Hybrid Car – More Fun with Less Gas

Swamp AC motor soft start -- possible?

register ::  Login Password  :: Lost Password?
Posted by I can't do that Dave on March 21, 2018, 3:08 pm

We have a swamp cooler and it is getting close to the time to put it into d
aily service. When the 1/2hp fan motor switches from Low to High, or High t
o Low, there s a short delay and then it starts up again. All good since it
 is a two-speed motor.

But when it starts each time the lights in the house momentarily dim, so I  
am wondering if it is possible to buy a soft-start whatever and wire it in  
between the motor and controller.

Last year I asked on groups about the swamp and dimming lights, but no one  
mentioned a soft start, but instead suggested I get the wiring checked. Got
 an Electrician in and he gave the entire house a clean bill of health. No  
surprise really, the guy who built the house was an Electrician in the Navy
 for thirty years.

I checked Amazon and can find nothing, but Wiki mentions them for three-pha
se motors.


Posted by David Lesher on March 23, 2018, 8:03 pm

Not feasible....


Friend bought a house from a retired Navy Chief electrician;
he'd rewired it & thought that black was neutral, just like in
the Navy.

Yep, 3-phase motors are another story entirely. You could
replace the motor with a 3-phase unit and a VFD; that would
allow soft-starting.
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close..........................
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

Posted by amdx on April 8, 2018, 1:43 pm
 On 3/21/2018 10:08 AM, I can't do that Dave wrote:

  Does the wiring to the 1/2hp motor go directly back to the breaker box.
  Just doesn't seem like it should cause the lights to dim.
  Which lights?
You have 220V coming in, which phase is it on? (I'm assuming it's a 120V  
  Does it help to switch that motor to the other phase?
Could there be a poor connection on your incoming lines.
  Do you have an electric dryer?
  An interesting test would be to monitor the voltage of one phase
while you start the dryer, then repeat for the other phase.
See if there is a difference in the voltage drop.
  You might need to remove any loads that might be drawing current,  
fridges, freezers, sump pump, furnace, air conditioner, to get a more  
accurate test.


Posted by Mark F on April 9, 2018, 5:45 pm

So questions:
1. What voltage does the motor run on? What are the ratings for
   the motor (voltage, running current,
      startup current [or at least the type of fusing specified] ?
2. What is the total service to the house
   (number of phases, voltage, current)?

3. What size wire and approximate run length for the circuit the motor
   is on?

4. You say lights dim.  Assuming you have 2 phases in the house
   and the motor runs on one phase that is 180 degrees out of phase
   with the other (which is normal in the USA outside or parts of
   Queens, NY, which gets 2 of 3 phases, for 208 instead of 240 volts
   nominal), have you looked at lights on the other phase to see if
   they get BRIGHTER when the motor starts.

   If the lights that get brighter share the neutral on the circuit,
   then the dimming might be normal with the usual required wiring
   for a 15 Amp circuit (#14).

5. Borrow a modern motor setup of the same horsepower. See how things
   act with it then evaluate replacing the "swamp cooler"

Also, to be sure we are on the same page:

Looking at Google for current swamp coolers of what seem to
be similar size, I see:

This is:
  0.5 horsepower, Maximum Amperage 11.5 Amps

 Can you measure the startup up current and compare it to 11.5 Amps?
 (Note, the 11.5 Amps in the spec might not be the actual maximum,
  so you'd need a fast meter or electronics)

Try looking at:

for circuit information there to see if you would need a 20 Ampere

Also, if the circuit is long you need to go one or more wire gauges.
So 15 Amp would need #12 of #10 instead of #14.
For 20 Amp #10 or #8 instead of #12.
(If the thing plugs into a receptacle probably should use
 pigtails since the connection on the receptacle are likely
 not be rated for #8 and would make things easier with #10)

I couldn't find a wiring diagram, but the web site points to:
You could look in there to see the Portacool thing has any special
startup stuff.

This has a picture of the $00 replacement motor for the Portacool:

You might be able to read the rating/wiring label on the motor and get
some information from it.

This Thread
Bookmark this thread:
  • Subject
  • Author
  • Date
please rate this thread