Building an Oven with pipes to heat my hot tub?!?!

[Travelinman]

JRPizza:

Good thread, thanks. Good ideas on that other thread.

Many good reasons to avoid my idea, BUT

If I wanted a purely logical Pizza Oven for the occasional pizza, I would not spend this much or $$. This is way to use the heat after I cook

It is true that the water will cool down the oven, I will try it and report back with data.

I will used infrared thermometer to register temps ad changes, empty versus filled with water. I will start without water, and see if there is a change in temps. If the whole idea fails, I will cut pipes and fill with vermiculite or vermicrete and cap.
I am putting two 1inch hard copper pipes under 4.5" fire brick floor.

I need to design a low profile heat exchanger for tub. Maybe a new auto tranny cooler with a safe plastic plate on top.
What happens if power goes out or pump fails? Maybe solar with back-up.

Fun stuff! Thanks.

[JRPizza]

I ran across a similar thread while looking for something else - here is a link if any of you are interested

https://community.fornobravo.com/for...oven#post11524

[cerveja]

Hi Travelinman, glad to find someone wanting to do the same project. I am also trying this build and having trouble with design.
Lets start with reasoning:
1. We have access to wood and we love pizza ovens but never use Hot tub due to time it takes to heat up. I went with a heat pump instead of element to save electricity costs but it takes too long to heat up. When you feel like jumping in you don't want to wait a day. 2-3 hours is best.
2. I want to use this concept on a chalet design which is offgrid and feel it would be a cool attraction for guests.

The best oven design I have found is the Russian oven design where the fire is in a separate chamber below the oven and it circulates the gases efficiently. You can then run the heat exchange piping in those chambers to capture the heat for heating hot tub. If you make the fire chamber big enough for a big enough fire and the oven as small as you need it then I am sure the loss of heat to the water will not be so much that you will not be able to heat the oven up.
Lopez labs did a heating unit for flooring but just did not have the pizza oven included but I cannot see why not.. check it out here http://heatkit.com/html/lopezs.htm
This is the best solution I have found. Would love to hear from all on this build and adapting it with a pizza oven (which would need its own door).
Cheers

[Travelinman]

Thanks for the help. I think I will give it a try and report back.

[MarkJerling]

The simple reality is that the water pipe (wet back as it's called in New Zealand) will "rob" too much heat from the fire to be able to make pizzas at the same time. So, it can work if you're only trying to heat the hot tub and, for the thermosyphon to work your hot tub will need to be higher than the oven, unless you're using a pump to move the water around. But yes, with a suitable wetback copper vessel and pipe setup you could heat the water. We had an old wood range which we used to heat water and it would boil 200l (about 54 gallons) after about 2 hours of fire. So, certainly possible.

[Neil.B]

I was thinking something simular for the oven and grill to heat my pool, the build is taking toooooo long as it is without making it even more complicated, so I didn't bother.

[Firebrick4]

I have never seen this done before, but I have seen wood burning hot tubs. I like the concept, but I don’t see this working out too well. Taking out the cost and time it takes, the concept doesn’t make sense to me. I don’t think it could heat up a hot tub, because most of the heat comes off the dome rather than the bottom. Maybe in addition to a preexisting hot tub heater, but I’m not sure. I’ve seen wood fired hot tubs but the pipe does not come out of the bottom. Goodluck

[Travelinman]

Hey Ricky:

I agree to your points.

To me it is a fun project. So I am ok with the cost and intermediate use of the system.

I will just give it a try and report back.

Regards

[Chach]

People have done things like this not sure if it was on this forum or not. I think it's not worth the trouble to be honest esepecially for the amount of use you may use your oven. If you fired it weekly then maybe you would recoup some savings in using this than your electric heater but you would need safety measures pressure relief and obviously a pump thermostat and or a heat exchanger...doesn't seem worth it unless you were off the grid IMO.

Ricky

[Travelinman]

Is this a new concept? I am building the dome style brick oven near my separate deck and hot tub. I want to run 1" copper pipe under the floor and into tub. Why waste the heat after your pizza is done.
Any ideas?