Protection Against Cavitation (Option 116) - Carrier AquaSnap 61AF 022 Installation, Operation And Maintenance Instructions

8 - WATER CONNECTIONS
Never switch off the plate heat exchanger and hydraulic circuit heaters
or the pump, otherwise frost protection cannot be guaranteed. The
main unit disconnect switch as well as the heater auxiliary protection
switch must always be left closed (for the location of these components
see the wiring diagram).
To ensure frost protection of the units with hydraulic module water
circulation in the water circuit must be maintained by periodically
switching on the pump. If a shut-off valve is installed, a bypass must
be included as shown below.
Winter position
Closed
Water
Closed
network
It is recomended to use a primary glycol loop for low-temperature
applications, as shown below:
Water
network
3
Legend
1 Primary glycol loop (minimum 10%)
2 Intermediate heat exchanger
3 Secondary loop
IMPORTANT: Depending on the climate conditions in your
area do the following when switching the unit off in winter:
- Add ethylene glycol or propylene glycol with an adequate
concentration to protect the installation up to a
temperature of 10 K below the lowest temperature likely
propylene glycol is added, ensure that the unit pump is
not used to add pure glycol and to apportion the fluid
amount (possible pump damage). Always add a mixture
that is measured in advance.
- If the unit is not used for an extended period, it should
be drained, and as a safety precaution ethylene glycol
or propylene glycol introduced in the heat exchanger,
using the water entering purge valve connection.
- At the start of the next season, refill the unit with water
and add an inhibitor.
- For the installation of auxiliary equipment, the installer
must comply with basic regulations, especially for
minimum and maximum flow rates, that must be between
the values listed in the operating limit table (application
data).
- To prevent corrosion by differential aeration, the
complete drained heat transfer circuit must be charged
with nitrogen for a period of one month. If the heat
transfer fluid does not comply with the Carrier
regulations, the nitrogen charge must be added
immediately.
Unit
Closed
2
Unit
1

8.4 - Protection against cavitation (option 116)

To ensure the durability of the pumps in the integreated hydraulic
modules (options 116), the control algorithm of the 61AF units
incorporates anti-cavitation protection.
It is therefore necessary to ensure a minimum pump entering pressure
of 40 kPa (0.4 bar) during operation and at shut-down. A pressure
below 40 kPa will prohibit unit start-up or cause an alarm with the
unit shutting down. In order to obtain sufficient pressure, it is
recommended:
- to pressurise the hydraulic circuit between 1 and 4 bar
(maximum),
- to clean the hydraulic circuit before charging water (see
chapters 9.2 and 9.3),
- to regularly clean the screen filter,
ATTENTION: The use of integrated hydraulic kits in the open
loop is not permitted.