York YHAU-CE-JE Series, Установка, эксплуатация и обслуживание, Страница: 21 / 136

JOHNSON CONTROLS
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SECTION 2 – PRODUCT DESCRIPTION
FORM 155.33-ICOM2.EN.GB
ISSUE DATE:12/4/2017
2
Since the solution temperature in the generator is typi-
cally high enough, no crystallization will occur as long
as the higher temperature is maintained. Before the
unit is shut down, make sure the solution is sufficiently
diluted in all areas of the unit to prevent crystallization
during the off cycle. Remember, the solution tempera-
ture will eventually become equal to the ambient tem-
perature of the room.
All units employ some sort of dilution cycle, which ful-
fills this requirement. As long as the unit is allowed to
dilute itself during an orderly shutdown sequence, the
unit should be able to sit idle at fairly low plant room
ambient temperatures for extended periods of time
without any threat of crystallization. Typically, after
a dilution cycle, the average solution concentration in
the chiller-heater will be below 45% lithium bromide
by weight. Although the crystallization line on Figure
41 on page 116
or
Figure 42 on page 117
does not
extend that far, you can see that the solution at a 45%
concentration should not crystallize at normal ambient
temperatures.
WHY DOES CRYSTALLIZATION OCCUR?
The most common reason for crystallization is power
failure. If a chiller-heater is running at full load and
power is interrupted for a long time, the concentrated
solution in the high side of the unit eventually cools
down. Since no dilution cycle was performed, the solu-
tion concentration in some areas of the unit will still be
high. If the temperature of this concentrated solution is
allowed to fall low enough, the solution will reach its
crystallization point. Plant room temperature, insula-
tion quality and the solution concentration all play a
part in the determination of how long it will take before
the unit will crystallize. See SECTION 7 – MAINTE-
NANCE for information on water quality control and
crystallization. The Duhring Diagram (PTX Chart)
shows the specific temperatures and pressures of the
crystallization area. See Figure 41 on page 116 and
Figure 42 on page 117 .