Off Grid Solar Powered Maple Sap Vacuum System

The traditional method for gathering maple sap has been to drill a hole in a maple tree in early spring, insert a tap in the hole, and hang a bucket on the tap. You then collect the sap from the buckets and haul it to an evaporator for processing. I have used this method for decades. It's low tech, simple and effective. Carrying all that sap is also a ton of work and hard on your body if you have lots of taps in. This year, in northern Wisconsin, it would have been impossible given the heavy snow cover on the ground. In the last couple of years I have been pondering how to set up a 3/16 inch pipeline. The problem I faced is that my maple trees are on flat ground in a remote location away from any power source. Gravity fed 3/16 inch pipeline systems require 50-60 ft of drop from the first tap in the line to the collection point to develop maximum vacuum and I only have 6-8 ft. One way around this is to use a vacuum pump, but I have no access to power to run a commercial maple sap vacuum pump. Additionally, commercial maple sap vacuum pumps are large, expensive, and complex - designed for big operations with extensive pipelines and thousands of taps. I wanted an inexpensive, environmentally friendly 12-volt system I could power with solar panels that would serve a couple of hundred taps. Enter the Shurflo pumps and inspiration from Spruce Creek Farms in Ontario, Canada. These 12V pumps are designed for use in RV's and boats. They are diaphragm pumps that have two attributes that make them perfect for this application - they can run dry without damage to the pump and they can handle the freezing and thawing that is integral to maple sap production. I have now built such a solar powered vacuum pump maple sap system and it’s working great. This Instructable tells you how to replicate my vacuum pump system.

The smaller Shurflo 4008 pump (3 gal/min) shown in this Instructable will service around 200 taps and, in a decent year, should produce enough sap to make somewhere between 50 and 100 gallons of maple syrup. The larger Shurflo 4048 pump (4 gal/min) shown in the attached video will handle 300+ taps. In addition to the vacuum system you will need to purchase 3/16 inch tubing, taps, T-fittings and splices to set up your pipeline – I have about 5000 ft of 3/16 in pipeline with 240 taps strung over about 6 acres of maple trees. Generally, with 3/16 inch tubing they tell you to restrict the number of taps on each line to 25. I've read you can exceed this number, and I have several lines with 30-32 taps which seem to be working fine. Additionally, you will need a central collection tank (I use a 144 gal stock tank) and some sort of vehicle and transport tank to get your sap to your evaporator.

The attached pdf file has a complete list of components, suppliers and costs. I have no particular affiliation with the suppliers mentioned, they just happened to be the ones I used. Components may be available from other suppliers at other costs. The total cost of the system was just over $260.

The purpose of the pump box is to house the vacuum system and protect it from the elements.

Drill half a dozen ¾ in drain holes in the bottom of the 50 gallon plastic tote to allow drainage of any condensation or leaks

Screw the 2X4 rails along the bottom of the piece of plywood. This raises the plywood off the bottom of the pump box. Screw the battery box across one end of the plywood with a couple of ¾ in pan head screws. You are done with the pump box for now. After you get the system assembled you will need to drill some holes in the side to allow the 3/16 in tubing to come in from the trees and the ½ inch hoses to go into the collection tank from your pump and bypass. You will drill another 1 inch hole opposite the solar charge controller to bring in the wire conducting power from your solar panels.

Assemble the pump, screen filter, bypass valve, pipe fittings and star fittings. Use Teflon tape to seal all the junctions.

The only star fittings I could find were 5/16 so it was necessary to add some adapters to go from 5/16 to the 3/16 of my pipeline. (If you can find 3/16 star fittings this step is not necessary). Cut nine 4 inch long pieces of 5/16 in sap tubing. Insert a 5/16 in to 3/16 inch adapter in one end of each piece of tubing. Heating the end of the tubing in a cup of hot water makes this easier. Attach each tube to the star fittings. Screw the pump and attached plumbing to the plywood. I used a small block of wood to support the pipe under the star fittings.

Screw the bus bar onto the plywood next to the pump. With a sharpie, mark the positive and negative sides of the bus bar.

