Anyone using a tankless water heater?

[WVvan]

Hi All,
I was looking ahead in my build and started giving some thought to a hot water system. I'm thinking tankless is the way to go. Two advantages is space and fuel. No need for a separate hot water tank and since it's on-demand I could fuel it from a 1lb propane cylinder.

1 lbs of Propane ~=22000 Btus;
POWER GAS 5 L LPG 34,614 BTU/h / 60 ~= 577 BTU/minute ;
22000/577 ~= 38 minutes of hot water

On the down side I'd have to provide a powered vent but that shouldn't be too big a problem.
In no particular order, here are the leading 5 candidates:

Camp Chef Triton Hot Water Heater
Eccotemp L5 - Portable Tankless Unit (scroll down the page)
EZ 101 - Outdoor Tankless Water Heater
Marey Heater Corp. POWER MINI GAS
Marey Heater Corp. POWER GAS 5 L LPG

All of these model look somewhat similar. Heck for all I know they are all made in the exact same factory in China.
Yes I know some of them say to only use outside but that's just legalize so if you kill yourself they will be in the clear. This is not like a heater that would left on while you're sleeping. It will only be on while I need hot water which will most often mean I'm standing outside the van taking a shower with the doors open. Not too worried there.

Does anyone have any experience with using one of these particular heaters or insights on using a tankless water heater in general?
Thanks,
Dave

[Mike]

I had actually looked into it for our house, but the overall price was prohibitive,
and our local HVAC guy said it would take longer than our natural life expectancies
to recoup the costs. I laughed, he didn't????
He recommended (for the house types) a Japanese make called Takagi, over
the Bosch or Rheem ones sold at the big box home reno stores. Said they were
more reliable in design, less points of failure. More expensive, but I trust him on this.
I know this doesn't help an RV application necessarily, but if I had to decide on
tank vs. tankless I'd probably let short term price decide, assuming the performance
is about the same. A tank for our house would be just under $1000 installed, and a
Takagi Tankless was just over $3200 installed. Natural gas/propane is still cheap
enough that it would have taken well over 10 years (he already had the calcs!) for us
to achieve break even. Apparently tankless are noisier, and what happens if your
power vent fails? No hot water? They also generate a lot more BTUs much more
quickly than a tank, and I have no idea what the heat dissipation around the
installation location might be, or do? I'm going to assume it's got a flow rate
sensing system in it (in case your water pump fails or the pressure drops) so
that might be an issue to consider, although I'm not sure if it's relevant. If I
warm up a tank of water, and my pump fails, I've got a tank of hot water I can't
use either. The HVAC guy suggested it made more sense for a larger family, with a
greater or more frequent demand situation (tankless in your home).
Food for thought?

"Ah, some days, it really is a tankless job..."

[g1g]

I had a small 220v electric for a sink in the shop. I don't know the BTU on it but I was only able to run the water slow or it would be cold. Just trickling out it was hot but it just couldn't keep up with the flow I wanted. Surficed for washing hands but that is about it. I looked at the websites you mentioned, many say they will deliver water as hot as you want it but it never states how much or how fast. Only one showed the temprature rise and flow, and that was the 40,000 +btu unit. I question that a 16 oz propane tank can power that. They show it hooked to a 20# tank. You need so much surface area in the tank for the liquid propane to turn to gas for the amount of btu you are drawing. I would really want more specs than what some are giving, or see it in operation before I buy one .

[WVvan]

Hey Mike,
I'd actually done the same as you and looked at on-demand for the house. Came to the same conclusion. Too expensive when compared to a regular tank system.

Hey g1g,

I question that a 16 oz propane tank can power that.

You raise an excellent point. I hadn't considered that. Well that's why I asked the question in the first place. More research is required.

Thanks,
Dave

[WVvan]

UPDATE: This idea won't work with a 1lb propane cylinder. Best I can tell the max BTU/hr for a 1 lb cylinder is around 9000 BTU/hr. Too low for this application.
Back to the drawing board.

[Mike]

Too bad you couldn't somehow combine the water heater function with/or use heat
from the furnace (assuming you're adding one?) to heat your water.
Figure some (safe) way to use the furnace to heat some sort of copper/steel tubing perhaps,
or heat sink inside or near the furnace's venting to heat water, while not turning the van
into a sauna at the same time.

Ah, crazy me!!

[WVvan]

Hey Mike,
If you're crazy then that makes two of us since I had some of the exact same ideas as you've written. That's the beauty of DIY. The sky's the limit.
That is until the meteor of reality come flashing through that sky and hits your idea like it was the Earth in one of those disaster movies. Then you watch as your idea slowly dies like the last of the dinosaurs as it's smothered under all that logic that was kicked up when it was hit by reality.
I can't decide. Do I sound bitter or just crazy?

Dave

[Mike]

Neither.