Tankless water heater to heat air?

[woytovich]

Thoughts?

Playing around with the idea of using one of the tankless hot water heaters along with a water>air heat exchanger + fan etc to provide both hot water and hot air.... Goal would be a single system rather than a diesel heater for air and a propane system for water. (The flip of that: using a diesel air heater to heat water seems less practical.)

An Ecotemp style heater and add some infrastructure: fan, pump, thermostat, valving/switching.

Something like this:

 

[Ozarker]

Just guessing, but it seems the water piping in a heat exchanger where the water is heated may rely on water keeping the piping from burning out or burning through the piping material, copper or aluminum or steel (I don't know) but it could be thin walled materials. Stuff is usually designed as cheap as possible to barely accomplish the intended task.

 

[woytovich]

I'm confused by your comment. The propane on-demand water heater would be heating the water which would then be going to a heat exchanger that would blow air through it to blow heated air into the living environment.
Am I missing something in your comment?

 

[woytovich]

Here's a commercially made unit that is similar in functionality.

Aqua-Hot Gen1 - Combo Air and Water Heater - Gasoline - Aquahot Gen1-GA1 - Vanlife Outfitters

The Gen1 is a multi-purpose, single appliance designed to save space and weight in a vehicle while still providing the highest level of environmental comfort as well as 2.64 G of hot water. With 13,500 BTU of heating capacity (20,000 for Propane version). The Aqua-Hot Gen1 can heat water...

www.vanlifeoutfitters.com

 

[Victorian]

The most versatile hot water set up currently: hot-shower-upgrade-kit-2-0-combiboil-with-comfort-boiler-control-panel

 

[woytovich]

The most versatile hot water set up currently: hot-shower-upgrade-kit-2-0-combiboil-with-comfort-boiler-control-panel

Very very cool

 

[woytovich]

Any other thoughts?

 

[plh]

Thoughts on what? It could work, you would need to "engineer" a system. Generally my house runs like this. Instant hot water heater to pump(s) to radiant in-floor tubes (basically a heat exchanger) controlled by a thermostat(s).

 

[woytovich]

Thoughts on other options, other ways to approach this same system, alternate systems that might make more sense. Just trolling for input and ideas, brainstorming.

 

[Quattro]

Ready to go kit of what your looking to do: https://www.bobilvans.co.uk/product-page/new-bobil-air-hybrid
(no affiliation, just ran across it on YouTube)

I'm leaning towards an Autoterm 2D + CombiBoil. @Victorian do you have any concerns with losing heat from the CombiBoil through the ducting when not running the air heater? For example in the summer I may only use the electric heating element as a solar dump load but I'm worried I'll lose a bunch of heat to an already too hot cabin.

 

[Victorian]

Ready to go kit of what your looking to do: https://www.bobilvans.co.uk/product-page/new-bobil-air-hybrid
(no affiliation, just ran across it on YouTube)

I'm leaning towards an Autoterm 2D + CombiBoil. @Victorian do you have any concerns with losing heat from the CombiBoil through the ducting when not running the air heater? For example in the summer I may only use the electric heating element as a solar dump load but I'm worried I'll lose a bunch of heat to an already too hot cabin.

we have the combiboil on sale at blackfriday!
good question about the heat loss through the ducting. To be honest I haven’t really thought about too much as I have the boiler temp monitored by the comfort control panel and temp sensor.

 

[Trail Talk]

Thoughts?

Playing around with the idea of using one of the tankless hot water heaters along with a water>air heat exchanger + fan etc to provide both hot water and hot air.

We have this configuration using a Webasto ThermoTop C gas heater feeding off our main tank. Manual valves allow us to direct heated coolant to the cabin heat exchangers (air and water), truck coolant circuit, or both. As we run dry during winter travels, the hot water feature only gets used once temps are reliably above freezing and we have filled the fresh water tank. During those times, when wanting hot water only, we start the Webasto and wait about 10 minutes before running the faucets or showers. FWIW, it burns about 12 oz of fuel per hour. The heat exchanger will produce waste heat when the blower isn't running and this does warm up the pantry located above. To mitigate this we added extra venting slots to the access door.

 

[woytovich]

So the cabin water and cabin air exchangers heat by using Webasto heated coolant OR engine heated coolant. And the engine and Webasto coolant circuits can be joined or separated... is that right?

 

[Trail Talk]

So the cabin water and cabin air exchangers heat by using Webasto heated coolant OR engine heated coolant. And the engine and Webasto coolant circuits can be joined or separated... is that right?

Exactly!