Modification ideas for boondocking

SteveAE wrote:


Bluebeard,
Just some thoughts for you:
- If you use the same water heater that you have hooked up to your potable water, look for (or build) a radiator that is safe to use with potable water. I would not want to introduce a vehicle radiator into my water system.
- To get higher water temps (necessary to avoid the dreaded "wind chill" effect) you will want to increase the water heaters thermostat temp.
- As mentioned by another poster, you will have to drain the system whenever you want to store your trailer. Yes, you can get around this but using a separate water heater and system filled with a water/alcohol solution, but that adds expense...and also further reduces system efficiency.
- A typical RV water heater is about 12K BTU and has an efficiency of maybe 60% (on propane). Then you have losses in the plumbing...say another 20%. So you maybe get total system efficiency (as far a heat transfer goes) of 40%. Or, 4.8K BTU of heat output for your 12K BTU of energy input. On top of that, you then have to provide electricity to run the pump and fan. Assuming you only use 1 amp per hour, that's still 24 amp hrs per day...or about 12% of a typical golf cart battery. But, since you shouldn't draw a lead acid battery below 50%, this means that you just burned up about 24% of your of the usable power from a single golf cart battery just to run the system for 24 hours. Perhaps this would be acceptable for a mild climate, but in more severe winter climates, it is much more much more efficient to use a 6K BTU Wave heater (maybe 95% efficient so ~5.7K BTU heat out for 6K BTU of energy input) with zero electrical consumption at all. Yes, I do have to open the windows for both ventilation and to eliminate moisture. But gosh, even with an electric heater (for those rare times I have the luxury of plugging in), I still have to provide about the same amount of ventilation to get rid of the moisture that we (2 people and one dog) exhale.

So from my experience, and the temps that I camp in, the simple hydronic system using the domestic water heater just didn't cut it. Now had I had the $$$ to install an Espar diesel heater, then that might have been a different story. Anyway, just trying to save you some work and $$$, but whatever you do, I wish you the best and look forward to hearing your final solution.

The efficiency numbers are sort of moot point. The boiler doesn't need to put out 10K btu, it's not raising 40* water to 140, it's recovering 120* coolant to 140*. For our scale it's fine if it takes 2 extra minutes to recover, and consumes half the propane and less than half the power. On 8 hours of run time and a 50% duty cycle my 6v batteries don't fall below 12.3V, and my solar panel recovers them by noon.