Figure 13: Winter Position For Unit With Hydraulic Module - Riello NXHP Series Installation, Operation And Maintenance Instructions

4 -OPERATION
4.2.6 - Home Anti-freeze protection
This protection is used on NXHP , only with remote user interface or IAT sensor. It is used to maintain the minimum room temperature
which is by default set to 6°C. When the room temperature goes below the Home Anti-freeze setpoint[P427], the unit will run in Heating
mode until the room temperature is increased: [P427] + 2°C.
Steps Table
Set the minimum
AIR_STP 427
room temperature
Never switch off the unit, otherwise home anti-freeze protection cannot be guaranteed. For this reason the main unit and /
or customer circuit disconnect switch must always be left closed.
4.2.7 - Water freeze protection
When the OAT is low (and pump is stopped), the risk to freeze the
water exchanger and the water pipes is high. The pump shall be
turned on regularly or continuously to make water circulate and
decrease the risk. Likewise the BPHE and piping electric heaters
present on the hydraulic kit (refer to Figures 7 and 8) are activated
in some cases.
The pump is controlled as follows:
■ If OAT goes below AntiFreezeDeltaSetpoint
pump runs for 1 minute every 15 minutes at maximum speed.
■ If OAT goes below AntiFreezeDeltaSetpoint
EWT or LWT goes below AntiFreezeDeltaSetpoint
3°C, the pump runs continuously at maximum speed.
■ A 1K hysteresis is applied to exit these two overrides.
Steps
Define the criteria to activate the
water freeze protection
Never switch off the unit, otherwise freeze protection cannot
be guaranteed. For this reason the main unit and/or customer
circuit disconnect switch must always be left closed.
If a shut-off valve is installed, a bypass must be included as shown
below.
Figure 13: Winter position for unit with hydraulic
module
Unit
Open
IMPORTANT: Depending on the atmospheric conditions in
your area you must 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 to occur at the
installation site.
■ If the unit is not used for an extended period, it should be
drained, and ethylene glycol or propylene glycol should
be charged in the heat exchanger as a safety precaution,
using the water inlet purge valve connection.
■ At the start of the next season, refill the unit with water
and add an inhibitor.
■ The manipulation of glycol must be done according to the
best practices. Be sure to wear clothing protection while
manipulation glycol.
Par. Designation Description
Home This is the minimum room temperature that is allowed. If
Anti-freeze room temperature drops below this setpoint, the unit will
setpoint start to operate in Heating mode.
[P514] + 6°C, the
(1)
(1) [P514] + 6°C and
(1) [P514] +
Table Par. Designation
Anti-Freeze
GEN_CONF 514
Delta Setpoint
Closed
Water loop
Closed
The electric heaters are controlled as follows:
■ The electric heaters are energized during and for 1 minute after
defrost end.
■ The electric heaters are energized if OAT is below the
AntiFreezeDeltaSetpoint
(1)
or LWT are lower than AntiFreezeDeltaSetpoint
°C.
■ The electric heaters are de-energized if OAT is above the
AntiFreezeDeltaSetpoint
(1)
configured) and LWT are higher than AntiFreezeDeltaSetpoint
[P514] + 4.5 °C.
■ The electric heaters are energized if either alarm #50 or alarm
#51 is active and can still automatically be reset
(1) Modifying the pre-configured value is at the user's
responsibility.
Description
Outdoor air temperature criteria for
activation of the anti freeze protection
■ For the installation of auxiliary equipment, the installer
must comply with basic regulations, especially for
minimum and maximum flow rates, which 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 manufacturer regulations, the nitrogen
charge must be added immediately.
■ If frost protection is dependent on electric trace heaters,
never switch off their power.
■ If trace heating is not used, or during a prolonged power
failure, the unit water system must be drained to protect
the unit.
■ The heat exchanger temperature sensor are part of frost
protection: If piping trace heaters are used, ensure the
external heaters do not affect the measurement of these
sensors.
CAUTION:
Please note that "water freeze protection" and "home anti-
freeze protection" are two different modes. Water freeze
protection is used in order to reduce the risk to freeze the
water exchanger and the water pipes, whereas the home anti-
freeze protection is used to maintain the minimum room
temperature.
Range Default Ex.
6,0 to
6 10
12,0
[P514] + 6.0 °C and if either EWT
[P514] + 4.0
(1)
[P514] + 7.0 °C or if both EWT (if
Range Default Ex.
0,0 to
0 3
6,0
Unit
°C
(1)
Unit
°C
55