metrics vary considerably from one model to anoth-
er. For example, pull down and warm up can vary by
three times or more between manufacturers.
A lab manager can use these metrics to see how a
ULT is performing, but care must be taken before
using these metrics to decide if a ULT should be re-
placed. For example, the metrics mentioned come
from specic locations in a ULT, and where they get
measured matters. Pull-down time in the center of a
ULT, for example, can be very dierent from the top
or bottom.
Dollars and sense
In some situations, especially when a ULT contains
hundreds of thousands of dollars’ worth of samples,
a lab manager might prefer to replace a unit before
it acts up. In a case like that, a small investment could
prevent a tragedy.
“If a freezer is ten years old, think about replacing it,”
Richardson suggests. “You don’t want to wait until
a unit fails, because you could lose $100,000 of cell
samples when you could have purchased a replace-
ment ultralow for a fraction of the cost.” Instead of
taking that risk, some lab protocols call for changing
out freezers after some number of years. Alternative-
ly, lab managers use a metric based on energy use
and performance to decide when to replace a ULT.
For example, a plug-in energy meter can be used in a
4-6 hour test of the voltage, wattage, and amperage
draw of a ULT. Tracking that over time can help a lab
manager estimate the best time for a replacement.
As a baseline to use, a ULT’s energy consumption in-
creases by about 3% every year.
The economics of ultralow replacement can be
pretty simple. If a compressor goes out, that’s a
$3,000–4,000 repair. That’s about half the cost of a
new freezer, and it’s time to get a replacement. “If a
repair is 25% of the cost of a new one, then replace
it,” says Richardson, “especially if the freezer is over
ten years old.”
It’s not just a compressor failure that can trigger a
replacement. Other damage, often caused by im-
proper use (see “Best Practices”, page 6), can cost
enough to make replacement the best choice from
an economic perspective. As an example, replacing
all of the gaskets costs a couple of thousand dollars.
That hits or surpasses Richardson’s 25% rule, and it’s
time for a new freezer.
Ultimately, a lab makes up its own rules for when
and why to replace a ULT. The key is making sure that
the rules in place prevent a disaster. That requires a
set of testing procedures and decision points based
on the results. Then, the testing must be performed
as planned. That way, a lab manager can follow an
objective method for keeping ULTs working as need-
ed. Only then can a lab’s precious and pricey samples
stay safe.
Blizzard Ultralow Freezers come standard with a built-in mon-
itoring system that displays system performance with multiple
alarm conditions to keep your samples safe. A voltage monitor
displays power input and automatically makes adjustments to
supply consistent power to the freezer.
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