Natural Gas Stove Top Evaporator

[HowardR]

I tried out my home-made gas-stove-top evaporator today. I pour the sap into a 15 gallon pot with a spout at the bottom controlled by a float in a float pan. The float keeps the sap about 2" inches high in the float pan and in the next three connected pans, each on its own gas stove. I had near-syrup trickling out the end of the last pan into a stainless steel bucket. I can work inside on my computer and just go out and fill up the 15 gallon pot about once every hour or hour and a half.

Here is a picture of the evaporator as a whole:

StovePotEvaporator.jpg

Here is the sap entering the evaporator through the float pot which uses a stainless steel float valve that I bought on Ebay:

FloatPot.jpg

Here's the 1/2 inch stainless steel pipe, valve and union as the sap travels between a pair of pans:

ValveBetweenPans.jpg

Here is the near-syrup exiting the evaporator:

SapExitingEvaporator.jpg

My first estimate is that it boils off about 7 gallons of water if the sap entering the pot is already hot.

[maple flats]

Just be careful for foaming. You may not want to let it go unattended that long. As the sap is boiled down the likely hood of it foaming up increases big time. If it starts to foam up, it could quickly ruin a pan and the sap that is left in it. An hour is a long time unless you set up a automatic defoamer, otherwise it's a sure recipe for disaster.

[HowardR]

Dave,

Thanks for the tip. That is certainly something to worry about.

But I may already have that under control. I have a thermometer in the last pan and increase or decrease the trickle rate out, to keep the sap from getting too hot. (I'm not trying to get it all the way to syrup in the evaporator.) Also, I suspect that there is less danger of foaming in a stove-top evaporator, given that the heat under the pans is lower.

[HowardR]

Maple Flats wrote last year:

Just be careful for foaming. You may not want to let it go unattended that long. As the sap is boiled down the likely hood of it foaming up increases big time. If it starts to foam up, it could quickly ruin a pan and the sap that is left in it. An hour is a long time unless you set up a automatic defoamer, otherwise it's a sure recipe for disaster.

Now that I have has almost 2 seasons experience with the Stove Top Evaporator, I can definitely say that there is no danger of foaming below 218 degrees. I even let the temperature get up to 219 in the last pot one time by mistake, and yet there was no foaming.

Foaming is caused by a low sap-volume-to-heat-source ratio. You can prove this by finishing up a batch of syrup on your kitchen stove. When it starts to foam at about 217 or 218 degrees, turn down the flame and it will stop foaming while you gradually heat it up to 219. My Stove Top Evaporator has a much higher sap-volume-to-heat-source-ratio than a standard evaporator.

[Cedar Eater]

This really makes me wish that I had natural gas to my house. Propane destroys the economics of doing this. Good job!

[Daveg]

"Sap foaming" and "syrup foaming nearing the finishing point" seem to be two different things. At times, I have to put defoamer in the flue pan (212°F), but rarely in the finishing pan (217°F, 218°F, 219°F). You mention turning the heat down when it foams at 217°F. What happens if you don't turn the heat down? Does it foam even more? If you put less sap in The Stove Top Evaporator you can have a lower sap volume to heat source ratio. What guage metal are your pans? The thicker the metal, the poorer the heat transfer. 20 and 22 guage are the most common in the industry.

[Haynes Forest Products]

Neat set up I take it you have good gas pressure at the house? I didn't see the WiFi camera....................you do have one right.

[maple flats]

Foaming can start well under the 219-220 target temperature.

[HowardR]

Foaming can start well under the 219-220 target temperature.

I'm aiming for just 2-4 degrees above boiling in the evaporator. Then after I've collected a day's worth of sap, I finish it off on the kitchen stove. I've got a batch boiling in my kitchen right now.

[HowardR]

Neat set up I take it you have good gas pressure at the house? I didn't see the WiFi camera....................you do have one right.

Yes. The pressure at the gas regulator that feeds my house and garage is set at 7 oz, which is a bit higher than normal. The typical gas stove requires 4 oz. of inlet pressure to operate with full-size flames. My evaporator would work at lower pressures, but it wouldn't boil as much sap away per hour.

I don't have a wifi camera. Never thought of using one. My most important hi-tech app is the countdown timer on my smart phone. My dog starts heading outside just before me as soon as it goes off.