Inverter peak continuous wattage
kansas
Solar Expert Posts: 100 ✭✭
I would like to have a dehumidifier in the cellar under my cabin. The most efficient I've been able to identify is a Frigidaire that is rated at "3.2 amps(cool)" and "320 watts(cool)." Two questions: 1) does anyone know what "cool" wattage and amperage are? I've emailed Frigidaire but so far no response. 2) What would happen if I attempted to run the dehumidifier using my Morningstar 300 watt Sure SIne inverter? Would it run hot or shut down, or both? The temperature in the cellar is a constant 60%. Thanks - Bill
Two 140 watt Kyocera panels, wired in parallel; Ironridge top of pole mount; two 6 volt, 242 AH US batteries, wired in series; Morningstar ProStar 30 charge controller and SureSine 300 inverter; Trimetric 2025-A meter; IOTA DLS-45 charger, Honda EG3500X generator; Aermotor 702 water pumping windmill.
Comments
The dehumidifier, if I am analyzing correctly, may actually use less energy per quart of water removed if the air temperature is higher. But the compressor will be working against a higher average pressure, so the straight wattage would be higher at higher temperatures.
You also need to allow for the unit cycling on and off under the control of a humidistat if you want to know the energy consumption over 24 hours rather than just the power.
A motor with a 320W running load will pull several times the current when starting, so you 300W inverter is likely to trip (turn off) every time the humidifier tries to start.
As for the 320W versus 300W, the inverter may drop the output voltage slightly as it nears its peak rated output. Seeing the lower voltage the compressor motor will try to keep producing the same output by drawing more current, causing the inverter to shut down on overtemperature.
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The rule is that motors can take up to 10 times the current/watts at start up. Up to means that all depends on the kind of motor and the load attached to it at the time of starting the motor. So it looks like you will need a higher watt inverter. In reality we are talking about in the neighbor hood of needing 4 to 5 times the power rating at start up.
Your signature says that you have two 140 watt panels and that is not enough to support the combined power requirements of your dehumidifier and batteries.
You have to really study them to figure out what type you are getting (many call the generic replacement parts kit for a failed starter assembly a "hard start kit" (I believe--I am not in the industry).
-Bill
The power is stored in the capacitor so it lightens the load on the Line. Also it will get the compressor to running amps about 50% faster so even less strain on the inverter.
Three phase motors do not a starting capacitor/windings--The three phase power is already "naturally" a rotating field in a three phase motor.
The capacitor does not store multiple cycles or multiple seconds of energy--So it cannot reduce the starting current unless the new capacitor is smaller (lower capacitance) than the original capacitor. (the capacitor, besides "shifting" the timing of the current is also helping to limit the actual current flow to the start windings).
-Bill
That is all fine but a dehumidifier will not come that way and you would need to modify it to do so. Easier to just get a variable speed compressor with little load on start up. A dual capacitor say 35/5 35micro for compressor 5 for fan gets an added benefit from the hard start cap of 450 micro for a short burst to make it easier to start under low power conditions or heavy compressor load/pressure.