Operating instructions

22 IMM AGSB-60
NOTE: The heaters come from the factory connected to the control power circuit. If desired, the
3 KVA control transformer can be unwired and a field 115-volt power source wired to terminals
TB1-1 and TB1-2 in the control panel for circuit #1 (do not wire directly to the heater). If this is
done, the disconnect switch should be clearly marked to avoid accidental deactivation of the
heater during freezing temperatures. Exposed chilled water piping also requires protection.
It is required that the chilled water pump’s starter be wired to, and controlled by, the chiller's
microprocessor. The controller will energize the pump whenever at least one circuit on the
chiller is enabled to run, whether there is a call for cooling or not. The pump will also be
energized when the controller senses a near-freezing temperature at the chiller outlet sensor to
assist in cold weather freeze protection. Connection points are shown in Figure 27 on page 40.
For additional protection to -20°F (-29°C) and to protect against the consequences described
above, it is recommended that at least one of the following procedures be used during periods
of sub-freezing temperatures:
1. Addition of a concentration of a glycol anti-freeze with a freeze point 10 degrees F
(5.5 degrees C) below the lowest expected temperature. This will result in decreased
capacity and increased pressure drop.
Note: Do not use automotive grade antifreezes as they contain inhibitors harmful to
chilled water systems. Only use glycols specifically designated for use in building cooling
systems.
2. Draining the water from outdoor equipment and piping and blowing the chiller tubes dry
from the chiller. Do not
energize the chiller heater when water is drained from the vessel.
CAUTION
If fluid is absent from the evaporator, the evaporator heater
must be de-energized to avoid burning out the heater
and causing damage from the high temperatures.
3. Providing operation of the chilled water pump, circulating water through the chilled water
system and through the evaporator. The chiller microprocessor will automatically start up
the pump if so wired.
Table 13, Freeze Protection
Percent Volume Glycol Concentration Required
For Freeze Protection For Burst Protection
Temperature
°F (°C)
Ethylene Glycol Propylene Glycol Ethylene Glycol Propylene Glycol
20 (6.7) 16 18 11 12
10 (-12.2) 25 29 17 20
0 (-17.8) 33 36 22 24
-10 (-23.3) 39 42 26 28
-20 (-28.9) 44 46 30 30
-30 (-34.4) 48 50 30 33
-40 (-40.0) 52 54 30 35
-50 (-45.6) 56 57 30 35
-60 (-51.1) 60 60 30 35
Notes:
1. These figures are examples only and cannot be appropriate to every situation. Generally, for an extended margin of
protection, select a temperature at least 10
°F lower than the expected lowest ambient temperature. Inhibitor levels
should be adjusted for solutions less than 25% glycol.
2. Glycol of less than 25% concentration is not recommended because of the potential for bacterial growth and
subsequent loss of heat transfer efficiency, or add inhibitors.