A contrary position: two pumps has long been the traditional way of
dealing with deep wells off grid, using a DC pressure pump and an
AC/generator or PV-direct pump. That has been changing, as Flex pumps
go deeper, as AC pumps are offered with soft-start, and as inverters
have become available with both more capacity and split-phase output.
But here are a few benefits of two pump systems:
1) In a single-pump system, if the pump goes down, you are out of
water, which is worse than being out of electricity. With two pumps, if
the well pump fails you have one tank's worth of water to live on until
it can be pulled and fixed or replaced, providing you have a low tank
alarm and learn of the failure before the tank goes dry.
2) If a gennie or inverter fails, you still have water.
3) You gain a small reservoir of stored water to tap in case of a fire
- especially valuable in a remote location with a VFD.
4) In all my years I have never heard of sickness from stored water.
I'd expect that if had happened to one or more of my off-grid clients
I'd have heard about it. Part of this may be that I recommend a buried
tank, which prevents light getting in and allowing microorganism
growth. Not expecting trouble, I haven't cleaned, disinfected, or
filtered our family'sburied well storage tank in ten years of
continuous use - just lucky, I guess.
I'm doing a single-pump system now, running off of a Magnum 4024AE, for
an occasional-use cabin, as it's way cheaper than dual-pump and is used
intermittently. I expect that we will do more single-pump systems in
coming years, but we have generally had good experience with dual-pump
systems.
On 6/15/2010 9:44 PM, R Ray Walters wrote:
We've done a few set ups with storage cisterns too. While
it definitely takes the load off the inverters, it has some downsides:
1) if the genie goes down, you are out of water, which is worse
than being out of electricity.
2) Even the best cisterns filled from a clean water source, get
nasty after a while and need regular chlorination to be safe.
Systems with tanks and float switches will fail, not if but
when. After a few years, the float hangs up or goes bad, and then
either the tank goes dry, or overflows.
I've lived with such a system for almost 10 years (along with
mild dysentery), and was glad to convert to a single pump system. Less
hassle, and cleaner water (dysentery cleared up amazingly).
Taos realtors do water quality tests on most real estate sales,
and guess what? The cisterns were not passing. (chloroform bacteria
levels too high)
Since I'm all about safety, I quit putting my name on these
potential disease pools, and started converting systems over.
The closer the water system is to normal, the less liability you
are assuming.
R. Walters
Solar Engineer
On Jun 15, 2010, at 3:45 PM, Jeff Yago wrote:
We
designed and installed a few off grid systems out west about 10 years
ago and found all the wells there drill halfway to China. Since here
in Virginia most wells hit quality water at 30 feet, we know there was
no way the single SW4048 could handle a 2 or 3 HP pump.
So we installed a 300 gallon plastic tank, ( the non-pressurized kind
they sell farmers to store chemicals) on the concrete floor in the
basement, and used a float switch to signal the 12 kW generator to
start and run the deep well pump until the tank was full. Since the
float ball was adjustable, this usually means the pump and generator
only runs every few days, and since it takes over an hour to refill, we
good a good charge on the batteries at the same time.
We installed a DC pressure pump at the bottom outlet of this tank which
supplies the regular expansion tank and house through a carbon filter
and a ultra-violet filter first. We later found we needed a sand filter
on the line from the well to the tank as after a year you will get a
layer of sand in the bottom which the DC gear pump does not like.
These tanks are cheap, strong, clean, and you can get about any size
and shape, including some "flat" designs than will go sideways through
a door and look like a stack of pancakes.
The 4 kW inverter runs all house loads and has no major large motor
loads. The generator not only easily runs the well pump and charges
the batteries when solar is low, but we added several outside faucets
on the well pump side of the tank for fire protection and car washing.
Here is a link to photos ----> http://www.backwoodshome.com/articles2/yago71.html
Hope this helps,
Jeff Yago
DTI Solar
Netscape. Just the Net You Need.
List sponsored by Home Power magazine
List Address: [email protected]
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
_______________________________________________
List sponsored by Home Power magazine
List Address: [email protected]
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
|
