Cost of three phase vs. RPC's

I saw Ox's thread about his RPC issues. I need to power up the new shop, and got a price for the 3ph. transformers from the electric co. for 22K plus a new pole line 6K plus run the service from the meter box into the shop. The house currently has a 200 amp 240V 1ph service. I'm wondering if I just upgrade to 400A 240V 1ph and run RPC's if it would be cheaper, Probably not over the long run, but right now I have a lot of budget eating projects on the go, and if I can save a few buck up front I can spend the cash on other stuff. I'm not sure how to do a head to head comparison, have any of you guys looked into this?

You need to determine how your utility structures its
rates. Do they require a peak demand meter for three
phase service?

Jim

You can run a 20 hp Phase Perfect on a 125-amp circuit for a whole lot less than the electric company is asking, and avoid any 'peak demand' charges too.

I'm running a 10-hp PP on a 60-amp circuit with no problems at all.

That sounds quite pricey, how long do they have to run it for? 1km?

I paid about $40/meter for high voltage 1ph, tax, and poles and such included, even the low voltage run from transformer to meter. I thought it was very good.
If you're that far from the road you should have high voltage all the way in, don't you?. So they should be able to drop a 2nd 200amp service from it to your shop, or 400amp...

400amp entrance was about 5-6K(meter, 2panels and such). I'm sure it can be done for less... Actually, do they allow you to wire your own stuff in Ontario?

Phase perfects will save you energy vs RPC's by a pretty good amount.

I highly doubt that you'd save a dime with 3p and quite likely pay MORE for "store bought" rather than "roll your own". (Not even including the initial drop costs.)

The more hydro you use - more likely the more you'll save by rolling your own. Once you start to git hit my Industrial Rates as well as demands - things can git crazy. No idea what hydro costs in your area?


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Christopher was asking the astronomer
"Can your telescope tell me where the sun's gone?"
And I'm still sittin' with my next door neighbour
Sayin', "Where'd ya get the gun, John?"
Ox

I have a 7200v 3ph line 200ft from my shop.......to get 400A 240v 3PH to my shop.....$12,000! I'll stick to RPCs, thank you very much.

mine free brothers 15000 dont dim lights!!!! 400 amp single

400 amp 3phase free 100ft 60ft single phase 400 free

3 phase

About 15 years ago when I was planing to expand out of the garage,it was going to cost 40,000 to run 800 ft.Bought the place kitty corner from me,already had 3 phase ,a 2400 sq.foot steel building,and a moble I'm renting out,for 59,000 on 8 acres.
I think it just depends on how much power the equipment is going to use.If less than 5 hp you could use a vdf and not spend to much,if more hp then a rpc would be less pricey.
but even now just running the 1 ph mig is a hole lot cheaper in the new shop than the 180 buzz box that i had at the house.
jim

Steve, we looked into it and did it. 200amp single $600-$800+ a month, at the end we were running a 20hp and a 30hp RPC. Went to a 320amp continuous, 400 peak 240V 3 phase. Bills are now $300-$400.

We're saving, conservatively $3500 a year, plus we got to sell the RPC's and now we can run the lathe in high gear (thats realllllllly nice, 1200 max rpm sucked), and we can run the mill that is coming off that panel at the same time now, for a decent little productivity bump.

Granted we aren't running full hp cuts 24/7 and honestly our spindle up time is probably single digit percentages due to the work we do, and when they are running odds are they are pulling less than 1/2 hp cuts, so most of our savings was probably not having to spin those RPCs.

Talk to your electric company, I know out here they'll bring in the juice for free if you can prove (reasonably) that you are going to use a certain amount. They dropped 3phase in here for free based on 1 year of very high electric bills, before we asked and the electric companies engineer looked at our usage, they wanted over $7k.

The electrician was still over $8k. He came 50ft under our parking lot, put up a new meter box and a new main panel(those aren't cheap) and then simply had to plumb that into the 2 3ph panels and 2 single phase panels.

This was a wonderful day, as you can see they didn't have to pull the 3ph very far, it still took them 2 days.

My estimate for running 3-phase to the shop was $21k for about a 1/4 mile run. I got my PhasePerfect for $4500 and haven't looked back. Love that thing after running rotary converters for seven years.

Eric

You have to buy the transformers? At previous locations that was called "primary power" and was about 1/3 the cost of standard power, but you were buying all the transformer losses.

Remember all your rotary phase converter losses should show up as heat. As far north as you are, I expect that will be beneficial most of the year. Electric resistance is high dollar heat, but there will be some cost recovery.

I have installed 2 480V electric services recently. In both cases, the power company installed the transformers and located the meter and connection box at the bottom of the pole for no cost. Everything from there was on my nickle.

As far as load, we have (2) Mazak 2 axis lathes, a Hurco VM-1, (2) manual lathes and mills each, a couple welders, 2 saws and a couple grinders. since there is only 3 of us we can only run maybe all the CNC's at once or a couple CNC's and a a couple others. The shop is about 800' from the road. A lonnnnng time ago I built my own RPC for the first manual mill I had, But my needs are quite a bit more now and I'm in the business to run machines, not monkey with power all day. What is the preferred setup, should each CNC have its own RPC, all the manual machines on 1 RPC? A separate one for the welders? How about phase balance?

Sounds like a good 40hp RPC min should doo the trick for you at this stage. A 50 would allow some growth room. You don't really hafta worry about "overloading" the RPC. You aint gunna hurt it at all. If you "overload" it will simply mean that you may not git quite the hydro on L3 as you would have.

