System Operation Strategy - Dantherm HCV500 Service Manual

System operation strategy

Introduction
Electric preheater
Defrosting and fire-
place function
Bypass cooling and
summer mode
14
This section describes the operation strategy under a variety of conditions.
See more under user instructions on page 26
If a heating element is mounted it will ensure the heating of fresh outside air while also
reducing the need for defrosting.
The heating element can be enabled/disabled via the remote control (HRC3) in

installer mode
, if the preheating module is set to enable (active) via PC-Tool
during installation.
The heating element is added after the T1 sensor.

If the outside temperature is under -3°C or the supply air is under 16.5°C then

the heating element will function at 10%.
The heating element will increase or decrease the effect by 10% every minute

depending on the T1 or T2 temperature.
If 100% preheater power is not sufficient, boths will be lowered in a balanced

manner.
Setpoints cannot be changed.
During extremely cold periods with T1 temperatures under -3°C and the exhaust tem-
perature, T4, at less than +2°C there is a risk of condensate in the heat exchanger
freezing to ice, which is inadvisable.
The automatic function prevents this via the following procedure:
Heat is added if a heating element has been mounted.

The supply fan gradually reduces in speed until the minimum RPM is reached.

After 10 seconds at this speed the supply fan stops

while the extractor fan continues to circulate warmer air through the heat ex-
changer, thereby thawing any frost or ice that has formed.
Once T4 has again achieved over +8°C, the supply fan will start at minimum

RPM and gradually increase the speed until the original speed has been
achieved.
The procedure is repeated for as long as is necessary.

If the outside air, T1 is under or at -13°C for more than 4 minutes and 15 sec-

onds – also in defrost mode – the unit will stop for 30 minutes and then resume
normal operations.
This is not possible if the unit is equipped with a heating element.
The default defrost strategy can create underpressure in the house. This may cause
smoke from e.g. a fireplace to be drawn back into the house. Select fireplace mode in
PC-tool house settings. If selected unbalanced defrost is blocked ad the unit will stop
for 4 hours.
Setpoints cannot be changed.
During defrosting an HRC3 remote control will show: "dEF" in the display.
If the frost protection has stopped the unit, the T1 temperature on the display will flash.
See page 28