what to look for when buying small-scale secondhand evaporator?

[SapTsunami]

Looking for advice on what to look for when buying a secondhand evaporator

Small-scale backyard operation with access to ~40 taps, all red maples, maybe 1/3 yard trees and 2/3 woods trees.

Will be running an RB15 R.O. Bucket on two passes to yield 8% concentrate.

Plan to setup ShurFlow vac system to collect. I have seen estimates of 20 gallons/tap per season on vacuum, is this reasonable to expect?

Check my math here:

40 taps x 20 gal/tap = 800 gal raw 2% sap for the whole season. 40:1 boiloff yields ~ 20 gallons of finished syrup

8% concentration is 4:1, so 200 gal of concentrate to boil.

40:1 boiloff ratio becomes 10:1 after concentration, so 180 gallons to boil off

If the season last for six weeks, I can boil once per weekend on average, with 30 gallons boiled off each time

Obviously there will be feast-and-famine periods depending on when the sap runs

Is 6-8 gallons per hour reasonable to expect for a small hobby-scale evaporator?

What size should I be looking at?

What are the most important features?

Upgrading from single chamber pan to divided pan?

Upgrading from flat pan to raised/drop flue?

Adding preheater pan (seems DIY easy)?

Adding a forced air blower (seems DIY easy)?

[DRoseum]

If your vacuum is tight and tubing install is good, yes, you can get 20 gallons per tap off red maples over course of entire season (depending on weather). However, I suspect you won't see 2% sugar off reds for entire season. I predominantly reds (some yard with big crowns, lots in forrest with small crowns) and am lucky to 1.5% early on and then it dips over course of season to closer to 1.1%.

There are great options for small evaporator by Smoky Lake (starcat, dauntless), leader (half pint, half pint supreme, or smoky lake full pint), or CDL (18inch wide x various lengths) and lots of 2x 4 options from all the main suppliers. There are hybrid pans from SL too. The main thing I don't like about hybrid pans is that you cannot reverse the flow to cut down on niter build up. That becomes more problematic the more sap you plan to boil and the longer your boiling sessions will be.

I moved to divided drop flue pan after exceeding 50 taps and going to vacuum
If you ever plan to grow beyond 40 taps, I'd recommend a drop or raised flue setup. But a lot depends on how you plan to operate. I boil every day that the sap runs and like the continuous flow pans now and leave them full woth the gradient from day to day. When smaller, it was easier to do batch boiling and finish it all off daily.

[maple flats]

When I had a 2x3, 4 channel evaporator I got about 6 gal/hr evaporation, no blower. My next evaporator was a 2x6, I never had anything in between those. On the 2x6 I got 25-27 gph evaporation. Both were with no RO. a lot depends on the dryness of the wood and how small it is split. If split wrist size and completely dry a 2x4 combo pan will likely do about 20-22 gph. If the wood is not split wrist size but more like 3" x 4" avg and not fully dried you ight be doing well to get half that.
Split the wood small and refuel by using a timer. On my 2x6 and then my 3x8 I fueled every 7 minutes until I added high pressure air over fire (AOF) at which time the fueling changed to 9 minutes and the evaqporation increased about 15%. There are too many variables to give a more precise answer. My suggestion is to prepare 2x what you think you will need, split it wrist size and any left after the season will be better seasoned for the following year.

[SapTsunami]

If your vacuum is tight and tubing install is good, yes, you can get 20 gallons per tap off red maples over course of entire season (depending on weather). However, I suspect you won't see 2% sugar off reds for entire season. I predominantly reds (some yard with big crowns, lots in forrest with small crowns) and am lucky to 1.5% early on and then it dips over course of season to closer to 1.1%.

There are great options for small evaporator by Smoky Lake (starcat, dauntless), leader (half pint, half pint supreme, or smoky lake full pint), or CDL (18inch wide x various lengths) and lots of 2x 4 options from all the main suppliers. There are hybrid pans from SL too. The main thing I don't like about hybrid pans is that you cannot reverse the flow to cut down on niter build up. That becomes more problematic the more sap you plan to boil and the longer your boiling sessions will be.

I moved to divided drop flue pan after exceeding 50 taps and going to vacuum
If you ever plan to grow beyond 40 taps, I'd recommend a drop or raised flue setup. But a lot depends on how you plan to operate. I boil every day that the sap runs and like the continuous flow pans now and leave them full woth the gradient from day to day. When smaller, it was easier to do batch boiling and finish it all off daily.

thanks I will adjust my Brix estimates down to a less optimistic level

are most arches and pans interchangeable at a given size? I see some 2x4' arch evaporators for sale on Facebook Marketplace, thinking about grabbing one of those then buying a new raised flue pan to pair with it.

