Tankless Water Heater - NOT 110 VAC

[Eleveniron]

I'm looking for an outdoor tankless water heater, with a fixed temperature output, and low voltage (like the 2 D-cell ignition). I currently have an Onsen portable outdoor unit with its own temperature and flow dials. The hot water output goes to a standard shower control valve (also with a cold water feed). The problem is when we adjust the temperature using the shower control valve, the temperature wont adjust properly because the Onsen unit doesn't like when the hot water out is restricted or less restrictive... it can get very cold or very hot and shut the heater off. For example, adjusting the shower valve colder reduces the water flow through the heater, slowing down the flow and making the water so hot it shuts off the heater via the overheat (no automatic thermostat, only the manual dial). Or if we select the shower valve even colder, it reduces the flow (hot water) through the heater so much it will shut off the heater. I need something like a standard household tankless heater, but I can't rely on 110V for power... it needs to be low voltage (ie. D-cell batteries or even 12VDC would work). My heater is installed outside but under a roof so its always out of the weather and can be vented right out the top without powered ventilation. Has anyone found one that would be suitable? Thanks!

 

[Bannerman]

Perhaps a natural gas/ propane tankless heater running on 110 VAC + a 12 VDC to 110 VAC power inverter?

 

[Sponsor]

 

[Fitter30]

Normally what is your water source? Model of heater?

 

[Eleveniron]

Normally what is your water source? Model of heater?

The Heater is the Onsen 10L Portable Tankless Water Heater. I use it as the hot water source for an outdoor shower where we have our RV setup. The water source is the campground water... connected to the heater via a garden hose. The 110VAC campground power is only available during the regular season (May through October). I use a generator outside that time period, but I don't want to rely on 110VAC to run the water heater. I thought about using a small inverter (off the RV battery) dedicated for the water heater, but wouldn't be my first choice.