On demand Pump

I currently use a 12V DC on demand Flo Jet that puts out 2.9 Gpm at 40 psi for my cabin. The problem lies with my on demand hot water heater that requires 2.1 gpm flo to operate properly. So sometimes the heater will kick off.
So I am looking into getting a better on demand pump. I have 24 volt solar setup with 1500 watt psw inverter so I have a choice of 12V/24V DC or 110V AC type. These are the three I am looking into, just not totally sure what
one is my best choice. Any input would help..
make model switch gpm/lpm psi/bar max draw valves/diaphram ports volts connection
seaflo SFDP1-050-060-51 Demand 5.0/18.9 60/4.1 17.0A EPDM/Santoprene 1/2"-14 MNPT 12V DC 2-Pin/Leads
seaflo SFDP2-050-060-51 Demand 5.0/18.9 60/4.1 9.0A EPDM/Santoprene 1/2"-14 MNPT 24V DC 2-Pin/Leads
seaflo SFDPA1-045-040-41 Demand 4.5/17 40/2.8 1.0A EPDM/Santoprene Quick connect 110V AC US grounded
So I am looking into getting a better on demand pump. I have 24 volt solar setup with 1500 watt psw inverter so I have a choice of 12V/24V DC or 110V AC type. These are the three I am looking into, just not totally sure what
one is my best choice. Any input would help..
make model switch gpm/lpm psi/bar max draw valves/diaphram ports volts connection
seaflo SFDP1-050-060-51 Demand 5.0/18.9 60/4.1 17.0A EPDM/Santoprene 1/2"-14 MNPT 12V DC 2-Pin/Leads
seaflo SFDP2-050-060-51 Demand 5.0/18.9 60/4.1 9.0A EPDM/Santoprene 1/2"-14 MNPT 24V DC 2-Pin/Leads
seaflo SFDPA1-045-040-41 Demand 4.5/17 40/2.8 1.0A EPDM/Santoprene Quick connect 110V AC US grounded
Comments
OR, better yet I think, I'd find a water heater that would work with a reduced flow rate and also save water. There are on demand heaters that will start on less than 0.6 GPM and continue to heat water with a flow through the water heater as low as 0.26 GPM. (Rinnai) What's the flow rate of the shower head or sink faucets you have? The fed standard is a maximum of 2.5 GPM and ours are all less than that. Also that is full flow, hot and cold mixed, so the flow through the water heater should be less than the flow out the faucet/shower. No wonder then that your heater will shut off at times when cold is being mixed with the hot. That results in less than the minimum flow through the heater. I am not sure a higher capacity pump will solve the problem.
Also be sure to avoid the 120 volt AC demand pumps... they work on high voltage DC which will ruin the negative brush.
http://forum.solar-electric.com/forum/solar-electric-power-wind-power-balance-of-system/solar-water-pumping/21544
--vtMaps
I know people who just crack open the sink hot water faucet while they shower. Wasteful, but it works.
I am available for custom hardware/firmware development
How do you power the demand water heater?
Just curious.
installed Feb 2014 at 19.796189° -70.893594°, Classic 150 + WBJR, KISAE SW1210, MN Battery Monitor, IOTA DLS 55/IQ4, 4- Solar World 275w, 4-6v x 225ah Trace Batteries
installed Feb 2015 at 19.795733° -70.893372°, same components as above
Honda PowerMate PC0497000, 7000/8750w generator - powers the well and chargers maybe once a week
That is hilarious! Those on demand heaters are supposed to save money and from what I have seen, they are more trouble than they are worth.
Very fussy about quality of water going into them (silt and minerals) fussy about pressure and flow and more expensive to purchase initially.
My 5 gallon (oops 6 gallon....) RV heater is starting its 32nd season and is fed with lake water containing a fair amount of silt and still works fine.
I think there is something to be said for the traditional water heater that has been a staple for so many years.
One thing never mentioned is the fact that any waste heat radiated from the tank will tend to heat the structure that contains it.
Not great everywhere, but actually a benefit in Canada where the furnace runs most of 8 months oer year.
not to mention that you need a tank to heat water with the sun, the old fashioned way.....
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Late to this conversation but...
I had the exact same issue with my propane water heater. My fix was to change the 1 handle faucet for the 2 handle faucet: open the hot side fully and then adjust temp with the cold side.
The only downside side now is that when I cycle the the hot water on and off (as when I'm shaving) the darn water heater does not fire fast enough before I turn the water off. The work around for that was to leave the hot water running for the task duration. Wasteful...
If that water heater dies, I will go to a basic water heater with tank...
Louis R.
http://zoneblue.org/cms/page.php?view=off-grid-solar