Redneck pool heater 3.0

[LD1]

Do those blow-up pools have a pump and filtration system like a full-sized pool?

IF so, you already have a pump.

We (at my parents) tee'd into the pressure line coming out of the sand filter with a ball valve for a solar heater similar to yours. Dont expect instant results.

We were flowing ~5gpm through the solar heater and the result was about 4 degrees F warmer. On a 10000 gallon swimming pool, and only circulating on the 12 sunniest hours of the day, it takes 3 days to circulate all the volume and gain 4 degrees. But in theory, 10 degrees warmer in a week isnt bad.

But aside from the solar heater, do you have a solar cover? If not..GET ONE. The benefits are two-fold. It helps warm it during the day, but the biggest benefit is keeping the heat in at night.

 

[Egon]

Will the coil be flat or vertical.

Consider a vertical stack with vertical tubing inside with the exhaust having to travel down the exterior of the vertical stack with more coils on the outside of the stack. Might have to add some air to the top to get more vapour burning. Water pump and PSV also required. Consider forced draft fan controlled by water temp.

This should qualify as a water tube boiler rather than a firetube boiler. Might have to watch temperature with the copper tubing. HP STEEL tubing may be an option?

 

[NS Gearhead]

The coil will be laying flat/ horizontal. The combustion gases will be directed in the center of the coil. I'm considering putting a diffuser plate between the coil's center and the chimney. That way the gases have to travel across the top of the coil as well.



Steel pipe would rust and the water that sits in it would brown, then get pumped into the pool. SS would be ideal, but obviously $$$. As long as the water's flowing I'm not worried about the copper.

Yes the pool has a pump and fitler. 1.5" in/ out. The sump pump I got is 3/4" slower flow... and takes the water off the bottom of the pool where it's coldest compared to the pool's pump that takes it 3/4 of the way up the water level.

 

[NS Gearhead]

Yeah, we really need to get a solar cover. When I looked at it, it was $45 I didn't want to spend at that time...but if it's going to make a difference it'll be worth it.

 

[NS Gearhead]

Just looked it up; copper has a melting point of 1085C. Chimney temp gages show 500C as being the in the danger zone... although this is 18" up the chimney and not direct flames. The water going through is cooling the copper, and won't get passed 100C, so I'm confident it'll be fine.

 

[Fiziksgeek]

True...the rate of heating is directly proportional to the contact area and the temperature difference. The best way to extra heat from anything is lots of area and lots of flow (to maximize the temp difference). Can't beat physics...I've been trying for a while now...

I would have to disagree. The longer the water stays in the tubes will make the water hotter, yes, but overall btu's will increase with more flow. The temperature difference will be greater and heat will transfer faster. Raising 100 gallons of water 1 degree is better than raising 10 gallons of water 9 degrees.

The surface area part is correct.

 

[Raspy]

^^^^ You guys are right. I agree. And it works for solar or house heating or any other application where maximum heat transfer or efficiency is desired. Solar is a perfect example. The best efficiency comes from designing the system to "cool" the collectors, not "heat" the water. A very important distinction in heat transfer and efficiency.

I love backyard projects! They end up making us think about physics and efficiency and cost and practicality and on and on. Especially when everyone gets involved.

 

[Loadstar]

Just switch the condenser off your ac from air cooled to water cooled. Then at least your using wasted rejected heat.

 

[rasorbackq]

Gearhead I'm in Springfield NS I use a black poly pipe from 1/2" to 2" with several Tees Must have close to 400 ' I can get the pool (above ground 15' x48 deep) up to around 30c but its a losing battle when the temp at night drops to 18c. That little pool filter you have our lasted about 2 days and was pretty slow to do anything. We bought a a real pump and sand filter and use the poly pipe to move a lot of water . I turn the pump on a sunny day and its only a few degrees from scalding hot. . I have more spent on accessories for the pool then the $250 for the pool. Our pool is going on 10 years now.

 

[NS Gearhead]

Made the front draft




I kind of screwed up measuring and allowing enough plate to cover the last hole... oh well. It should never be fully closed anyway.

Chimney with damper




She ain't pretty... but like we used to say back home; I'm not building a piano.