Rixen Heat Exchanger size

[clark]

Originally Posted by i3enhamin

Side notes...

I don't know why these guys are building giant aluminum radiators out of their water heaters. I WON'T be copying that for summer months.

Yeah, I have mine valved so it doesn't circulate through the air heating unit during the summer.

[clark]

My expansion tank is not inside the camper either...

[i3enhamin]

My expansion tank will be under hood and I will have a 3-way summer valve, too.

I don't have the Rixen coolant tank... that functionality, for me, will be split across 2 components. I purchased this already and am looking at something like this for the AC heated / insulated buffer tank.

[clark]

Originally Posted by i3enhamin

One more instance...

This one you can clearly read is a 0.14m^2 Duda B3-14DW

Good enough for me! $66 on Amazon it looks like. I have an email out to the guy I bough my current heat exchanger from to make sure it's not my mixing valve that is the issue.

[i3enhamin]

I'm not certain yet that that "point of use" water heater is totally legit for this application, but I don't see any reason why not yet. Seems the temperature and pressure relief are sufficiently high that it will just act like a more affordable insulated buffer tank.

My system is written up here fwiw.

[clark]

you running the coolant or the water through the buffer tank? Rixen doesn't have a pressure relief valve on the water side and the expansion take with the radiator type cap should act as a pressure relief for the coolant as well as letting air in/out as you go up or down in altitude.

[i3enhamin]

I'm running coolant through the buffer tank. My expansion tank's 7-lb cap will appropriately make it act as the expansion tank. The 100-lb relief valve on the buffer tank should be moot given the difference. Any pressure vessel should still have a relief valve of some sort though, IMO... so, I think all is well.

I'm going for a very large coolant capacity to:
- Reduce cycling
- Provide lots of heat capacity for very long shower duration

And, I'm going with an adjustable electric heater so I can toggle back and forth between asking less of my batteries and asking more of shore power.

I might still be missing something, but if I am, I'm not seeing it.

[i3enhamin]

Of course the expansion tank needs to be installed higher than the buffer tank... and everything else for that matter.

[i3enhamin]

Fwiw... I'm a huge skeptic that a 17,000 btu / hr Espar D5 truly provides continuous on demand water.

Shower heat demand from the system:
1 gpm * 8.34 lbs / gallon * 50 deg F = 417 btu / min = 25020 btu / hr

Energy input into the system:
17000 btu / hr = 283 btu / min

I do not see how that can possibly provide continuous on-demand showers... hence the "shower-sized" coolant capacity. I figure a 7-gallon heater ~ a 6-gallon marine water heater sans heat exchanger coil.

[i3enhamin]

And almost all shower heaters are more like 35,000 - 40,000 btu / hr... this seems to support my skepticism as well.

Ecco-temp L5

I'm happy to be convinced otherwise, but these are my calcs / understanding of the matter.