Freeze Dryer Problem Diagnosis Guide
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How the Freeze Dryer Works
The freeze dryer should be set up in an area that has good ventilation and isn’t too hot or too cold. The ideal operating room temperatures for the freeze dryer are between 50 and 75 degrees Fahrenheit. A little hotter and colder is not a big deal, those are just the ideal temperatures. The freeze dryer should not be boxed into a corner or cabinet, but should have room to breathe, so to speak, on each side, to prevent overheating of the pump, electronics, and refrigeration components. The freeze dryer needs to be able to drain the water removed from your food at the end of the batch. The water cannot drain properly if the freeze dryer is on the ground. For proper draining, be sure the freeze dryer is set up on a horizontal surface at least 3 feet above the ground, with the drain hose dropping vertically from the freeze dryer (not resting horizontally on the same surface as the freeze dryer).
For foods, the factory settings on the Home Freeze Dryer are all set and ready to go and should not need any adjustment (although you are welcome to experiment). For candy, we recommend setting the tray or shelf temperature limit to 150 degrees Fahrenheit. For pharmaceutical products it’s usually best to set the shelf temperature down to around 45 degrees Fahrenheit, although experimentation is likely required to get the temperature just right for the desired results for each specific pharmaceutical product. If you find that a certain type of food is not finished at the end of the process, you can add extra dry time at the end of the cycle. The next time you freeze dry that food, you may want to go into your settings and add additional dry time beforehand. If you’re finding that a certain type of food is requiring additional freeze time, you may want to consider adding additional freeze time to this type of batch beforehand the next time. For more information about candy mode- watch this video: https://youtu.be/-7c1djFLf4c
A Note About Candy:
The Harvest Right freeze dryer was originally designed for food storage and preservation. Over the last few years, freeze dried candy has become very popular among customers and consumers alike. Harvest Right has done its best to create a software program that would help assist candy makers in getting better candy results and shorter run times. Activating that program on our latest software version is outlined step-by-step in the video linked in the previous paragraph (https://youtu.be/-7c1djFLf4c). The freeze drying process was designed to remove water from food. There are certain foods that do not freeze dry well, such as chocolate and foods that are high in oil or fats. Similarly, there are candies that do not freeze dry well due to the structure and ingredients of the candy and the difficulty of removing water from different substances and structures. Many times there is nothing functionally wrong with the freeze dryer, or any of its parts, and yet a certain type or brand of candy does not dry or puff up as desired. Unfortunately, we do not have all the answers as to specific settings, or preparation tricks, for each and every type of candy, however, we will always do our best to help in any way that we can. In turn, we ask that customers take the time to research and experiment with different candies in order to figure out what works best for them in their unique circumstances.
The purpose of freeze drying is to remove water from the food. Keep this in mind when preparing your trays of food and ask yourself the question: How can I prepare this food in a way that will allow the water to release easily? For items like blueberries, which have a consistent skin around the outside, it is necessary to poke holes in the skin or cut the berries in half in order to create a way for the water to escape during the freeze drying process. In general, cutting your food items into small, single layered slices is the best way to set yourself up for success in freeze drying. Each item needs to be touching the tray in order to fully dry properly, so, do not layer your food on top of each other. Another good rule of thumb to follow is not to let your food exceed the rim of the tray, especially for items with high water content like fruits, vegetables, liquids, etc. The more food you put into the freeze dryer, the more water there is that will need to be removed from the food, and the longer the batch will take. Smaller batches that finish in half the time are easier on my freeze dryer (and vacuum pump) and provide consistent, dry results as opposed to doubling the food and doubling the process time while risking errors and wear-and-tear issues that stem from overloading.
After pressing start, the freeze dryer will start a 15 minute pre-cooling process. You can insert your trays of food during this 15 minute pre-cooling process or you can wait until the 15 minutes are up. It’s important not to delay putting the food into the freeze dryer after the 15 minute pre-cooling process is up and the screen prompts you to load your trays. Your freeze dryer will continue to freeze while it waits for you to load your trays. You don’t want your freeze dryer to be freezing colder and colder without your trays inside. In order to have your food frozen down to the proper temperatures, and in order for your food to freeze at the same rate as your freeze dryer, the food needs to be inside the freeze dryer while the machine is freezing (even if your trays are pre-frozen). The longer your food has a chance to freeze inside the machine during the freeze cycle, the better and more smoothly the rest of your batch will go. It is imperative that all of the water inside each particle of food is frozen down to the very core at -10 degrees (not just frozen on the surface of the food). If this does not happen during the freezing cycle, the unfrozen moisture in the center of the food will not sublimate properly and will get sucked into the vacuum pump when the pump kicks on in Vacuum Freeze. Water is the number one thing that will wear and tear on your pump and cause vacuum issues, which is why the freezing cycle, along with not overloading the trays with too much food (and water content), is so important.
