diy solar

diy solar

Electric Hot Water Options

To be clear, I use dc to the water heater elements, I do not use the temp switch that comes on a AC element, but a digital temp controller and a SSR to shut it off when it reaches temp.
I also use low voltage ( parallel panels at 20-32vdc typically). I found the 36v elements were just a right resistance match for my panels and since my entire system is based on matched equipment with compatible voltages ( Electrodacus) it made sense For me.
Frick, Can you send me whatever plans or a picture of your setup. I want something like this to temper my incoming water and provide me some additional water storage.
 
Consider that a tankless water heater using hard water will crust up where the heat transfer occurs. This will require flushing to remove mineral buildup and restore some performance.

How much hot water will you require? Can you get by with less?

An infrared thermometer will help you determine the best temperature for your needs if heating water manually like in a pot on a stove.

Given that we live off grid in a low water environment, I (but not my wife and 12 year old son) use a battery powered water bottle water heater (used for coffee and tea) set to about 130 degree F for washcloth wiping face and body. Then when the bottle is about 1/2 full, filling it with room temperature water yields a temperature suitable for using soap to clean feet. Regularly I take a real shower as well. Our conventional tank propane water heater is set at the lowest hot setting, and just the pilot light keeps things warm most of the time. It is located in a small closet within our passive solar sunroom, so that helps a lot, though at night the temperature in the sunroom is low in winter. We basically never use much hot water in the morning. It is easy enough to turn the thermostat up about 15 minutes before use if a lot of hot water is needed for city folk visiting, etc. Remembering to turn the t-stat down after that is the challenging part!
 
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You do NOT actually run off DC, you use an Inverter to give you VAC ! Only a total git would try to run an AC device using DC Power.
I've run a standard 120 volt water heater on 48 volts DC and it worked fine, albeit a bit slower.

The McGuyver is not strong in you grasshopper.
 
Have a check. I have deleted my email add. So it is not an advertising.
What is your primary Demographic for this heater?

My well water is about 55 degrees. So to heat 21 gallons of water to 120 degrees would take 10 hours?

Total KW would be 3.34 KWs assuming no heat loss and 100% transfer.

I’m not flaming you I just don’t think it would be something most homeowners would use unless you live in very warm climates and like Luke warm showers.

To heavy for camping. Maybe a first step heater for an RV???
 
I heat all my hot water at camp with excess PV. Small tanks tend to be as expensive as big ones. I have found you can get BOSCH ES4 4 gallon water heaters on ebay for $48 shipped. I just got one, it was brand new and just an open box someone had brought back. These have good insulation. I also have a 40 gallon tank for my laundry. These tall tanks easily stratify and the top 15 gallons heats easily and the lower section is preheat. Here is a camp setup with only 600W of panels and it has enough excess to heat water. It operates in parallel with charge controller, but uses no power from controller or batteries. They are always left fully charged. Nobody else knows how to heat water on this board.

So you recommend this or heat pump hot water heater?
 
Electeic Instantaneous water heaters are extreme energy hogs... even if you put one on each sink and shower, the small ones pull tons of watts.
A tank style heat pump water heater is the most efficient electric type, direct solar would be better...
Actually direct solar to heat pump is the best, but no one makes them.

I had to build my own 1 ton unit.
The efficiency of a direct solar panel decreases as water temperature increases.
So I run it on the cool side and pump the heat into another loop that transfers the heat into a solar hot water tank.
 
Actually direct solar to heat pump is the best, but no one makes them.

I had to build my own 1 ton unit.
The efficiency of a direct solar panel decreases as water temperature increases.
So I run it on the cool side and pump the heat into another loop that transfers the heat into a solar hot water tank.
There is fridge on this principle of work.
No problem to invert process from cooling to heating.
Combinate it with Fancoil cooling/heating system.
 
There is fridge on this principle of work.
No problem to invert process from cooling to heating.
Combinate it with Fancoil cooling/heating system.
I use a water to water heat pump. It is much more efficient and more easily adapts to existing solar hot water panels and to solar hot water tanks that use water to water heat transfer.
 
So you recommend this or heat pump hot water heater?
There is no single answer. With a really big system a heat pump is just an additional load on the system. Typically figure an additional 1KWH expansion of battery. HPWH are not a suitable dump load as the draw is pretty load. Rather than just waste possible energy it can be dumped into resistance in large amounts and rapidly. I have a HPWH supplemented by PV resistive.

The real appeal is as a diversion load that can operate in parallel with a MPPT charge controller and not use any charge controller, battery or inverter resources. That makes it a very low cost method to heat water. It is just beyond the capabilities of 99% of the solar community.

The system has to be an engineered system considering how much excess is available, typical water use and time of need. Since nobody else does this, it doesn't seem very plausible. If I set up a system for a month, you would never let me take it away.
 
even though i'm a big electric tankless fan, i agree with the others that a heat pump tank unit is the most efficient, however, don't be scared by the wattage ratings on tankless units. that number is normally the max value and you are unlikely to get anywhere near it. i have an ecosmart 18k in my house and never go above 9000 watts for a single point use. i'm also currently testing the power draw of the ecosmart 6T for my van. it is listed with a max of 6500 watts but i've been able to use it for a warm shower with less than 4000 watts and a hot shower with less than 5000 watts.
 
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