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INSTALLATION & SERVICE MANUAL FOR PROFESSIONALS
Product description
: Control system strategy
en
Control system strategy
This section describes the control system strategy under different conditions.
If a preheater is installed, the unit can add electrical heating to T1 outdoor air to reduce de-
frosting situations and increase the supply air temperature.
• Preheating is applied after the T1 sensor.
• If the outdoor air is < -3 °C, or supply air is < 16.5 °C, the preheater will be activated at 10%
of its maximum capacity.
• The preheating effect will increase/decrease by 10% every 60 seconds depending on
temperature conditions.
The set points for the temperatures during operation with an active preheating surface are
fixed and cannot be changed.
In cold conditions where T1 is below -3 °C, and exhaust air T4 is < +2 °C, condensate could
build up as ice in the heat exchanger.
The following procedure is initiated to avoid this if preheating is not installed:
• The supply air fan speed will decrease until the minimum RPM is reached.
• After 10 seconds, the supply air fan will stop completely while the extract air fan
continues to run continuously to remove any ice.
• When T4 is > +8 °C again, the supply air fan will start at minimum RPM and
increase speed until the originally requested speed is reached.
• This procedure is repeated as long as necessary.
• If T1 is ≤ -13 °C for more than 4 minutes 25 seconds, even with defrost mode activated,
the unit will stop all operation for 30 minutes and will then attempt to start under the
previous operating conditions. If electrical preheating is connected, operation stop mode
is disabled.
Defrosting operation will lead to a negative pressure inside the house. This may cause
smoke, for example from a woodburning stove, to be drawn back into the house. If
woodburner mode is activated and there is still a need for the defrosting function to be
active, the unit will instead stop all operation for four hours.
Setpoints for defrosting cannot be changed.
When defrosting is active HRC 3 will show "dEF” in the display.
When defrosting has shut down everything, the display will flash the T1 temperature
See ”Temporary Modes (Override)" section on page 9 and page 10.
Introduction
Preheat
Defrosting/wood-
burner function
Bypass cooling
and summer mode
Summary of Contents for HCV 300
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