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All installations and services must be performed by qualified service personnel.
3.101.1 Dirty air filters may restrict the airflow across the evaporator coil resulting in
frost on the coil.
3.101.2 Are the duct system and air blower setup to move enough air to have an 18-20
degree F. drop across the coil?
3.101.3 Are there any registers or dampers closed restricting the airflow of the duct
system?
3.101.4 If the evaporator coil frosts, this indicates a low charge or insufficient air
movement.
3.101.5 The coil may not frost up, but still not cool properly. Is the system slightly low
on refrigerant? Check for an 18°F temperature drop across the coil.
3.101.6 Make sure the liquid line has not kinked or collapsed slightly causing a
restriction.
3.101.7 Hold bulb in hand to see if the pressure changes (this action should increase
the suction pressure).
3.101.8 Check out the supply/return air blower to make sure it is functioning properly.
3.201.0 Check the following items for high suction pressure and low liquid pressure.
Allow at least 5 minutes off time for valve to close when pressures have
equalized if compressor has internal pressure relief valve.
3.201.1 There may be a restriction in the condenser coil. This could be caused by
water or other contaminants in the system. A restriction in the coil is a very
rare problem.
3.201.2 Check the expansion valve for restriction of the metering orifice.
3.301.0 For high suction pressure and low superheat temperatures, review the following
items.
3.301.1 If the system is overcharged with refrigerant, the system will become flooded.
Consequently, the evaporator coil will not effectively absorb heat from the
airflow. The temperature drop across the evaporator coil will be low.
3.301.2 Check for a properly sized expansion valve.
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