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The fan defrost HRV is equipped with an electronically
controlled fan defrost system to remove frost that collects
on the warm air side of the aluminum heat transfer sur-
faces of the heat exchanger core. When the outside air
temperature drops below 27°F (3°C), defrost is activated
which provides for an automatic defrost cycle. During the
automatic defrost cycle, the fresh air supply is shut off
while the exhaust fan continues to operate. This allows the
warm inside air to flow through the heat exchanger core
melting frost accumulation. After the defrost period, the
fresh air supply fan returns to the normal speed and fresh
outside air continues to be drawn into the building. Water
from the melted frost collects in the bottom of the drip
pans and drains out through the bottom drain connections.
The defrost cycle repeats automatically until the air tem-
perature rises above 27°F (-3°C).
Defrost Operation
Dehumidistat Operation (HRV only)
The optional HRV remote controls include a dehumidistat
which controls humidity levels during the heating season.
The control has a selector knob with set points ranging
from 20% to 80% relative humidity (RH). Most people are
comfortable when indoor relative humidity levels are in a
range from 30 to 45%.
The dehumidistat switches the ventilator to high speed
when the moisture level in the building exceeds the
desired setpoint. The dehumidistat switches the HRV back
to low speed ventilation when the humidity has been
reduced below the setpoint. The dehumidistat should
only be used during the heating season. It must be set
to OFF position throughout the rest of the year.
Defrost Cycle DIP Switch Settings
Defrost DIP Switch Settings (located on the circuit board)
can be adjusted to increase the unit’s run (ventilation)
time. The three minute defrost time cannot change.
HS
REMOTE
DFR2
DFR3
ON
SW1
*Lengthening the run time may result in ice build-up on the core.
HS
REMOTE
DFR2
DFR3
ON
SW1
HS
REMOTE
DFR2
DFR3
ON
SW1
OFF ON
OFF
ON
Factory Setting
3 minute defrost time
17 minute run time
Option 1*
3 minute defrost time
25 minute run time
Option 2*
3 minute defrost time
30 minute run time