Heating using the hot water tank.

[Shadow Catcher]

New project. We will be heading out this summer for Teddy Roosevelt, Tetons, and Yellowstone National Parks and my "plan" (subject to change with out notice) is to head out in early June and while we have the Espar diesel heater, it and its fuel tank take up precious room.
We have a 6 gal water heater and I was thinking of using an old heater core I had (or thought I did) in the garage and setting it up with computer case fan and 12V solar hot water pump to provide some heat, we do not need much.
I have watched a number of episodes of "Hoarders" to inspire me to clean and the old heater core was one of the victims. I am however not sure that is a bad thing because it was soldered and old enough to have been with lead solder and it was a lot less than clean, and likely contaminated with antifreeze. I purchased a new aluminum heater core and am getting ready to order the pump and make a housing. I will write it up as I go along.

 

[lrrowe]

Shadow Carcher,
I had been in many posts last year on this topic. I believe in it. I think it would work. But I was not going to use this water for potable water. Too nervious about the water being contaminated. I was going to go with the Attwood "exchanger" unit to keep the waters seperated. Good luck but please be cautious.

 

[MtnDon]

Hey Shadow Catcher. I have plans for trying this out to. I have the pump and a "never seen oil or anything but straight potable water" transmission cooler plus a couple of computer fans. I have been slacking off for the past few months. There are a couple more unfinished things that I still need to get done before I do the final assembly and test. My plan is to circulate the hot water from the suburban water heater through the core and use the fans to blow cabin air through the core. I'll probably use a digital temperature controller or maybe pickup an old style, non electronic, RV thermostat.

the pump I have, but I've had it so long it was $2 less....

 

[lrrowe]

MtnDon,
Are you calling the transmisson cooler ok for potable water because it has no lead? Or is there another reason?

 

[MtnDon]

1. It's basically new and has never had petroleum products or anti-freeze pass through it; only potable water.

2. It's all aluminum, just like the tank in an Atwood water heater. It's one continuous length of aluminum tubing with 3 u-bends and the fins attached externally to the tubing. Approx 6 x 12 inches.

 

[lrrowe]

I understand now. All aluminum so welding is same.
Please keep us posted with your results. I just refreshed my memory and studied up on Atwood water heaters again and for me, the best deal is the 6 gal, gas only with pilot. $303.

 

[MtnDon]

I like the pilot light versions as years ago we found we can get all the hpt water we normally use by leaving the heater on pilot only (not turning the selector valve to the "burn" position. Once the water is hot I return the selector to pilot only. Possibly the extra foam insulation I use around the tank helps, but pilot only gives enough hot water for even one shower. Short navy type.

 

[48Rob]

Don,

Mine is the same, the pilot does a great job of keeping the water hot.

The burner never kicks in unless you drain a lot of water from the tank.
Very easy on fuel...

Rob

 

[lrrowe]

I read that about the pilot before from either you guys or someone else in this forum. That is why I am considering it. It sounds logical to me.

 

[Socal Tom]

Have you thought about running some tubing under your mattress and circulating the water through there? Based on some estimates I made last night, roughly 1800 btu ( less 350 per person) should be adequate to maintain a 30 degree difference in temp from outside. It would be slow to warm up, but it should be nice even heat, vs a heat zone near the heater and still cold near the walls
Tom

 

[lrrowe]

I read that about the pilot before from either you guys or someone else in this forum.

 

[MtnDon]

In my case I doubt that heating pipes/tubing under the mattress would be very effective. Then ten / eleven inch thick pillow top queen size mattress is too thick, IMO. And it might be too warm for me to sleep on if there was sufficient heat to warm the air. Maybe a better idea for a TD with a thinner mattress. I do agree that radiant heat like that in a home floor provides nice even heat. However, that sort of heat is best suited to a system that is on long term. At least that is my experience with radiant floor heat in homes. Very nice to walk and live on a radiant heat floor.

 

[lrrowe]

In my case I doubt that heating pipes/tubing under the mattress would be very effective. Then ten / eleven inch thick pillow top queen size mattress is too thick, IMO. And it might be too warm for me to sleep on if there was sufficient heat to warm the air. Maybe a better idea for a TD with a thinner mattress. I do agree that radiant heat like that in a home floor provides nice even heat. However, that sort of heat is best suited to a system that is on long term. At least that is my experience with radiant floor heat in homes. Very nice to walk and live on a radiant heat floor.

I live now in a radiant floor heated home. It is great.

 

[bdosborn-SMB]

Subscribed and interested. This idea has been bouncing around the forum for years and I don't think anyone has ever done it.


Bruce

 

[Socal Tom]

I recommend you include a gate valve in the system to control the water flow.
Tom

 

[Shadow Catcher]

In our case the mattress is 5" foam so not much help under bed. We also have a fairly high interior volume, for a teardrop, 400cubic feet.
Our Atwood is a 6 gal direct spark ignition.
I ordered the pump today and I am looking at tubing, it has to be food grade, handle pressure and temperature. Tygon seems to have tubing that fits those requirements.
I figure I can regulate the temperature by using a couple of PWM modules, one for the pump and one for the fan.
I am debating whether to use quick disconnects on the hoses and yes there will be a couple of ball valves.
I will document what I find and where.

 

[lrrowe]

In my conceptual plan, I was going to regulate the on/off of the pump and fan(s) using a thermostat and some sort of relay.
I do not know much about thermostats, so there is more for me to research on them. And the tricky part, if possible, is to keep the fan(s) running for a short while to take advantage of all the heat left in the raditor after the pump stops. But then again, that might be too much work for the small amount of heat left. The rules of dimenishing returns applies here.

 

[Shadow Catcher]

My thinking is regulate the speed of the pump and keep a constant but adjusted fan speed, the reason for the PWM modules. I am seeing 120MM case fans that list PWM control but I am wondering how that works if the computer is controlling it. OK a bit of research and it is a separate controller. I have a couple of $10 digital PWM controllers that seem to work well.

 

[Socal Tom]

It's not intuitive, but pumps draw less amperage if you reduce the flow, so having a way to slow it down to give your heat exchanger a little more time to pull the heat out of it would probably save some power and maybe even improve the heating. It also takes some time for the water heater to do its job, to too short a dwell time could cause problems.
Tom

 

[bdosborn-SMB]

I ordered the pump today and I am looking at tubing, it has to be food grade, handle pressure and temperature. Tygon seems to have tubing that fits those requirements.

Why not use PEX?

Bruce