Anyone using a tankless water heater? - Page 4

TomH · 11-18-2010, 04:07 PM

Quote:

Originally Posted by WVvan

...The amount of BTUs that a propane tank can release/hr is directly related to the "wetted" surface of the propane, along with a bunch of other stuff (pressure, humidity, temperature). Think of it as the cross section area of the tank where the gaseous propane meets the liquid propane. This cross sectional area has to be large enough to satisfy the BTU requirements of the appliance.....That's why they make these funny looking fat and squat tanks, to increase the cross section - "wetted" surface area....

......The smaller sized tanks with the limited wetted surface just won't cut it....you'd need a tank almost as big as your average BBQ tank....Everything I've just written may be totally wrong.

No, I totally get it. I remember from chemistry the Ideal Gas Law: PV=NKT dealing with water evaporation. Natural gas exists as a liquid only under pressure that is significantly higher than that of the Earth's atmosphere. The Liquified Propane inside the tank must evaporate off as a gas to flow through the tube. The greater the surface area of the top of the liquid, the more molecules that can change state from liquid to gas. The volume of liquid remaining in the tank, the ratio of that volume to the volume above, the temperature of the liquid, the pressure of the overlaying gas on the interface with the liquid, all play into how rapidly the liquid can evaporate into gas. The volume of gas boiling off per second limits the BTUs. It makes complete sense.

One way to increase the rate of evaporation is to increase the temperature of the liquified propane in the tank. Maybe that's what DaveB is doing in this other shot. Just hope he doesn't build enough internal pressure in the tank for it to have a pressure explosion as that would vaporize all the propane, leading to an instantaneous second and larger oxidation/reduction explosion.

gallery/image_page.php?album_id=108&image_id=3940

Boom-BOOM!!

(

DaveB; hope I didn't hurt your feelings. I couldn't resist.

)

**daveb** · 11-18-2010, 09:58 PM

I don't even have to look at what pic you're talking about. But Don (member Doubled) was standing by the tank not me. Yep it was cold and not off gassing enough, so we warmed it up a bit

Can you say boiling liquid expanding vapor explosion

windguy · 11-21-2010, 06:32 PM

Dave,
Thanks for the hiking/history info. very interesting.
didn't recall that there were trees that large on the east coast. those are some old growth trees they mowed down. bummer.
I'll still give you credit for some elevation hiking

now back to your shower design

BTW - I'm in agreement with your comment earlier about it being nice to have a hot shower after a day of physical activity.

gerrym51 · 12-12-2010, 05:26 PM

in researching water heaters. sportsmobile has as an option a 3 gallon electric water heater on the option sheet. does anyone have one or have any info on it. it is described as fast recovery?

thanks

billwilson · 12-12-2010, 06:40 PM

My orginal build had a propane water heater and suburban forced air unit

both are 30 year old technology

however, they work great

granted i have a EB, but i do not feel they hog space or eat up propane or battery amphours

from what i have read, the espar/propex heaters are problematic

dont know about the water heater

FWIW
i just unloaded the rig for Wilsons Spa treatments

reloaded today

i have tons of room left
the overhead is clear

the XL storage is 1/2 full
the rear aluminess is 1/2 full

and my baja box is 1/4 full

I personally do not feel i have sacrificed space with the suburban and water heater
AND i dont have to worry about them........

bw out

BIGRICH805 · 02-21-2011, 12:04 PM

I have a rig on the production line at SMB West and we are considering having one of these installed. http://tweetys.com/girard-tankless-rv-w ... bAodtltkow I'll keep everyone posted on the outcome.

BIGRICH805 · 02-21-2011, 12:19 PM

...and some FAQ's on the unit we are prolly going to be using. The winter use device (WUD) looks interesting. http://greenrvproducts.com/faqs/

billwilson · 02-21-2011, 12:24 PM

I like it
Sez less propane
And no waiting
Prob pretty cool

Greggd · 02-21-2011, 10:17 PM

Bill ,
You should drop by their facility they are in your backyard .
Greggde

louie · 03-29-2011, 01:04 AM

Quote:

Originally Posted by windguy

Quote:

Originally Posted by Roonie

Here is the one I will probably install. It is a tankless on demand hot water heater and the same one Jimapal is using. I saw his in action and it is a small little box that takes up no space under the sink. No outlet and no other fuel source. Wires into electrical panel easy enough. Made for a boat or RV. I was really impressed by it.

http://www.eemax.com/EX2412M

Is a 33deg temp boost adequate?

I want to piggy back onto the 33 degree question. The way this heater works is it raises the temperature if the water a max of 33 degrees? So if it's 50 degrees in my van I am looking at an 83 degree shower? This is doable, but those tankless propane heaters look pretty sweet. Is the tank inside the unit with the propane tankless heaters or do you have to somehow run an external propane tank to it?
Thanks, L