[SapTsunami]

When I had a 2x3, 4 channel evaporator I got about 6 gal/hr evaporation, no blower. My next evaporator was a 2x6, I never had anything in between those. On the 2x6 I got 25-27 gph evaporation. Both were with no RO. a lot depends on the dryness of the wood and how small it is split. If split wrist size and completely dry a 2x4 combo pan will likely do about 20-22 gph. If the wood is not split wrist size but more like 3" x 4" avg and not fully dried you ight be doing well to get half that.
Split the wood small and refuel by using a timer. On my 2x6 and then my 3x8 I fueled every 7 minutes until I added high pressure air over fire (AOF) at which time the fueling changed to 9 minutes and the evaqporation increased about 15%. There are too many variables to give a more precise answer. My suggestion is to prepare 2x what you think you will need, split it wrist size and any left after the season will be better seasoned for the following year.

I'm definitely a believer in dry wood. I heat my house with wood and I have two years seasoning at all times.

The rates you're quoting, are those with flat pans, or raised flue / dropped flue pans?

[SapTsunami]

all other factors being equal, how much faster would you expect a raised flue plan to boiloff compared to a flat pan?

[ecp]

all other factors being equal, how much faster would you expect a raised flue plan to boiloff compared to a flat pan?
The short answer is a lot faster. Pretty simple concept but more surface area equals more heat transfer. Maple flats is right that there are too many variables to give an exact recondition. Best advice I have get something along the size of a 2x6 and keep it fun. a note - Hobby rigs seem to hold resale really well so before buying a used one i would look at a new one to compare price.

[DRoseum]

Many people estimate the evap rate to nearly double for the flue pan area compared to a flat pan. A 2 x 6 flue pan might be a little big for only 40 taps and using an RO. If you plan to grow, then perhaps that will be fine. Yes, many arches/pans are interchangeable, but not all.
Ive heard some manufacturers vary on actual width (not all 2 foot wide pans are exactly 24 inches. Do your research is my advice and ask for actual dimemsions.
all other factors being equal, how much faster would you expect a raised flue plan to boiloff compared to a flat pan?

[maple flats]

Things to look for on a used evaporator. If soldered make sure it's lead free solder. Most that are lead free will have a lead free decal on them. The only exception I know of is some Amish made ones. Ask, they will be honest. In fact I bought a new 2x6 this summer from A&A Metal shop, It's soldered, and is lead free. You can test for lead, older hardware stores will have lead test kits.
Another thing to look for is dents, and scorch marks. Look the pans over closely. Look for leaks too.
If an evaporator is welded it is lead free.
On any used evaporator check carefully to determin if any parts are missing that will be needed for you to use it.
As mentioned above watch the sizes. I had 3 evapoators that labeled their size wrong. Many will call them 2x3 or 2x6 but when you measure them they are not those sizes. On my old 3x8 I ordered new pans. The original pans were labeled 3x2 and 3x6, I ordered new pans in 3x3 and 3x5, but when they arrived, they would not fit. I measured them and the sizes were exact, but trying to put them on the old arch they were too long. The originals had been sold so I couldn't measure them, but the originals had a 1" thick gasket between the two pans and left about 1/2" to spare in length. The new pans with only a 3/8" thick gasket were too long by just over an inch. I then had to make a new rear support for the base stack. I made it using 3/8" thick steel and made it shorter enough that the new pans fit well. I made the difference in the base stack takeoff. It was shorter in length but wider enough to be able to use the base stack that came with the new pans. While it worked well it was just another chore I had to do to get the new pans to fit. The original pans only rested on about 3/8" on each side, the new ones were on by 3/4" on each side. All because I failed to measure the old pans and order the same, I believed the size labels, never again!

[ebliese]

We used to have a 2x4 divided pan from Smoky Lake and 50 taps on gravity. We'd have about a four hour boil if the sap flowed well. Average boil rate was 10-11 gallons per hour. Having a 2x4 divided pan was a great learning experience for us and our entry into evaporators. We did pick the 2x4 size because it allowed us to upgrade pans thru Smoky Lake. If considering upgrading in the future, you may want to go with a 2x4 because it seems there's more options for upgrades than if you went with a 2x3.