The more induction motors that you have on the circuit [running] the more help you have at balancing things out. This does NOT seem to be the case on the CNC's.

I [normally] have a real nice 60hp "Phasemaster" that is built on a Lincoln frame. I love it! OK - so some caps finally took a dive after 12 yrs of service - mostly 24/7. The 50hp I have running right now won't start my 50hp lathe in high gear. So I guess I doo need the 60. (I usta run a 50 AND a 60!)

With that unit I could power everthing in my shop that I wanted - including up to 50hp CNC lathes. Only the one machine was too finicky for the situation - and as I noted before - it seems to have been an issue when it was on the grid as well.

The only time that I have a real issue is when starting a bigger induction motor. The quick in-rush would kill some CNC's. I don't know if this is ever an issue on grid power or not? I would think the closer you got to max entrance KVA (transformer/cable size/distance) that the grid guys sould have issues too? I would like to hear on that...

I have noticed that my 10hp air comp will mess up some machines a bit now and then. Also - if I was to run a big Acme (20hp) these last so many yrs (seldom it seems) I would go around and put the CNC's in feed hold and then go start it, and then come back and hit the cycle start buttons. Kind of a pain, but as long as I wasn't starting/stopping all day long it was fine.

I finally installed a "soft start" on an Acme a few months ago so that I could run a busy job on it. I fired it up many times in a three day period and never had a CNC fault out at all! I am a happy machinist!

Thinking about maybe puting one on the A/C, but generally I jist let it run on continuous.

If you can't find a deal on a used RPC, and hafta buy new, I would check seriously into the PP tho. They say that the new ones are "add-on" friendly, so if you git what'chew need now - you won't be out in the cold once you outgrow it b/c you can jist add another 20 on to it. With that said tho - I hear/tell that you can stack RPC's too? I've never done it.

They dropped 3phase in here for free based on 1 year of very high electric bills, before we asked and the electric companies engineer looked at our usage, they wanted over $7k.

Click to expand...

Exactly! Work the damn power company. Get one of their engineers out to your site, and talk him up. Give him your machinery list and the kva's you'll be using.

Never settle with their initial quote to run 3 phase. Take your case up the ladder if you have to. Talk to a manager. Talk to your local supervisor. Talk to your local congressman. Oftentimes it is amazing what a little "political influence" can do to help you with the power company.

I still say true 3 phase from the utility is the way to go for a cnc machine shop...

Just my two cents, when I built my house I had 400 amp service run to the house meter. They installed some type of buss bar that split it to 200 amp to the house and ran 200 amp to my barn, about 125 linear feet. Currently I am running a 10hp RPC, which is hooked up to a 100 amp breaker. My highest electric bill has been 300.00 and that was running the shop, house, 3 refrigerators, 1 freezer, central air in the house, ac in the shop, welder, pool pump and about a dozen lights that didn't NEED to be left on but I have a teenager so what can you do there?
I never checked with the electric company on how much service would cost but just to run the #2 line from the meter to the barn, with a 200 amp panel was under $1,000 when the electrician was wiring the house. It was a drop in the bucket compared to having the utility company come out and run 3 phase for sure. Down the road, I would like to put in a Phase perfect converter so I would add another vote for going that route

Ox said:

With that said tho - I hear/tell that you can stack RPC's too? I've never done it.

Click to expand...

Ox, where did you hear that? Are you talking about putting two in parallel? I did not think that was possible because the phases of each would be slightly different. I would be interested in that because it would solve a problem I have in one shop right now where I need a bigger RPC for a machine but already have 2 smaller ones running in there and the 2 combined would do the job perfect and I do not have enough power to run all of the machines at once anyway. Basically (2) 10HP RPCs. I need (1) 20HP for another machine.

I am about to the point of just making a PP as a project for the hell of it because it sounds like where I want to build our new shop will have high amperage single phase so I might need to build a **100KVA** PP.

100 KVA?

You really got that much going on?

I think I only have a 75 hanging on pole - but they did challange me to "Blow that!". I'm still working on it.

I've blown a fair amount of smaller ones as they would replace them sequentially in size.
I've been working on this one for prolly 10 yrs now.
Light bills been awfully high this last yr, so I guess I'm working on it. LOL!


As the PP's are stackable as well - I would think it best to have a cpl smaller ones so that:

A) if one dies - you can limp through
B) Just ass_u_me_ing that they are like a X and will consume a set amount of juice at idle. ???




Let me clarify in case there is some cornfussion:

(I usta run a 50 AND a 60!)

Click to expand...

I usta run two convertors at the same time. But on diff sides of the shop on seperate buss lines. L3's never saw each other.



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Think Snow Eh!
Ox

Viper, you should check more to confirm this, but my understanding is that you can run 2 (or more) RPC's in parallel, yielding the sum of their currents.

This is similar to the situation when you have multiple machines running off a single RPC. It turns out if one of the machines doesn't have much load, it adds on to the generated 3rd phase also, adding on to the RPC's output so the one machine actually running under load now gets 3rd phase power both from the RPC and the lightly loaded machines motor.

I would go for matched motors if possible, and of course make sure to carefully wire them correctly, other wise it would be be smoke and sparks time.

Paul T.

i feel sorry for you guys over there with your constant battle to achieve thee phaseness. over here even residential service is three phase, newer houses usually have it ready to go at the box and older houses normally just need a new meter, main breaker and RCCB to get it going. running a garage/basement shop is no biggie in this regard.


dave (who now has 2,000 amp service)