After the food is frozen down to the initial freeze temperature in your settings (default is -10 degrees Fahrenheit), your freeze dryer will move into the vacuum freezing process. During this process, the vacuum pump turns on as signaled by the freeze dryer. Be sure that your vacuum pump power cord is plugged into the back of the freeze dryer (not the wall) and that your vacuum pump power switch located on the back of the pump is in the (I) or ‘on’ position. In order for your pump to pull a deep vacuum, you need to ensure that you have a closed system. This means that the drain valve needs to be closed tightly, the door needs to be closed tightly (turn the latch twice), and the vacuum hose needs to be connected tightly at both ends. For reference on making sure each of these things is done correctly and that there are no air leaks, check out this short video: https://youtu.be/nVvTP_MoQ0M
As long as you have a closed system and your vacuum pump has been well maintained (clean/transparent oil in the sight glass for oil pumps), the vacuum pressure in your vacuum chamber should start to drop. As the pressure starts dropping, the process of sublimation starts to occur. Sublimation is the process of water going from a solid (ice) to a gas without passing through the liquid state. The frozen water in your food will start turning into a gas and will rise out of your food and freeze onto the chamber walls, forming ice on the walls. This sublimation process starts to happen while your vacuum pressure is in the thousands, and will happen more and more as the pressure continues to drop. During this time, our freeze dryer is sensing the rate that the vacuum pressure is dropping and monitoring that rate to make sure your batch will be successful.
One thing that can cause the vacuum pressure not to drop very well, is if there is unfrozen water still in the core of your food. If this is the case, that water will be getting sucked into the vacuum pump. The pump is only supposed to be vacuuming air (not water) and if it is vacuuming water, the pressure won’t drop as well. If the freeze dryer recognizes a slow pressure drop rate, it will assume that this is happening and that the food needs more freeze time to ensure that unfrozen water does not continue to go into your pump. This is a safety feature that will add years to the life of your pump by not putting excess water into it. If this happens, your pump will temporarily turn off and the freeze dryer will go back into the freezing cycle for 30 minutes to an hour to ensure everything is frozen properly. After doing this, the freeze dryer will go into vacuum freeze and turn the pump back on and try again. If you find your freeze dryer is repeatedly doing this, it would be wise to check to be sure that you have a closed system. It’s possible that the reason the pressure isn’t dropping is because there is air getting in through the drain valve or the vacuum hose, etc.
These videos can help you find air leaks:
How to Run a Vacuum Test: https://youtu.be/G1FIk0YVDEc
How to Check for Big Leaks (mTorr above 1000): https://youtu.be/nVvTP_MoQ0M
How to Find Micro Leaks (mTorr below 1000): https://youtu.be/V8waJpZ19XA
The drying cycle comes after vacuum freeze and this is where the majority of the sublimation takes place. As long as the vacuum pressure is in a low enough range, the heating elements will turn on. Applying the heat to the shelves increases the rate of sublimation which causes lots of moisture to be removed from your food as a gas, re-freezing to the chamber walls which stay cold throughout the entire process. During the drying cycle, the temperature will fluctuate a lot. Don’t be alarmed if you see temperatures in the single digits at times as well as temperatures in the triple digits at times (depending on what your tray temperature limit is set to). Because applying heat increases the amount of water being released from the food, the freeze dryer will turn the heat on and off throughout the drying process to ensure that the water is released from the food at a manageable rate for the vacuum pump to keep up with, so that the water vapor can freeze to the chamber walls without getting sucked into the pump. This is why foods with high water content take longer to dry – the heat is applied in increments according to how well the vacuum pressure is keeping up and how low the mTorr is getting at that time. If the vacuum pressure is not low enough, the heat will not trigger to turn on. If the vacuum pressure IS low enough and the heat is not coming on, this will cause the ‘Mid Batch Heater’ failure to trigger, which often means that you need a new relay board. Assuming no errors, the heat will cycle on and off over and over again until the heat can stay on without the vacuum pressure rising. When this happens, the freeze dryer detects that there is no more or very little moisture being released from the food, signaling that the food is almost dry.
