Soft start for swamp cooler
mmag Solar Expert Posts: 57 ✭✭✭✭
hello, i use a swamp cooler to cool my home, i am trying to find a way to reduce the power surge of the swamp cooler when it turns on, its a 4000 cfm swamp cooler, thanks
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What is the motor? 120 VAC 60Hz at X amps? What type of motor? (capacitor start, permanent capacitor)?
You could 'soft start' the air side. A closed damped on the outlet of the unit that slowly opens as the unit comes up to speed will reduce the starting load a bit. If the wheel can't move air, there is far less resistance to it turning. Usually better done on the inlet of the blower, but obviously not as practical on a swamp cooler.
The motor is 120 volts 60 hz and the whole unit is 6.9 amps but that includes the pump, i am not sure what type of motor it is i will go look.
I really don't know how to tell what type Capacitor it has
OK, there are two major types.
One is a capacitor start motor. Basically there is a switch inside the motor (may be electronics in newer motors) that turns on when the motor is stopped and turns off when the motor is near operating speed. This turns on a Motor Start capacitor+winding. Very high starting torque, fairly efficient motor. Obviously, switches (and capacitors) can fail.
Another is a permanent split phase capacitor motor. These use a smaller capacitor and winding always turned on. These motors have less starting torque and tend to be less efficient. Used for smaller systems and popular in air handling systems where high starting torque is not needed.
Motor Run capacitors are smaller (lower MFD rating).
Motor Start capacitors are larger (higher MFD rating or ~10x the capacitance of Motor Run Caps).
The first thing to try is use a size or two smaller capacitor (just take the numbers off the capacitor, keep the same voltage rating, but lower MFD rating).
And there is always the question about why your present (off grid?) power system is having problems starting the air handler. Does the inverter have larger enough surge rating, does the DC wiring have low enough voltage drop, is the battery bank large enough to manage the surge, are all the batteries/cells in good shape to provide surge current, etc.?
Another quick test--Take a 100' "cheap" extension cord (14 or 16 AWG) and plug the air handler into the extension cord. The extra resistance of the cord can be enough to significantly reduce the starting current (and a bit more "running' losses).
There are "hard start"/current limiting black boxes made for A/C systems... I have never used any, but perhaps somebody here can give some examples of useful devices.
cool thanks for the help, my off grid system runs the cooler fine, it just has a high startup surge which causes a bit of light dimming.
The newer cooler motors are junk. Half the weight of the old ones and they use the high speed side of the motor to start and then go to the low side of the 2 speed motor to run. I guess the chineese are trying to save a buck on the copper content. I put a replacement motor on mine last season and it burnt up in 2 weeks. When I returned it, the guy at the hardware store said it was common for 1 out of 20 to fail?? Unacceptable in my opinion.
If you have an adjustable pulley on your motor (as most do), you can try opening it a couple of turns, that should help a bit on the starting current.