64
the type of application, and whether or not a device pro-
viding additional unloading steps is employed. The mini-
mum fluid in circulation must equal or exceed the values in
the following table. Note that in process cooling applica-
tions, or for operation at ambient temperatures below
32 F (0° C) with low loading conditions, there should be
more volume than is required for normal air-conditioning
applications.
MINIMUM FLUID VOLUME IN CIRCULATION
LEGEND
To achieve this fluid volume, it is often necessary to install
a tank in the loop. The tank should be baffled to ensure
there is no stratification and that water (or brine) entering
the tank is adequately mixed with liquid in the tank. A fluid
storage tank is available as an accessory.
The piping between the chiller and the accessory tank can
be done to allow the tank to be on the return side of the
chiller (tank piped to chiller inlet) or the supply side of the
chiller (tank piped to the chiller outlet). However, it is rec-
ommended that the tank be piped to the return side of the
chiller to buffer any changes in load to allow more stable
chiller operation.
Tank volume and weight
A properly baffled storage tank is available as an accessory
on 30RAP010-060. These tanks are designed to
physically fit beneath the corresponding 30RAP unit, tak-
ing up the same footprint. Available volume is as follows:
30RAP010,015 83 gallons (314 liters)
30RAP018-030 119 gallons (450 liters)
30RAP035-060 241 gallons (912 liters)
Storage tank weight (water weight included) is as follows:
30RAP010,015 1673 lb (759 kg)
30RAP018-030 2193 lb (995 kg)
30RAP035-060 4361 lb (1978 kg)
NOTE: This tank will obtain power from the main unit. No
separate power source is required.
NOTE: Units with storage tanks weigh considerably more
than units without tanks.
Cooler fouling factor
The fouling factor used to calculate tabulated ratings is
0.00010 ft
2
hr °F/Btu (0.000018 m
2
°C/W). As foul-
ing factor is increased, unit capacity decreases and com-
pressor power increases. Use the NACO (North American
Commercial Operation) Packaged Chiller Builder for cor-
rections to published ratings.
Cooler and hydronic system freeze protection
Freeze protection for down to –20 F (–28.9 C) for the
cooler and hydronic package is available as a factory-
installed option. Since power is sometimes lost for extend-
ed periods during winter storms, freeze protection provid-
ed by heater tapes will be effective only if a back-up power
supply can be assured for the unit’s control circuit, heater
and cooler pump. If not protected with an antifreeze solu-
tion, draining the cooler and outdoor piping is recom-
mended if the system will not be used during freezing
weather conditions.
Two conditions that must be considered when determin-
ing antifreeze concentration are leaving water set point
and ambient freeze conditions. Both of these parameters
can help determine the recommended concentration level.
Higher concentration must be used to adequately protect
the machine.
NOTE: Use only antifreeze solutions approved for heat ex-
changer duty.
For applications in which the leaving water temperature
set point is less than 40 F (4.4 C), a suitable inhibited anti-
freeze solution must be used. The solution concentration
must be sufficient to protect the chilled water loop to a
freeze protection (first crystals) concentration of at least
15° F (8.3º C) below the leaving water temperature set
point.
If the chiller refrigerant or fluid lines are in an area where
ambient conditions fall below 34 F (1º C), it is required that
an antifreeze solution be added to protect the unit and fluid
piping to a temperature of 15º F (8.3º C) below the lowest
anticipated ambient temperature.
30RAP
UNIT
SIZE
NORMAL AIR
CONDITIONING
APPLICATION
gal/ton (L per kW)
PROCESS COOLING OR
LOW AMBIENT OPERATION
APPLICATION
gal/ton (L per kW)
Std Unit HGBP Digital Std Unit HGBP Digital
010,015 12 (13) N/A 3 (3.3) 12 (13) N/A 6 (6.5)
018-030 6 (6.5) 4 (4.3) 3 (3.3) 10 (10.8) 10 (10.8) 6 (6.5)
035-090 3 (3.3) 3 (3.3) 3 (3.3) 6 (6.5) 6 (6.5) 6 (6.5)
HGBP — Hot Gas Bypass
Application data (cont)
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