Carrier MINIMUM LOAD CONTROL ACCESSORY 30RB060-390, Installation Instructions Manual, Page: 45 / 76

45
SYSTEM PRESSURIZATION — A proper initial cold fill
pressure must be established before filling of the unit. The
initial cold fill pressure is the pressure applied at the filling
point to fill a system to its highest point, plus a minimum
pressure at the top of the system (4 psig minimum [27.6 kPa])
to operate air vents and positively pressurize the system. The
expansion tank is very important to system pressurization. The
expansion tank serves several purposes:
1. Provide NPSH (net positive suction head) required for the
pump to operate satisfactorily.
2. Set system pressure.
3. Accommodate expansion or contraction of water due to
temperature changes.
4. Act as a pressure reference for the pump.
The expansion tank pressure must be set BEFORE the
system is filled. Follow the manufacturer’s recommendation
for instructions on setting the pressure in the expansion tank.
The net positive suction head pressure required information is
provided on the pump curves in Fig. 39-51 for units with facto-
ry-installed hydronic kits. See Table 6 for pump impeller sizes.
Once the system is pressurized, the pressure at the connec-
tion point of the expansion tank to water piping will not change
unless the water loop volume changes (either due to addition/
subtraction of water or temperature expansion/contraction).
The pressure at this point remains the same regardless of
whether or not the pump is running.
Since the expansion tank acts as a reference point for the
pump, there cannot be two reference points (two expansion
tanks) in a system, unless manifolded together. Where two or
more 30RB chillers with the hydronic option are installed in
parallel, there should not be more than one expansion tank in
the system, unless manifolded together as seen in Fig. 36. It is
permissible to install the expansion tank(s) in a portion of the
return water line that is common to all pumps, providing that
the tank is properly sized for combined system volume.
If the application involves two or more chillers in a primary
secondary system, a common place for mounting the expan-
sion tank is in the chilled water return line, just before the
decoupler. See Fig. 36 for placement of expansion tank in
primary-secondary systems.
If a diaphragm expansion tank is utilized (a flexible
diaphragm physically separates the water/air interface) it is not
recommended to have any air in the water loop. See the section
on air separation on page 42 for instructions on providing air
separation equipment.
FILLING THE SYSTEM(S) — The initial fill of the chilled
water or heat reclaim system must accomplish three goals:
1. The entire piping system must be filled with water.
2. The pressure at the top of the system must be high enough
to vent air from the system (usually 4 psig [27.6 kPa] is
adequate for most vents).
3. The pressure at all points in the system must be high
enough to prevent flashing in the piping or cavitation in
the pump.
The pressure created by an operating pump affects system
pressure at all points except one — the connection of the
expansion tank to the system. This is the only location in the
system where pump operation will not give erroneous pressure
indications during the fill. Therefore, the best location to install
the fill connection is close to the expansion tank. An air vent
should be installed close by to help eliminate air that enters
during the fill procedure.
When filling the system, ensure the following:
1. Remove temporary bypass piping and cleaning/flushing
equipment.
2. Check to make sure all drain plugs are installed.
Table 6 — Pump Impeller Sizes
*Option Code refers to the Hydronics Option (position 11) in the model number. See Fig. 1 for
option identification.
NOTE: Pump Selections are chiller size dependent. For example, dual pump “C” on a 30RB170
chiller is not the same as dual pump “C” on a 30RB130 chiller.
UNIT
30RB
PUMP
Hp
SINGLE PUMP DUAL PUMP
Option
Code *
Rpm
Impeller Dia.
(in.)
Pump
Curve Option
Code *
Rpm
Impeller Dia.
(in.)
Pump
Curve
060
070
3 0,F 1750 6.5 I 6,M 1750 6.5 V
5 1,G 1750 7.3 I 7,N 1750 7.3 V
7.5 2,H 1750 8.15 I
8,P 1750 8.15 V
9,T 3450 5.25 VI
10 3,J 3450 5.4 II B,Q 3450 5.4 VI
080
090
100
5 1,G 1750 7.3 I 7,N 1750 7.3 V
7.5 2,H 1750 8.15 I 8,P 1750 8.15 V
10 3,J 3450 5.4 II B,Q 3450 5.4 VIIA
15 4,K 3450 6.1 II C,R 3450 6.0 VIIC
110
120
130
5 1,G 1750 7.3 I 7,N 1750 7.3 V
7.5 2,H 1750 8.15 I 8,P 1750 8.15 V
10 3,J 3450 5.4 II B,Q 3450 5.4 VIIA
15 4,K 3450 6.1 II C,R 3450 6.0 VIIC
150
160
170
190
5 1,G 1750 6.5 IIIA — — — —
7.5 2,H 1750 7.4 IIIB 9,T 3450 5.0 VIIB
10 3,J 3450 4.6 IVA B,Q 3450 4.6 VIIIA
15 4,K 3450 5.2 IVB C,R 3450 5.2 VIIIB