02-2010
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8.
Application, Function and Description
8.1 Description- refrigeration unit
Refrigeration of the user cooling medium generally takes place in an insulated open vessel
via plate heat exchanger or a special heat transfer pipe as evaporator. The heat taken up in
the cooling agent evaporator is released from the air-cooled condenser into the
surroundings or depending on model, into a local water supply über via water heat-
exchanger. Alternatively, the refrigeration unit can also be built as thru-flow cooler without
tank and pump or as a closed system or as immersion cooler.
Regulation of the medium temperature takes place via electronic temperaturre regulator or
through a customer-sided software program.
Through the installation of a time relay, there is a standstill time of 4 minutes when the
refrigeration unit is switched on(to protect the compressor from “chopping”). The
refrigeration unit does no cooling during this time! There is a possibility of a malfunction
message in this time!
Function and setting of the temperature regulator can be taken from the description.
An oil sump heating (with selector switch above a certain size) has the task of evaporating
the cooling agent from the refrigeration machine oil in case of low surroundings
temperatures and during long standstill times of the refrigeration unit. If this does not
happen, then the compressor primes with liquid, which renders the compressor a write-off
.
This immediately relinquishes the warranty
.
Points to be observed after long periods of standsstill and low storage or surrounding
temperature:
- Machines without selector switch are to be connected to the mains supply 24 hours before
being putting into operation. During this time the oil sump heating runs and evaporates the
cooling agent away. Then after 24 hours have passed, the unit can be put into operation.
- Units with selector switch are to be connected to the mains supply 24 hours before being
putting into operation. As soon as the selector switch is switched on, the oil sump heating
runs and evaporates the cooling agent out. The refrigeration unit can still be prepared
further for putting into operation. It can only start run-up when the selector switch is
switched off again. The selector switch can be switched off after 24 hours.
Option: Mixing Valve Control
The option Mixing Valve Control is typically used in two cases:
1. To realize different temperature levels in chillers with more than one cooling circuit
2. To realize highly accurate control of outlet temperature in systems with more than one
cooling circuit, different media, that cannot be cooled via a joint evaporator, as well as
significant variations of required cooling capacity across the different cooling circuits
3.
The option Mixing Valve Control is realized using a central water reservoir, which is cooled
down to a temperature level below the lowest required outlet temperature. From this water
reservoir for each cooling circuit either a separate heat exchanger (water / outlet medium)
is supplied or water is directly taken with a separate consumer pump into a water outlet.
Temperature control is realized via electronic controllers and temperature sensors in the
outlet of the heat exchanger or in the outlet itself in case the heat exchanger is used. The
controller actuates a 3-way-mixing-valve in the water circuit. The mixing valve controls the
outlet medium temperature in the respective cooling circuit by adjusting the mixing ratio
between cold water and warm inlet water.
Содержание Typ BR 058-31
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