low flow DC pressure pump advise

System

I'm looking for a water pump to run a 'misting' system, like you might use on a patio, in a remote, off grid location, on the cheap. I'd like something I could run off a marine/rv style battery for at least 12 hours per charge.

the misting system I have runs off garden hose water, so I'm assuming thats 60PSI or so... It uses about 4 gallons per hour, and I'm planning on using a 100-200 gallon water tank as the supply, as this will be used at a campout astronomy event for several days in a row (assuming a portable generator can recharge the battery once a day)

so... as I figure it, the pump has to be comfortable delivering ONLY 4 gallons/hour (thats like 8 fl. ounces per minute) at 60psi, and not draw much over about 4 amps at 12V.

anyone got any ideas where I can find a inexpensive pump that will do this? Would a Shurflo 8000 work for this low flow application? Do you think I'll need a pressure accumulator tank?

icarus

Re: low flow DC pressure pump advise

Does your current system (on grid) just run off of water pressure? If so any small pump that can pressurize your tank should work. Does the mister need a momentary blast of water, or constant pressure? If it needs a blast, then a normally closed solenoid valve could open to blast through a nozzle. If it is a continuious mist, it should have a range of psi that it needs at the nozzle. Should be easy to rig up a simple (shurflow or other) pump to keep the tank within the required range.

Tony

System2

Re: low flow DC pressure pump advise

its continuous, and yes, it runs off garden hose pressure, which I'm guessing is 50-70PSI. I've asked hte mister vendor whats the acceptible pressure range, their literature is quite vague on this.

I've tried running the misting kit off a pressurized garden sprayer bottle (the kind with a hand air pump in the lid) and even pumped about as hard as those pumps will allow, the pressure is somewhat inadequate to generate a good mist, i'm guessing its around 30psi from the force required to pump it and the size of the pump.

I just looked up the ShurFlo 8000 on their website, ouch, 7 amps... that would suck our batteries down fast... OTOH, with a 2G or 4G pressure tank, I guess the duty cycle would be fairly low at 2G/hour total consumption. But, I can't seem to find anything smaller that would do the trick.

icarus

Re: low flow DC pressure pump advise

Just for example. My shurflo submersible draws 7 amps (12vdc) but it pumps ~4gpm into 60 psi. If you are only going to 4 gph your duty cycle would be very short. I would consider a fairly large P-tank so that the pump wouldn't have to run very often. In rough numbers, let say you have 20 gallons of draw on a p-tank, that would be about 5 minutes of running to fill, every 4 hours, or ~ 20 minutes per day. Let's round it up to 1/2 hour. So 7 amps X .5 hours = 3.5 amp/amp/hours/day, if you are going 24/7, not too bad. If you had a ~75 ah battery, and only wanted to draw down 50% you could run your batter ~10 days without recharging.

Tony

Brock

Re: low flow DC pressure pump advise

I would agree with Tony, just get a larger pressure tank and use a "standard" sized marine pump. Sure it might take more amps than your thinking while running but it shouldn’t run very often as Tony pointed out. On some of the larger boat I have worked on I swapped out larger pumps for smaller ones and bigger tanks. I often found larger pumps pulling the voltage down to 8 volts while running, which is what I think killed them. I replaced them with smaller units and the voltage was up in the 11 range and actually had more water with a shower running and the pump ran less and used less power to boot.