This is a question that any average person should ask when they have just arrived home with a new food dehydrator and are excited to start drying food. The first trial is often something from the refrigerator or a few pieces of fruit.
It is not uncommon for there to be enough food for just a few trays, so the question about safety and the number of trays involved pop up.
Will my machine be damaged if only some trays have food and the rest are unused? We believe we can answer your question for you.
After many years of using several dehydrators, we can categorically state that it is completely safe to run your dehydrator with trays removed during the drying operation.
How dehydrators work
Food dehydrators operate by the airflow of low heat passing over moist food, and this airflow pulls the moisture from the food and removes it from the dehydrator.
Fresh cool air is pulled past the heating element and pushed into the drying chamber or stacked trays.
This warm, dry air then attracts moisture from the surface of the food and removes it from the chamber when the air is expelled from the machine. The fresh warm, dry air then replaces the expelled moist warm air.
This is a dynamic process that continues until you either turn the device off manually or the dehydrator you have has a built-in timer that takes care of that for you using a predetermined time frame.
It does not matter how full or empty your machine is with trays, the heater still gets warm, and the fan blows air across the heating element.
The only thing that will change with just a few trays vs. a full machine of trays is the time required to dry the food to the level you require entirely. Fewer trays are often faster.
Reasons why only a few trays are needed
The reasons why only some trays are needed could be because of not having enough food to run a full machine or because the food to be dried is thicker, and you need the extra airflow.
This is more for the cabinet-style of dehydrators like the Excalibur.
The round stacked driers often don’t have this ability with the off-the-shelf kits, but some have spacer rings/trays available that allow taller items to be placed in the machine.
They are limited to the size of food that a tray can fit below the tray above it if you don’t have access to a few spacer tray rings to allow the extra headroom.
Using spacer rings is a process some people use for setting homemade yogurts. These round dryers help create a tall empty chamber much like a low temp oven, which sets an example of a machine operating with few trays but a larger space. No harm is done at all.
Airflow changes with less trays
The airflow inside a machine can change with fewer trays, which is likely to be a benefit because the same volume of air is available for less food.
This is the case for the cabinet driers.
The round stackable style machines will be faster to dry with fewer trays because of less impedance to the flow of air and less moisture needed to be removed.
The machines we are personally familiar with are the fan with heat in the base unit machines. They dry food faster with fewer trays involved, but this can equate to more cost per tray to dry in the long run. We prefer to load them up.
We also run two simultaneously when heavy fruit loads come in from the self-sufficient garden. Then it is all trays loaded up, and the machines don’t stop for weeks at a time.
Will damage be done
No damage will be done to a dehydrator if only some of the trays are used in the machine, with the unused trays having been removed.
It makes little difference to the machine if it is empty or half full and possibly will shorten the time needed to dry your product.
If bench space is not available to stack the spare trays for a day or two while drying, then, by all means, put them in the machine with the produce-loaded trays, using the empty trays as spacer trays.
The takeaway here is it comes down to your personal situation with space. The machine will not be bothered or damaged one way or the other.
How to use a dehydrator with only a few trays
We have experience with the round stacking machines as we have four operating machines and one needing repair(or used as spare parts).
No matter how many trays we require, we will always use a single empty tray with a catch sheet at the bottom to help disperse the airflow around the edges of the trays and to help keep the base unit from being covered in food that drips or dries so small it falls through the cracks.
We then place how many trays we have food for on top. This can be any number between 1 and 30 trays (depending on the machine in use). We have run the machines with just a single tray on top of the base tray and they operate just as well as if it is 10 or more trays high.
The need to rotate and shuffle the trays as the food dries is still there, but the single tray process only needs to be rotated less regularly.
The overall time taken to dry the foods will vary, but no harm is done to the machine if it takes longer or a shorter amount. Some foods need to be watched over as high-sugared fruit will go brown.
We don’t like to run an almost empty machine often, but the odd occasion does pop up. A dehydrator with all available trays is far more effective and efficient.
Sometimes the food cannot wait and needs to be processed straight away.
We can say that the machines are a little noisier when running with just a few trays, and that is because the airflow is moving faster through the machine.
When the machine is full, the trays act like sound mufflers. It’s no big deal and hardly noticeable, but worth mentioning.
We recommend you follow all directions related to your particular brand and model.
Unless there are specific sections warning against operating the machine less than full, we believe that all of the information above is relevant and applicable.
Naturally, we cannot be held liable for anything you do with your machine, so please use common sense. If you are still in doubt, contact the manufacturer and ask for their advice and assistance.
Article by Tim Blanch for TheTropicalHomestead.com. He is a qualified Permaculture designer.