On Tue, 11 Jul 2017 17:53:47 -0700, wrote:

On Tue, 11 Jul 2017 14:40:03 -0700 (PDT), "Dave, I can't do that"
wrote:

Hi, we recently installed a window version of a swamp cooler. As such, it plugs into a wall outlet in the lounge-room. It has a new 1/3-hp (252-Watt) two speed motor from HomeDepot.

When it turns on either in Low or High, the voltage dips for almost a second from 125vac to 117vac then back up to 125vac. The dimming is maybe 20% longer for the High speed.

Is there some way we can soft-start this or what? It makes the lights dim in the house for that short period.

Before anyone launches into "house wiring," etc rest assured it is 11-years old, copper, in metal conduits and all up to code with 200-Amp coming into the house.

I used a 14g, 3-wire extension lead in a bunch of other outlets on different circuits and still get the same issue. I then hard wired the extension into the main breaker panel. Same again.

I have cleaned and oiled the fan bearings, adjusted the belt and the fan turns quite freely by hand.

What can be done to alleviate this momentary voltage drop?

Thanks
Since you hard wired the motor in the breaker panel did it get its own
breaker? I would be surprised if the voltage sagged that much if wire
directly to one leg of the 220 volts coming into the panel. Also since
you hard wired the thing is the motor perhaps a dual voltage motor? If
so changing it to 240 volts and using both legs of the incoming power
will make a big difference in the lights dimmimg. This is because the
dimming of incandescent lights is not linear with the drop in voltage.
A small voltage drop will result in a larger drop of visible light.
Induction motors can draw up to 6 times the running current when
starting. So the amperage draw can be quite high. Especially when the
motor is a crappy one. Lots of import motors are crummy motors. They
sometimes use less wire in the start windings which leads to lower
resistance and higher current draw. Soft start controllers are
available but can be expensive. Is the motor a capacitor start motor?
Maybe the cap is not up to snuff. Still, I'm surprised that if the
motor is wired to a 100 amp supply the voltage would sag that much if
nothing else is using the same leg of the incoming supply the same
time. What other loads are connected to the leg supplying the swamp
cooler motor?
Eric

I live in Swamp Cooler Country. Far too many of the low end
portables come with utterly crappy motors and Ive seen this many
times. It may be better to simply replace the motor with a decent US
made motor, with proper run/start caps


---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus