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These are photos of my Cajun Conversion of my gas grill Redneck Pool Heater. I got the idea and inspiration for this Cajun Conversion from another DIY Maker, Bob Warne. Bob tried to build a very small Redneck Pool Heater using his BBQ but it was just not big enough and the pipes he used where to small. He wrote me for help but in the end he helped me more. Bob Warne's idea was to use a very large propane burner from "Cajun Outdoor Cooking" in a metal box with the the copper coils. His idea worked so well it inspired this Cajun Conversion of my Redneck Pool Heater. WOW! what a difference the Cajun Conversion made! It just goes to show you that if you share your ideas somebody is bound to help you out in return. Link to Bob Warne's Site
Being I was heating a pool and not a hot tub I got two of the very biggest Cajun pot burners with the extra 25,000 BTU upgrade sold at "Cajun Outdoor Cooking". This conversion no longer uses my gas grill but it does give me 420,000 BTUs instead of the old 65,000 BTU gas grill.
The Cajun Conversion heated by 8000 gal pool from 80F to 93.5F in 3hours flat. I used just under 2 tanks of propane, one for each burner. My pool was already heated 13 degrees F to 80F when I started. The old gas grill Redneck Pool Heater took 1.5 days to heat the pool from 67F to 80F. The Cajun Conversion did this same 13 degree F increase in just 3 hours. That means I should be able to heat me pool from ~65F to ~85F in ~5 hours in the winter using less fuel than before.
For a comparison test of the Cajun Conversion I heated 60 gallons of water in a small kiddy pool. As in the past I using a small circulating pump (see warnings below) to pump the 60 gallons from the kiddy pool through the heat exchanger and back into the kiddy pool. The old 65,000 BTU gas grill Redneck Pool Heater would heat the 60 gallons from 80F to 100F in 30 minutes. With the Cajun Conversion seen in these photos and using the same Redneck Pool Heater coils I was able to heat the 60 gallons form 80F to 100F in 4.5 minutes. But as stated in the warnings below the pump was too small and the water started boiling in the coils faster than it could flow through. The coils started to make some very scary popping noise and started shaking and rocking. I quickly turned off the burners to avoided a disaster.
For burners I used two Kick A Banjo Burners from Cajun Outdoor Cooking:
185,000 BTU for $69 with the 30psi upgrade to 210,000 BTU for $19
Unless you are like me and want to trick out everything I don`t recommend getting the 30psi upgrade hoses because there is more than enough heat coming from these burners when using the standard 20psi hoses that come with the burners.
If you plan on building one of these there are some serious WARNINGS!!!!.
1) The tread plate fire box gets very hot and you will burn yourself if you touch it so don`t let kids near it when it`s in use.
2) You can never leave these burners running unattended. The tanks chill to subzero as the fuel is consumed so fast and as the tanks get cold the flames could go out. When the tanks start to warm back up the fuel will start pouring out into your yard which could find an ignition point and BOOM! I rapped the heated hose around the bottom of each tank to keep them warmed but they still got down to 24F. Without the heater hose around the tanks the burners just stopped at about 1/4 full tanks.
3) You don`t want the water to super heat. If the water flows too slowly through the heater coils because of a small pump or line restrictions the water will reach boiling and the whole thing will become a boiler BOMB. If that happens the copper pipes could burst and scalding water could burn anybody to close. This maybe an open system but with this many BTUs under it if the water flow is too slow or stops the device will heat the water faster than it can escape and it will explode. To be safe tee off from your pool pump like I did and make sure the output water is around 120F. This way the output water will not scald anybody and the water flow will be enough to prevent an over heat. Don`t use 1/2 copper pipe for this like I did. Use 3/4 because you want as much water flow as possible. Also make sure to manifold each end of your coils so that the water has multiple paths through the heater.
4) Use a pool pump. A small pump will let the water super heat and BOOM! If you only have a small pump than just get one burner or smaller burners. Or use larger pipe. Or turn the flames down and keep a meter on the output so you know you are not getting your water too hot. Better to heat slower than scald yourself or others with an exploding boiler.