Technical information

Page: 66
VL Series Portable Chillers, 2 to 40 Tons UGH021/0301
8.2 OPERATION BELOW 48°F
A. A chiller typically operates with a setpoint of 50°F or higher.
However, if setpoints between 20° - 48°F are required, special
precautions must be taken to prevent freezing and possible
damage. Attention must be given to freeze protection, water supply
and safety adjustments.
B. FREEZE PROTECTION
1. It is understood that untreated water freezes at 32°F.
Therefore, an inhibited propylene glycol and water solution
must be used in lieu of ordinary water. Prescribed amounts
are listed in figure 8.2A.
2. On initial installation of the unit, the
water/glycol solution should be premixed, then added to
the reservoir. After the pump has been started, water lines
filled and air purged, it may be necessary to add more
water/glycol solution to maintain the recommended
reservoir level. Note: a hygrometer should be used on a
regular basis to determine the mixture strength according
to freeze point. The freeze point temperature should be 25°
below the lowest required setpoint. Water will evaporate
from the mixture, and if you continue to add a premixed
solution eventually you will have too much glycol. It is
necessary to add water or glycol to maintain proper freeze
point temperature.
3. PLEASE NOTE THAT A CHILLER IS NOT DESIGNED TO
ACCOMMODATE AUTOMOTIVE TYPE ANTI-FREEZE. This
is due to the fact that automotive type anti-freeze contains
silicates that adhere to heat transfer surfaces of the system
preventing maximum heat transfer. Also, improper portions
of inhibited propylene glycol to water inhibits effective heat
transfer. Consult the chiller’s operating manual for specific
details.
C. WATER SUPPLY
1. The automatic water supply (if equipped) restores the
reservoir water level as needed. However, if untreated water
is added to an water/glycol solution, dilution will occur
OPERATING ANTI-FREEZE MIXTURE
TEMPERATURE GLYCOL WATER
40°F 20% 80%
25°F 25% 75%
30°F 30% 70%
Figure 8.2A