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• ULT freezers are not ash freezers or blast
freezers. They are meant to store and conserve
product that is already frozen. Excellent
freezers might be able to tolerate being
loaded full of warm product, but regular ULT
freezers will break down with time under that
type of use. It is best to load the chamber at
most a quarter full with free-frozen product,
and avoid putting warm product into it. A
facility such as a blood bank, which has a
high volume of warm product which must be
cooled quickly, might make the mistake of
purchasing a ULT freezer when a blast freezer
would be more appropriate. Continued use of
a ULT freezer to rapidly cool warm product can
cause the freezer to suer mechanical failure
more quickly.
Avoid side by side spacing unless a ULT freezer is locat-
ed in a specially designed freezer farm. There should
be no storage on top of a ULT freezer.
• Another major consideration is if the freezer
will need to pass through a standard-sized
door opening. Most freezers are built to
international standards of 90 cm (35 1/2”)
wide and 2 m (78 3/4”) high, the size of a
standard European door. A rule of thumb
manufacturers recommend is to purchase as
big a freezer at the best price per ft3 capacity
that still will be able to pass through the door.
Larger freezers should have parts which can
be removed to t it through a door.
• The decibel rating of a ULT freezer becomes
important if it will be located next to an
oce or other quiet work space. Good
quality freezers need not be noisy; NuAire
ULT freezers are rated at only 47dba, versus
competitive freezers rated at as much as
73dba.
Avoiding frost
• Frost can accumulate on ULT freezers when
water vapor comes into contact with cold
interior surfaces. Frost build-up can interfere
with closing inner doors or even the outer
door if excessive frost turns into ice. Every ULT
freezer will accumulate frost, this is simply the
nature of very low temperature surfaces when
humidity is present.
• The best freezers provide features to minimize
frost build-up. For example, claw latches to
secure inner freezer doors, tighten the hinge
against the gasket. Low-wattage halo bypass
heaters help keep gaskets around the outer
door clean. Insulation on the inner doors
as well as the outer doors help maintain
temperature to the greatest extent possible.
When installing multiple freezers in a row it is import-
ant to space the freezers at a minimum 5-inches (127
mm) a part and away from the walls, as well as allow
for at least 8-inches (203 mm) of spacing between the
ULT and ceiling.
