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note on generator fuel - with the running cycle/life of a generator, it will serve you greatly by 1. ONLY using ethanol free gas, and 2. draining the carb after running the generator by running the carb dry, or opening the drain on the bowl to let all the fuel out.

our last shop location had a motor-generator 3 phase converter. this one worked fine, just had to start it before running any 3 phase equipment. But, if you only have single phase/residential, just buy your equipment that way. or if you get such a deal on a piece of 3 phase equipment, change the motor to single phase.
 

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At a minimum I know Multiquip made a genset with a selectable 120/240 1-P and 120/208 3-P, and I suspect that Generac does too. (I've been out of that business for too long, though) So yes, even though it was selectable, you couldn't output both at the same time. On the other hand, most medium and large 3-phase gen sets included 50-amp single-phase convenience outlets that were active while the main 3-phase bus was active....but these would be major overkill for powering a house.

That being said, the first thing that you want to consider is that if you go with any generator-delivered 3-phase, it will be 120/208...as opposed to a wild-leg transformer setup that can provide 120/240, 3P. I am not familiar with any generator that can provide 120/240 wild-leg three phase.

The reason that this is important to consider is that all of your appliances that are expecting 240 volts, will only be getting 208 volts. Ffor that reason, you really don't want your whole house configured for 3-phase power unless the utility company provides a 120/240 wild-leg system.
 

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Discussion Starter · #24 ·
First, thanks to all of you for the input.

I talked to Generac. They said their standby generators would not work because they aren't made to be a primary source of power, they are just for short term use when your normal service is out. So, the idea of using one to supply three-phase equipment is out on that alone, without even considering comments made in this thread.

I fully understand the comments that I don't need three-phase. I agree, but I have a lot of things I don't need that I'm glad I have and would not consider getting rid of. Just saying we don't always need to do the things we do, but doing them makes life more fun.

@JayArr hit on one reason I am even considering three-phase: a killer deal on a piece of equipment or something you've always wanted. I've had a few opportunities like that (free, actually, just take it). I passed because of the three-phase requirement. The compressor I mentioned in one of my posts falls into the free category. I didn't take it, but my buddy did. He had room to store it until the day he or I have three-phase.

At this point, I know there are several ways to run three-phase equipment. When work starts on the new house, I'll see where the possibility and cost is with the utility company and make decisions from there.

Thanks again to all of you for the input.
 

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Discussion Starter · #25 ·
@GeorgeC - fwiw, the older I get the less I want to take chances, especially when a bad outcome can be severe or cause a lot of damage. So I understand your uncomfortable feeling with a 17 year old unit, I'd feel the same (even if it might be irrational).

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@Rick Christopherson - thanks for time you spent and the clarity of your explanation. It helps a lot.
 

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Ancient Termite
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In 2005 when we did the addition with all new higher voltage appliances, I had the brilliant idea to go three phase. There is three phase on the pole less than 75 yards away. The logic was that three phase machines, used are inexpensive. I asked the electric company how I could get three phase service. A good deal they said, only about $25,000.
 

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Discussion Starter · #27 ·
In 2005 when we did the addition with all new higher voltage appliances, I had the brilliant idea to go three phase. There is three phase on the pole less than 75 yards away. The logic was that three phase machines, used are inexpensive. I asked the electric company how I could get three phase service. A good deal they said, only about $25,000.
So, are you glad you got three-phase? :)

Obviously, I would assume, they just didn't want to bother and got rid of you with that price. Odd that sometimes companies don't seem to be in the business of selling more of their products by taking care of their customers.
 

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I put a rotary phase converter in to power my 5hp table saw and my drill press. It was around $1000 iirc to get one big enough to run my saw. If you get a 3 phase generator I’m assuming you will have to install some type of gizmo that turns it back to single phase power before it hits your panel to power all your non 3 phase equipment.
 

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At your new location, is three phase available at a reasonable cost from your power company? If not then I wouldn't get any three phase equipment.
Totally agree. The normal hobby woodworker has no need for 3 phase.

I have had a standard whole house standby generator for 17 years. it is used ONLY as a standby. It really has been needed very little in that time.

I am beginning to feel a little uncomfortable about the age. Am having a thought that maybe it is time to update. I just want to be sure that if we lose power for several days during a hurricane that it will continue running.

george
Lots of people run 3ph machinery off 1ph service. Rotary phase converters (rpc), phase perfect digital phase converters (pp), vector frequency drives (vfd) or least desirable the static phase converter are all common options.

3 phase machinery is inherently better.

That said I wouldn't run it off a backup 3ph generator. Just convert after the panel like normal.
 

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.... If you get a 3 phase generator I’m assuming you will have to install some type of gizmo that turns it back to single phase power before it hits your panel to power all your non 3 phase equipment.
We had a commercial application where we used Power Distribution Units (PDUs) to feed both single phase and 3-phase loads as needed. Utility (and generator power during utility power outages) fed 3-phase power to the PDUs. Each PDU was a free standing unit (about the size of a refrigerator) that contained a transformer and several circuit breaker panels. The transformer provided single phase and 3-phase power to those internal circuit breaker panels, which then distributed power to the various equipment. Those PDU's were north of $20K each.
 

