The exterior door gasket provides an excellent seal that protects product,
provides an energy efficient thermal barrier to keep cold air in and room
temperature air out and reduces frost build up on the inner doors.
Because the door gasket seals so well, a vacuum can be created after a door
opening. Warm air enters the cabinet, cools and contracts, creating a
vacuum that pulls the door in tightly against the seal.
To equalize the pressure inside the cabinet after a door opening requires
1.5-3.0 cu.ft. of ambient air to be drawn into the cabinet. The amount of
air required to equalize the pressure varies depending on the cabinet size,
cabinet temperature, duration of door opening, inventory volume and the
temperature/humidity of the ambient air. The unit is designed with a
“vacuum relief port” that allows the pressure to be equalized.
The time required to draw 1.5-3.0 cu.ft. of air into the cabinet depends on
two factors,
a) Size and number of paths available for the air to enter the cabinet, and
b) Pressure difference between the internal cabinet and the ambient room.
Cabinets with the vacuum relief port operating normally, (i.e. vacuum
relief port is not iced over) will require a minimum of 30 seconds up to a
maximim of 120 seconds for the cabinet to equalize. This is also a good
indication that the exterior door is well sealed.
The vacuum relief port requires routine maintenance. It will ice over unless
preventive measures are taken. If the vacuum relief port becomes iced over,
the freezer will take several hours to equalize pressure.
Caution
Do not leave the freezer unattended with the door unlatched. The
vacuum could release, resulting in a door opening and the potential for
product loss.
s
Vacuum Relief Port Maintenance
Monitor the inner port opening on each door opening for frost and ice
build-up. Remove any frost with a soft dry cloth. If the tube should
become clogged with ice, it must be cleaned. Clear the vacuum relief tube
completely free of ice to prevent rapid ice formation.
Factors that can affect the performance of the vacuum relief port include:
high ambient temperature, high humidity conditions and frequent door
openings. Maintenance should be performed weekly, or as needed.
Caution
Failure to maintain the vacuum relief port may result in excessive
ice build-up inside the tube, clogging of the port, and the inability to open
the door. The vacuum relief port may need to be cleaned more often with
frequent door openings and high humidity environments.
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4-4
Isotemp Basic
Fisher Scientific
Section 4
Maintenance
Clean Vacuum Relief
Port (min. monthly)
Summary of Contents for Isotemp Basic -86C
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