Heating DHW with Back Boiler in Tiny Home

[OffGridSquid]

Hi, I am hoping someone may have some helpful tips or direct me in the right direction on heating domestic hot water with a back boiler in a tiny house. I have spent countless hours researching these hot water systems but still cannot piece it together!The science seems pretty straight forward and there is alot of info on plumbing these systems for larger homes but the problem I am facing is incorporating this system into a much smaller space.


I am building a tiny house on wheels 8'X21' with a large loft space. I recently purchased the Hobbit stove from Salamander Stoves which also has the option for a back boiler. I am hoping to heat my DHW with this stove and position the tank in the loft space (or in nearby closet) so the hot water may travel upwards via convection. I am trying to figure out how I should position the fresh water tank, the hot water tank and the plumbing connections to the fixtures (supplying hot and cold).There will be a kitchen and sink faucet as well as a shower. All 3 fixtures will be positioned under the loft. I was hoping this could be a non-pressurized, gravity-fed system. After alot of research I am beginning to think I will need to rely on a pump to make this an effective system. Any thoughts on this topic would be very helpful! Thank you!!

 

[pen]

Did the company have any recommendations for you? If they did, were there concerns?

My grandfather made a system similar to what you are mentioning for using with his fisher wood stove, and the tank of an electric hot water heater. A few thoughts are this: As a kid, I still can hear my grandmother yelling as I entered the kitchen or bath, "Wood stove is on, be careful of the hot water!" She said this for good reason, it was hot enough to make tea with, and heating a 50 gallon tank,,,,, a small tank may have greater concerns. My grandfather had the overpressure valve plumbed outside in the event that the thing ever tripped from getting too hot, but it never did in ~25 years of using the system, at least to my knowledge. When he was diagnosed with kidney cancer, what might have been the first thing he did while he was still able, was to tear that system apart, as he didn't want anyone other than him operating it for fear of what could happen.

In all, just be careful, and be smart. My Papa made out well with it, but he was a tradesman in plumbing and heating for many years and knew systems that had failed, the real dangers, and as it turned out, built one that was safe for the time they used it. His response to the system and his cancer diagnosis stuck with me and is the reason I don't have one in my home, even though I could have made the exact same setup.

Good on you for reaching out here and looking for info, and I hope you can find a way to safely get this done. I simply caution to really make certain you know the system inside and out, and understand the risk and its proper use and setup and don't settle on any information you get, whether it be from here or elsewhere.

Good luck,

pen

 

[EatenByLimestone]

How much water do you need? You can do an awful lot with just a few gallons of water. Maybe not shower, but certainly cook and bathe. Maybe a tub beside the stove that is heated by radiant heat will satisfy your needs. It's thermal mass would also even out temp swings in tiny place.

 

[OffGridSquid]

My plan was to use a 30 gallon tank located nearby and above the stove either in a closet or in the loft. The wood stove is designed for very small spaces such as a boat or small cabin or even a kitchen in a larger home. It only takes 7" logs.. so I am not too concerned with it overheating but I intend to vent it to the outdoors in the case that it might. It would be ideal to use the stove in the winter and have a solar batch heater I could use alternatively in the summer. Interchangeable but plumbed to the same tank.

 

[larboc]

I have copper tubing laying against the outside of the firebox inside my hot air furnace. Made from 3/4" copper. Upper and lower manifold with 8 T's and 2 elbows so that there are 5 vertical tubes held against the fire box. 3/4" pex out of the manifolds go to a junkyard water heater that is mounted higher than the stove. Upper connection in the manifold T'd into the "Hot" port, lower manifold tee'd into the drain port. Cold water from my well goes into the "Cold" connection of the junkyard water heater.

My electric heater's "Cold" is plumbed into the T at the "Hot" port from the pre-heater tank.

I can control the temp in the preheater tank by spacing the tubing. Works great, I can shut off my electric water heater in the winter. My wife loves it, infinite hot water!

 

[OffGridSquid]

Thank you all for the responses.. still haven't quite pieced it together though . Larboc your system is very similar to what I was hoping to do. It seems most systems liek this use the wood stove as a preheater to their primary water heater. I am hoping that the junkyard water heater will be my primary tank and I can connect it with the fresh water tank through a tempering valve to supply the faucets. So I am hoping to have only two tanks.. fresh water and the water heater tank all looped together. Has anyone seen a set up like this?