed for 230, but will function (if not overloaded) at 207. Working from a 208 volt power source, it ain't easy to deliver 207 to the motor.

[ferrret3238]

I like to look at the service factor also. A 1.00 isn't very tolerant of variables but a 1.35 will take a lot of abuse and keep on running. My old college professor had an amazing motor book that folded out into 4 flaps with motors and winding diagrams on each side. I never figured out what book that was and he passed shortly after I graduated.

[ronsii]

Been there, done that. It's less fun when it is a sewer pump. I got hepatitis A or B, I can't remember, the kind you get over, and you aren't contagious afterward. I can't prove it was a septic pump, but the timing doesn't disprove it. Be careful with that stuff!

Well..... actually I used the term wastewater as a generic term for a septic holding tank for the two restrooms they had TI'd into the warehouse earlier in the year and then found out the sewer main's IE was higher than the outlet from the building.... so needed a pump station not real big just big enough for one guy to climb down in it for the motor install about 5-600 gallon.

[ronsii]

Been there, done that. It's less fun when it is a sewer pump. I got hepatitis A or B, I can't remember, the kind you get over, and you aren't contagious afterward. I can't prove it was a septic pump, but the timing doesn't disprove it. Be careful with that stuff!

Not to derail this thread too far... just a few sewer pics .... and it is about how 3phase power will work/not work with motors...

I found some pics of one of the times we pulled the pump for the lift tank, it looks like the tag says 2HP could've sworn it was bigger anyways not fun and I think it would have worked properly had it been run on the full 230vac.... but I don't make the decisions... I just climb in the sewer and git-r-done



The pump/motor assembly has a pitless type mount on it so technically you're supposed to be able to just lower it on the rails to install it.... WRONG!!! the original installers used some non-stainless hardware on the lower end of it that rusted apart so the rails were not fixed at the base.


The guys that installed this setup did a right fine job of constraining the wiring....






::end of derail::

Back to the shop power 3 phase install!!!!!