Screw a small block of wood 1.5in by 1.5in by 2.5in on the plywood next to the bus bar. You will attach the temperature controller to this block with a zip tie. Screw the solar charge controller and relay to the plywood next to the battery box. Screw the switch box for the master on/off switch to the plywood

Wiring

Use 10 gauge wire for all connections between the battery, solar charge controller, relay, bus bar, master switch and pump. Use 12 gauge wire between the temperature controller, relay and bus bar.

Fuse and Master On/Off Switch

The purpose of the fuse and master off/on switch is to protect the circuitry and provide a way to turn the entire system on and off.

Crimp a small ring fitting on the end of the fuse holder wire and attach to the positive bus bar. Depending on the size of the pump a 10 or 15 amp automotive spade fuse fits in the fuse holder. Use a butt crimp fitting to attach a 1 ft piece of red 10 gauge wire to the fuse holder and run into the switch box and attach to one terminal of the switch. Attach a second 1 ft piece of red 10 gauge wire to the other terminal on the light switch. The other end will attach to the red wire of the relay.

Relay

The purpose of the relay is to allow more power to run to the pump than the contacts in the temperature controller can handle. When the temperature controller turns on, it sends a signal to the relay to turn on, which in turn sends power to the pump motor. The relay should have five colored wires coming out of it – white, black, red, blue and yellow. The yellow wire in the center is not used and can be cut off. Crimp a small ring fitting on the black wire and attach to the negative bus bar. Use a butt crimp fitting to attach the blue wire of the relay to the red wire of the pump. Crimp a small ring fitting on the black wire of the pump and attach to the negative bus bar. Use a butt crimp fitting to attach the red wire of the relay to the red wire coming from the master off/on switch. The white wire on the relay will attach to the red trigger wire coming from the temperature controller once the controller is installed.

Solar Charge Controller

The purpose of the solar charge controller is to charge the deep cycle battery from the solar panels. It also monitors how much power the pump is using and compensates by sending the right amount of power to the battery to keep it charged.

The controller will have 3 slots each accepting a positive and negative wire. The first slot is the input from the solar panel. Attach a 2 foot piece of 10 gauge red and black wire to the positive and negative terminals. The wire coming from the solar panel will attach to these two pigtails with red twist on wire connectors. The second slot is to the battery. Crimp on large ring connectors at one end of a 2 ft length of 10 gauge red and black wire. Red connects to the positive and black to the negative battery terminals. The other end of the wires attach to the positive and negative terminals of the battery slot on the charge controller. The third slot is labeled “load” or will have a little light bulb icon. Crimp small ring connectors at one end of a 2 ft piece of 10 gauge red and black wire. Red connects to the positive bus bar and black to the negative bus bar - this connection "powers" the bus bar. The other end of the wires attach to the positive and negative terminals on the load slot of the charge controller. When attaching power to the charge controller always attach the battery before the solar panel. Reverse the process when disconnecting.

Temperature Controller

The purpose of the temperature controller is to automate turning the system on and off. Maple trees run best when it freezes in the 20's at night and thaws in the 40's during the day. The controller measures the outside temp and turns the system on and off automatically.

The temperature controller will have 3 slots each accepting 2 wires. One slot should already have a temperature sensor attached. When the system is fully assembled the temperature sensor should be run outside the pump box on the shady side of the box through a small hole. The second slot is the power slot. Crimp on small ring connectors at one end of two 1 ft pieces of 12 gauge red and black wire. The red wire attaches to the positive bus bar, the black wire attaches to the negative bus bar. The other ends attach to the positive and negative terminals of the power slot of the temperature controller. The third slot is the trigger slot. Crimp on a small ring connector at one end of a 1 ft piece of 12 gauge red wire. The ring connector attaches to the positive bus bar. The other end attaches to one of the terminals in the trigger slot. To the other terminal in the trigger slot attach another 1 ft piece of 12 gauge red wire. This wire will attach to the white wire of the relay using a butt crimp fitting. Once the temperature controller is wired use a zip tie to attach to the block of wood you screwed to the plywood.

Set your temperature controller to “cooling mode” to turn on at 33F and off at 32F. When the outside temp hits 33F and the temp controller turns on it will send a positive voltage to the relay, which in turn will turn on and send power to the pump. When the temp drops to 32F it will turn off.

