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Installation instructions
18. Antifreeze function
18.1 With integrated modulating electric resistance
In the event that the unit is installed in a cold climate (winter
outside design temperature below -5°C), we recommend
the use of versions with an electric anti-freeze resistance on
the external air intake circuit (MODELS RHR-CF-V - ER/
EL/ PRO ER/ PRO EL).
The electric resistances available for units preheat the air
entering the heat exchanger in order to avoid freezing of the
humid air extracted and discharged by the heat exchanger
in the opposite circuit.
In fact, when the outside air falls below the critical
temperature, which can lead to freezing during extraction,
the electric heater is activated and provides the minimum
thermal power such that the temperature of the extracted
air is kept above freezing conditions (set point 4°C).
The electric resistances are selected in order to maintain
the minimum conditions of indoor comfort at outdoor
temperatures down to -10°C, and in order to avoid the
degenerative formation of ice at discharge down to -15°C
outside.
The electric resistance is fitted with a safety thermostat that
turns off the unit in case of uncontrolled heating. In case
the resistance does not start up, instead, the unit will turn
off if the intake air temperature falls below 5°C.
Activation of the resistance as a result of the anti-
freeze function is represented by the icon
Fig. 72
DAY
The operating logics and alarm signals are shown in the
table at the end of the chapter on ANTI-FREEZE
FUNCTIONS.
44
.
°C
Lindab reserves the right to make changes without prior notice
2022-01-28
li n d a b | w e s i m p l i fy c o n s t r u c t ion
18.2 With external modulating electric heater
For units not equipped with integrated electric resistance, a
duct modulating electric resistance is available as a
preheating accessory.
The use of the external modulating ducted electric heater
allows to obtain the best anti-freeze solution at the expense
of the best energy saving because the operation of the
preheating element is aimed at keeping the inlet
temperature of the ventilation unit above 0°C.
When using the external electric heater, please carefully
follow the installation and configuration instructions given
in the accessory kit.
To enable the operation of the external modulating electric
heater, DIP SWITCHES 2 and 9 must be enabled.
18.3 Without electric resistance
In case the unit is without an electric antifreeze resistance, the
unit has preventive operation logic which, below -5°C,
automatically sets running of the intake fan at minimum for
10 minutes every hour.
Also, in case the temperature falls below -10° C, the unit
stops automatically and an alert appears on the display of
the controller: " FROST ".
When the Frost alarm is triggered, the unit switches OFF
and restarts automatically when the critical climatic
condition disappears. The Frost alert remains until the next
time the unit is switched off and back on.
18.4 With preheating hydronic coil or ON/OFF resistance
As an alternative to the use of versions with the electric
preheating resistance, a hot water or ON/OFF resistance pre-
treatment coil can be used to perform the antifreeze
function, mounted on the outdoor air inlet duct.
The hydronic coil or ON/OFF resistance is not available as an
accessory. However if the configuration DIP SWITCHES 2
and 3 are activated, the power board is capable of
managing the opening of an on/off valve or an ON/OFF
electric resistance stage for the preheating function.
The valve opening and closing logic is shown in the table
below.
The opening of the water supply valve of the coil is or of the
ON/OFF electric resistance stage is represented on the
display with the icon
RHR-CF
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