[TowerTalk] US Tower Dayton AC Motor issue

TexasRF at aol.com TexasRF at aol.com
Sat Sep 13 19:04:54 EDT 2008

Scott, you have described a classic case of an open start winding circuit.  
The most common cause in this part of the country is mud wasps building a nest  
around the start circuit throwout switch, causing the contacts to not make  
connection. The second most common cause is a defective start capacitor but 
this  usually noticeable because of swollen areas on the end of the capacitor.
The motors I have worked on have four long screws that clamp the end bells  
to the motor body. Removing these screws allows one to trmove the end bells and 
 gain access to the throwout switch to examine and clean.
Make note of all the wire colors and locations so you can return to the  same 
electrical arrangement after fixing the problem.
Hope this helps.
Gerald Williamson K5GW
General Manager, Texas Towers
In a message dated 9/13/2008 2:01:14 P.M. Central Daylight Time,  
kc2pih at gmail.com writes:


I am in the middle of getting a used US Tower ready to put  up. It has
the MDLP1000 unit with the Dayton 1HP motor. Without the belt on  the
output shaft of the motor (free), I am unable to get it motor  going
full speed. It will just hum, spin slowly (like 1RPM) and blow  the
break within 3 seconds. I am able to spin the motor up to speed  by
hand and then hit the switch and it will spin up to full speed.  The
output shaft on motor spins freely and easily.

I have a 50 foot  run of #10 back to the service entrance on a 20 amp
breaker.  Nothing  else is on that breaker.  Without the motor I see
120V coming into the  control box at the tower. When I hit the switch,
the voltage drops to 107.5  Volts and the amperage draw is 52 amps. It
will actually hum and slowly  spin for about 3 seconds until the
breaker blows. I am using a fluke clamp  on amp meter. Not sure how it
can pull 50 amps for 3 seconds through that  20 amp breaker, but that
is another story.  If I check things on the  main breaker, I see the
voltage drop from 120 volts to 110 volts and 55  amps when I start the

If I spin up the motor by hand and the  motor spins up to normal speed,
it draws 9 amps (still with the belt off -  no load on it).

So I have read about voltage drop problems people have,  but geesh, I
am running #10 right to the breaker and its 50 feet  long.  Do I need
heavier cable or is it something else? Like maybe the  starter
capacitor in the motor?  Its a 1HP Dayton 6K622N model ("Farm  Duty
Capacitor Start"). I could probably run 220 VAC / 30 Amps to it  as
well, if this would help (and is possible).

Scott,  WU2X

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