Appendix
IX
evaporation (sublimation) may be expected; otherwise the system must be
heated and dried while switched off.
A system without visible internal formation of ice or condensation should
be heated up with its own heat dissipation, as homogeneously (and subse-
quently as slow) as possible; the ambient temperature should then always
be lower than the one of the outgoing air.
If it is absolutely necessary to operate the cold system immediately within
warm ambient air, this air must be dehydrated. In such a case, the absolute
humidity must be so low that the relative humidity, related to the coldest
system surface, always remains below 100%.
Ensure that the enclosed air is as dry as possible when powering off (i.e.
before switching off in winter, aerate the room with cold, dry air, and re-
move humid objects as clothes from the room).
These relationships are visible from the following climatogram. For a con-
trolled procedure, thermometer and hygrometer as well as a thermometer
within the system will be required.
Example 1: An OB-van having an internal temperature of 20 °C and relative humidity
of 40% is switched off in the evening. If temperature falls below +5 °C,
dew or ice will be forming.
Example 2: An OB-van is heated up in the morning with air of 20 °C and a relative
humidity of 40%. On all parts being cooler than +5 °C, dew or ice will be
forming.
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