Tankless Water Heater as Heat Source

[OverTheTopCargoTrailer]

You might want to check and make sure they don't use lead solder or something like that if you're going to run potable water through it. It's probably fine but it's something to think about...

Bruce

JUST use PEX

[lrrowe]

So are you saying that you basically have two tanks of hot water radiating warmth to "heat" your trailer.?

YES ... I can heat up to 80 gallons or more to 140 deg...

for example with 20 deg at night, 40 gallons at 120 will work to keep my trailer at 75F

Lower temp = more & hotter water, or maybe refill smaller 20 gal tank during the night

Interesting....something to ponder!

[MtnDon]

You might want to check and make sure they don't use lead solder or something like that if you're going to run potable water through it. It's probably fine but it's something to think about...

Bruce

Excellent point Bruce. The water that would be run through that system is not to be used for drinking; shower, dishes, general washing up. The finned coolers cum heaters are aluminum and that should be okay as the Atwood water heater tanks are aluminum as well. Of course most folks don't drink water from their water heater; or do they? Anyhow the potable water will be in a separate tank.

No trailer RO system. We have a RO system in the house though.


On the subject of on demand tankless water heaters... one addition note. There may be warranty restrictions. Often if the water is harder than 11 grains warranties may be voided, shortened or have special provable maintenance requirements. That made it a no-go for us at home here, in addition to my other dislikes about tankless. Limits also can occur when used for space heating as well as regular hot water.

[bdosborn]

Of course most folks don't drink water from their water heater; or do they?

Sure, anytime we cook spaghetti. Or make hot chocolate.

Bruce

[lrrowe]

Or use a heat exchanger similar to this:
http://www.pextubingstore.com/


I use a much more costly one in my home radiant system. Input water at 110 degrees, output never less then 10 degrees, usually 5 degrees.
Using this comparison one could put 140 degrees into one side and hopefully get 130 out the other side. Probably enough for MtnDon's idea.

This prevents mixing potable and non-potable water.

[MtnDon]

A few years ago I did an experiment with the RV water heater and a transmission cooler (I'll call that the radiator). I found that having the radiator as little as 12 inches above the top of the RV water heater there seemed to be good convection circulation. I might try this without the pump, place the radiator higher and try using a 120 mm computer cooling fan to move air through the radiator fins.

[MtnDon]

Of course the potential problem with that is lack of temperature control.

A 12 VDC pump could likely be controlled with an old style non electronic RV thermostat and a small DC relay.

[dustboy]

Wow, I like this hydronic heat idea. We add safe heat for the cabin and get hot running water at the faucet at the same time!

[lrrowe]

MtnDon,
For less then $100, one can order a Digital Thermometer (with sensor) ($35) and a 1 zone Relay ($67) from Radiantec in VT.
The sensor can go anywhere, floor, wall, etc.
I used them (Radiantec) almost exclusively for my home radiant system and and extremely impressive with their knowledge and support. In fact I am going to call them next week and talk to them about our discussions.
Their parts I am talking about are at: http://www.radiantec.com/store/store.php?catID=13

This thermometer and zone relay control 2 zones in my floors with any issues. And I designed and installed the system almost 95% myself with their excellent support, so that could also explain how simple it is.

Now maybe there are more cost effective items out there to search. But I do like what I know works.

Bob

[OverTheTopCargoTrailer]

[MtnDon]

Appreciate the links to the controls. However, my desire is to try this as a low budget affair. The non digital old thermostats use no power when idle. They simply close a circuit. I like that too.

My ideal heater would be a Propex. IIRC, they are 93% efficient. They cost more, much more, than I want to spend at present. $700+

[lrrowe]

Jerry,
The way I look at it is that one man's idea causes another man to have another idea and so on. By the end of the day, just maybe a great result is achieved. I believe no idea is bad if it causes you to think about it and work out the kinks.

Many ideas never get implemented, but for me at least the formulation and research process is well worth the effort. If one does do not find the idea acceptable after giving it due process then at least he knows it is not for him and does not wonder about it later. Everyday it seems I learn something new from this forum.

Bob

[bdosborn]

This guy was using a hot water pump as a hot water circulator, so he didn't have to waste water running it down the drain till it got hot.

Big RV Link

Scary Expensive hot water pump El Sid

I've got one of these in the garage, I was going to put hydronic heat in, bought all the parts and never installed it. I bagged it when I realized I was going to run potable water through a transsmission cooler. I put an Espar in instead.


Switftech

Hot water pumps are expensive so the convection route would be great it it worked.
Hydronic heat has been bounced around the forum for years but I don't know of anyone who has done it with an RV water heater.

Old Thread

Bruce

[lrrowe]

Appreciate the links to the controls. However, my desire is to try this as a low budget affair. The non digital old thermostats use no power when idle. They simply close a circuit. I like that too.

My ideal heater would be a Propex. IIRC, they are 93% efficient. They cost more, much more, than I want to spend at present. $700+

I agree, while interesting and compact, it is $700 added to the cost of what ever system you want for hot water (should you want hot water) is quite high. And should I want one, I would have to see more on how it works. Must be convinced no propane burning emissions seep into the hot air flow. It bring back memories of my early 60's VW and when I got carbon dioxide poisoning.

[Prem]

Love it. $7. Works great . . . and tankless: