After much consideration it may be. Two methods I've brought up in other threads seem viable at this point.
1) I had become enamored with a DIY design based around a 12V 100W heating element that would be installed in an insulated storage tank. This would be controlled by relays to heat the water any time the engine is running, and, on demand by thermostat when the House Battery Voltage was at or higher than some set point.
It would require a lot of fabrication and design for the control circuitry, the tank, the insulation, but it might make an interesting project for someone with the time and the inclination. I'm not sure I'm so inclined after considering the time this will take to build and test and fine tune.
2) Siogreen's Model I30-POU Tankless water heater. (~$200 on Amazon)
At first glance it appeared that the 3.4 KW rating put it out of the running, as that exceeded the rating of the inverter's AC output. This was pointed out in another thread some time ago where I suggested this device, and I had dismissed the idea at that time.
Further research revealed how the unit has (from their Amazon page):
Manual - 4 Power Levels
IR30 POU operates in manual mode with 4 power levels from 1 to 4.
You can adjust the current from 8-28 amps resulting in 0.85kW to 3.4kW of power so that it fits any application. (my emphasis)
End Quote
Now, this setting isn't mentioned in their manual. I have one of their units installed at home that shares the same instruction, so, have some familiarity with the controls.
I called to ask about this elusive feature and was told how the secret to changing these settings is to hold down the Up arrow (usually used to adjust output water temperature higher)* for a couple of seconds, and it switches the readout to level-setting mode where you can choose between power levels 1, 2, 3, and 4.
*Correction: After writing this up I tried to access the settings on the unit installed in the house. It is actually the Power button that must be held in order to switch modes. Then, not 4, but 8 different levels are available to select from. Though this is a higher output unit and the one for the van may only have 4 settings. Looking forward to finding out.
Which, based upon the amp range above, I'll consider to be as follows:
At 8 Amps/120VAC it uses 960 Watts. On the 12V side this translates to 80 Amps. For 5 minutes of actual use (1/12 hr.), 6.6 Ah. The water may only be marginally warmer, but electrically it would be a very frugal way to get a warm shower.
At 15 Amps, 1800 Watts. This translates to 150 Amps at 12V, or, for 5 minutes of actual use, 12.5 Ah. Warmer and still not a huge hit on the House reserve, nor does it exceed the rating of a 2000W inverter.
At 21 Amps, 2520 Watts. Translated, 210 Amps at the battery (perhaps exceeding some batteries' delivery rating), and for 5 minutes of actual use, 17.5 Ah.
Each of the above examples are ballpark and do not factor in losses in the conversion from 12DC to 120AC.
By "actual use" this is based on taking a shower where the water will be turned on and off to conserve the water supply. A ten minute shower may have less than 5 minutes of actual hot water usage.
This is looking better and better as a source of hot water for the build. Particularly with the advantage that the Power setting can be changed when I am on Shore Power and run the unit at max. (though, frankly, if I'm on Shore power there is probably s shower nearby with unlimited hot water)
If my numbers are right, I figured this might be of interest to others, and a good idea to share this new information.
1) I had become enamored with a DIY design based around a 12V 100W heating element that would be installed in an insulated storage tank. This would be controlled by relays to heat the water any time the engine is running, and, on demand by thermostat when the House Battery Voltage was at or higher than some set point.
It would require a lot of fabrication and design for the control circuitry, the tank, the insulation, but it might make an interesting project for someone with the time and the inclination. I'm not sure I'm so inclined after considering the time this will take to build and test and fine tune.
Which leads to Door Number 2, next to where Carol Merrill is standing ...
2) Siogreen's Model I30-POU Tankless water heater. (~$200 on Amazon)
At first glance it appeared that the 3.4 KW rating put it out of the running, as that exceeded the rating of the inverter's AC output. This was pointed out in another thread some time ago where I suggested this device, and I had dismissed the idea at that time.
Further research revealed how the unit has (from their Amazon page):
Manual - 4 Power Levels
IR30 POU operates in manual mode with 4 power levels from 1 to 4.
You can adjust the current from 8-28 amps resulting in 0.85kW to 3.4kW of power so that it fits any application. (my emphasis)
End Quote
Now, this setting isn't mentioned in their manual. I have one of their units installed at home that shares the same instruction, so, have some familiarity with the controls.
I called to ask about this elusive feature and was told how the secret to changing these settings is to hold down the Up arrow (usually used to adjust output water temperature higher)* for a couple of seconds, and it switches the readout to level-setting mode where you can choose between power levels 1, 2, 3, and 4.
*Correction: After writing this up I tried to access the settings on the unit installed in the house. It is actually the Power button that must be held in order to switch modes. Then, not 4, but 8 different levels are available to select from. Though this is a higher output unit and the one for the van may only have 4 settings. Looking forward to finding out.
Which, based upon the amp range above, I'll consider to be as follows:
1 = 8A
2 = 15A
3 = 21A
4 = 28A.
2 = 15A
3 = 21A
4 = 28A.
At 8 Amps/120VAC it uses 960 Watts. On the 12V side this translates to 80 Amps. For 5 minutes of actual use (1/12 hr.), 6.6 Ah. The water may only be marginally warmer, but electrically it would be a very frugal way to get a warm shower.
At 15 Amps, 1800 Watts. This translates to 150 Amps at 12V, or, for 5 minutes of actual use, 12.5 Ah. Warmer and still not a huge hit on the House reserve, nor does it exceed the rating of a 2000W inverter.
At 21 Amps, 2520 Watts. Translated, 210 Amps at the battery (perhaps exceeding some batteries' delivery rating), and for 5 minutes of actual use, 17.5 Ah.
Each of the above examples are ballpark and do not factor in losses in the conversion from 12DC to 120AC.
By "actual use" this is based on taking a shower where the water will be turned on and off to conserve the water supply. A ten minute shower may have less than 5 minutes of actual hot water usage.
This is looking better and better as a source of hot water for the build. Particularly with the advantage that the Power setting can be changed when I am on Shore Power and run the unit at max. (though, frankly, if I'm on Shore power there is probably s shower nearby with unlimited hot water)
If my numbers are right, I figured this might be of interest to others, and a good idea to share this new information.