Our small concrete mixer blew the start cap so we have to spin it by hand to get it going. It is a 110 volt motor, probably 1/3 hp. It uses a 40 mfd, 400 volt cap. The closest Grainger has that I can find is a 43-50 mfd, 250 volt. Would that work, or do we need to get a 40 mfd? What about the voltage rating, is 250 ok since this is a 110 volt motor, or do I need to stick to a 400 volt rating?
-- Dennis
The tolerances for start caps is uneven. Something like - 20 % plus
100%. I don't think you will have any problem with using the 43-50 mfd 250 volt. If you rewired the motor for 240 volt operation, it should still be okay. Typically the start winding is always used on 120 volts.Dan
Thanks. I went down to Surplus Electronics near me and found a 40 mfd 250 v cap for. I also discovered the switch on the mixer had gone bad so I picked up a weatherproof 20 amp switch. Everything works fine again, only ten bucks spent.
-- Dennis
According to DT :
Make sure that it is *marked* as a start capacitor. 40 uf 250V sounds like a common DC rating, and a surplus electronics place is more likely to have DC caps than the AC rated ones needed for motor starting duty.
If it is DC rated -- you'll be lucky if it lasts a single start.
O.K. So you *did* get a motor starting cap, not a DC one. Good.
BTW I find it good practice to have a couple of spares on hand, since they tend to go out in the middle of a project just late enough into a weekend so you can't buy replacements until Monday. :-)
Enjoy, DoN.
Have something to add? Share your thoughts — no account required.
Ask the community — no account required