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Midnight Brilliant Heating Idea! (or maybe not?)
#11
Thanks for the link John61CT!

That is very similar to what I'm thinking about except for the need for the diesel. I have seen how effective hydronic heating is and how nice it can be. No forced ventilation, just even heat that comes up from the floor. I noticed that he insulated the floor under the PEX tubes.

I guess I will have to set up some kind of system to register when the batteries are full and there is plenty of daylight left to pull power from the batteries to heat the water system. It should be pretty easy to set up a Arduino or something to do that.
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#12
I would use a small RV water heater and a 12-volt circulating pump. it's way better to have too much heat, than possibly not enough. A small propane water heater would warm up the water in the loop fast, then stay off more than it ran. A simple system with it's on 6-gallon storage tank.
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#13
Great idea!


such a small space, insulated as well as you're planning, isn't going to require much to heat- Regardless of temps.

You will need some type of heat exchanger-
Going to the nines insulating and heating, then opening a window for ventilation unbalances all the work you've done.

Even so, living in a warm, oversized coffin might not be enjoyable for long, LoL
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#14
I would not bother with the excess solar load dumping unless **lots** of panels, say a kW.

Yes gasoline or propane heater is just fine if diesel isn't your fuel.

Def want to tap into the propulsion motor when driving

Also a diesel genny or passive solar or solid fuel furnace if you had that (off-grid cabin or bigger boats).
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#15
Whole point of all those controls is you stop circulating, or go slower, to a specific zone when thermostat shows it's warmed up.

For a smaller space just one radiator will do, but HWS is nice year-round.

Otherwise just use an air heater version, much simpler of course.
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#16
(12-10-2017, 04:18 AM)Riverman Wrote: I would use a small RV water heater and a 12-volt circulating pump. it's way better to have too much heat, than possibly not enough. A small propane water heater would warm up the water in the loop fast, then stay off more than it ran. A simple system with it's on 6-gallon storage tank.

A typical RV water heater has a rating of about 10,000 to 12,000 btu INPUT.

But they blow a lot of the heat outside the coach. I figure about 25% to 50%. My estimate (if it is close to correct) means that you would get about 6000 to 9000 btu of heat inside the trailer. Maybe.

So they are very inefficient, but for 10 minutes use in the typical RV for heating up water for a shower, it's not a big deal. 

But using one for heating an entire RV or trailer all winter long, would get expensive....
Never trust a camp cook with lots of shiny new pans...
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#17
Those propane-fired instant "on demand" "tankless" HWS allow for 3-4 gallons per minute through rates, recirculating get temps very high.

Anything even the most efficient purpose-designed hydronic units will burn through a fair bit of lpg.
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#18
For my application this is a cargo trailer conversion, so no onboard engine. I'm attempting to stay away from propane, just as a theoretical exercise Smile

The things I have read about using an on demand propane water heater is that the constant cycling would not necessarily be good to long term survival. Plus it defeats the getting away from propane idea.

I plan to have over 1kW of solar maybe 1200W so the idea is to use up the excess power generated when the system goes into float. I may choose to draw directly from the top of the batteries to heat the water (thus forcing the system out of float and maximizing the power). I may also adopt some kind of roof based solar thermal loop to boost the solar gain of the system.

As an example, 1KW of heat is equivalent to 3412 BTU/hour so if I can store the equivalent heat from the electric generation in addition to any solar thermal gain, I'm seeing if I can make do without the need for propane. I thinking if I can use the power excess for a few hours in combination with the solar thermal from the roof (say a few m^2) I can collect enough heat to maintain a comfortable temp as long as the space is well insulated and the temps aren't too extreme.
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#19
since it's coldest at night and you have no solar at night, what are you planning on batteries? and if you aren't going to use propane how are you going to cook? electricity? highdesertranger
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#20
I've also thought about having some significant amount of storage for engine waste heat.  The biggest difference is that I'd prefer to use paraffin wax or perhaps beeswax as a storage medium because its heat capacity is greater than that of water.  That said, water might be a good trade off between capacity and price, being exponentially cheaper than any kind of wax.  It depends how much weight and space utilization is acceptable too.

The more I think this one over though, it seems that simply relying on propane for heat is a heck of a lot easier.  For the amount of time, effort, and cost to do the heat storage experiment, I'm sure I could refill quite a few propane tanks.

Who knows, it can always sit on the back burner as an experiment to try once the "van life" begins for me.
What doesn't kill me makes me smarter
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