I replaced my two start caps on my irrigation well with ones of a lower voltage rating (220V 300 MFD) and have water flowing... No smoke so far, but I know it won't last.
I'm looking for 330 volt rating 270 - 320 MFD start caps. Grainger,McMaster, Newark, and Digikey don't go this large. Any other suggestions for a vendor?
I will clobber a bunch of smaller 330 volt rated caps for temporary if/when the 220 volt ones blow, but they wouldn't fit inside the control box.
Karl
Mouser.com is another one to check.
Grainger,McMaster,
I'm looking for 330 volt rating 270 - 320 MFD start caps. Grainger,McMaster, Newark, and Digikey don't go this large. Any other suggestions for a vendor?
Surplus Center.
It is the run caps which must be rated 1.56 times the line voltage, or 330 volts for a 240 volt line.
check out
My local motor shop had them in stock. I start a 30 hp ilder for a phase converter... Most any motor shop that works on motors of any size should have them, or have a source.
Pete
HMMM, a 15 hp motor. This may not be much help, but I will put a few thoughts here for you. If you are running the motor on 240 volts, then a starting cap rated for 240 VAC ought to be good. Right the peak voltage is higher than 240 volts, but the caps are rated for 240 volts AC. That means they are rated for the peak voltage, the large currents during starting, and limited in the number of starts per hour.
If you are using 480 volts to power the motor, then I don't see that caps rated at 330 volts are going to work.
Were the original caps DC rated caps and wired is series with the polarities opposite each other. That would be about the same as a 240 VAC rated cap.
Dan
The link to the results page was too long to include here, but search motor (capacitor, capacitors) for an eBay search term to see quite a few sellers that are listing a lot of motor start and run caps of various values and voltages.
You haven't specified whether your motor(s) are single or three phase. For single phase motor start caps, my motor shop folks say that 500uF per HP is the general rule of thumb for choosing the appropriate capacitor value. These are precisely the same values I've seen used in the cap start motors I've disassembled for cleaning and service. In the dual voltage (120/240VAC) motors I use, the start caps have only been rated at 120VAC, but some are rated 277 or a similar voltage.
WB ...............
Grainger,McMaster,
I did some googling and if you really need 330 VAC caps, then try Cornell Dubilier. I found their web site via Google and don't remember the URL. But their web site lists 330 VAC motor start caps and has a place to find distributors. I would go with Newark. It may not be in their catalog, but Newark used to be the best as far as getting things that were not in the catalog. That was a few years back so things could have changed.
Dan
Karl, Don't confuse motor start caps with motor run caps. Start caps are rated for very intermittent (read infrequent) duty and they are generally round in shape and all I have seen are black. You can get much more capacitance for the buck in a start cap package. Also, as someone pointed out the voltage rating for start caps will be the same as the line operating voltage - probably 240. I think you will be surprised how long they will last.
Bob Swinney
Grainger,McMaster,
Thanks, everybody, for all the help.
This is a single phase 220 VAC 15hp. well pump. The original equipment is the 330 VAC 300 MFD start cap. I have had a ton of trouble with the control box on this unit. Virtually everything in it has fried at least once. Right now, I run it with the cover off and all the wires arranged so they don't touch each other. Insulation on several wires has boiled and looks tough.
I found a source for these 330 VAC caps. I'm ordering them as a spare and will run the 220 VAC start caps until the smoke comes out. I see most here are betting on "last long time". Not me. Anyone here care to take my wager on fried before memorial day?
Karl
in it has fried at least once. ...
Assuming those aren't Sears hp and 75% efficiency in the motor, you're talking almost 70 amps! No wonder everything has fried. Bob
I resemble that remark! All the "frying" you mention may be the result of inadequate wiring in the control box. Could it be the original control box was for another, lower powered application? You (naw, certainly not you) may have modified it to operate higher powered equipment and the original wiring is not adequate. Overheated wiring is almost always the result of insufficient wire size vs load.
Bob Swinney
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