hot water

bsolarbsolar Solar Expert Posts: 103 ✭✭✭
Hello everyone, im trying to come up with a plan for hot water off my solar and im definitely on a budget. I have roughly 1800W of panel and (2) 2500 watt inverters 1 for each leg of my panel box. What im thinking of experimenting with is two of these:
Camco 2103 RV 1000 Watt water heating elements
.. in my regular home 230V 4500W 30gal hot water heater, and have a couple of questions for you electrical engineer savvy folks ..

1) do you know if those elements are going to fit a standard house water heater element bung?

2)if i rewire the 230V to 115 for the elements will it work with the existing thermostats?

.. i do plan on externally switching the elements so i can use either 1 or both as i have the power available ..

any other ideas in the bargain basement category id love to hear ...

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: hot water

    Back the solar-powered truck up a moment.

    You have 1800 Watts of panel feeding what sort of inverter? Is this an off-grid install you're looking to make use of "surplus" energy (after charging batteries) from? That's the only way this would make any economic sense; capturing potential solar power that would otherwise go "unharvested".

    Otherwise, a couple of notes about hot water heaters (electric). The use their elements separately. You can put low-power 120 VAC elements in. But unless those inverters were meant to be "stacked" they will not play together and power a 220 VAC element, nor will it function powering two 120 VAC elements one from each inverter, as the WH's thermostats are designed to use first one element, then the other; not both at once.

    This isn't to say you can't do some significant rewiring of the whole set-up. no doubt someone around here has. Just trying to make sure you understand how each of the components would work under normal circumstances before you start changing things around.
  • bsolarbsolar Solar Expert Posts: 103 ✭✭✭
    Re: hot water

    yes sir, im trying to get off grid and so far the panels are sitting there going to waste alot of the time .. the inverters are not stackable and im not trying to get 240V out of them, but i wasnt sure on the thermostats. Sounds like that approach wont work and i would have to direct wire and switch the 120V elements using the existing parts .. its likely the 1000W elements would never fully heat the water anyway in a full offgrid situation im guessing .. i could always strap a thermometer to the can and do it manually :p
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: hot water

    As Cariboocoot noted, if the inverters are not designed to be stacked,you're going to see smoke if you try running anything on 230 volts. Furthermore, unless you need and use 230 volts, or have loads greater than one inverter can handle, you can eliminate the load of running one of those inverters, by (if you're off grid and not using a 220 volt generator) inserting a jumper across the two legs of your breaker panel, so the single inverter will power the whole panel with 120 volts. Furthermore, if you feed your electric water heater with 120 volts instead of 220/230/240, and don't change any of the wiring connections around the thermostats etc, it will work just fine - - - only thing your 3000 watt 220 volt elements will now consume 750 watts on 120 volts. Much easier on the inverter/batteries etc, just takes 4 times as long to heat the water on 1/4th the power. It's not recommended to rewire the elements to both run together at the same time. The design is for only the top element to operate until the uppermost roughly 10 gallons is heated, then the power is automatically switched to the lower element only, to slowly heat the rest of the tank. If both elements are wired together, the upper portion of the tank can continue to get hotter and hotter until someone gets scalded, the blow-off lets go, or the over-temp breaker pops and shuts the whole thing down. Furthermore, although the spec plate on the tank may say 4000 watts, they almost always come with 3000 watt elements. The 4000 watt being the absolute max size elements that can be used.
  • bsolarbsolar Solar Expert Posts: 103 ✭✭✭
    Re: hot water
    As Cariboocoot noted, if the inverters are not designed to be stacked,you're going to see smoke if you try running anything on 230 volts. Furthermore, unless you need and use 230 volts, or have loads greater than one inverter can handle, you can eliminate the load of running one of those inverters, by (if you're off grid and not using a 220 volt generator) inserting a jumper across the two legs of your breaker panel, so the single inverter will power the whole panel with 120 volts. Furthermore, if you feed your electric water heater with 120 volts instead of 220/230/240, and don't change any of the wiring connections around the thermostats etc, it will work just fine - - - only thing your 3000 watt 220 volt elements will now consume 750 watts on 120 volts. Much easier on the inverter/batteries etc, just takes 4 times as long to heat the water on 1/4th the power. It's not recommended to rewire the elements to both run together at the same time. The design is for only the top element to operate until the uppermost roughly 10 gallons is heated, then the power is automatically switched to the lower element only, to slowly heat the rest of the tank. If both elements are wired together, the upper portion of the tank can continue to get hotter and hotter until someone gets scalded, the blow-off lets go, or the over-temp breaker pops and shuts the whole thing down. Furthermore, although the spec plate on the tank may say 4000 watts, they almost always come with 3000 watt elements. The 4000 watt being the absolute max size elements that can be used.

