Manual Part 5

Combined Climate Unit
The outside air circula tes through one side of the heat exchanger and the i nside
air circulates through the other side. DC-powered fans force the air through the
heat exchanger. The inside air is cooled by the outside air.
4.2 Active Cooler
This unit consists of the following:
• compres sor
• reducing valve
• condenser
• evaporator
• AC-powered condenser fan
The liquid coolant passes through a reducing valve, where it evaporates to a
cold low-pressu re gas. This gas flows through the evaporator and cools it. T he
inside air that has passed the h eat exchanger is blown through the evaporator,
cooled, and returned to the cabinet subracks.
The compre ssor compresses the coola nt to a liq uid state again in th e
condenser. Th e cool ant and the condense r become hot in the pro cess. An
AC-powered fan circulates the outside air through the condenser and cools it.
The coolant used is HFC 134 a (tetrafluoroethane).
When the temperature exceeds the compressor start point, the CCU supplies
mains voltag e, first to the condenser fan and then to the compressor. The
condenser fa n runs when the compressor is running and a lso for one minute
after the c ompressor is switc hed off. The compressor cannot start again
before the condenser fan has stopped. This is done to equalise the pressure
differences in the cooling system before the compressor s ta rts.
When the temp erature decrea ses below the compressor stop valu e, a
compres sor stop signal is activated but the compressor continu es running
for at least 10 minutes.
If th e mains cur re nt to the compressor is m issing, This is reported as
compres sor failure.
The condenser fan is provided with a rotation signal output. I f the signal is
missing, an active cooler fan alarm is reported.
4.3 Heater
The heater is placed in the inte rnal air circuit and heats the air if the am bient
temperature is too low for startup.
5 (10)
EN/LZT 720 0239 Uen R2A