Waste Heat Recovery

Has anyone attempted to heat the inside of a TM by recovering the heat that is normally wasted?

While we were boondocking in cool weather and trying to conserve energy, I noticed that there was quite a lot of heat coming from the flue gas of the water heater and refrigerator. This heat associated with the flue gas is being exhausted to the atmosphere.

I'm thinking if one could somehow reroute these flue gases so that the ducts ran through the TM before exhausting to atmosphere, a small amount of heat could be radiated for warming in moderately cool weather without the use of a fan motor.

Just a thought. Any comments?

RVs in general use packaged heat/water systems with fireproof materials and direct venting to atmosphere to reduce fire risk and exhaust gas suffocation. IMO the benefit is not worth the risk.

You're right, MisterP. The flue gas contains CO and it is hot so there is an asphyxiation and a fire concern. To mitigate these two risks, the flue gas would have to be vented to the exterior and probably routed through the interior through a double walled duct.

There may be no benefit for the amount of trouble it would be to do this. I was just wondering if anyone had any thought about it before or tried it.

Thanks for your input.

Recovering the heat is an interesting idea. Google has 9,090,000 results for "heat exchanger" so there is probably a way to do it.
I understand some of the new high efficiency home furnaces do that.

The fridge, water heater and the furnace cycle for various times so it's not a constant heat.

Piping the exhaust gasses back into the TM then into a zigzag or radiator then back out at the top would work, but as MisterP was saying, ANY LEAK could be deadly.
You also would need a way to get the hot gas back thru a wall without lighting the Styrofoam.
Adding any pipes to the exhausts might require some engineering for safe volume / air flow.
Plus you would have to remove the radiator stuff to fold the TM for travel.

An external heat exchanger box against an open window might also work. No new holes in the TM.


So far I think it is too much work for the benefit.
Simply bringing an extra battery/generator and propane is the easiest and probably the safest solution.


There are other posts here and in various pop-up (tent) camper forums that discuss insulating your camper.
Just ask if you need references to them.

ps.
A 70 kg person generates about 222 btu/hr at rest, that same person generates 65 watts at rest and more if active.
So get lots of close friends.
Just 23 friends will provide a 5200btu/1500watt heater.

.

.

[ShrimpBurrito]

An interesting though. Here's a do-it-yourself article about doing just that -- using the water heater to provide heat in the RV through an exchanger:

http://www.solarhaven.org/HPArticle.htm

And in fact, so-called hydronic heating systems are fairly common in larger RVs, like diesel pushers. Friend of ours have one in theirs, and they love it. Of course, it doesn't heat very quickly, but that's less of an issue in a pusher because you are already in the RV on the road, unlike a trailer, so it's already warm from engine heat.

Maybe a more efficient furnace is also an option. You wouldn't do it to save money though, you'd do it to save propane and battery power, both precious resources on extended winter campouts. They make residential furnaces now that are 90% efficient, and they exhaust through a PVC pipe. But they are larger and heavier than less efficient furnaces, so that might not be an acceptable compromise in an RV.

It looks like Atwood does make 2-stage furnaces, which presumably would be more efficient, but it doesn't appear to be a drop-in replacement for the one in the TM.

http://www.pplmotorhomes.com/parts/r...-excalibur.htm

Dave

One more consideration is weight. If you're boondocking,you are probably carrying a full load of water. Not sure the added weight is worth the small amount of heat you will recover.

And any heat exchanger for the frig and hotwater heater would have to be bypassed when the air conditioner is used. Sounds complicated ...

[Wavery]

I'm getting a headache just thinking about it.

I installed a hydroponic heater in my house. At the moment, it just runs off of the 50G water heater. At some point, I will install a solar system on the roof of the house (when I install my photovoltaic system). I'm just waiting for them to work the bugs out of those things. I've noticed that a lot of people that install them, remove them after a year or two.

What a great group in this forum. I needed some help on this subject and I certainly received some quality brainstorming from each of you.

Liveticker - Your thoughts on BTUs/person are interesting. I could keep the weight down by making friends with women my age (hot flashes would generate more BTUs/person, right)?

ShrimpBurrito - That's a very interesting article at solarhaven.org.

HarveyRV - I agree whole heartedly with you. I have developed a huge headache just thinking about this.

Maybe the next generation of TM will have solar heating on top of the rear shell with the hot water circulated through the floor for heating. But then I couldn't afford one.

I think I'll put the idea to bed. And, I seriously thank you all for your input.

[ShrimpBurrito]

Originally Posted by dw8ite

Maybe the next generation of TM will have solar heating on top of the rear shell with the hot water circulated through the floor for heating. But then I couldn't afford one.

I think I'll pass on the solar and heat exchanger heating methods. Too many compromises. I'm going to wait for a better option -- I have heard they are close to modifying the existing nuclear fusion heaters relatively new in the marine industry for RV use. Very small footprint, minimal propane use, lightweight, and no fan, and thus no electricity, is required -- the heat just circulates due to the Avogadro effect.

Dave