Pv water heating

martinruss7
martinruss7 Registered Users Posts: 23 ✭✭
in Solar Beginners Corner #1
Wanting to Input a 48v battery bank(60v) into a 120v 2000 watt water heater element. Is this possible and enough power to heat 40 gal tank?
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #2
    Simply connecting a load to a battery without control would be a recipe for disaster.

    A diversion controller can be used to divert unused PV current once the battery is fully charged, using excess to heat water.

    Without details of your system it is impossible to answer your question or suggest solutions, there are ways to do what I think you have in mind but anyone here will need details, the more the better, controller model, battery capacity, array size etc.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    edited November 2016 #3
    Might be OK if you retain the thermostat - just slower to heat up.

    I looked at this some and it makes sense to me.  Maybe you should consider running direct from PV.

    http://www.ebay.com/itm/Solar-Water-Heater-EZ-Kit-Save-No-Pipe-Changes-Hot-Water-System-PV-MPPT-/302144306890

    I am available for custom hardware/firmware development

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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #4
    martinruss7 said:
    Wanting to Input a 48v battery bank(60v) into a 120v 2000 watt water heater element. Is this possible and enough power to heat 40 gal tank?
    If you are asking if you could hook up 60 volts DC directly. It should be possible. It has been recommended to me to hook it up through a relay attached to the thermostat. I guess some thermostats are pretty basic and create enough of a gap to handle the shutdown, others might arc and/or even bind the contact (bad words, right idea) To give you an idea, a 2000 watt at 120 volt thermostat will run at @500 watts at 60 volts (1/2 the voltage = 1/4 the load)

    I'm running a 3600 watt 240 element at 120 volts on my 30 gallon water heater. It runs at 900 watts, and It takes a while to lift the temps. It's roughly 7-10 degrees per hour. With 40 gallons to heat and a 500 watt heating element you might be looking at a couple days of heating while the sun's out.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • martinruss7
    martinruss7 Registered Users Posts: 23 ✭✭
    #5
    Yes I have a dump load controller that I can configure dump voltage set point
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  • martinruss7
    martinruss7 Registered Users Posts: 23 ✭✭
    #6
    My array size is 10 72 cell 320 watt panels
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  • Anawa
    Anawa Solar Expert Posts: 225 ✭✭✭
    #7
    In March of 2015, I sought guidance from the forum for my PV water heating system via "auxiliary load" through the controller. The thread is long, but comprehensive as many point-of-views were shared. At the end of the thread, I posted a very detailed wiring diagram in PDF form that you may find useful. My system has been operational since April 2015 and heats water effectively. The set-up cost me about $180 including relays, breakers, breaker box, wiring and electrical connection, etc. I mention this as the overall cost is something you may want to consider.

    I may have an issue with where I configured the DC controller wire on the shunt, but that may only affect how the DC current is being monitored in the FNDC, not of any consequence with the water being heated. Perhaps another thread someday.

    If this thread interests you, I'm not knowledgeable enough to instruct you how to get to it. Maybe someone that knows how will weighin and advise.
    Paul 
    in Georgia

    System 1: PV- 410w Evergreen, Mppt- Blue Sky Solar Boost, Batt - 225ah Deka AGM, 12v led house lighting,
    System 2: PV- 215w Kyocera, PWM - Morningstar PS30, Batt- 225ah Deka GC's, 12v led house lighting, Dankoff 12v water pump,
    System 3: PV- 1.5kw Kyocera, Grundfos 11 SQF well pump, 3000 gal above ground water storage, dom water & irrigation,
    System 4: PV- 6.1kw Kyocera, Mppt- Outback FM80-2ea, Inverter- Outback FX3648-2ea, Batt- 804ah GB traction, Grundfos BMQE booster pump 240v, Mitsibushi mini-splits 240v, 18k and 15k
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #8
    As Photowit said half the voltage equals quarter the load, in order to heat a 2000W 120V 40 gallon water heater it wold not work that we'll @ 500W, you would need in the region of 8Kw heating elements to achieve the same peformamce at the rated 120V AC, not prectical but wasted energy is energy wasted, perhaps pre warming and feeding into an instantaneous water heater could be the answer, not sure.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
    · Share on Twitter
  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #9
    Anawa said:
    In March of 2015, I sought guidance from the forum for my PV water heating system via "auxiliary load" through the controller. The thread is long, but comprehensive as many point-of-views were shared.
    I think this is the thread;
    http://forum.solar-electric.com/discussion/332880/series-piped-water-heaters-opportunity-load-and-propane#latest

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Anawa
    Anawa Solar Expert Posts: 225 ✭✭✭
    #10
    Yep, that's it. Thanks PW.
    Paul 
    in Georgia

    System 1: PV- 410w Evergreen, Mppt- Blue Sky Solar Boost, Batt - 225ah Deka AGM, 12v led house lighting,
    System 2: PV- 215w Kyocera, PWM - Morningstar PS30, Batt- 225ah Deka GC's, 12v led house lighting, Dankoff 12v water pump,
    System 3: PV- 1.5kw Kyocera, Grundfos 11 SQF well pump, 3000 gal above ground water storage, dom water & irrigation,
    System 4: PV- 6.1kw Kyocera, Mppt- Outback FM80-2ea, Inverter- Outback FX3648-2ea, Batt- 804ah GB traction, Grundfos BMQE booster pump 240v, Mitsibushi mini-splits 240v, 18k and 15k
    · Share on Twitter

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