Use some wire staples to secure all the wires to the plywood. Set the system in the pump box. Drill 1 inch holes in the end and sides aligned with the ½ inch hose outputs from the pump and bypass. Attach 3 ft long pieces (or longer depending on your collection tank arrangement) of 1/2 inch hose to the pump output and bypass and secure with 1 inch hose clamps. Both hoses will exit the pump box and run to the collection tank. Drill four 1 in holes opposite the star fittings to allow your 3/16 inch sap lines to come into the pump box and attach to the star fittings. Drill another 1 inch hole opposite the pigtails from your solar charge controller to run the wire from the solar panels into the pump box. Use standard red twist on electrical wire connectors to attach the solar panel wire to the pigtails. Drill a 3/16 inch hole near the top of the back of the pump box. The temperature sensor will exit this hole and sit outside the pump box by an inch or two. Orient the pump box so the temperature sensor is in on the north side in the shade.

Solar Panels

Using the smaller Shurflo 4008 pump shown in this Instructable 160 watts of solar panels should be sufficient to run the pump and keep the battery charged. The larger Shurflo 4048 pump in the video draws more power so I added an additional 100 watt panel for a total of 260 watts. DC current needs big wires to flow any distance, so I recommend at least 10 gauge wire running from your panel(s) to the charge controller. Keep the wire the minimum length necessary. I have my panels about 75ft from my pump box in a clearing in the woods where they get maximum sunshine. I built some simple hinged frames out of 2X4’s to hold the solar panels and adjust to face south and angle up at 45 degrees to get maximum sun exposure. As mentioned earlier, always attach the battery to your charge controller before you attach the solar panels. Reverse the process when disconnecting.

Vacuum Gauges

A vacuum pump is most effective when there are no vacuum leaks in the system The best way to monitor this is with vacuum gauges. I attached one to an incoming sap line close to the pump box to measure the vacuum at the pump. I also put one at the end of each line. By monitoring these gauges you can tell if you have a vacuum leak. If there is a leak in the line, the vacuum will be much reduced or zero. You then need to walk the line and find the leak. It might be due to a squirrel chewing a hole through a line, or a fallen branch, or a damaged or dead tree leaking air into the system. You will see tubing full of sap with a few little bubbles up to the leak and tubing full of air after the leak. Have some splices handy to fix these leaks and you should be able to maintain 20-25 in of Hg near the pump and 15-20 in of Hg at the end of the lines. Long lines with more taps generally will have lower pressures at the end of the line.

Optional 12 volt transfer pump
You will need some sort of pump to pump the sap out your collection tank into whatever tank you are using to transfer the sap to the sugar shack. I use a 12V 350 gal/hr transfer pump to transfer the sap from the collection tank to a 125 gal transfer tank on the back of my gator. The transfer pump is connected to the battery with large ring terminals. I have a short piece of garden hose with a shut off tap running out of the collection tank and another hose running from the transfer pump to the transfer tank.

Take your finished pump box, your battery, your solar panels and your collection tank to the sugar bush. I set my collection tank and pump box in a little depression in the middle of the bush so the pipelines extend out like crooked spokes on a wheel. Set the pump box on top of your collection tank and run the 1/2 inch hoses from the pump and bypass into the tank. Install the battery and connect the large ring terminals from the "battery" slot on the charge controller. Set your solar panel(s) up in a sunny area as close as possible to the pump box. Arrange the panels facing south angled up at 45 degrees to catch maximum sun. Run a length of 10 gauge house wire from the panels to the pigtails coming from the charge controller. Keep the wire as short as possible. Inside the pump box attach the wire to the solar charge controller pigtails with red twist on wire connectors. Run your 3/16 in sap tubing in through the holes on the back of the pump box and attach to the 3/16 inch adapters extending from the star fittings. Set the temperature controller to a "cooling cycle" to turn off at 32F and on at 33F. If necessary, calibrate the temperature controller to the correct outside temperature. Set the bypass valve to route sap through the pump, turn on the master switch and wait for the sap to run. You are ready to go!