Pump Modification/Trimming; Freeze Protection; Preparation For Winter Shutdown - Carrier AquaForce 30XA Series Installation Instructions Manual

PUMP MODIFICATION/TRIMMING

Since the pumps are constant speed, the only way to obtain greater
flow with a given pump/impeller is to decrease system head. This
will allow the pump to "ride" its curve to the right, resulting in in-
creased flow. If greater flow is necessary, consider opening the
combination valve. Also, verify that the strainer is clean, and that
no unnecessary system resistance is present, such as partially
closed isolation valves.
Once the combination valve is set, note the stem position. If later
service work requires the valve to be closed, it will be easier to re-
balance the system, if the original balance point is known.
Increasing system resistance by closing the balancing valve will
force the pump to "ride" its curve to the left, resulting in less flow.
Although this does reduce power consumption slightly, it may not
be the desirable method of reducing the flow, especially if a large
reduction is needed.
The other method for reducing flow on a constant speed pump is
impeller trimming. The impellers in the pumps provided in the
30XA hydronic kit can be easily removed for this purpose. Refer
to the vendor literature packet supplied with the hydronic package
information on Seal Replacement in the Service section, and fol-
low instructions for impeller removal and trimming. See Fig. 56
and 57 for pump envelope curve information. Trimming should
only be done by a qualified machine shop that has experience in
this operation. Contact your local Carrier representative for a rec-
ommended machine shop.
CAUTION
After trimming, the impeller MUST be balanced. Failure to
balance trimmed impellers can result in excessive vibration,
noise, and premature bearing failure.
Impeller trimming has the added benefit of maximum bhp (brake
horsepower) savings, which can recover the cost incurred by per-
forming the impeller trimming.

FREEZE PROTECTION

The 30XA units are provided with a flow switch to protect
against freezing situations that occur from no water flow. While
the flow switch is helpful in preventing freezing during no-flow
situations, it does not protect the chiller in case of power failure
during sub-freezing ambient temperatures, or in other cases
where water temperature falls below the freezing mark. Appro-
priate concentrations of inhibited propylene or ethylene glycol or
other suitable inhibited antifreeze solution should be considered
for chiller protection where ambient temperatures are expected
to fall below 32°F (0°C). Consult a local water treatment special-
ist on characteristics of the system water and add a recommend-
ed inhibitor to the chilled water. The Carrier warranty does not
cover damage due to freezing.
If the pump will be subjected to freezing temperatures, steps must
be taken to prevent freeze damage. If the pump will not be used
during this time, it is recommended to drain the pump and hydron-
ic package and backflush these components with inhibited glycol.
Otherwise, a glycol-water solution should be considered as the
heat transfer fluid. Drains are located on the pump(s) and suction
guide/strainer for units with hydronic kits. Units without hydronic
kits have a drain plug mounted on the bottom of the cooler head at
each end of the cooler, or at the bottom of the shell.
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.
Use an electric tape heater for the external piping, if unit will be
exposed to freezing temperatures.
Ensure that power is available to the chiller at all times, even
during the off-season, so that the pump and cooler heaters have
power. Also make sure that the piping tape heaters have power.
On units with pump packages, a heater is supplied with the hy-
dronic package that will protect this section from freezing in out-
door-air temperatures down to –20°F (–29°C), except in the case
of a power failure. The Carrier warranty does not cover damage
due to freezing.
Flooded cooler units only
All units are equipped with cooler heaters. Units are protected
from freezing down to 0°F (–18°C) through the cooler heaters and
control algorithms. If the unit controls the chilled water pump and
valves, allowing flow through the cooler, the unit is protected from
freezing down to –20°F (–29°C). The Carrier warranty does not
cover damage due to freezing.
DX cooler units only
Cooler heaters that will protect components down to –20°F
(–29°C) can be ordered as a factory-installed option. It
should be noted that these heaters will not protect the cooler
from freezing in the event of a power failure. The Carrier
warranty does not cover damage due to freezing.

PREPARATION FOR WINTER SHUTDOWN

If the unit is not operational during the winter months, at the end
of cooling season complete the following steps.
Failure to remove power before draining heater equipped cool-
ers and hydronic packages can result in heater tape and insula-
tion damage.
1. If the cooler will not be drained, do not shut off power dis-
connect during off-season shutdown. If cooler is drained,
open the circuit breaker for the heater, CB-13 or shut off
power during off-season shutdown.
2. Draining the fluid from the system is highly recommended.
If the unit is equipped with a hydronic package, there are ad-
ditional drains in the pump housing and strainer that must be
opened to allow for all of the water to drain.
3. Isolate the cooler from the rest of the system with water shut-
off valves.
4. Replace the drain plug and completely fill the cooler with
a mixture of water and a suitable corrosion-inhibited anti-
freeze solution such as propylene glycol. The concentra-
tion should be adequate to provide freeze protection to
15°F (8.3° C) below the expected low ambient tempera-
ture conditions. Antifreeze can be added through the vent
on top of the cooler head for flooded units or the vent on
the top of the cooler shell for DX units. If the unit has a
hydronic pump package, the pump must be treated in the
same manner.
5. Leave the cooler filled with the antifreeze solution for the
winter, or drain if desired. Be sure to deenergize heaters (if
installed) as explained in Step 1 to prevent damage if the
cooler is drained. Use an approved method of disposal when
removing antifreeze solution.
At the beginning of the next cooling season, be sure that there is
refrigerant pressure on each circuit before refilling cooler, add rec-
ommended inhibitor, and reset the CB-HT (circuit breaker heater)
(if opened) or restore power.
132
CAUTION