Figure 14: Operation Of Booster And Backup - Riello NXHP Series Installation, Operation And Maintenance Instructions

4 -OPERATION
4.2.8 - Electric Heaters
NOTE:
The installer is responsible for ensuring that the installation
complies with the applicable legislation in terms of electrical
and thermal safety.
It is possible to include electric heaters in the hydraulic circuit to
ensure heating in case of low OATor heat pump failure.
When OAT is below Booster OAT Threshold [P604], then the
electrical booster heaters can be activated. The electrical booster
heaters can operate at the same time as the heat pump.
When OAT is below Min OAT for heating [P605] (backup OAT
Threshold), the heat pumps is stopped, and the electric heaters
can be activated.

Figure 14: Operation of booster and backup

Heating needs
Min OAT for heating [P605]
Boiler only
Electric Heaters +
or backup
heat pump
heaters
Depending on the configuration, it is possible to control up to three
electric heaters or three electric heat stages (refer to § 3.1 General
customer electrical connection on terminal block):
■ One electric heat stage with one discrete output: EH1.
■ Two electric heat stages with two discrete outputs: EH1 and
EH2.
■ Three electric heat stages with two discrete outputs: EH1 and
EH2.
■ Three electric heat stages with three discrete outputs: EH1 and
EH2 and EH3.
Each discrete output can control a contactor (not supplied with
unit).
Contactor Coil:
Characteristics 230 VAC
50Hz
Electrical
Refer to § 3.4 Installation with electrical booster
connection heaters
Refer to § 3.4 Installation with electrical booster
Configuration
heaters
56
Capacity
of heat pump
Booster OAT Threshold [P604]
OAT
Heat pump only
4.2.9 - Boiler
To satisfy the heating demand during periods very low ambient
temperature, it is possible to install a boiler. The boiler is considered
as a backup: when it is activated, the heat pump cannot operate.
Boiler is activated when OAT is below Minimum OAT for Heating
[P605] or in case of heat pump failure.
Contactor Coil:
Characteristics
230 VAC
(for DO#08/#09)
50Hz
Characteristics
Free potential contact
(for DO#05)
4.2.10 - Coil heating control for compressor
CAUTION: When the unit doesn't operate, the compressor
can be energized. The coil heating control has the function
of heating the compressor by applying a current to the
compressor whennot operating instead of using a case heater.
This control is for the purpose of preventing stagnation of
the refrigerant inside the compressor.
4.2.11 - Defrost cycle (traditional defrost)
When the outdoor air temperature is low and the ambient humidity
is high, the probability of frost forming on the surface of the outdoor
coil increases. The frost covering the outdoor coil may reduce the
air flow across the coil and impair the performance of the unit. To
remove the frost from the coil, the control initiates the defrost cycle
when necessary.
During the defrost cycle, the refrigerant circuit is forced into the
cooling mode. To prevent the water loop from cooling down, BPHE
and piping electric heaters may be started.
CAUTION:
Please note that "defrost" and "home anti-freeze protection"
are two different modes. Defrost is used in order to remove
the frost that is covering the outside coil, whereas the home
anti-freeze protection is used to maintain the minimum room
temperature.
4.2.12 - Energy Soft
Energy Soft extracts energy from outdoor air in order to melt frost
on the coil using fans while compressor is OFF.
Unlike traditional defrost, Energy Soft has almost no impact on
the water loop because the refrigerant circuit is not forced in cooling
mode.