Our 2x4 divided pan, when paired with an RB-25 from The RO Bucket, was able to handle 100 taps on gravity. Boils were about the same as 50 taps on gravity and no RO.

Some good advice I heard was to buy the best equipment with the money you have. But most importantly, have fun.

[SapTsunami]

wow those raised flue / drop flue pans are pricey! Had no idea the upgrade curve was that steep

Will be focusing my search on a flat bottom divided pan

[maple flats]

For sure. A flue pan either raised or drop flue takes far more metal and time to build. I don't know if you are too late for 2025 season, but one of the best prices will be found at A&A Metal shop. His pans are all lead free soldered. 540-326-1407. He's Amish, his phone is in a small shed about 100' down his driveway from his shop. You will need to leave a message and he will call back. I just bought a 2x6 evaporator from him for $3100 earlier this year, raised flue. Drop flue was the same price. He told me he prefers building raised flue. It likely won't help but you can tell him Dave Klish sent you (but it won't hurt either). He is in Monterrey, Virginia, almost in West VA.

[BAP]

Check out Randy Worthern in Spofford, NH. He builds flat pan evaporators. He advertises them on Facebook Marketplace. His number is 6zero3-7four8-99two7. Currently he has 2x6 all flat pan advertised for $2000. They probably aren’t they same quality as some of the big name brands, but if they get the job done and get you what you need then that’s all that matters.
https://www.facebook.com/share/ASu5SMjuRNAxPnTy/?mibextid=79PoIi

[On the ledge]

Also check out W.F. Mason in Maine. He makes very nice evaporators.

[maple flats]

My original 2x was a drop flue. While 25-27 was not the average, I did get it at times, whyen everything was right. My 3x8 was a raised flue.
As far as how much detter for raised or drop flue over a flat pan, it all depends on the amount of added surface area over that in a flat pan. I forget the number but a flat pan has a given max boil rate based on its surface area. Once the flues are added, th surface area is increased several times. For example, on my final raised flue pan on my 3x8 had flues that were 10" tall and in the 3x5 flues pan the raised flues were all of the 5' less about 2" on each end and flues repeated fully across except another 2" flat all of the width of the pan. Those flues were 5/8" apart and maybe 7/8" wide, maybe less. When the added surface area is totaled that's how much extra surface there is to transfer the heat from under to in the pan. I can't give a number but it is several times better. In an evaporator that is 3x8 with a 3x3 syrup pan (flat bottom) and a 3x5 flue pan over well 75-80% of the evaporation occures in the flue pan, maybe over 90%. Iv'e read the comparison someplace but I don't recall the numbers.
Just remember that it increases the surface area many times.
If I remember to check it in my new evaporator, another 2x6 I'll get a count, and try to do the math based on the measurements. Maybe someone on here will chime in.

[wvfdc4]

I ran a Mason 2x4xl for the past 2 seasons with absolutely no complaints. I replaced it this year with a 2x8 CDL unit as we have grown in taps beyond the little guy. It is for sale though if you happen to be interested, let me know

[SapTsunami]

I may be interested in that Mason 2x4. Sent you a private message

[wvfdc4]

Replied to your message

[berkshires]

Just to give you a sense of what to expect, I have run a mason 2x3 xl with a divided flat pan for a few years. Note that this is one foot smaller than the 2x4 you're looking into.

With dry wood and a blower (AUF) I average about 12 GPH over the year. Before the blower I was averaging about 7.5GPH.

To put it another way, in my biggest year, I collected and boiled 630 gallons of sap. I ran out of dry wood and had to use a lot of green wood, which really sucked. But even so, I only spent 56 hours boiling. 56 hours was a big season for me, but still manageable.

If your estimates are correct (and they seem fair for a typical season) you would be boiling 1/3 the amount of sap as I did, on a bigger evaporator. One thing to keep in mind is that every so often you may get a monster season (as much as 2 - 3 times normal sap). I think with your setup you would be ready for it. In my case I was not. The limiting factor for me was actually neither time nor the evaporator but wood. So I advise anyone to keep 1.5 to 2 seasons of wood available. It will give you a head start on your next season of wood for most seasons, and then when you do have a monster season you'll be ready for it.

So in my opinion, with dry wood and a blower, on a Mason 2x4, once you're operating efficiently (keep the sap level in the pans even and low, keep the fire fed well) you should easily be able to keep up with that number of taps with an RO on a typical season, and on a big season it will be a stretch, but doable.

Cheers,

GO