System Pressurization; Filling The System; Set Water Flow Rate - Carrier AquaForce 30XA Series Installation Instructions Manual

NOTE: Do not use automobile anti-freeze, or any other fluid that
is not approved for heat exchanger duty. Only use appropriately
inhibited glycols, concentrated to provide adequate protection for
the temperature considered.

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 mini-
mum 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 ex-
pansion tank serves several purposes:
1. Provides NPSHR (Net Positive Suction Head Required) for
the pump to operate satisfactorily.
2. Sets system pressure.
3. Accommodates expansion/contraction of water due to tem-
perature changes.
4. Acts 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 instruc-
tions on setting the pressure in the expansion tank. NPSHR in-
formation is provided on the Pump Curves in Fig. 56 and 57 for
units with factory-installed hydronic kits. See Table 4 for pump
impeller sizes.
Once the system is pressurized, the pressure at the connection
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 30XA
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. 44. 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-sec-
ondary system, a common place for mounting the expansion
tank is in the chilled water return line, just before the decoupler.
See Fig. 44 for placement of expansion tank in primary-second-
ary systems.
If a diaphragm expansion tank is utilized (a flexible diaphragm
physically separates the water/air interface) it is not recommend-
ed to have any air in the water loop. See the section on air sepa-
ration on page 120 for instructions on providing air separation
equipment.

FILLING THE SYSTEM

The initial fill of the chilled water system must accomplish three
goals:
1. The entire piping system must be filled with water.
30XA PUMP
UNIT SIZE Hp
Option Code*
5 1,G
7.5 2,H
090-162
10 3,J
15 4,K
*Option Code refers to the Hydronics Option (position 11) in the model number. See Fig. 1 for option identification.
Table 4 — Pump Impeller Sizes
SINGLE PUMP
Rpm Impeller Dia. (in.) Pump Curve
3450 4.5
3450 5
3450 5.4
3450 6.1
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 ade-
quate 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 pres-
sure 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 con-
nection is close to the expansion tank. An air vent should be in-
stalled 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.
Normally, a closed system needs to be filled only once. The actual
filling process is a fairly simple procedure. All air should be
purged or vented from the system. Thorough venting at high
points and circulation at room temperature for several hours is
highly recommended.
NOTE: Local codes concerning backflow devices and other pro-
tection of the city water system should be consulted and followed
to prevent contamination of the public water supply. This is criti-
cal when antifreeze is used in the system.

SET WATER FLOW RATE

Once the system is cleaned, pressurized, and filled, the flow rate
through the chiller needs to be established. On units with the hy-
dronic package, this can be accomplished by using the balancing
valve. Follow the manufacturer's recommendations for setting the
balancing valve. Local codes may prohibit restricting the amount
of water using the balancing valve for a given motor horsepower.
In this case, use the method listed in the Pump Modification/
Trimming section. See below for the type of combination valve in
30XA units with the optional hydronic package.
30XA UNIT SIZE
090-162
NOTE: Carrier recommends a differential pressure gage when
measuring pressures across the pumps or balancing valves. This
provides for greater accuracy and reduces error build-up that often
occurs when subtracting pressures made by different gages.
A rough estimate of water flow can also be obtained from the
pressure gages across the 30XA heat exchanger.
The Controls, Start-Up Operation, Service, and Troubleshooting
guide includes graphs that show the relationship between gpm and
heat exchanger pressure drop. It should be noted that these curves
are for fresh water and "clean" heat exchangers; they do not apply
to heat exchangers with fouling. To read the chart, subtract the
readings of the two pressure gages on the hydronic kit. Be sure to
use the correct graph for the cooler option (standard, +1/-1 pass,
DX cooler). This number is the pressure drop across the heat ex-
changer. Adjust the factory-installed balancing valve or external
balancing valve (in units without hydronic package) until the cor-
rect pressure drop is obtained for the required flow. (See Table 3.)
Option Code*
I 7,N
I 8,P
I B,Q
I C,R
130
SINGLE/DUAL PUMP
FTV-5 in.
DUAL PUMP
Rpm Impeller Dia. (in.) Pump Curve
3450 4.5
3450 5
3450 5.4
3450 6.1
II
II
II
II