question(s) about using a wood stove to heat a bath-tub

[Brando]

Hello everybody!

I'm new to skoolie.net but have been working on my conversion for a couple years. I have a 1984 Bluebird 40' located in Portland, Oregon and I'm almost done with the conversion. Ok, onto my question:

So I am putting a bathroom into the rear of the bus and I cut out a space into the floor on the rear driver's side of the vehicle (in the storage area) for a recessed bathtub. A few feet fore (in front of) of the tub i have my wood stove sitting nicely on a stand above the wheel-well. With the tub recessed into the floor and the stove on it's perch the stove is probably about 3 feet above the tub.

I hope to use a copper pipe induction heating system so that the wood stove heats the water in the tub--sucking cold water out of the bottom of the tub and delivering heated water out of another pipe above.

I've seen videos of this but only where both the stove and the tub are level to each other. Will the heat from the coiled copper in the stove provide enough suction to start this process? (I imagine it might not as the heat density of water is so much greater than air..) Or will I need some type of reservoir or other system closer to stove? Or perhaps some clever bending of the pipe such that there is consistently a good amount of water in the pipe?

Oh, the total distance from the tub to the stove is probably around 4-5ft, but of course, a couple of that being vertical.

any help much appreciated!

thanks!
-Brandon

[BlackJohn]

Great topic Brandon! So many ways to use a woodstove if you build one into a skoolie.

I need one in my climate and understand them well. i have an airtight with a cat converter that keeps me warm at -40 if I like, tee-shirt warm. It's hotter nearer the stove say than at the opposite end of the bus or the front for me.
I fed my hot water electric tank as normal and took the outlet for the hot to the stove via cooper 1/2 line, about 15 feet at most. everything is at about the same level as far as the run and valves go. No real head to be pumped up too. so a natural flow of hot water develops and goes pat the coil I have for the stove. Not sure how hot I am getting yet but the stove runs very hot with hardwood and not bad with softwood. It's actually a bit scary with hard wood running the stove wide open on a real cold day. Very hot near to the stove so that water is flirting with some pretty warm air. No pumping necessary at all, just a natural flow. It's too much really so I may divert for defrosting or melting snow and ice off the roof.
Your stove looks killer to me if you have the confidence to run it hot and maintain the chimney piping.
Any stove needs attention and knowing it's limits so a learning curve for each bus, depending on how systems are thought out.

A hot bath, a gagger and a cooler full of cold ones makes me continue to be a skoolie I guess. What a life!

Hope this helps,

John

[Brando]

Originally Posted by BlackJohn

Great topic Brandon! So many ways to use a woodstove if you build one into a skoolie.

I need one in my climate and understand them well. i have an airtight with a cat converter that keeps me warm at -40 if I like, tee-shirt warm. It's hotter nearer the stove say than at the opposite end of the bus or the front for me.
I fed my hot water electric tank as normal and took the outlet for the hot to the stove via cooper 1/2 line, about 15 feet at most. everything is at about the same level as far as the run and valves go. No real head to be pumped up too. so a natural flow of hot water develops and goes pat the coil I have for the stove. Not sure how hot I am getting yet but the stove runs very hot with hardwood and not bad with softwood. It's actually a bit scary with hard wood running the stove wide open on a real cold day. Very hot near to the stove so that water is flirting with some pretty warm air. No pumping necessary at all, just a natural flow. It's too much really so I may divert for defrosting or melting snow and ice off the roof.
Your stove looks killer to me if you have the confidence to run it hot and maintain the chimney piping.
Any stove needs attention and knowing it's limits so a learning curve for each bus, depending on how systems are thought out.

A hot bath, a gagger and a cooler full of cold ones makes me continue to be a skoolie I guess. What a life!

Hope this helps,

John

Thanks for the quick reply!

I suppose I could use the water heater tank but I was hoping not to (as it is under the sink in the very rear of the bus opposite the stove about 15 feet behind). I suppose I could run the lines underneath the bus but was looking for a more elegant solution.

Maybe I should reconsider.

So, just to be sure that I understand, you are taking hot water from your water heater and then running through the copper coil in the stove, making it much hotter, and then it goes to the bath?

I was wanting a system where i could keep the same bath water hot for hours when it's cold outside. So many considerations....

[12equiem]

Originally Posted by Brando

Hello everybody!

I'm new to skoolie.net but have been working on my conversion for a couple years. I have a 1984 Bluebird 40' located in Portland, Oregon and I'm almost done with the conversion. Ok, onto my question:

So I am putting a bathroom into the rear of the bus and I cut out a space into the floor on the rear driver's side of the vehicle (in the storage area) for a recessed bathtub. A few feet fore (in front of) of the tub i have my wood stove sitting nicely on a stand above the wheel-well. With the tub recessed into the floor and the stove on it's perch the stove is probably about 3 feet above the tub.

I hope to use a copper pipe induction heating system so that the wood stove heats the water in the tub--sucking cold water out of the bottom of the tub and delivering heated water out of another pipe above.

I've seen videos of this but only where both the stove and the tub are level to each other. Will the heat from the coiled copper in the stove provide enough suction to start this process? (I imagine it might not as the heat density of water is so much greater than air..) Or will I need some type of reservoir or other system closer to stove? Or perhaps some clever bending of the pipe such that there is consistently a good amount of water in the pipe?

