Panel size? for pond pump 120v 60hz 460mA 20watts

I've read through some of the threads and have been studying solar for a while, but I just can't seem to get it. Could someone tell me how large a panel I would need to run a pond pump that a friend gave me. It says it is 120volts, 60 hz, 460mA and 20watts.

Right now I have a little panel 5w 12v running a little pump. This one is a lot bigger. Would be nice to get at least a 2' rise out of it, but am happy with just having it drop into the pond.

Suggestions?
:confused:

Comments

  • BB.BB. Posts: 28,079Super Moderators, Administrators admin
    Re: Panel size? for pond pump 120v 60hz 460mA 20watts

    Your best bet--dig an 18"+ deep trench from your home (and GFI outlet) out to the pond and use the 120 VAC pump...

    It will be the cheapest, most cost effective, and most reliable solution...

    Otherwise, you are looking at, very roughly, spending about 10x your cost of electricity from your utility to buy solar panels, charge controller, batteries, inverter (if you want 120 VAC)...

    Problem is that most DC pumps are not that reliable or that large in capacity. AC pumps are better, and you can get some nice well pumps that will run off of solar panels--but that is probably way overkill for this appication--and you have the decision if this needs to run 5 hours per day or 24 hours per day (which needs batteries)...

    If this is a fun project to get your feet "wet" in solar--decide on what your pump (load) will be... AC or DC, wattage, hours per day, lift, etc...

    Once you have those numbers, figuring out the rest is just a relatively straight forwards working backwards exercise.

    Not knowing the load and power requirements--it is pretty difficult to give you a good idea of what the system would cost...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Panel size? for pond pump 120v 60hz 460mA 20watts

    Thank you for that info. I guess my main problem is knowing how to size a panel to run certain appliances. I am now running the pump with an extension cord, but really don't want to pay for the constant electricity flow. Don't mind paying for the panel to power the pump. Don't want the inverter/battery/surge protection, etc. If there's no sun, I have no problem with it not running. I'm not out there in the dark anyway.

    What is load and power requirements? So the volts/hertz/amps/watts don't apply to that? How would I figure those things out. As I stated in the first post, don't care if there is no lift if it means I have to buy a larger panel to get it. I'll be happy just running it.
  • BB.BB. Posts: 28,079Super Moderators, Administrators admin
    Re: Panel size? for pond pump 120v 60hz 460mA 20watts

    120 VAC at 60 Hz is the common North American utility power that comes out of your wall... Solar Panels and Batteries can only output DC voltage, and usually at a low voltage of 12 volts or so...

    The small solar pump you have now is probably designed to operate with a solar panel. The motor may either be a brushed motor--which will not last real long (think of your electric drill motor with sparks coming out the brushes).

    There are electronic motors that convert the DC into AC that last a pretty long time (the most common are DC powered fans used in computers).

    I have not run across a DC electronically commutated motor used in a small solar powered water pump--there may be some--but I have not seen any myself.

    So, if you want to do this small scale, find the DC pump you want to power, check the voltage and amperage requirement (best would be to use a Volt/Amp meter to measure the current under load). Then you would pick a solar panel that would best meet that load (using its own ratings for output voltage and current)...

    You could do more--but that runs the cost and complexity up--something that you don't want.

    Your basic cost will be--take the motor (say 12 volts x 2 amps = 24 watts) and look for a panel that has those specs... It will cost you around $5/watt *24W=$120 or more for the solar panel(s)...

    There are some other issues--but it would be best to identify the DC motor/pump first--but basically, a solar PV panel is not a great source of regulated voltage--so it is easy sometimes to damage the loads if they are not designed for the wide range in voltage a solar panel can put out.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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