Ok, this is a little off topic, but there are quite a few guys here who probably know the answer so I’m going to ask it.
I design screen systems to keep fish out of pumps and irrigation diversions.
I need to build a self cleaning screen for a 2500-gpm pump. I am modifying a design that is typically used for gravity diversions, and run with 1/4 horse, 24-volt gear motors, powered by batteries and solar arrays. (We are typically in isolated areas, and off the grid.)
Since this is going to be only 300-ft from the wet well and pump, I want to run it with a feed from the pump controls, and eliminate teh hassles with the batteries and solar arrays.
The pump, and it’s feed will be 3-phase. How hard is it to split off a feed from the three phase to the single phase gear motor?
The other option is a 3-phase gear motor, cost on either is about the same.
Replies
Well, 3-phase at what voltage? If it's 208V then likely you can get a version of your motor with a 208/240V rating and just run it between two phases.
Otherwise, you'd have to run a neutral along with the three phases (probably code lets this be a smaller wire) and wire the motor between neutral and one leg of the three phase. This assumes a 208V 3-phase setup if you have a 120V motor -- proportionally adjusted for other voltages.
(Of course, the above assumes a balanced 3-phase setup. There are also unbalanced setups where one leg is at ground potential. You need to find out what you have.)
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
just get a 3ø motor or else you might start running into problems with voltage drop to the gear motor if you use a neutral..
.assuming a 5A load on the gearmotor,
which is a number I just pulled out of the air,
you would have to run some #8 or bigger for that distance..from the pump controls..
also if you add that gearmotor to the pump controller you will have to adjust the overloads on the starter for the additional load
or run that gearmotor thru it's own starter ...... using the same circuit that feeds the pump from the panel
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, wer ist jetzt der Idiot ?
If the current unit is running off a battery, I doubt that the load of a 120V unit would be 5A.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
the point was that he should consider just getting a 3ø gearmotor..even 2A at 120 will drop 2% and that doesn't include the distance to the service from the controller.
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., wer ist jetzt der Idiot ?
I originally wanted to just use a three phase motor, but my boss is saying to go with a single phase. And not being that experienced with the electrical side, I'm not sure whether to argue with him, or how to argue the point if I do.
Other than using one less conductor, I'm not sure what single phase gains me. My intent was to have the screen motor come on for about three minutes before the pump starts to clean anything that has accumulated on the screen off, and then turn it off when the pump shuts down.
I'll try getting ahold of one of the two electricians who might do the pump wiring and get their input tomorrow.
The only time constraint I have is, that I would like to get direct bury wire ordered, so we can install it when we run the piping from the screen to the wet well.
good idea.......
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., wer ist jetzt der Idiot ?
"Other than using one less conductor, I'm not sure what single phase gains me. "With single phase you gain a start winding, a centrifical start switch, and starting capacitor.All failure points.I would use 3 phase..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
OTOH, a single phase motor won't run backwards. (Ever seen what happens to a carbon vane vacuum pump when it starts up backwards because someone crossed the phases?)
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
I saw a printing press do that. once..oboy!he has to buy a rotation meter ....AEMC sells them, they're about $150.....
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., wer ist jetzt der Idiot ?
I remember a story, must have been from when I was in school, that in GA or NC or SC there was a knitting mill. Rows and Rows of machines with spools and spools of yarn beging spun or woven.The power company was working on the lines and drop power. When they brought it backup the phase rotation was reversed.The discussion at the time was whether they should try and clean out this plant or just abandon it and build a new one <G>.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I can only imagine the mess in therethings can go bad in a hurry that's for sure..I was the guy who hooked that press up... after the operator assured me the rotation of the motor was correct I coupled her up and KAFLOOEY....German press parts everywhere.
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., wer ist jetzt der Idiot ?
Please don't consider my reply to be rude, or disrespectful.
Simply put, you need an electrician to see your set-up. What you propose raises far too many questions to be answered in general. Electricians have 4,5 years of classes on these very issues.
Also, there is the matter of ground fault protection, and bonding at the pond. This is one area where the NEC has been changed quite a bit in the last few edits.
I'm thinking what you have on the present design is a 24 Vdc motor, all setup to go, no mods needed if you had 24 Vdc??. So, do the simplest approach.
What I'd do with your admitedly minimal electrical knowledge is simply put a 24 V, 20A plug in battery charger on the 24 Vdc motor, batt charger plug into either 208 single phase or 3 phase, whichever battery charger you can come by cheapest - probably in the $150 range min for a 3 phase charger.
What I'd do myself is use a $15 surplus transformer, a $6 6 pole bridge rectifier, stick it in a surplus box and go, but you probably need all the UL stickers, etc on everything so go with a commercial battery charger or power supply (look on granger.com, surpluscenter.com, or kepcopower.com.