Use and Care Manual
27
TROUBLESHOOTING
9.1 FREQUENTLY ASKED QUESTIONS
Why has the freeze dryer been
running for over 46 hours and the
process is not complete?
There are a number of factors that
can contribute to longer cycle
times. Some of which may be a
combination of the following:
1. Some foods are more challenging
to freeze dry than others. Because of
their cellular structure and moisture
content, oranges, pineapple,
strawberries, blueberries, and other
foods/meals with high amounts of
liquid will take longer to freeze dry.
The freeze dryer is measuring the
moisture content and knows when
the process is complete.
2. There is so much water in the
food that the condensed ice ring has
begun to form on the trays. While
rare, if this occurs, the freeze dryer
will not be able to recognize that
the process is complete because it
will sublimate the ice that is coming
onto the trays. In a situation like
this, it would not be able to verify
that all of the moisture is removed
because of all the ice. If this
happens, simply remove the trays
and put them in the freezer, defrost
the ice in the freeze dryer, put the
food back in the freeze dryer, and
allow it to nish the process. Again,
this is very rare.
3. Your vacuum pump oil needs to be
changed after every batch. As the oil
in your vacuum pump gets older, the
cycle time for the foods will increase. If
the oil in your vacuum pump needs to
be changed, a batch of food that would
normally take 24 hours to complete,
could take 46 hours to complete.
4. The freeze dryer is working
properly if during the vacuum
pump/drying portion of the freeze
dry cycle, the vacuum is reading
between 400-800 mTorr. If the
reading is consistently above 800
mTorr, it is likely time to change
your vacuum pump oil, check for
leaks, or clean your vacuum pump.
After my freeze dryer completed
and I released the drain valve,
water came rushing into my
vacuum chamber. What happened?
Make sure to empty the sink or
bucket that your freeze dryer drains
into. If the drain hose is sitting in
water (from previous batches of
food) and the vacuum is released
through the drain valve, water
will suck through the drain hose
and into the freeze dryer vacuum
chamber like a giant straw.