First boil of the season on my new homemade electric evaporator.

[Cedar Eater]

I finally got enough sap to do my first boil tonight. I used the eEvaporator that I made from a steam table pan and a 4000W spa heating element. I detailed the construction in this thread. http://mapletrader.com/community/showthread.php?26094-DIY-Electrical-Evaporator-Design-Page-1

I started with 3 gallons of cold sap at 6:35 PM. It takes about 1.5 gallons to cover the heating element. It was boiling well within 20 minutes at an outdoor temp of 32F. I set a timer and checked the boil every half hour, scooping the foam off each time. I added cold sap twice, one gallon at a time and it killed the boil each time, but it quickly recovered. My final addition was just over a half gallon of sap at 9:30 PM. I stopped the boil by flipping a switch at 10:10 PM and was surprised to see that I had boiled away 4.5+ gallons of the total 5.5+. The heating element was not visible during the boil, but it was exposed to air when the boil settled. There was no sign of scorching on it. I easily set the rig on the ground and picked up the cool opposing corners of the pan and poured the nearup into an 8 quart pot.

So I calculated a boil rate of 1.25 gph from a cold start using well under half of the capacity of a 50 Amp 240 Volt circuit. It was an almost disturbingly trouble-free way to make nearup. This will work well with my 5500W kitchen sink on the same circuit.

These are pics of the boil.

The boil only rolled directly above the element and didn't even wet the edges of the pan.
http://i.imgur.com/mQ1yPmo.jpg

The steam drifted off under the awning and nothing dripped down from above.
http://i.imgur.com/rMjmftN.jpg

The element didn't coke up.
http://i.imgur.com/e3NornA.jpg

There is some sugar sand on the bottom of the pan.
http://i.imgur.com/dz9pJrs.jpg

[TrapperX]

Glad to here you were able to do your first run.
How do you feel the GPH vs propane cost wise? I thought you estimated 2.5 GPH originally, I might be wrong.
I still want to build one and was thinking of cutting the section of the heating element are out and welding a section so it would sit a little lower.
Do you think going with a bigger element would have an advantage?
You said that the boil was limited to the area where the element was, I didn't know if you were thinking that was good or bad.

[Cedar Eater]

Glad to here you were able to do your first run.
How do you feel the GPH vs propane cost wise? I thought you estimated 2.5 GPH originally, I might be wrong.
I still want to build one and was thinking of cutting the section of the heating element are out and welding a section so it would sit a little lower.
Do you think going with a bigger element would have an advantage?
You said that the boil was limited to the area where the element was, I didn't know if you were thinking that was good or bad.

With current propane prices, it may well be cheaper to run propane. Next year, it could be different. Someone who's willing to work the math can have at it. I calculated a per gallon syrup cost of $17.16 at my current kWh rate of around $.135. As I recall, that is lower than last year's propane cost per gallon syrup for me. The ease of use of these electricals is definitely worth something. Not having to deal with soot alone is a big plus for me.

Welding a well into the bottom of a pan for the heating element is an interesting idea, but it might not be worth it to put too much modification into a steam table pan. The goal of this design was low cost and ease of use, so I wanted to keep the amperage under 20 and the splashing of small drops outside the pan to a minimum. The 4000W element does those nicely.

I don't recall guessing at a GPH for either this or my In-Sink-Evaporator. I could be wrong. There was a stat used last year for a theoretical max GPH per sqft of surface area. That may be where theoretical max rates for these pans were assumed. I'm pretty happy with the GPH that I got. It's higher than what I was getting with the same sized pan in an old gas grill. It could possibly be increased by using a larger element and/or a fan to blow the vapor away. I haven't insulated the box yet either.

Having the boil limited to right above the element is not a problem. You want to maximize the surface area of the water to maximize the release of water molecules, but you don't want waves washing over the sides of the pan or drops of sap splashing out. I found that a 5500W element caused a lot of splashing when used during warmer weather, plus it required a 30 Amp circuit instead of a 20A. If you want to maximize your boil rate and cost is not an issue, I would suggest using a 5500W element and a 10kW controller with a 30A circuit. But if you are going with that much power, the kitchen sink might be a better option because it has much more surface area and is wider in the narrow dimension to contain the splashing better.