[RE-wrenches] Retrofit variable speed drive to old well pump? // Franklin products

[Windy Dankoff]

Dan,

I stand corrected on my advice. This Franklin document describes a MonoDrive 2W model. 2W stands for 2-wire pump! I didn’t know it existed. 

http://franklinwater.com/media/116400/225417101_m1560_sd_manual_05-13_web.pdf

Nevertheless, I would expect inferior results and would not use it to retrofit an old 2-wire pump if it may be on its last legs. However, it IS what you are asking for, to replacing the pump! It’s up to you to determine if it’s the BEST option in the short and long run.

I would run this by a very knowlegable Franklin distributor, as well as your local driller.

Keep Shining // Windy



> On Dec 13, 2016, at 1:39 PM, Windy Dankoff <windydankoff at mac.com> wrote:
> 
> 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
>