Installation manual

Problems Possible causes You should try this
5. The defrost cycle • Ice deposits may be hindering • Remove the ice.
does not work the damper operation.
(the fresh air duct is
frozen OR the fresh air • The damper rod or the port • Inspect these parts and replace if necessary.
distributed is very cold damper itself may be broken.
OR the “AIR EXCHANGE”
light flashes). • The damper actuator may • Plug in the unit and select “MIN.” or “MAX.” Press the
be defective. door switch and see if the port damper opens. If it doesn’t
open, feed 120V directly to the damper actuator. If the
port damper still doesn’t open, replace the damper
actuator.
• The circuit board may • Unplug the unit. Unplug the defrost sensor wire (see J4
be defective. on electrical diagram Section 7.). Plug the unit back in.
Select “MIN.” and make sure the unit is adjusted for
low speed operation (turn dehumidistat knob on main
wall control maximum counterclockwise). Wait 3 minutes.
The unit should switch to high speed and the damper at
the fresh air intake port should close (defrost mode). If
this doesn’t happen, then replace the circuit board.
• The thermistor may be • If the defrost mode works well after having disconnected
defective. the thermistor wire (above test), this means the thermistor
is probably defective. You should replace it.
11. Troubleshooting (cont’d)
12. References
• HVI, “Installation Manual for Heat Recovery Ventilators”, 1987 edition.
• ASHRAE 1984 Systems Handbook, chapter 11, “Air Distribution Design for Small Heating and
Cooling Systems”.
R 2000