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Not too different from us with getting the overhead wires buried. We didn't do it, wasn't worth it for $2,500.

I've heard numerous stories about people trying to get three-phase power. It seems each power company is different and even within one company there is no standard for whether they will do it or what it would cost. We had something similar with AT&T. The house next to us has them for internet and TV (wired, not a dish). Much better price than we have with our cable company. So we called AT&T. They said it was not available for our address, we'd have to get a dish. I asked how that could be, given our neighbor has it. They told me we were too far from the node (we have 1/4 acre lots, houses are pretty close together). I found out later that the house on the other side of us also had AT&T wired. Apparently they leave existing customers but want new ones to go with their dish system.
Actual three phase is usually only available in industrial areas and some major streets. If you are away from a major street they probably would have to run a line that distance to you. That alone would make it expensive.
 

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biggest reason for not using 3ph is cost.
it cost more to get it and it cost more to keep it. an un-used meter base around here is $15/mth, probably 10x that for 3ph. you can pick up a 5000w 1ph genny for $500, 5000w in 3ph is $5000

3-phase is rarely used on motors less than 5HP.
in an industrial plants a 3ph machine is 3ph. the main drive motor on a lathe may be 10hp 480v 3ph, but that 1/4hp coolant pump is still 480v, 3ph. probably more motors under 5hp, than over 5hp in a big plant

hp is hp, a 5hp 1ph motor has the same hp as a 5hp 3ph motor. main reason for using high voltage 3ph power is again cost. for the same amperage: transmission wires are smaller on the pole, buss bars are smaller in the plant, control wiring is smaller, and motor windings are smaller. a 1hp motor wired for 120v draws 16a and can be wired with #12 wire. that same 1hp motor on 230v draws exactly half the amps and then on 3ph 230v almost half again 4.2a. step up to 460v and the amps drop in half again to 2.1a.
basically a 1hp motor running on 460v could use #26 wire in an industrial setting. there's a lot more calculation involved, but you get the idea. this is an old chart, nominal voltages are 120, 240 & 480 since the 80s. bump up the motor to 10hp and you see the big difference. 100a on 120v vs 14a on 460v

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where's my table saw?
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That's all well and fine ^, but as you say it's all about cost. It will cost more to get the 3 phase via a generator, than he will save in buying 3 phase equipment, unless it's the older, heavier industrial machines that are basically too old to keep in service in production. My buddy, a custom door maker, who lives down the road, has an entire pole barn filled with those old industrial machines, a 16" Porter jointer, a cross cut swing saw, a 24" thickness planer, a 4" wide bandsaw for resawing, a straight line rip saw with tracks, giant 7 ft tall drill press. a twin 10 HP motor shaper, and a 10 HP 42" wide belt sander. He runs it all off a rotary phase inverter to get 3 phase for the power.
My concern for the OP is that anytime he wants to run the woodworking machines he will need to fire up the generator, no doubt a noisy and heavy machine that may vibrate the entire house unless it's well isolated. My 15K propane powered unit disturbs the neighbors 500 ft away.
I don't think the idea of a standby 3 phase generator makes financial sense or is practical when a rotary converter would work just as well.
If you want a 3 phase shop, rent a loft in the city or an industrial building.
By definition, a "stand by generator" is only used to supply power until the grid comes back on. Having the thing run 8 hrs at a time would drive some folks nuts ..... like me.
 

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i'm not seeing this limitation. most of the 3ph generators are available in both 208 & 240v
Generac Protector RG03224JNAX ® QS Series 32kW Automatic Standby Generator w/ Mobile Link™ 120/240V 3-Phase
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Yup, I pulled up their spec sheets and they do offer a Delta-configured 120/240 3P unit. Nice!! Now that I see it, I do remember a mechanic at Ziegler (Cat Dealer) was rewiring one of their rental units for a Delta configuration at the request of a customer. This was probably 30+ years ago, and raised some eyebrows at the time. At least at the time, nearly all generators were internally wye-configured, and required a mechanic to go in and do any reconfiguration.

Screen grab from the Generac Install Manual.
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For anyone who is thinking of using a rotary converter. Here is a picture of mine.
(I use this to test three phase industrial drives that I repair for a living)

It takes in 240VAC single phase and outputs 240VAC three phase. You can step up the output to 480VAC or 600VAC with a transformer.

It's basically two sets of capacitors, a contactor (relay), a "pony" motor that does nothing but spin and some switches.

As you can see it can easily be built into a standard large electrical box that can be hung on the back of the table saw or whatever you're trying to power.

This used to run a huge metal lathe, when my neighbor bought a three phase milling machine he built a bigger one to run both and sold this one to me.

It works, it's cheap and it could be built in an afternoon.
Circuit component Electronic engineering Audio equipment Electrical wiring Electronic component
 

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I’m real happy running my couple of 3ph machines on VFDs - plus, they offer a number of other advantages if it’s just a basic on/off arrangement - easy to program them for slower startup, auto-braking, and adding variable speed and remote controls -
 
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