AboutWill Expertise Three phase electic motors, controls and related problems or failures, three phase motor installation issues, performance issues, connections, data and duty cycle information. All other electic motors. Specialty motors, repair concerns, performance concerns, obsolete motors and solutions. Other specialty equipment issues. Lost nameplate data and identification, lost connection data.
Also DC motors of all types.
See my profile under Home/electrical at this site
Experience 30 plus years in the electrical motor and apparatus repair industry. VP level management of repair facilities, current owner of my own specialty repair and consulting firm.
Organizations EASA, IBEW [retired], other specialty organizatons, Lubrication, Vibration EDI, Triboelectric Councils
Publications Currently fielding concerns at this site under "Home Electrical"
Education/Credentials 4 year technical, College level specific courses, EASA repair courses, vibration analysis electronic and electrical trade school.
Expert: Will Date: 5/20/2008 Subject: Replacing start&run Capcitors on a elec motor
Question QUESTION: I have an emerson electric motor Model# MCo15502SJ but no run or start capacitors on it, I have the capacitors and want to install them on the motor to use but am not sure where they go. The markings on the wires are T7, T8, & T9. There is also a wire that is not marked at all.
T7, T8, and the unmarked wires come out into one cap. And T9 and the unmarked wire comes out in the other cap.
This is a 2HP running 4.5HP max HP motor meant for single phase.
ANSWER: Michael, You have done well, in keeping track of the wires and where they go. You have T7 AND T8 on one cap, then the unmarked wire is one end of a jumper to series to the next cap, T9 [might be T6 double check] goes on that cap with the other end of the jumper.
So one lead T7 on one terminal of the first cap, T8 and the unmarked jumper on the second terminal of the first cap, T9 on the one terminal of the second cap, and the other unmarked jumper on the other.
Now to be clear you say you have three wires on one cap, and two on the other, so that means 5 total correct?
And can you confirm the unmarked is jumper and simply the ends of one jumper wire?
This shouldn't be too hard to figure out, now what happens, in most cases when someone gets a motor with no caps, is the motor quit, the simplest thing to get to is the caps, and they go to replace the caps, can't read the values, or are able, but try new caps and that is not the problem, so they take them out and sell the motor.
Now when you put new caps in, how do we determine if it is my wrong guess on the wiring scheme or there are other motor issues?
ONE step at a time marked down on paper, tried x and x to cap1, x1 and x3 to cap2-no start hums.
Swap x3 with x, motor begins to rotate but stalls,,,,,,,,,,so on
But you really don't have not too many combos to try.
If you have dry compressed air and a blower attachment, if the motor has openings, blow out the motor everywhere you can while rotating the shaft by hand, and we might blow out something hanging up the start contacts.
Experiment around with the proper cap sizes should not create more problems, there is x voltage at the cap box, and if we get them back wards they will just not be in the right order, then we swap and should be done.
Tell me the exact cap values and verify number of wire ends, and if you can tell, of all wire ends, is one a jumper wire only, from one cap to the other?
As the motor comes to speed, the switch [internal] takes BOTH off line so that is why we can play a bit without too much worry, it is almost obvious, from a very good description you provided, and with that, I say proceed as above and see what happens.
Will
---------- FOLLOW-UP ----------
QUESTION: The T9 is labeled as such with nine spelled out. both caps have a jumper cable running between them. I have installed the caps as follows a black (Start Cap) 189-227MF 165VAC with the 3 wires and a Silver (Run Cap) 30 MF 370VAC with the 2 wires. The motor started but then tripped a 20A breaker after 2-3 seconds. I have not had a chance to switch the caps to see if this is the problem, but am concerened that I might damage the Caps is this possible if wired incorrectly?
Also the Black (Start) Cap has 8 connectors 4 of them come into one and then into the Cap so essentially there are 2 areas going into the cap does it matter where the wires are plugged into the cap? Similar to the Silver (Run) Cap however this only has 4 connectors two each into a single enrance into the Cap. As of now I have a jumper and T9 plugged into seperate conncetors on the run Cap and I have T7 and T8 on seperate connectors on the Start cap and randonmly placed the jumper on this cap tried in two differnt locations same outcome trip the breaker.
Motor is a 2HP run 4.5 Hp start 120V
One last quick question I was once told that it used to be start Caps were the large caps and Run caps were smaller is that the case?
Answer Michael first, the twenty amp breaker might not take the inrush current and your wiring is fine
20 amp breaker is pretty tight for that motor. You will not hurt the caps,
next write me a service@emrrepair.com where you can attach a diagram photo, whatever or my home wbwill@sbcglobal.net
If you can temp wire into a thirty amp breaker or fuse a 50 amp circuit the motor may start.
In either case write me at one of those addresses the logistics on here are tough for wiring problems.
