Big 3 phase machines in a single phase shop??????

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Forum topic by DonnBialik posted 04-21-2018 03:37 AM 1143 views 0 times favorited 36 replies Add to Favorites Watch
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45 posts in 3743 days

04-21-2018 03:37 AM

Topic tags/keywords: 3 phase vfd variable frequency drive rotary phase converter rpc wide belt sander three phase

I moved in to a huge woodworking shop in an Amish area in Ohio. The shop is powered by a huge John Deere diesel generator so it has 3 phase through the diesel, but we wanted to bring in 3 phase from the grid.

Sadly, this is cost prohibitive. So we are looking at VFDs but several of our machines are 7.5HP or much larger. Can anyone compare cost savings of VFDs vs Rotary Drives. Also, I hear you can convert the diesel generator to run on natural gas. Anyone know about this?

Someone on here said VFDs don’t work with machines that have pneumatic components to them like wide belt sanders. Is this true?

Our dust collection is HUGE.

Air compressor is HUGE (30HPmotor)



36 replies so far

View Loren's profile


10477 posts in 4422 days

#1 posted 04-21-2018 04:08 AM

You’d need a separate VFD for each machine. With
a rotary converter you can run all your machines
on the one converter.

View darthford's profile


612 posts in 2698 days

#2 posted 04-21-2018 09:49 AM

View Davidg1974's profile


2 posts in 810 days

#3 posted 04-21-2018 11:29 AM

i am afraid u are in a bit over your head. if u are going to rub all that u will have to bring 3 phase in or stick with the generator. VFD are only there to improve efficiency and monitor for problems and look inside u will see u already have one for each motor any more is overkill and likely to cause more harm than good. sorry to be bearer of bad news but talk to any industrial electrician they will tell u the same. i would say previous owner just didn’t want to shell out the money for 3 phase or worse went broke trying to run his business on a generator. this isn’t a foreclosure or bank or going out of business sale is it?? If so I would run away or proceed very carefully.

View Davidg1974's profile


2 posts in 810 days

#4 posted 04-21-2018 11:36 AM

VFDs will work with any machine with a 3 phase motor if set up correctly. pneumatics has nothing to do with it. Sounds like u are getting some sketchy advice. u need someone with real firsthand experience to see wgat u have and what your options are. hey that goes for me to i am on the other end of the world looking at a screen I could be wrong about u needing 3 phase from the grid but I don’t think so

View Rollie's profile


16 posts in 1536 days

#5 posted 04-21-2018 12:29 PM

Sell the gen set and use the proceeds to subsidize the costs of of having 3 phase run in. The power cos. have such huge economies of scale you just can’t compete on cost/kwh. With the RPCs. you have the costs of purchase as well as potential additional power factor costs. Are there any other commercial facilities nearby to share construction costs? I realize it isn’t my money, but I believe if you balance amortization costs against those of buying all the VFDs, RPCs, or feeding that thirsty gen. set you will be surprised. Too, when it comes time to sell the facility it will be much more valuable. I am that industrial electrician, Rollie

View CRAIGCLICK's profile


117 posts in 848 days

#6 posted 04-21-2018 12:39 PM

Have you considered selling the generator to help pay for the cost of bringing in 3 phase?

Running a diesel generator as much as you will be running that one is fairly expensive between fuel, maintenance, and repairs…remember that a productuon shop with no power to the machines is basically dead in the water, and idle time costs money too.

I think the upgrade would be well worth the money.

-- Somewhere between raising hell and amazing grace.

View bigblockyeti's profile


6577 posts in 2495 days

#7 posted 04-21-2018 01:11 PM

Sounds like you’ve got quite a shop there, so far you’ve gotten some good advice and some not so good advice. VFDs have nothing to do with the pneumatic control aspect of those machines having both, having been around a machine or two as a millwright for a while, the pneumatic controls are at minimum using single phase AC if not being rectified and operated at 12-24VDC. A RPC large enough to run what you have would likely cost more (not by a while lot) than what the generator could be sold for, which would be heavily dependent on condition and hours. The gen set could be converted to NG but it may not be worth it. Going from compression ignition to spark ignition could require a new head and different pistons in an engine of that size, very large gen sets sometimes have the ability to be used as spark ignition much more easily as it’s built into them vs.having to be extensively retrofit. If by chance you have free NG from a well, it may be worth exploring.

-- "Lack of effort will result in failure with amazing predictability" - Me

View DonnBialik's profile


45 posts in 3743 days

#8 posted 04-21-2018 01:20 PM

Davidg1974 – We’ve had electricians trying to sell us on VFDs. The previous owner just moved into a shop twice the size because his business is doing so well, and we are doing the same. We can afford to keep using the diesel but since we aren’t Amish we are looking into other, cheaper options.

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45 posts in 3743 days

#9 posted 04-21-2018 01:21 PM

Bigblockyeti – We’d have to tie in to NG at the road. It wouldn’t be free.

View DonnBialik's profile


45 posts in 3743 days

#10 posted 04-21-2018 01:22 PM

Bigblockyeti – The engine is 2 years old. Probab;y could be sold for $4k-$6k is my rough guess.

View DonnBialik's profile


45 posts in 3743 days

#11 posted 04-21-2018 01:26 PM

Rollie – The shop is DEEP in Amish country. All the area shops are Amish run and owned, the one we bought was as well. The power company is estimating 50k-200k to bring it in. They want 6k just for a bid to bring it in. And apparently there are right of way issues from the past that they stated “they are afraid of opening that can of worms.” Apparently they would have to cross private property to bring it in. What are your thoughts?

View DonnBialik's profile


45 posts in 3743 days

#12 posted 04-21-2018 01:29 PM

Davidg1974 – The shop worked perfectly for 2 years. It works well as is. We are just exploring the cost/benefits of getting back on the grid. Trying to see if there is a cheaper way to power the shop.

View ohtimberwolf's profile


984 posts in 3127 days

#13 posted 04-21-2018 01:34 PM

Not trying to be nasty, just curious; did you do your homework before buying this setup?

-- Just a barn cat, now gone to cat heaven.

View DonnBialik's profile


45 posts in 3743 days

#14 posted 04-21-2018 01:42 PM

ohtimberwolf – We’ve built a successful business over the past 5 years working out of an Amish shop we rent space in. We are familiar with working out of an of an grid shop, but now that we own the land/shop/tools, we are exploring other options. Obviously, 3phase power from the grid would be cheaper than diesel fuel so we are looking into it. In that process, several industrial electricians have suggested VFCs or RFCs as an option. I posted this to get “first hand” knowledge from people who might have stayed with single phase and bought VFCs or a big RFC.

Do you have any first hand experience with VFCs or RFCs and large 7.5-30HP industrial motors?

View dhazelton's profile


2839 posts in 3071 days

#15 posted 04-21-2018 01:51 PM

To change an engine from diesel to gas requires changing from ignitors over to spark plugs, changing compression ratios and probably changing the valves or valve timing so head work, adding a catalytic converter…’d be better off changing the engine out to one that already is built for natural gas.

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