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

[Allan Sindelar]

Dan,
I have never had to work with a two-wire pump, so I'm on shaky ground 
here, but I refer back to what I learned years ago from Windy. The third 
wire in a three-wire pump carries the starting surge from the capacitor. 
A two-wire pump lacks this, and thus gets its entire surge-under-load 
from the AC source. This will be intrinsically difficult for an 
inverter, as compared to grid. So Shasta's surge question below is 
relevant. I'd determine both instantaneous surge and voltage drop; it 
may be that the combination - of battery voltage leading to reduced AC 
from the Magnum, voltage drop on the wires, and simply using the Magnum 
- will keep it always problematic.

Years ago, when Dankoff Solar Products was in its prime as a 
distributor, Phil U did a load capacity test on various inverters of the 
time, including the Magnum MS4024. It had remarkably strong surge 
capacity, but did this by allowing a much greater voltage drop - down to 
around 80 VAC, if I recall, on a 120 VAC inverter.

You may be dealing with a structural issue, for which upgrading the pump 
may be the best solution.
Allan

*Allan Sindelar*
allan at sindelarsolar.com <mailto:allan at sindelarsolar.com>
NABCEP Certified PV Installation Professional
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder (Retired), Positive Energy, Inc.
*505 780-2738 cell*

**

On 12/10/2016 11:06 AM, Shasta Daiku wrote:
> Dan,
> Have you measured start up current?
>
>> On Dec 10, 2016, at 9:39 AM, Drake 
>> <drake.chamberlin at redwoodalliance.org 
>> <mailto:drake.chamberlin at redwoodalliance.org>> wrote:
>>
>> The usual wire I see running to most pumps is #10 UF cable. A 450 
>> foot run might create too much voltage drop. Maybe a buck boost 
>> transformer would help.
>>
>> Drake
>>
>> At 12:11 PM 12/10/2016, you wrote:
>>> Hi Bob; I checked the connections for corrosion, and the wire size 
>>> looks like "the usual" for up here in this area, it's only about 100 
>>> feet and the usual well depth around here is 350 ft. Running stouter 
>>> wire might be an option to consider...but that's a lot of digging. 
>>> I'm just hoping VSD might be a quick and dirty solution.
>>>
>>> Dan Fink
>>> Adjunct Professor of Solar Energy Technology, Ecotech Institute
>>> IREC Certified Instructorâ„¢ for:Â
>>> ~ PV Installation Professional
>>> ~ Small Wind Installer
>>> Executive Director, Buckville Energy
>>> NABCEP Registered Continuing Education Providers™
>>> 970.672.4342 <ttel:970.672.4342>
>>>
>>> Â
>>>
>>> On Sat, Dec 10, 2016 at 9:53 AM, RE Ellison <reellison at gmail.com 
>>> <mailto:reellison at gmail.com>> wrote:
>>>
>>>     Don't know about the variable speed but are the wires feeding
>>>     the pump large enough for the distance?
>>>     Sounds like it might be voltage starved because of a high
>>>     resistance / bad connection or a long wire run and the need for
>>>     a larger wire ?
>>>
>>>     Just a thought,
>>>     Bob Ellison
>>>
>>>     On Dec 10, 2016, at 11:39 AM, Dan Fink <danbob88 at gmail.com
>>>     <mailto:danbob88 at gmail.com>> wrote:
>>>
>>>>         Esteemed Wrenches;
>>>>
>>>>         I have a client in a very remote mountain location who is
>>>>         having trouble with his inverter starting his well pump
>>>>         when battery state of charge is below 75%. 24v system,
>>>>         Magnum inverter.Â
>>>>
>>>>         It's a 2-wire pump, unknown age, model, horsepower, or well
>>>>         depth. It has always given him trouble, that's why he
>>>>         upgraded to 24v, and the situation is better, but not ideal
>>>>         yet. I don't think adding a hard start capacitor would help
>>>>         as there should be one inside the pump itself, though I
>>>>         suppose it could be blown.
>>>>
>>>>         Because of the distance and the rough road, it would be
>>>>         super expensive for a well company to come up there, pull
>>>>         the old pump and set a new, modern soft-start one.
>>>>
>>>>         Has anyone here had any experience with retrofitting
>>>>         variable speed drive units to an unknown pump? If so, what
>>>>         models have you tried and what do you prefer?
>>>>
>>>>         Thanks;Â
>>>>
>>>>         Dan Fink
>>>>         Adjunct Professor of Solar Energy Technology, Ecotech Institute
>>>>         IREC Certified Instructor™ for:Â
>>>
>>
>>
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