Defrost - Swegon GOLD RX Operation And Maintenance Instructions

6.4.13.3 Defrost

In environments where the extract air can occasionally
be humid, the defrosting function can be activated to
protect the heat exchanger from frosting. The func-
tion continuously monitors the condition of the heat
exchanger rotor to prevent it from becoming clogged due
to condensate that has frozen inside the exchanger.
The function requires a separate pressure sensor (preset for heat
exchanger defrosting) wired to the control unit inputs for exter-
nal BUS communication and connected to the AHU pressure
measurement tappings. See special installation instruction for the
TBLZ-1-23-aa pressure sensor.
The pressure drop across the rotor must then be calibrated to
establish a reference pressure drop for monitoring purposes.
Calibration is put into effect by setting Calibration to the On
position.
When the defrosting function is activated the pressure drop
across the heat exchanger is continuously measured and the
reading is compared with the calibration reading. If the pressure
drop exceeds the preset limit value, a defrosting sequence is
implemented in which the rotor speed is gradually ramped down
(ramp time max. 4 minutes) to the speed at which the pressure
drop across the heat exchanger decreases to half of the preset
limit value. The lowest permissible speed of the rotor is 0.5 rpm.
During the defrosting process, the warm extract air thaws any
possible ice that has formed on surfaces. A delay time of 4 min-
utes gives the heat exchanger time to dry, before the rotor once
again is ramped up (ramp time max. 4 minutes) to its ordinary
speed.
The defrosting operates for a max permissible period of 30
minutes. If the pressure drop has not decreased within that max
permissible period after six tries during a 24-hour period, an
alarm will be initiated.
Note that the heat exchanger performs less efficiently while
defrosting is in progress and that the supply air temperature will
also drop downstream of the heat exchanger.
Settings:
Value
Defrost
Defrost limit value
Calibration
We reserve the right to alter specifications without notice.
Setting Factory
range setting
On/Off Off
30 - 100 Pa 50 Pa
On/Off Off
Defrost
Connection principle for the defrosting function with
separate pressure sensor.
GB.GOLDSKE.160901
Extract air
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