RV style pump to fill a 86 gallon bladder tank?

[SupraSPL]

The brushed DC diaphragm pumps do get damned got after 15 minutes but they do work very efficiently compared to a 230V jet pump.

The 120V AC diaphragm pump makes sense in terms of not getting hot and doing the job with less starting current than the big pump and only taking a little longer to do the job.

If Ryobi/TTi can make nice $50 brushless drills, you'd think there would be tons of cheap 12V 18V 24V brushless diaphragm pumps on the market. Hopefully that will be coming soon. A 24V 12.5A (300W) brushless diaphragm pump would probably do the same job as a 120V 10A (1200VA) jet pump and without the massive startup current and without getting hot.

 

[12VoltInstalls]

A 24V 12.5A (300W) brushless diaphragm pump would probably do the same job as a 120V 10A (1200VA) jet pump and without the massive startup current and without getting hot.

Watts is in essence an expression of ‘work.’

While understanding they’re differing designs… I’m an idiot. Please explain to me how one does the same work with 25% of the watts.

 

[SupraSPL]

Watts is in essence an expression of ‘work.’

While understanding they’re differing designs… I’m an idiot. Please explain to me how one does the same work with 25% of the watts.

A very good question. The VA (volt amps) figure is basically Watts but with imperfect power factor taken into account. Misalignment of volt and amp waves on AC circuits increases current draw. Power utilities don't bill residential based on power factor so when you're on the grid don't have to worry too much about imperfect pf although it does have to be taken into account for wire size. When you are off grid your batteries have to provide that extra power along with the extra inverter losses on top. So that is one part of the answer.

Simple and cheap single phase AC motors are inefficient on top of that. They are brushless and reliable but 1350 VA to get 1/2 HP of work, that seems pretty bad. Cheap DC motors are also inefficient (65%?) but in this case maybe that is an improvement.

Another part is diaphragm vs centrifugal. I'd estimate the (non electrical) centrifugal pump efficiency about 60% but have been unable to find any data about small diaphragm pump efficiency.

For empirical proof, a 260 watt 12V RV pump (Vevor $90) draws water from a shallow sand point well and pressurize my tank to 53 psi in 46 seconds vs my 120V 11.3A (1350VA) Goulds (1/2hp) taking 39 seconds. So the 12V is 5X more efficient and I did verify they both pumped about 2.5 gallons into the pressure tank and the results repeatable.

That said, both pumps use very little power overall (40wh/day and 200wh/day) per person so the energy savings isn't huge but due of the startup current of the big pump, I would need 1 less 3000 watt inverter in my off grid system if I use the 12V pump which saves another 120wh/day in standby power.

The 12V pump does have downsides, the 260W one is too loud for normal household use and the sound is inside the water pipes so there's not much you can do to quiet it down. It is brushed so longevity is unknown whereas the Goulds is bulletproof for decades. The 220W 12V version is quiet but overtemp protection kicks on and off after 15-20 min of shower.

 

[12VoltInstalls]

The 12V pump does have downsides…It is brushed so longevity is unknown whereas the Goulds is bulletproof for decades

Hear that but I have a 12.V 6.5A flojet in service for ?5? years of daily use with no signs of giving up.
So it appears not to be a worry ? since that puts it in the $20/year category at this point, and every day it lasts, the amortized cost shrinks.

 

[Doggydogworld]

In addition to the power factor issues mentioned above, jet pump ejectors use a very simple but inefficient pressure drop mechanism. So even with perfect power factor they'd be much less efficient than a decent positive displacement pump like a diaphragm pump.

 

[740GLE]

So we have a camp with a dug well that gravity feeds to the camp at about 1-2 psi.

For the past two seasons I’ve used a cheap ecoflow (came with our L10 on demand water heater) 12v diaphragm pump plus a 25 gallon pressure tank. I have the pump wired to an adjustable well pressure switch. So far no issues with the AC rated switch working with the DC motor and breaking the 8 or so running amps.

The pump works flawlessly except the pressure taps out at about 35-38psi. This poses a challenge for our Moen auto balancing shower valve, the low PSI never allows you you adjust the temp, it’s full hot, cold water doesn’t cut in.

So far we’ve managed by running the hot water faucet a small amount but def not ideal.

So in preparation of upgrading our entire system from 12v to 24v, I’ve started looking at 24vdc pumps.

Anyone have any experience with this one, Or higher pressure diaphragm pumps in general?

Aquatec 5513-2F12-B736 Pump 5.15 gpm, 1/2 FPT, 24V DC NO Cord

The Aquatec 550 Series Pumps are used to either draw water from a holding tank and pressurize it, or boost pressure from a low pressure source. Although designed to operate intermittently, many 550 versions can run continuously for several hours at a time. These pumps can be operated either in...

www.freshwatersystems.com

With my well pump switch, I figure I’ll be able to adjust it down 40-55psi and it should solve my shower issues

 

[Larry12]

I use only Shurflo RV style pumps and I install water systems for people who want to move community water up a mountain to rural homesites. Yes they can run dry for six hours no problem. Someone let one run dry for a week and fried it. They have to be plumbed in a box or under a roof as they are for "indoor use only". The pressure tank makes life so much better, the pump comes on once, pressurizes the tank and system and then shuts off and doesn't come on again until you flush the toilet 2 or 3 times (12 gallon bladder pressure tank at 28 psi). Without it the motor has to cycle all the time when you run water, very annoying sound and presumably a shorter lifespan (maybe, though I used one without a tank for 10 years and had no problem). These are powerful and use little power. I use 3 in series to lift water ~ 90 meters.

 

[TGPB]

Been using a Johnson 64534 Washdown Pump 12v 5.2gpm to pressurize our bladder pressure tank at 70 PSI for the last 13 years. Works great!!!

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