Hey Dan!
A 2-wire pump does not have a built-in capacitor. It has NO capacitor. Starting
any single-phase induction motor is like a one legged bicyclist. Without a
start winding and capacitor (and a device to switch it out), it’s a LAME
one-legged bicyclist. Only marketed for those who must have the cheapest option
(on grid power).
Now, you CAN use Franklin MonoDrive with a 3-wire single-phase pump, but that
is (in my understanding) far inferior to a true variable-speed drive combined
with a 3-phase pump. I imagine the only reason they make a single-phase version
is to retrofit existing 1-ph 3-wire pumps, and that’s fine … BUT if replacing
the WHOLE pump, why not do it right and go 3-phase. A 3-ph motor requires no
special starting circuit, so it’s much simpler and in general, it’s cheaper
than a 1-ph cap-start motor! Also, I expect the electronics for V speed would
be cheaper. So ...
I strongly suggest you get a quote on the Franklin 3-ph SubDrive system. It
will draw a gentle starting rise of maybe 2X … not really a surge at all. It
can work in either soft-start full-speed mode, to work like any conventional
pressure pump, or as a “constant pressure” pump. The latter will rack up many
hours running at reduced speed which is also reduced pumping efficiency. It’s
intended for using with tiny pressure tanks, but not so energy-efficient. I’d
recommend keeping the full-size normal p tank, and using full-speed mode.
Incidentally, 3-ph variable speed drive is at the heart of solar pump
controllers made for conventional pumps. And those items are for non-battery
systems! They are only made for 3-ph motors. Nobody makes one for 1-ph. even
though there would be high demand. Above 2HP, all AC subs are 3ph. Solar
controllers are handling them PV-direct approaching 100 kW now!
I’ve been researching this whole topic for my book (Solar Water Pumping, Taylor
& Francis for 2017) and I think it’s the best advice for your customer. Any of
you other guys have experience with VS 3-ph and constant pressure pumps?
Please tell me what you end up recommending, and how it works out!
RE John B’s previous comment: "All the things us solar guys get involved with
...” All I can say is:
Somebody’s got to do it.
Windy
or in my case: Somebody’s got to write about it!
http://www.windydankoff.com
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