Update: flap in the foam around the water heater?

A can of spray foam will make it right again.
If the location of where you want to outlet the heat is adjacent to the water heater plumbing, why not make something more functional like a small heat exchanger and fan?

westend, a heat exchanger with a fan would be more effective. But also more work! (And the fan would use a little electricity and would make a little noise.) I am trying this halfway measure just to see if it works at all. If it does, maybe I will try something more elaborate -- maybe an old-fashioned radiator??

westend wrote:
A can of spray foam will make it right again.
If the location of where you want to outlet the heat is adjacent to the water heater plumbing, why not make something more functional like a small heat exchanger and fan?

Be careful about using just any foam as a replacement. There might be heat ratings for the foam used to insulate these water heaters. I don't know, but just make sure you don't create a fire hazard unknowingly.

Larry

I think you have a good idea. It would save the main batteries and probably be more cost effective than a Buddy type heater. Also I would consider cutting a 4 in hole in the dinette seat vertical wall and installing a computer fan to distribute the heat once you have determined enough heat is coming off of the HWH. Just be aware that you are not getting free heat but the savings will be in battery power and using a cheaper source of propane than those little bottles.

Larry, that is a good point about the heat rating of the foam! I probably would not use the spray anyway -- too messy, and it would stick to the tank. And Gjac, you are right that this is not a free source of heat -- but I have propane to burn, so to speak!

profdant139 wrote:
westend, a heat exchanger with a fan would be more effective. But also more work! (And the fan would use a little electricity and would make a little noise.) I am trying this halfway measure just to see if it works at all. If it does, maybe I will try something more elaborate -- maybe an old-fashioned radiator??

Yup, no free lunch, lol.
Forum member smkettner, along with others, have blazed the ground with hydronic heating. I am considering it as it's very efficient and quiet. I haven't pursued it seriously since my furnace/heater is silent and operates at fairly low consumption. I'm also thinking of stretching out my solar output, using a heating element in either the water heater or my fresh water water tank. I have a steel tank so am able to store quite a few BTU's in that tank.

Just with a few minutes searching: Heat exchanger $18. 120 mm computer fan $10. Misc. plumbing and wiring may push this project North of $50, might be worth it. This assumes that a pump won't be necessary because the exchanger is close to the tank and there will be circulation from heat differences.

Good luck with the passive model, it may be just what you need.

UPDATE

So, I am getting ready to slice into the foam -- I was all set to create a velcro hinge for my foam flap, to drill into the cabinets for vent holes, yada yada yada -- and I decide (for reasons of diplomacy and domestic tranquility) to check with DW. I drag her outside to the trailer to explain the whole thing.

She nods and says (politely), "Good idea! But how is this so different from a hot water bottle? I could boil water on the stove, fill the bottle, and put it on my lap, under my lap blanket, while we are eating dinner or reading." (That's how cold it gets when we boondock -- we often use lap blankets and wear warm ski hats while we are inside.)

I sputtered a little, disappointed that I was not going to get to do yet another "mod." But she had a point -- yes, it is a little more trouble to boil the water and fill the bottle. And it might waste a couple of quarts of water per night. But it means that the water heater will not have to cycle on and off, I don't have to cut the insulation, I don't have to drill any holes, and the heat is right where she wants it -- under the blanket -- rather than indirectly warming the interior of the trailer.

Darn.

Even without cutting the foam the water heater puts out heat, A few small holes would allow some of it in to the cabin. A small computer fan would help, it just depends on how often the WH fires. Ours in under the bottom bunk and in the summer with the WH on it would miserable to sleep there. Quite toasty in the winter though.

I thought about doing a solar water heater diversified load and decided it would be a lot of money for hot water we don't need later on in the day. With a tank the size of a fresh water tank I think you would be better off with a hot water panel and do it old school. You could even paint a white hose black and coil it under your solar panel, pump your fresh tank thru it and pick up more BTUs than the PV can do alone.

JiminDenver wrote:
Even without cutting the foam the water heater puts out heat, A few small holes would allow some of it in to the cabin. A small computer fan would help, it just depends on how often the WH fires. Ours in under the bottom bunk and in the summer with the WH on it would miserable to sleep there. Quite toasty in the winter though.

I thought about doing a solar water heater diversified load and decided it would be a lot of money for hot water we don't need later on in the day. With a tank the size of a fresh water tank I think you would be better off with a hot water panel and do it old school. You could even paint a white hose black and coil it under your solar panel, pump your fresh tank thru it and pick up more BTUs than the PV can do alone.

Jim, this is another thing I've thought about, making a solar heater on top of the trailer. The downside is that I'd be adding even more weight to the roof and that isn't a good thing. Who knows, maybe we'll all be looking for portable solar heaters in the future.

West
When I first started looking I saw dual purpose panels with a wet side under the PV side. It's what gave me the idea for a coil of hose under the panel you have now. I don't think it'll add too much weight.