The final dry cycle is the last 2 hours of the drying cycle (unless you set extra dry time, then it will be longer). The freeze dryer is doing the same thing during final dry that it is doing in the drying cycle. Usually in final dry the temperature stays pretty close to the temperature set point and you will see less temperature fluctuations.
When the batch finishes, the screen will say ‘Process Complete.’ The freeze dryer will stay on this screen with the freezing component running unit you are able to come to the machine. The freeze stays on so that the ice that has formed around the chamber walls does not melt and rehydrate your food. The freeze dryer will sit like this, maintaining your freeze dried food, for days if necessary. You don’t need to be there right when the batch finishes. If the chamber is really cold when you get to the machine, you can click the ‘warm trays’ button which will warm your trays back to room temperature. If you want to check to see if your food is fully freeze dried, simply open the drain valve, open the door and check the food. If it is not fully dry, you can click ‘add more dry time’ and select the amount of time you would like to add. Be sure to close the drain valve and the door tightly again upon resuming otherwise the drying will not be able to continue.
Is My Food Dry?
The best way I know to check if the food is completely dry is to have one larger slice of food on each tray. When the freeze dryer says ‘process complete’, open the door, and break in half the larger/thicker slice of food on each tray. If that slice is dry and there is no ice in the core, then most likely the rest of the smaller/thinner slices willbbe dry as well. For liquids, check in the center of the tray for dryness.
Defrost and Cleaning:
When your freeze dryer finishes a batch of food it is imperative to ensure that the freeze dryer is fully defrosted, drained, cleaned, and dried before starting the next batch. Any remaining water in the chamber, when the next batch starts (whether that is ice on the walls or water droplets left over in the drain hose), has the potential to create a vacuum error on your next batch if that water is sucked into the vacuum pump. The whole point of freeze drying is to eliminate the water and dry the food, so doing your part to clean and dry your chamber in between batches by eliminating the leftover water will help significantly with the success of your next batch. Be sure to pull the shelving rack out and wipe underneath it as water can sometimes pool up underneath and is not visible until the shelf is removed.
Whether you choose to run the defrost cycle and heat the trays to melt the ice or just turn the freeze dryer off and leave the door open to let the ice melt on its own is not significant. Just be sure that the water is all gone before the next batch, unless you’re doing candy. There is hardly any water in candy, so you can run batch after batch of candy up to 5 batches without defrosting. Be sure to defrost and clean your chamber at least every 5 batches of candy though.
Clean your freeze dryer primarily with hot soapy water, using a dishwashing brush or brand-new toilet brush to get in between the shelves all the way to the back.
Freeze Dryer Set Up
HOW TO REHYDRATE FREEZE DRIED FOOD
BEFORE YOU START, FOLLOW THIS CHECKLIST:
- Is the drain valve closed? (The small handle on the valve should be perpendicular to the direction of the drain tube.)
- Have you cleaned the door?
- Is the black rubber gasket (door seal) clean?
- Have you replaced the oil in the vacuum pump?
- Is the vacuum pump filled with oil to the middle of the sight glass?
- Is the door closed and compressed tight?
HOW TO REMOVE AND CLEAN THE SHELF AND VACUUM CHAMBER
2. Then wash the shelf and the inside of the chamber with warm soapy water and rinse with warm water.
HOW TO REPLACE YOUR DOOR
WHAT YOU'LL NEED WHEN YOU TALK TO A HARVEST RIGHT TECHNICIAN
In order to talk with someone in Technical Support you will need the following:
- Your name
- Serial Number of your freeze dryer (found on the back of the unit)
- Your freeze dryer “log files.” These files contain all the information about how the freeze dryer has been working. You can get the log files by doing the following:
Put a blank thumb drive into the USB port on your freeze dryer.
Power off your freeze dryer and wait for 10 seconds.
Power your freeze dryer back on and wait for the files to load onto the thumb drive. This could take a few seconds, or a few minutes, depending on how many batches you have run.
