Quincy compressor/3-phase redux

Well, people were so nice here helping me through my compressor/power woes, I figured I would let you know how it turned out.

After over a month of waiting for word from the power company as to what their decision was going to be on my being able to get 3-phase, they called me back yesterday.

They are willing to supply me with 3-phase power, but since they will need to put a transformer on the pole, they want me to put a deposit down to guarantee 5 years of service from them. Over the course of 5 years, they will credit me for the distribution part of my power bill and at the end of that time, they will pay me back the portion of the deposit that actually used. As in if the bill was $200 for one month, about $75 of that would be the distribution charge. After 5 years, I could get the $75 portion back. And yes, that is what I would have to use each month to get back the $4500 deposit they wanted.

So, while I was thinking about it, I looked on ebay and found this:

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The 10-17HP seemed weird, so I called Baldor up. Turns out it is a custom built motor, and from the data package they sent me, it appears that it actually just a 15 HP single phase motor with long leads and a funny way of stating it. But it should be able to run continuously at 15 HP, which is what I need to run the compressor. (For those that weren't paying attention, my compressor is actually a 20 HP model, but the motor was replaced with a 15 HP one, which Quincy says will work, but a 10 HP motor will not.)

Well, for $107.50 + shipping (probably about $200), that seemed a much better deal than $4500, so I went for it.

I'll have to make some adaptions to fit it, since it is a slightly different frame and shaft size, but it looks doable.

Thanks again everybody!


Reply to
Todd Rich
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This is the deal of the Month!!!

Watch the Air Over part though, you may need to add a fan for cooling? (no big deal)

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Reply to

Ignoramus4770 wrote: (snip)

I'm keeping that in mind. It is an open frame motor, so I'm tentatively planning to make a shroud and fan to keep it cool and keep stuff from falling in. I'm not sure how open the frame really is, or if it has a fan at all. Todd

Reply to
Todd Rich

First, it is "air over", so it is a purpose-built motor for use in big fans. You will need to supply a serious external fan to cool the motor, or it will smoke pretty quickly. They should have told you this.

Second, starting a 17 Hp motor with a 73 A rating off a residential 240 V service may cause computers to crash, air conditioners to stall and trip breakers, etc. It might even trip your service entry breaker if another heavy load (air conditioning, electric oven or clothes dryer) was running at the same time, unless you have 400 A service.

I wouldn't go for the $4500 deposit, either. I'm afraid you will find the 17 Hp motor a major problem. You will also have to provide a magnetic starter for it, which will cost a bundle. Finally, unless the compressor has an unloader, the motor may not be able to start the compressor. The type of "unloader" that bleeds air from the pressure switch probably will not provide enough delay before pressure builds up for that fan-duty motor to get the heavy compressor flywheel up to speed.

I would have recommended a VFD and keeping the original 3-phase motor. Definitely keep the old motor until you are sure the single-phase unit will work OK.

(Also, I suspect the varying HP rating indicates a multi-speed motor, you may end up calling Baldor again for more info, unless all the docs are incuded in the box.)


Reply to
Jon Elson

Wow - nowhere in that listing does it actually say that it's a *motor*. He really missed his market on that one. Bob

Reply to
Bob Engelhardt

I am sure that the OP can solve this, though it will require some effort.

I have 450 cfm muffin fans that should probbaly be enough with some shrouding.

400a is usually supplied through two 200a panels.

Otherwise, I will keep my fingers crossed for Todd, as the issues you raised, are very valid.

I just sold a size 6 mag starter for $99. It is rated for up to 200 HP at 220v (3 phase). So he can get lucky and get something like that.

Definitely a possibility. Fan duty probably means low starting torque, and all.

It is an interesting experiment, "on the edge of possible". Keep us posted Todd.

If you remember my 10 HP Quincy, what ended up happening is that my acquaintaince who is a repeat buyer, bought it from me and decided to install a 10 HP single phase Baldor motor made for compressors. The price was very sensible. I did get it to run from the VFD, however.

So, my point is, if this motor does not work out, maybe Todd could double check with Quincy again and see if this thing would somehow run from 10 HP? Maybe not at full efficiency or something. Most QT-s that I read about, can run from half rated HP.

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I wasn't sure on this, but I figured it might be a possiblity. However they didn't tell me this when I called. I'll be calling back Monday to find out how much airflow it needs.

