Supplies; Electrical Connections; Environmental Conditions - Thermo Scientific 7451 Operating And Maintenance Manual

Supplies

Electrical
Connections
Environmental
Conditions
Thermo Scientific
The Controlled Rate Freezer requires a clean, low pressure (22 PSIG,
±30%) LIQUID nitrogen supply. Do not use the gas fitting on the supply
tank! A dedicated supply tank/source is recommended for optimum
operation. The tank hose connection, 1/2" flare fitting, is located on the
back of the unit in the bottom left corner. Do not over-tighten when
connecting. Internal plumbing could be damaged. Teflon tape is NOT
recommended when installing LN
low temperatures of this application. See Figure 2-1 for the connection
location.
Refer to the electrical schematics or serial data tag on the unit for electrical
specifications for the Controlled Rate Freezer.
1. Verify the power switch on the back of the unit is off.
2. Attach the power cord to the inlet on the back of the freezer. Connect
the power cord to the appropriate power outlet.
The Controlled Rate Freezer is designed to be electrically safe in the fol-
lowing environmental conditions:
• Indoors
• Altitude: Up to 2,000 meters
• Temperature: 5°C to 40°C
• Humidity: 80% RH at or below 31°C, decreasing linearly
to 50% RH at 40°C
• Mains Supply Fluctuations: ±10% of nominal.
• Installation Category II
• Pollution Degree 2
• Class of Equipment I
1 Installation category (overvoltage category) defines the level of transient overvoltage
which the instrument is designed to withstand safely. It depends on the nature of the
electricity supply and its overvoltage protection means. For example, in CAT II which
is the category used for instruments in installations supplied from a supply comparable
to public mains such as hospital and research laboratories and most industrial
laboratories, the expected transient overvoltage is 2500V for a 230V supply and
1500V for a 120V supply.
2 Pollution Degree describes the amount of conductive pollution present in the
operating environment. Pollution Degree 2 assumes that normally only non-conductive
pollution such as dust occurs with the exception of occasional conductivity caused by
condensation.
supply. The tape cannot withstand the
2
1
2
Section 2
Set-Up and Operation
Controlled Rate Freezer 2-3