You will know that it has finished when the screen comes back to “Start” on your freeze dryer.
Then take out that thumb drive and insert it into your computer and e-mail your Harvest Right technician the file that was downloaded onto the thumb drive. That file is titled “Harvest.”
PACKING UP YOUR FREEZE DRYER TO SEND TO HARVEST RIGHT
FREEZE DRYER REPORTS A VACUUM ERROR1. Watch and follow the instructions in the video, “Vacuum Error”
2. Download and follow the instructions in the “Vacuum Error Solutions” document
UNIT STILL CANNOT GET A VACUUM AND EPOXY PLUG LEAK IS INDICATED
If your unit still cannot get a vacuum and it is determined by a Harvest Right Technician that the problem could be your Epoxy plug that the heater wires come through then watch the following videos to solve this problem:
1. Watch the video, “Removing the Panels from Your Freeze Dryer”
2. Watch the video, “How to Confirm and Fix an Epoxy Leak”. This video will show you how to detect a leak as well as repair a leak.
EPOXY PLUG NEEDS TO BE REPLACED
REPLACING DRAIN VALVE
REPLACING VACUUM SENSOR
STEP 1: CHECK FOR FROST PATTERN
a. First check for a frost pattern by powering on the freeze dryer.
b. Press “Start” and sequence through the screens until the unit begins “Freezing.”
c. Open the freeze dryer door and let it run for 60 minutes.
d. After 60 minutes you should see a frost pattern that extends ½ the length of the chamber or more. Touch the walls of the chamber, if they are not cold, or if you do not get a frost pattern then proceed to STEP 2
STEP 2: CHECK CONDENSER FAN & RELAY BOARD
a. Check to make sure your refrigeration condenser fan is running. You can hear it and you can feel it blowing air out the sides of your freeze dryer. If you want to be certain, take a thin strip of toilet paper and hold it next to the side of the freeze dryer where the holes are. On one side of the freeze dryer it will be sucked to the holes and on the other side it will blow away from the holes. If the fan is working then do the following:
b. Check to see if the computer relay chip for freezing is switching on. You can do this by watching the video, “Testing Computer Relays.”
c. If the relay is faulty, the entire board will need to be replaced. You can purchase one from Harvest Right and replace it by watching the video, “Relay Board Replacement.”
IF THE RELAY BOARD IS NOT THE PROBLEMIf the relay board is not the problem, then it is likely that you have a bad refrigeration condenser. It may have a leak and will need to be charged with refrigerant. At this point you should talk to a Harvest Right Technician as you will likely need to send Harvest Right your freeze dryer or hire a refrigeration repair person.
If you hire someone, please have them follow the directions found in the document titled, "Refrigeration Repair Information."
STEP 1: IF YOUR FOOD NEVER GETS DRY
a. First power on your freeze dryer. Press start and go through all the buttons until the screen says “Freezing.” Then press the “Cancel” button. This will take you to the “Process Complete” screen. Then press “Defrost.” Wait for a couple of minutes and check the heater pad on each shelf to see if they are heating. You should also check the roof of the top shelf to make sure that one is heating too.
b. If your heaters do not get warm, then check to see if your heater cable has wires pulled out of it and that it is connected properly. You can do this by watching the video, “Shelving Plug Connections.”
If the heater wires are not the problem, proceed to STEP 2
STEP 2: IF THE HEATER WIRES ARE NOT THE PROBLEM
STEP 3: IF THE RELAY BOARD IS FAULTY
STEP 1: RECALIBRATING TOUCH SCREEN
When you push the buttons does it not respond properly?
This likely means that the screen needs to be recalibrated. To do that, watch the video, “Calibrating Your Display.”
STEP 2: IF YOU GET A BLACK SCREEN
Make sure the power plug is plugged firmly into the wall and into the back of the unit.
Make sure the switch on the back of the unit is switched to “On.”
Check your electrical outlet for power. Plug something else into the outlet so you can be sure that you are getting power.
If everything checks out, you may need to replace your LED Screen and computer board. This can be done by purchasing the computer board and screen from Harvest Right and by watching the video, “LED Display Screen Replacement"
If the power receptacle is shorted out, watch the video, "Replacing Main Power Harness"
Watch and follow the instructions in the video, "Replacing Power Receptacle."