View Full Version : Suggestions for an off-grid booster pump?
June 8th, 2009, 9:50 PDT
I called our host to order a 115V Flowlight from Conergy, but they suggested that I should seek a water pump from Goulds instead with no recommendation of model etc.
I think our needs are pretty low and the storage tank is about 12 ft above point of use. When calculating pump efficiency do I need to account for only the pressure to be added (say 25psi) or the total pressure (say 30psi)? Would any efficiency gain available here be more available with one type of pump than another, say jet pump vs. diaphragm pump?
We do plan to run a washing machine, but may gravity feed that and the toilet by not pressurizing the whole system. I've even thought about only pressurizing the hot water, but suspect said practice might cause problems at the mixing valves. Any thoughts on that?
Anyway, I commonly see the Flowlight pumps suggested for off-grid boosting applications, but haven't really seen other booster pumps suggested. Does anyone have experience or opinions about other booster pumps? Does anyone know of a reason not to go with the Flowlight?
June 8th, 2009, 14:36 PDT
Are you off grid full time? How many people using the house. Where are you pumping water out of,,, surface,, lake, creek,, shallow or deep well?
Are you pumping into a gravity tank,,, and then pumping into a pressure tank? If so,, why the two tank system?
June 8th, 2009, 15:22 PDT
Ok, the basics: (Sorry you had to ask for them.)
My wife and I are off grid full time in a small house. We use an air-lift to pump water 30 feet from a well in sandy conditions to a large storage tank on top of a small hill. This storage tank is large enough to store a couple weeks worth of water, but I like to pump more often as the pumping action aerates the water as well. The well has a 2" casing which limits our options in regards to pumps. Currently, the air is from a gasoline powered compressor but I hope to fabricate a suitable windmill compressor in the future.
Unfortunately, the hill isn't tall enough to provide a good shower or the required pressure to operate our Takagi Tk Jr. Hence, our need for a booster pump and pressure tank.
Another possibility could be a reciprocating pump that filled the pressure tank directly, but I'm concerned that the sandy conditions would be hard on a reciprocating pump - almost certainly at high volume - perhaps at low volume too.
We filter the water as it leaves the storage tank, but the ability of a pump to handle some grit would be a plus.
Any advice you can offer would be greatly appreciated!
June 8th, 2009, 17:00 PDT
I can't comment on the air well pump, as I know less than zero about them. I think it a sound strategy to pump large amounts rarely rather than small amounts often.
As for pumping from the storage tank into the house. A simple pressure tank, down hill from the gravity tank,, boosted by a small 12vdc (or 24-48) shurfo type pump works pretty well. You can pump into a large pressure tank once a day when the sun is out,, or just let the pump cycle as needed. Then you would have water pressure to the faucets just like a "real" house,, and any demand water heater will work fine, as will the washing machine.
Such a system wouldn't draw too much power since it is only pumping from ~5 psi (the pressure from the gravity, to ~50 psi and not having to lift at all.
June 8th, 2009, 18:19 PDT
I've got the same booster pump you're looking at. My cistern tank water level is above the pump position, so no lift...like you. The 2.5 gpm that it delivers is fine for our TkJr, and more than enough for modern low flow shower heads, washers, sinks and toilets.
It's power consumption is great. I put a Kill a watt meter on it for a week and it used less than 300 watt hours in that time. It's cycle for boosting from 30 to 50 psi on a biiiiig pressure tank is about 3 minutes, several times per day. The draw varies from 120-140watts, higher just before shutoff.
The filter on the suction side of the pump needs to be changed sometimes. I started hearing clacking sounds coming from the pump and thought something had gotten past the filter...ah yes the filter...it was clogging up (1 year without changing it) and the impeller was cavitating. The cavitation would eventually pit the impeller and probably cause premature failure. If it's not in your house be sure to listen to it cycle every so often.
Good luck, I really like ours.
June 8th, 2009, 18:34 PDT
Well, that's just about what I figured except that I thought of using an AC pump to simplify wiring and since I'm running a 48 volt battery bank. I didn't realize that there was a Shurflo for 48 volts. Do you have a model number?
I guess I was pretty much planning on the Flowlight all along and surprised when they steered me away from it.
One thought to reduce demand on the pump is to only pressurize the hot water, but I wonder if that wouldn't cause problems at the mixing valve - and encourage the use of hot water when it is not needed.
Another is to leave the toilet and washing machine cold supply on the gravity feed and pressurize the rest. I like that idea.
Another idea to encourage the filling of a pressure tank during the day, without having to manually control the pump, is to put two pressure switches on the pressure side, one set to a higher pressure than the other. Then the Flexmax could trigger the higher pressure switch when it goes in to float or something.
