On demand Pump

boomadgeboomadge Solar Expert Posts: 25 ✭✭
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

Comments

  • Mountain DonMountain Don Solar Expert Posts: 494 ✭✭✭
    If the battery bank is 24 volt, I'd go for the 24 volt version myself.

    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.
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
  • boomadgeboomadge Solar Expert Posts: 25 ✭✭
    Its the shower that only gives me issues, so i changed the shower head to a 1.6 gpm and it helped but when you combine cold and hot together it likes to trip the tank. I have made adjustments with tank flo and can resolve the issue most times, but its a pain to keep adjusting. Was thinking a bit stronger pump might be better.
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    I agree with Don... get a better water heater. I think your problem is not the pump... If your showerhead only allows 1.6 gpm, and your water heater needs 2.1 gpm, the system wn't work no matter how large the pump is.

    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
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • jonrjonr Solar Expert Posts: 1,384 ✭✭✭✭
    Get a bucket and measure the flow rate. You will need approximately the rated 2.9 gpm of total flow to satisfy the water heater's need for 2.1 gpm of hot water flow (maybe more, it varies with the temp of the incoming water). The wrong head and/or small pipes might be too restrictive and something like a 60 psi 4+ gpm pump would help. A higher flow head would be cheaper.

    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

  • hemmjohemmjo Solar Expert Posts: 90 ✭✭
    Why not install a pressure tank to provide the short term flow you need save the on/off cycles of the pump?

    How do you power the demand water heater?

    Just curious.
    Two systems in the Dominican Republic  http://villagemountainmission.org/
    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






  • boomadgeboomadge Solar Expert Posts: 25 ✭✭
    It is propane with electronic ignition, and works perfect If I use hot/cold at kitchen sink. When using the shower open hot valve tank kicks on fine, then slowly open cold to get temp of water good. jump in shower and randomly without warning I can hear the on demand heater shut down and then the water is naturally cold. Shut off cold/hot valves repeat process..
  • 706jim706jim Solar Expert Posts: 371 ✭✭✭✭
    jonr wrote: »
    I know people who just crack open the sink hot water faucet while they shower. Wasteful, but it works.

    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.


    Island cottage solar system with 2400 watts of panels, 1kw facing southeast 1kw facing southwest 400watt ancient Arco's facing south.Trace DR1524 MSW inverter, Outback Flexmax 80 MPPT charge controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 27th year.
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,508 ✭✭✭✭✭
    706jim wrote: »

    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.....
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • petertearaipetertearai Solar Expert Posts: 446 ✭✭✭✭
    What about a booster pump . Turn on when having a shower.
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home 
  • boomadgeboomadge Solar Expert Posts: 25 ✭✭
    I replaced the the flowjet with a seaflo 5.5 gpm and problem solved. Woot no more hot water issues..old pump might of been tired.
  • DeveakDeveak Solar Expert Posts: 38 ✭✭
    whats the pressure like on the seaflo? I m looking for a good pump but i cant seem to find any that can handle decent pressure or flow. Its one or the other. They advertise 45 psi but its at 1 gpm or so. I want 2 gallons per minute at 45 psi.
  • ramlouiramloui Solar Expert Posts: 103 ✭✭
    edited January 2016 #13

    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.

    Off-grid cabin in northern Quebec: 6 x 250 W Conergy panels, FM80, 4 x 6V CR430 in series (24V nominal), Magnum MS4024-PAE
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    A quick fix for this might be to just add another identical flojet in parallel. Those pumps run quite well in parallel. But agree with the others the problem is the califont. The (cheap) unbranded one we use runs fine off a shurflo 2088.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • just startingjust starting Registered Users Posts: 235 ✭✭✭
    I have a 4.3 gpm marey flowthro water heater and a 5gpm 60 psi seaflow pump with a 20 gal pressure tank my water tank sometimes freezes and with ice chunks in tank. water still gets to 125°f and I'm at 10k above sea level been in place for 17 months works great
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
  • just startingjust starting Registered Users Posts: 235 ✭✭✭
    Had to bypass pressure switch in pump and put in a real pressure switch
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
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