Electric Heaters; Boiler; Defrost Cycle - Riello NexPolar Series Installation And Technical Service Instructions

FUNCTIONS
auxiliary pump logic
[P573]
Based on the room
temperature, but off
when DHW is enabled

4.8 Electric heaters

The installer is responsible for ensuring the system's compliance
with the applicable requirements in terms of electrical and ther-
mal safety.
Electric heaters can be mounted on the water circuit in order to
ensure heating in the event of a low OAT, or if the heat pump is ex-
periencing a fault or malfunction.
4.11 aUxIlIarY aND EMErGENCY FUNCTIoNS
Once the configuration has been completed, it is possible to control
up to three electric heaters or three electric heating stages:
— One electric heating stage with one custom output only: EH1
— Two electric heating stages with two custom outputs: EH1 and
EH2
— Three electric heating stages with two custom outputs: EH1
and EH2
— Three electric heating stages with three discrete outputs: EH1,
EH2 and EH3. This configuration cannot be activated if a DHW
heater is present.
4.9

Boiler

In order to meet the heating capacity requirements at extremely
low room temperatures, a boiler can be installed. The boiler is con-
sidered an emergency device: when it is activated the heat pump
cannot function. The boiler is activated when the OAT is lower than
the minimum OAT for heating [P514], or in the event of a heat pump
fault or malfunction.
local remote
control control Mode off
panel panel
N.A. yes Off
Cooling/heating mode
request
request
met
Based on IAT
On
vs air setpoint
When the OAT is below the additional threshold [P604], the auxiliary
electric heaters can be activated. The auxiliary electric heaters can
be made to operate in conjunction with the heat pump. When the
OAT is below the minimum heating threshold [P514], the heat pumps
are stopped and the auxiliary electric heaters can be activate.

4.10 Defrost cycle

When the external air temperature is low and the room humidity
is high, there is a greater risk of ice forming on the coils' external
surfaces. The frost covering the external coil can reduce the flow of
air through the same, thus decreasing the unit's performance. The
control unit activates the defrost cycle whenever necessary in order
to eliminate the frost from the coil.
During the defrost cycle, the circuit is forced into cooling mode. In
order to prevent the water circuit from cooling, the BPHEs and the
pipes' electric heaters can be activated.
9
It should be noted that "defrost" and "home freeze protec-
tion" are two different modes. The defrost function is used
to eliminate the frost covering the external coil, while the
home freeze protection function is used to maintain the
minimum temperature within the rooms.
52
Boiler DHW
on off Enabled Disabled
On N.A. Off N.A.