I don't really need to take it that far, but I like thinking about the possibilities.
Do you find the Shurflo pumps to be durable? I think I remember reading that you use a submersible, but not a booster?
Thanks for your thoughts on this!
June 8th, 2009, 18:52 PDT
When you say you have the one I'm looking at, you mean the Conergy Flowlight, right?
How big is your pressure tank?
I was planning on a large pressure tank as well, but am limited in space. I can fit a 120 gallon (50 gallon capacity) tank no problem, or a larger one if I could find a large horizontal pressure tank.
June 8th, 2009, 18:56 PDT
To be perfectly honest, I don't think they are available in 48 vdc,, but a voltage reducer might work pretty well. (I have a link from another vender but I don't want to link it here out of deference to our host. Send me a note if you wish a link).
24 vdc are available.
Shurflos come in a number of different qualities,,, from simple RV to industrial. I have had good luck with the simple ones. They are field rebuldable and are pretty reliable. And they are comparatively cheap. The reality is that the pump capacity can be quite small if the P-tank is large the pump doesn't have to pump the same volume as you might draw. For example,, you might logically use 2-3 gpm,, but if you have 30-50 in the tank,, you can draw down to cut in pressure,,continue to draw, with the tank supplying the 2-3 gpm for a pretty good long while,, while the pump is putting it back in a say 1 gpm.
I have a shurflo submersible and I'm very happy with it. I think it delivers ~1.5 gpm into 60 psi drawing ~4 amps 12vdc. (I boost it to run on 24vdc.) The one rub with most shurflos is that they are a diaphragm type pump,,, and they do induce a bit of noise into the plumbing. You can mitigate the a bit by proper design,,but getting buzz from the plumbing can be an irritant. ( When I here the pump run late in the evening,, I will kill it at the breaker,,, and save the draw for when the sun comes up,, just to be a bit more efficient with the pv.)
If it were me,,I would pressurize the whole house for all the trouble it would be to do a dual system.
June 9th, 2009, 3:41 PDT
Yes, I have the 115vac Flowlight, and ditto Tony's point about pressurizing the whole house system. If you're going to pressurize at all, and not just rely on gravity pressure, then by all means do the whole house.
Our pressure tank is about 4.5'high by 2'accross, not sure of the # of gallons, but the pump only cycles a couple of times per day unless it's laundry day. It replaced an old jet pump, a real power hog.
The Flowlight boosters are available in 12, 24, 48vdc and 115vac (maybe even 240vac) voltages. If you've already got a sine wave inverter then there's probably not much power savings in going with the dc motor. The DC motor units are almost 2x the price of the AC motor units! (where I sourced them anyways) No brainer on that decision.
However, a whole house with DC wiring and appliances would be an interesting concept. Anyone make a DC toaster or coffee maker? Yes Tony, everything can be done with propane. What size inlet connector is on your computer, for a 20pound BBQ tank or smaller camping cylinder type?:D
June 9th, 2009, 5:39 PDT
They do make 12vdc coffee makers and toasters for the RV market. I don't recommend them for the same reasons that I don't recommend 120vac heat generating appliances.
I'm not sure I get the reference to propane power computer?
June 9th, 2009, 8:03 PDT
I think the propane powered computer will come out at about the same time as the nuclear powered impact wrench. When I was an auto mechanic, I was always asking the Snap-On guy for one of those. 8)
June 9th, 2009, 8:31 PDT
Oh, but I do have a nuclear powered impact wrench! I needed it last weekend on my step son's 1992 Subaru "Rust bucket".
June 9th, 2009, 9:45 PDT
I am thinking... A propane powered impact wrench--that would be exciting! :D
Found a propane powered fence post driver...
June 9th, 2009, 10:01 PDT
I shouldn't ever say this publicly, but I built a propane powered heat source for a composting toilet,,,, that exploded in my face while beta testing on the bench,,, and nearly severed my nose! Hundreds of stitches later with a plastic surgeon and all you can see is a faint circle through my nose and lower lip!
Don't play with gas lightly!
PS Forever known as a Turd burner! Not really a burner,,, just a heat source for the composter. Actually worked great,,, but cost way too much propane. BTW beware of composting toilets as they NEED heat to work,, and the 120 vac is ~500 watts,,, hence the idea of propane!
June 9th, 2009, 10:06 PDT
Yea--I have myself a good set of burns on the back of my hand and removed my eyebrows when lighting a natural gas water--it lit real good. :cry:
Powered by vBulletin® Version 4.1.10 Copyright © 2013 vBulletin Solutions, Inc. All rights reserved.