Oh, the total distance from the tub to the stove is probably around 4-5ft, but of course, a couple of that being vertical.

any help much appreciated!

thanks!
-Brandon

For proper natural convection current heating of your tub through piping you're going to need an intake of cold from your low point to your heater coil and an output from the top of that coil to a couple inches down from the top of your water level. both points must be submerged at all times. the highest point on your heating copper must be that hot water output into the tub.

in your case, thanks to gravity theres no natural way for water to even get into the pipe that would be higher than your tub. all youll be doing is heating an air filled copper pipe. also even if you were able to get water in there hot water is less dense and therefore would not naturally circulate back down into the tub. it would remain in your copper pipe and inevitably turn to steam.

i think you're going to need a small pump. pick up a small aquarium pump and install it on the tub side pushing water towards your heating coil. that should do the trick for you. and if you want any sort of heat with any speed you're really going to need to zig zag that tubing back and forth over your fire.

good luck man!

[BlackJohn]

Originally Posted by Brando

Thanks for the quick reply!

I suppose I could use the water heater tank but I was hoping not to (as it is under the sink in the very rear of the bus opposite the stove about 15 feet behind). I suppose I could run the lines underneath the bus but was looking for a more elegant solution.

Maybe I should reconsider.

So, just to be sure that I understand, you are taking hot water from your water heater and then running through the copper coil in the stove, making it much hotter, and then it goes to the bath?

I was wanting a system where i could keep the same bath water hot for hours when it's cold outside. So many considerations....

I am taking water from the hotwater tank yes, through a loop at the stove and returns to the tank, not directly into the tub. Gives me ample hot for all purposes without using electricity for heating.

Aren't you a bit afraid of that stove being so high up? How did you anchor it to stay in place in transit? That's about the only issue I can see with the installation and if lowered your plan might be more feasible.
Everyone has their own ideas so whatever works for you.
Good luck.

John

[Brando]

Originally Posted by BlackJohn

I am taking water from the hotwater tank yes, through a loop at the stove and returns to the tank, not directly into the tub. Gives me ample hot for all purposes without using electricity for heating.

Aren't you a bit afraid of that stove being so high up? How did you anchor it to stay in place in transit? That's about the only issue I can see with the installation and if lowered your plan might be more feasible.
Everyone has their own ideas so whatever works for you.
Good luck.

John

The stove is bolted into a stand that is welded/bolted into the frame so not super worried about it moving on me

I was wanting to do the hotwater tank stove loop option like you have but the limitations of my space design are just not very conducive. I think i am going to try having a little aqua pump at the tub pushing the water up through the stove.

Also thinking about having an additional loop with some lines running to a radiator heater at the front of the bus to spread out the warmth on cold days.

[cadillackid]

what do you do with the heat when you dont want it.. stove is going but you dont want bathwater heated or any water heated... have to pressure release, expand, and deal with potentially explosive pressures if things get too hot....

-Christopher

[BlackJohn]

That question you asked Chris is why I ran through my hotwater heater with pressure relief valve. No issues so far touch wood.

John

[cadillackid]

that should be good enough.. a small expansion tank might help too.. but the main thing is to make sure no pressure trap can occur.. where water can be trapped in a portion of the pipe that both sides adjacent to the trapped water get superheated and may be just air or vapor but causes that area of water to swell and if unlucky burst the pipe its a rare occurance.. and having your stove be higher than the water lines and a pressure relief near the stove.. your system sounds small enough you are likely fine with just the one relief valve.
-Christopher

[BlackJohn]

Still in the building stage so haven't really put it to a long term test other than burning the stove all winter. rarely has the electric water heater been turned on yet. The system holds about 75 gallons say and just circulates on a bypass from the tank to the stove and back, without heating the cold water supply.
Just an experiment till I get this bus finished up. The coil at the stove area is in an area where when I have checked is about 200*f most of the time in winter temps. Summer, that's going to be electric till I figure out some solar widget on the roof deck. I think I should build a swimming pool beside the bus and heat that too.

John

[BlackJohn]

Originally Posted by Brando

The stove is bolted into a stand that is welded/bolted into the frame so not super worried about it moving on me

I was wanting to do the hotwater tank stove loop option like you have but the limitations of my space design are just not very conducive. I think i am going to try having a little aqua pump at the tub pushing the water up through the stove.

Also thinking about having an additional loop with some lines running to a radiator heater at the front of the bus to spread out the warmth on cold days.

All of your thoughts are doable with the right plumbing pipe layout and valving so just design it a step at time while leaving an easy option to expand to other areas.
Ever thought of a bilge pump in an area to circulate the tub water constantly?

John

[cadillackid]

for summer maybe you need a glycol loop outdoor solar exchanger instead of electric.. at least to preheat the water..... you just wouldnt turn the loop on in winter.. or on sunny days a small solar pump could keep the water preheated.. perhaps even the cold water supply at above worry of freezing.. even ifyou were away from the bus..
-Christopher

[BlackJohn]

Originally Posted by cadillackid

for summer maybe you need a glycol loop outdoor solar exchanger instead of electric.. at least to preheat the water..... you just wouldnt turn the loop on in winter.. or on sunny days a small solar pump could keep the water preheated.. perhaps even the cold water supply at above worry of freezing.. even ifyou were away from the bus..
-Christopher

I'll do more solar if and when I find a workable heat exchanger I can immerse in the main tank. Might be too much without a bypass too. Lots to workout though yet. Not so worried about cold water supply unless on shore power. Would need a heat trace cable to feed the bus.
Otherwise inside piping will always be warm, either from electric, the woodstove and the bus running. I kept the bus heaters and routed my piping over top about an inch, like a rad over each heater, so I'd be getting almost 180* F heating at each heater as the water circulates. Pipes are well insulated everywhere except over those heater locations so hot right from the engine out and back.

I think I'll be ok till the next IceAge......

John