Well, the computer has a 1500VA UPS, the air conditioner currently doesn't work (though it may be fixed by next year). When we bought the house, it was on 60 A service, and we upgraded it to 200 A with the shop being on it's own 100 A line. I'll make sure that we don't have heavy loads running when the compressor is due to be fired up. My use for it is a power hammer, so I have a restricted time of use planned for it.

Also, talking over my change of plans with the engineer from the power company, he let me know that they would be more than happy to upgrade my service to 400 A, or run a separate 200 A meter to the garage, which would be done at almost no charge. I may take them up on this anyway, as it seems a sound idea, in which case I would pick up a 25 HP 3-phase motor to make into a converter.

It does have 2 unloader valves, but it looks like they are only the bleeder type that alow the compressor to run continuously to allow the motor to be kept cool (when it isn't being use with an air over open frame motor that is...)

Well, I'll keep the current motor for a while until I've verified if this will work or not. It will be cheaper for me to pick up a 25 HP 3 phase motor and make a converter with an upgrade in service than the best price I've found so far for a VFD. But I do understand that I'm looking at a marginal setup that may not work.

According to what I've got, the speed should vary less than 100 rmp under normal operations. I've e-mailed you a copy of what I got.


Reply to
Todd Rich

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Well I'm almost sure that's the same style motor I picked up years ago to make a cut off saw ( and it might have worked for a cut off saw but in your application I don't think it will) I'm almost sure that you have just purchased a crop dryer motor made to sit in the center of a HUGE fan and blow air into a grain silo. Baldor has made these for years for farmers that don't have 3 phase power but need large motors. For a continuous run cycle I bet it will be very hard to cool down no little fan will move the air like these things sit in i.e.. 1000's of CFMs.

My information about the compressor ( Remember I have one set to run at

20hp) is that you can run the pump from 7.5 to 20 hp power levels, so you could get a real single phase 10hp non crop dryer motor if you wanted {not for $100 though more like $600-700.00})

Another poster also mentioned that your going to have problems with the start up of the single phase crop dryer motor at the max load amps of 73 at

230v . My machine (20hp) runs at 480V and it SLAMS the ole power at 135 amps peak at startup! Now I know it's 20 hp and the weird crop dryer motor is 10-17hp but if we play along we have ..... 270a at 240V and then more amps for the single phase to 3 phase conversion.


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Actually, a separate 200A or 400A 120/240V 3-Ph Open Delta feed for the shop doesn't sound like that bad of a deal, especially if you have other 3-phase equipment in the shop like a lathe or mill that you'll be running.

One thing that may affect your decision to install real 3-Ph is if they will charge a lot more per KWH because it's a "commercial service" with a demand charge adder - find out the rates first. If you are doing work for hire that doesn't matter as much, plus your accountant will like the separate meter since the power is an overhead expense to itemize and write off. Either way it is far better to have the shop on a separate meter and feed, and even a totally separate transformer bank if you can. The surges and dips will get back to the house and can mess up computers, and both the neighbors and your wife will not be amused.

Even with the house main upgraded to 200A, starting up 15-HP motors is going to blink the house. And if you are in the shop running a plasma cutter or a big welder and the compressor kicks while the AC and a lot of lights are on at the house, you seriously risk tripping out the main.

It worries me that you didn't say what the duty ratings were for that motor. A compressor needs a high torque start to get up to speed before the unloader lets the compressor start pumping - a fan duty motor isn't going to reliably start a compressor.

Well, give it a try - if it works, great. If it works but you start tripping out the house main, you may still end up putting in a new dedicated service for the shop. (And buying SWMBO something big and sparkly and really expensive for Christmas in atonement.)


Reply to
Bruce L. Bergman

Well, not all of those 1000's of CFM are cooling the motor - only the part actually flowing over it. You would get appropriate cooling by duplicating the velocity of air over the motor.


Reply to
Bob Engelhardt

If you run a 400A to the house and tap off a 200A sub to the garage you still pay residential rates. If you go for a seprate service to the shop you pay commercial rates PLUS PA sales tax on the electric bill. Like another poster said , compare rates.

Also like was said you might want a 30HP rortary converter. If you might ever get CNC machines in there then you will need real 3PH or a higher dollar converter to out put clean enough power for the CNC.

In my case 240V open delta 3 PH was the same price as a new converter, so I got the real thing.

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