Hot water and hydronic heating

[westend]

The water treatment/circulation for the fresh water tank from another thread got me thinking.....:R

How would using the fresh water supply work if a guy also used that water for hydronic heating? My initial thought was to plumb the hot water tank outlet through a small heat exchanger and use the fresh tank as the reservoir. I could probably control the output of the water heater with a thermostatic valve.

Or, would it be better to establish new plumbing for the hydronic system?

If an RV'er wasn't worried about the supply lines freezing (mine are all inside), using heated water for some heating and to circulate back to the tank could be really nice for Winter camping. In my special case (steel fresh water tank under dinette seat) it would keep the dinette warmer, too.

[westend]

toddb wrote:
topsflo ts5

Thank you!

I really don't know if I'll go forward with this as I am doing less camping in cold weather but it is nice to know it can be done (and successfully). This morning would be an excellent time to have this installed. Currently, it is 6f and the forecast calls for a dropping temp until tomorrow morning. Fortunately, I'll be inside the house day dreaming about this and watching millionaire football players freeze their keesters off, lol.;)

[toddb]

topsflo ts5

[westend]

Todd,
What are you using for a pump?

[toddb]

The pictures of the first system are of my first attempt. I switched to an atwood 6 gallon water heater with 140* stat dedicated to heat, I think I can go up to 160 but didn't find it necessary. This way I can run coolant to protect the aluminum. Same heater core and fan setup, works wonderful in our 25' toy hauler. I consume 1/2 the propane and very little power, 2 6v batteries never fell below 12.3V. It's quiet and doesn't suck the moisture out of the air.

[lawrosa]

C Schomer wrote:
It's been nearly 40 years since I did a lot of steam and hot water work but radiant is way more efficient because of the lower boiler temp and less stack loss. Using the WH for the heat source and cycling the fan coil unit with a t stat wouldn't be as efficient as a real low temp radiant system... if that help you any. Craig

Yes but with radiant you need triple the sq ft of tubing or more. Its not finned tube....

And where are you going to put that? In floor of RV and in all the walls and you probably still will not have enough heat..

Just my 2 cents...

[C_Schomer]

It's been nearly 40 years since I did a lot of steam and hot water work but radiant is way more efficient because of the lower boiler temp and less stack loss. Using the WH for the heat source and cycling the fan coil unit with a t stat wouldn't be as efficient as a real low temp radiant system... if that help you any. Craig

[westend]

All good caveats but maybe some more background is needed. I have a whole-house solution for heating. It is a vented 20K BTU heater, propane fired, that is efficient. It does not have a fan or need any power to operate. This is the third RV this heater has been in and is a tested-to- (-20f) solution.

What I'm about is taking some of the heated water from the onboard water heater and circulating it to the fresh water tank. This is similar to what member Profdant139 did here. I will hard plumb everything and don't need an exterior fill solution like he did, I have fittings on the steel fresh water tank.

I would also like to pull out a bit of heat through a heat exchanger and fan or baseboard heater. I don't expect it to anyway come near to a whole house solution for heating. If I can get 70f at the exchanger, I would be happy. I'm wondering if circulating the water like this will have any adverse effects like algae, contamination, etc. I'm not too worried about the latter as I already have a steel tank and deal with a little iron discoloration now and then. Filtration takes care of that. I'd also be interested if anybody has pump recommendations. I know member SMKettner has one of those magnetic vane pumps and likes it a lot. They are expensive, though.

[christopherglen]

How efficient is the water heater VS furnace? Are you going to be spending more on propane heating water then just running the furnace? If you are planning on electric, why not just get a oil filled heater?

[lawrosa]

Well all in all it depends on the reasoning for trying to get a different heat source..

If staying on grid and just dont want to use propane I would say add an electric element to your RV heater...

see here

cheap heat.... RV systems

But many do it with the wave heaters so as to not use electric of the furnace fan and to reduce propane usage... This is for off grid..

[westend]

Yeah, for supplemental heat, an RV owner with forced air furnace might choose a different appliance. I already have a different appliance, a propane fired heater that is vented and uses no electricity.

I'm also thinking of this as supplemental heat rather than the main source. My goal is to bring the fresh water tank to an equilibrium between ice cold and room temperature. At the same time, I could be drawing a bit of supplemental heat from the system.

I was worried about any type of adverse conditions ensuing from using the potable water in a heating situation like mentioned. Roy B has the closest application to what I envision.

[Gene_Ginny]

lawrosa wrote:
..I would probably get a wave 3 or 6 and hang it on a wall somewhere... Wave 3 heater

From the link above:
•For use in vented areas only

[pianotuna]

Hi lawrosa,

Initially catalytic heaters produce little CO however as the pad ages that increases. It also increases dramatically as Oxygen is depleted. I will not use an unvented combustion heater of any kind.

[lawrosa]

pianotuna wrote:
Does this calculation hold for a fan assisted heat emitter? Or does the fan have the effect of extracting more heat from the working fluid?

Its the same. Fan assist is due to the nature of the housing.

On baseboard air enters the bottom and heat outputs the top.. In a fan type case there are no inlet slots for air to enter hence why the fan..

As far as CO for the wave heaters, they produce no CO as far as I know... I will check specs though...

[pianotuna]

Does this calculation hold for a fan assisted heat emitter? Or does the fan have the effect of extracting more heat from the working fluid?

lawrosa wrote:
So my 200 sq ft camper would need 7000 btu as a heat sourse at a minimum..

200 sq ft x 35 btu per sq ft = 7000

7000 / 550 btu per ft of baseboard @ 180f = 12 ft of base board...( But wait)!!!!!!

I dont have 180f water. And as the chart for heat emmiters goes@ 120F water I would get maybe 200 btu per ft..

so 7000/ 200 btu per ft @ 120f water = 35 ft of baseboard...


Now where the heck will I put 35 ft of baseboard...???