    way way way WAIT .. so your saying i can run my hot water heater on 120V the way it sits? im liking that plan ... ok i understand i cant run things that are 240V off of two inverters, and ive already jumpered my panel box before to run both legs on one inverter ... but i got a second inverter and now the scheme is one inverter for each leg simply to divide loads .. is this in itself a bad idea?
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: hot water
    bsolar wrote: »
    way way way WAIT .. so your saying i can run my hot water heater on 120V the way it sits? im liking that plan ... ok i understand i cant run things that are 240V off of two inverters, and ive already jumpered my panel box before to run both legs on one inverter ... but i got a second inverter and now the scheme is one inverter for each leg simply to divide loads .. is this in itself a bad idea?

    YES, you can just supply your 220 volt water heater, as is, unchanged, with 120 volts. Everything will operate exactly as with 220 volts - - EXCEPT that the elements will now consume 1/4 the power in watts, thus produce 1/4 the heat, and therefore take 4 times as long to heat the water. No big deal at all.
    As per the two inverters, unless you have loads too large for one inverter to handle, there is no need to run two inverters, thus saving energy for other things that are useful. Running two inverters is not a bad idea if you have energy to spare. Most of us do not have that extra energy.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: hot water
    bsolar wrote: »
    way way way WAIT .. so your saying i can run my hot water heater on 120V the way it sits? im liking that plan ...

    Yes. Ohm's law and all that; it's just a resistance element. Cut the Voltage, the Amps go down - and so does the power and heat.
    ok i understand i cant run things that are 240V off of two inverters, and ive already jumpered my panel box before to run both legs on one inverter ... but i got a second inverter and now the scheme is one inverter for each leg simply to divide loads .. is this in itself a bad idea?

    Not necessarily. All depends on the size of the box and how much total loads are being connected to each one. There are dangers with shared grounds and neutral - you can accidentally get some ground loops going. MSW inverters could have more problems, especially with shared DC.
  • bsolarbsolar Solar Expert Posts: 103 ✭✭✭
    Re: hot water
    YES, you can just supply your 220 volt water heater, as is, unchanged, with 120 volts. Everything will operate exactly as with 220 volts - - EXCEPT that the elements will now consume 1/4 the power in watts, thus produce 1/4 the heat, and therefore take 4 times as long to heat the water. No big deal at all.
    As per the two inverters, unless you have loads too large for one inverter to handle, there is no need to run two inverters, thus saving energy for other things that are useful. Running two inverters is not a bad idea if you have energy to spare. Most of us do not have that extra energy.

    thanks so much for that info, so now i have at least 'warm' water covered to live off the grid ..
    .. on the inverters i dont really use much energy the only thing really is the microwave will tax one inverter if a few other things are going, but reality is i will most likely never be using the microwave and have an induction hotplate in the works for cooking. .. i just wanted to be sure i wasnt doing something known to fry inverters, because the grounds and commons are together from both of them ..
    thanks again, im one step closer ..
  • bsolarbsolar Solar Expert Posts: 103 ✭✭✭
    Re: hot water
    Yes. Ohm's law and all that; it's just a resistance element. Cut the Voltage, the Amps go down - and so does the power and heat.



    Not necessarily. All depends on the size of the box and how much total loads are being connected to each one. There are dangers with shared grounds and neutral - you can accidentally get some ground loops going. MSW inverters could have more problems, especially with shared DC.

    shared grounds and neutrals oh boy, they are shared. They are pure sine wave .. i would rather put one in the closet and save it for a spare than risk frying my hardware .. what exactly would make a ground loop?
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