Centrifugal switch

Discussion in 'General Electronics Chat' started by jpanhalt, Jan 1, 2010.

  1. jpanhalt

    Thread Starter AAC Fanatic!

    Jan 18, 2008
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    This is centrifugal switch from a 1/4 HP single-phase ("split phase") motor.
    [​IMG]

    The motor is flange mounted to an Armstrong water recirculator for a heating system. It appears that the contact fingers on the switch (pointer) are worn to the point that the starter winding does not always engage. Does anyone know from where a replacement switch is available?

    John

    Edit: Those are just mechanical contacts to a slip ring. The switch contacts are controlled by the spring attached to them. I could just bend the contact a little to make it work, but that is not an ideal solution for the household heat source.
     
    Last edited: Jan 1, 2010
  2. gerty

    AAC Fanatic!

    Aug 30, 2007
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    Have you contacted a motor rebuilding shop ?
    Some are reluctant to sell parts, but most will.
     
  3. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Have you checked Graingers?
     
  4. jpanhalt

    Thread Starter AAC Fanatic!

    Jan 18, 2008
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    I was planning on contacting a motor shop on Monday. I discovered the failed pump on Wednesday afternoon, so the New Years holiday has hurt my hunt.

    It seems like an obvious replacement item, but our throw-away society has made finding the part from usual Internet sources impossible.

    I was really wondering whether anyone else had had success finding such a part for an FHP motor.

    John
     
  5. PackratKing

    Well-Known Member

    Jul 13, 2008
    850
    215
    Switch contact, or "make" is controlled by height of endplay washer stack on the switch end of the armature, or rotor.

    The centrifuge ass'y lives on the rotor, and should not be loose. Parts can be had, tho' " liability " issues often cause jobbers not to sell parts to a diy.

    I see from the picture, your motor was far enough apart to perform this test: { I have seen far worse looking switches } extend the switch wiring carefully, and lay the endbell down flat on your workbench. Install the rear rotor bearing journal into its bearing, and observe the switch contacts as the rotor seats on the endplay washers.

    Switch should firmly contact at roughly 2/3 of travel to fully seated. With the rotor seated, operate the disc of the centrifuge to its limit. This must completely open the switch. Contact point is controlled by adding or removing end-play washers. Bending contacts should be a last-ditch effort.

    once you are certain of this function, remove the rotor and reinstall the endbell in the proper orientation, being sure all wires are out of harms way. Reinstall the rotor, and the other endbell. Tap the endbells into place where they are normally. With both endbells in place, tug upward on the shaft. Normal endplay for the shaft should be appx. 1/32 inch.

    This should get you back in business. Once running, if your motor " purrs like a kitten " in a pulsating manner, or just grunts and refuses to turn, this indicated either partly worn / dry bearings, or bearings bad enough to allow the rotor to lock over against the stator, the latter being new motor time.

    Hope this helps...............
     
    Last edited: Jan 23, 2010
  6. jpanhalt

    Thread Starter AAC Fanatic!

    Jan 18, 2008
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    Thanks. I got the switch contacts working just fine. Now, the return seems to be sticking. End play is OK, and when it starts, it runs just great. However, sometimes the switch hangs up and doesn't return. A very slight tap on the motor makes it return. I wiped and blew the switch off, then added a very small amount of molybdenum disulfide to some of the moving elements. It was really quite clean to begin with.

    It works when horizontal, but is intermittent when operated vertical. Maybe the return springs have gotten just a little weak with age?

    John
     
  7. PackratKing

    Well-Known Member

    Jul 13, 2008
    850
    215
    The springs on the centrifuge serve to control the rpm at which it opens the switch, and kicks the start windings out. If the springs are weak, the motor would fail to come up to speed, and continually trip the thermal protector. allowed to continue, would burn the motor out rather quickly. Fairly certain this motor was intended to run horizontally.
     
    Last edited: Jan 2, 2010
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