Geofkaye, you raise some good points. I would be curious how a toilet safe works with an incinerating toilet. If you told me it was a Tupperware container inside your black water tank I might understand. Depending on the fire, I expect something inside a water tank might survive even if you didn’t get it out, especially since the tanks are usually mounted under the truck and most of the heat of a fire would be going up.
As for generator cooling, I have the Eu2000i set up to be removable. If I am in a place where I can do it, I will take it out of the generator bay and chain it to a nearby tree. Not only will it get better air flow, but it will reduce the noise and vibration back into the truck. As a stealth camper there will be many times when I need to run with it in the truck though.
You mention the exhaust going straight up, and that is a concern for me as well. I know some rigs have an exhaust pipe that runs up all the way above the roof line, but that isn’t really a practical option for me. Since it dumps the warm exhaust air under the floor of the box I am concerned that it could rise up and come up through the floor registers. They are probably 12 ft. away, and with some big stuff in between, like the rear axel, but air can find a way. I am thinking to add a vertical plate in front of the left rear tires. The idea would be to block the flow of rising air a bit, and a side benefit would be to reduce the tire sling on to the diesel tank.
On a different but related subject, I am rethinking the cross flow heat exchanger idea (Heat Recovery Vent) I know you use yours to rapidly change out the air. I am thinking I can do that with the overhead vent fan. Yes, it would imply dumping the warm/cool air overboard so there would be a price in terms of heating or cooling costs, but I don’t really plan to do it that often, especially not when it is blistering hot or freezing cold outside. That and anyone who sprays hair spray inside my truck will find themselves standing on the side of the road…
My original thought was for a very small but constant flow of air to keep the inside air from going stale. I am vaguely worried about waking up with headaches or dead because there just isn’t enough air in that small space for two people overnight.
As I continue the build I am seeing more small air leaks that are somewhat unavoidable. For example, the floor registers for make up air have dampers, but they don’t seal super tight. If I pull air in through the heat exchanger via a tiny fan, then I was assuming the internal overpressure would push air out the other side of the heat exchanger to complete the circuit and transfer the heat energy. If there are several other small leaks then the air just sneaks out that way and doesn’t exit via the heat exchanger and no heat is recovered. If I was pushing a high volume of air then those other small leaks would not be significant, but I don’t want to push high volume. I could add a 2nd fan, one to pull and one to push, so as to balance the external and internal pressure, but this all just keeps getting more complicated for a dubious benefit.
I started to make my own small low flow cross flow heat exchanger but the more I thought about it the more I thought that it probably wasn’t going to recover enough heat or cold to be worth the trouble. I might as well mount a tiny 12V muffin fan somewhere to continuously exhaust air and then add a couple of tiny closable vents directly into the sleeping quarters from the outside. If there is any significant temperature difference between the inside and the outside then chimney effect alone would probably be enough to get the air flow I need, without even turning the fan on.
If it really is nearly the same temperature inside as outside then I can open the ceiling vent and probably get all the air flow I need with no fan at all. All this mental masturbation leads back to the idea that I don’t even need the tiny 12V fan, just a couple of little closeable vents into the sleeping quarters.
As an engineer, I don’t like all this gut feel analysis, but there are too many unknowns to do any serious math. I guess I will just have to finish building it and see if it kills me.
