I'm working on my install plan for my new 16KW diesel heater. I originally bought it for heat while parked as well as preheating the engine coolant for warm starts. I still haven't figured out my hot water heater.
Originally, i was going to use a hybrid propane/120v water heater like the below.
https://pantherrvproducts.com/94022/
I don't plan to have propane heat fridge or stove. I plan to have 10KWH of battery storage as well as 2-4k watts of solar on the roof. I hope to run water heat on solar/120v as much as possible. I do want a backup source as well and don't want to carry propane (might do 1lb bottles for grill).
So back to my coolant heater. Its a monster and i honestly don't plan many cold trips to even use it.. I was maybe going to repurpose it into using water and additional hot water tanks for showers. Just blew my mind finding 120v marine water heaters with 5/8 coolant ports for heat exchanging. I can easily plumb it into my coolant loop.
So they have a
6,11, and 20 gallon. What i wonder is which size might be best.
They all have 1500w burners, so each one should theorically take twice as long to heat at 120v as the smaller one. Also, i can utilize my 180ish engine heat to circulate and preheat the water. This is makes much more sense in a boat except maybe the few cases where my family would shower right after stopping (in which case the 20 gallon heated for free would make sense).
Which size might be optimal to be matched with the 55k BTU diesel heater, so that i can flick it on before showers in order to have "unlimited" hot water powered by my diesel fuel.
Based on my
initial calculations, the 11 gallon one would take 56minutes to heat from ambient to 120F with the 1500watt element. On the other hand, assuming the 16kw diesel heater has 50% efficiency 8000watts of energy through the heat exchangers would take 11minutes. This would give me "unlimited" hot water from my diesel. So all the sizes will pretty much give this, but the 11 gallon gives me enough reserve for sinks and things without having to carry more hot water than i need and keep it warm using the 1500w element.
I haven't seen anyone do this with a Diesel coolant heater (other than a few very fancy hydronic heat systems which I'm not interested in). Anyone have any input before i forage down this rabbithole? Ill have to navigate the sailboat forums for some tips and they might be a stranger crowd than schoolbus folks!