Derek Broughton wrote:
bruce wrote:

Yes, I've used LGs and they make good plug in pumps.

Not in the opinion of most. They make low end, short life-span, pumps.

It's been a while since I bought one, have they fallen that much in
quality?

What brand would you reccomend I check out should I decide to go
plug-in?

Generally the solar panels can be configured to put out most any
voltage, the panels I'm considering put out about 24v open circuit, but
they can be arranged to get most any voltage
(power remains the constant).

While you're right that they don't "generally" put out 12V, I'd be surprised
if you have panels that put out "24V open circuit", unless you built them
yourself. "Open circuit" voltage of a commercial nominal 24V panel is
generally 34-40V.

I was specifying in "nominal" terms but you are right, the internal
resistance (and sunlight) makes the panels put out what ever they
please at any given moment 8^)

Open circuit voltage of a 12V nominal panel is generally
17-20V. I haven't seen anything with an OC voltage of 24. (I have 5
different brands of 24V panels on my home). All of which is pretty
irrelevant anyway, because as soon as you attach a load, that voltage comes
down.

The big difference between "solar" pumps and standard pumps is that the
"solar" pumps are designed to run under changing voltage and current
conditions as well as run under lock up where there is insufficient
power to make the rotor spin. I use "solar" in quotes since I believe
these pumps are not designed specifically for solar power, they just
happen to have the qualities to survive operation from solar power.

It's my understanding that it's just the way DC motors work. Going to
inverted AC has no advantages.

Yep, too many losses by converting from DC to 115vAC. Brushless motors
have the ability to better regulate themselves over standard DC motors
which are generally a slave to the available current. Of course
brushless motors are in effect converting to a form of AC anyway. I
think the big deal is really to just avoid brushes and have some form
of feedback to regulate the speed somewhat. AC motors are "ideal" in
the sense that they can be sealed.


I only intend to let the system run when solar power is available (day
time). A friend had a pond for many years that only had a pump running
for a few hours during the odd day he'd have it plugged in.

As long as you're not loading the pond to the point where the fish rely on
the pump for aeration and filtration, that's fine.

Hopefully. Just some simple water plants and room for Guppies in the
summer to feed the wifes angel fish in the winter 8^(

The pond
was cement lined and had a nice amount of lily pads and tropical fish
that seemed to keep the natural balance in tact (natural ponds usually
don't have pumps either 8^).

Natural ponds don't have a dozen koi in 1000 gallons of water, either (not
to suggest you do, but people will do that...).

Yes! The ones I have seem usually turn sour real quick. It is my
opinion that if a pond requires a filter (and hence, maintenance), only
someone who is really into the pond and/or aquatic life in general will
take the time and effort to maintain the systems over the years.
Usually it's kept up for a season or two then things break or get
neglected. A "simple" pond will tend to live longer but it is still
subject to the effort spent by the owner.

Thanks for the thoughts Derek.

-Bruce



The biggest problem with solar powered pump systems is that the biofilter
needs actively flowing water to work, and it quickly dies from lack of
oxygen when the pump is off.

I doubt i'll save money 8^)

Not likely :-)
--
derek