Sterlco 30RA Outdoor Air Cooled Central Chillers 10-60 Tons - Manual (Page 13)

13
AIR SEPARATION — For proper system operation, it is
essential that water loops be installed with proper means to
manage air in the system. Free air in the system can cause
noise, reduce terminal output, stop flow, or even cause pump
failure due to pump cavitation. For closed systems, equipment
should be provided to eliminate all air from the system.
The amount of air that water can hold in solution depends
on the pressure and temperature of the water/air mixture. Air is
less soluble at higher temperatures and at lower pressures.
Therefore, separation can best be done at the point of highest
water temperature and lowest pressure. Typically, this point
would be on the suction side of the pump as the water is return-
ing from the system or terminals. Generally speaking, this is
the best place to install an air separator, if possible.
1. Install automatic air vents at all high points in the system.
(If the 30RA unit is located at the high point of the
system, a vent can be installed on the piping entering the
heat exchanger on the ¼-in. NPT female port.)
2. Install an air separator in the water loop, at the place
where the water is at higher temperatures and lower
pressures — usually in the chilled water return piping.
On a primary-secondary system, the highest temperature
water is normally in the secondary loop, close to the
decoupler. Preference should be given to that point on the
system (see Fig. 12). In-line or centrifugal air separators
are readily available in the field.
It may not be possible to install air separators at the place of
lowest pressure and highest temperature. In such cases, prefer-
ence should be given to the points of highest temperature. It is
important that pipe be sized correctly so that free air can be
moved to the point of separation. Generally, a water velocity of
at least 2 feet per second will keep free air entrained and
prevent it from forming air pockets.
Automatic vents should be installed at all physically elevat-
ed points in the system so that air can be eliminated during
system operation. Provision should also be made for manual
venting during the water loop fill. It is important that the
automatic vents be located in accessible locations for mainte-
nance purposes, and that they be located where they can be
prevented from freezing.
WATER CONNECTIONS — The water connections are cop-
per or brass FPT. Any connecting pipe to the 30RA pump
package must be of a material that will not cause any galvanic
corrosion. For this reason, galvanized steel pipe or other dis-
similar metals must not be used unless joined by a dielectric
coupling. The connection sizes for the 30RA unit sizes 010-
030 are 2-in. FPT. Sizes 032-055 use 2
1 /
2
-in. FPT.
Follow the steps below when connecting pipe to the unit
water connections:
1. Remove side panel(s) of unit to access the piping area.
2. Remove access covers of pump box.
3. Use a backup wrench on internal water connections to
prevent twisting of internal piping, using a good sealant
that will also allow for disconnecting the pipes if needed.
4. After connection is made, replace access covers of pump
box and side panels of unit.
WATER SYSTEM CLEANING — Proper water system
cleaning is of vital importance. Excessive particulates in the
water system can cause excessive pump seal wear, reduce or
stop flow, and cause damage of other components. Water
quality should be maintained within the limits indicated in
Table 2.
1. Install a temporary bypass around the chiller to avoid cir-
culating dirty water and particulates into the pump pack-
age and chiller during the flush. Use a temporary circulat-
ing pump during the cleaning process. Also, be sure that
there is capability to fully drain the system after cleaning.
(See Fig 13.)
2. Be sure to use a cleaning agent that is compatible with all
system materials. Be especially careful if the system
contains any galvanized or aluminum components. Both
detergent-dispersant and alkaline-dispersant cleaning
agents are available.
3. It is a good idea to fill the system through a water meter.
This provides a reference point for the future for loop
volume readings, but it also establishes the correct
quantity of cleaner needed in order to get the required
concentration.
4. Use a feeder/transfer pump to mix the solution and fill the
system. Circulate the cleaning system for the length of
time recommended by the cleaning agent manufacturer.
a. After cleaning, drain the cleaning fluid and flush the
system with fresh water.
b. A slight amount of cleaning residue in the system can
help keep the desired, slightly alkaline, water pH of 8
to 9. Avoid a pH greater than 10, since this will
adversely affect pump seal components.
c. A side stream filter is recommended (see Fig. 14)
during the cleaning process. Filter side flow rate
should be enough to filter the entire water volume
every 3 to 4 hours. Change filters as often as neces-
sary during the cleaning process.
d. Remove temporary bypass when cleaning is
complete.
A strainer with a blow-down valve is standard on all 30RA
units, both with and without hydronic packages. The blow-
down valve allows removal of particulates caught in the strain-
er without complete removal of the screen. A female NPT
connection is provided on the valve, allowing hose connection
for drainage outside the unit.
The Sterlco ComfortLink™ controls provided have a built-
in feature to remind building owners or operators to clean the
strainer by discharging the blow-down valve at a pre-set time
interval. Properly installed and cleaned systems will rarely
need the strainer cleaned after the initial fill. This time interval
is user-configurable.
Table 2 — Water Quality Characteristics
and Limitations
*Sulfides in the water quickly oxidize when exposed to air, requiring that
no agitation occur as the sample is taken. Unless tested immediately
at the site, the sample will require stabilization with a few drops of one
Molar zinc acetate solution, allowing accurate sulfide determination up
to 24 hours after sampling. A low pH and high alkalinity cause system
problems, even when both values are within the ranges shown. The
term pH refers to the acidity, basicity, or neutrality of the water supply.
Below 7.0, the water is considered to be acidic. Above 7.0, water is
considered to be basic. Neutral water contains a pH of 7.0.
†Dissolved carbon dioxide can either be calculated from the pH and
total alkalinity values, shown below, or measured on the site using a
test kit. Dissolved Carbon Dioxide, PPM = TA x 2
[(6.3-pH)/0.3] where TA
= Total Alkalinity, PPM as CaCO
3
.
WATER CHARACTERISTIC QUALITY LIMITATION
Alkalinity (HCO
3
- ) 70 – 300 ppm
Sulfate (SO
4
2- ) Less than 70 ppm
HCO
3
- /SO
4
2- Greater than 1.0
Electrical Conductivity 10 – 500 µS/cm
pH 7.5 – 9.0
Ammonium (NH
3
) Less than 2 ppm
Chorides (Cl - ) Less than 300 ppm
Free chlorine (Cl
2
) Less than 1 ppm
Hydrogen Sulfide (H
2
S)* Less than 0.05 ppm
Free (aggressive) Carbon
Dioxide (CO
2
)†
Less than 5 ppm
Total Hardness (dH) 4.0 – 8.5
Nitrate (NO
3
) Less than 100 ppm
Iron (Fe) Less than 0.2 ppm
Aluminum (Al) Less than 0.2 ppm
Manganese (Mn) Less than 0.1 ppm