Checking Airflow; Checking Refrigerant Charge; Charging Units With R-410A Refrigerant - Rheem R-410A Installation Instructions Manual

15.0 CHECKING AIRFLOW

The air distribution system has the greatest effect on airflow. The duct system is
totally controlled by the contractor. For this reason, the contractor should use only
industry-recognized procedures.
The correct air quantity is critical to air conditioning systems. Proper operation, effi-
ciency, compressor life, and humidity control depend on the correct balance
between indoor load and outdoor unit capacity. Excessive indoor airflow increases
the possibility of high humidity problems. Low indoor airflow reduces total capacity,
and causes coil icing. Serious harm can be done to the compressor by low airflow,
such as that caused by refrigerant flooding.
Heat pump systems require a specified airflow. Each ton of cooling requires
between 340 and 450 cubic feet of air per minute (CFM).
Duct design and construction should be carefully done. System performance can be
lowered dramatically through bad planning or workmanship.
Air supply diffusers must be selected and located carefully. They must be sized and
positioned to deliver treated air along the perimeter of the space. If they are too
small for their intended airflow, they become noisy. If they are not located properly,
they cause drafts. Return air grilles must be properly sized to carry air back to the
blower. If they are too small, they also cause noise.
The installers should balance the air distribution system to ensure proper quiet air-
flow to all rooms in the home. This ensures a comfortable living space.
These simple mathematical formulas can be used to determine the CFM in a resi-
dential or light commercial system.
Electric resistance heaters can use
volts x amps x 3.414
CFM =
1.08 x temp rise
Gas furnaces can use
BTUH
CFM =
∆T x 1.08
An air velocity meter or airflow hood can give a more accurate reading of the sys-
tem CFM's.

16.0 CHECKING REFRIGERANT CHARGE

Charge for all systems should be checked against the Charging Chart inside the
access panel cover. Before using the chart, the indoor conditions must be within
2°F of desired comfort conditions and system must be run until operating conditions
stabilize (15 min. to 30 min.)
CAUTION
THE TOP OF THE SCROLL COMPRESSOR SHELL IS HOT. TOUCHING THE
COMPRESSOR TOP MAY RESULT IN SERIOUS PERSONAL INJURY.
IMPORTANT: Use industry-approved charging methods to ensure proper system
charge.
NOTE: The optimum refrigerant charge for the (-)PRL-0-36 & (-)PRL-048 is affected
more by the application than the other (-)PRL models due to the relationship
between the indoor and outdoor coil volumes. Therefore, multiple charging charts
have been developed to assist the field technician in optimizing the charge for the
application on these two models. Refer to the "Specific Charging Instructions" note
shown on the charging chart attached to the unit and choose the appropriate chart
for the specific application being installed or serviced. New installations utilizing a
downflow or horizontal right air-handler or a coil installed on a gas furnace may
require removal of refrigerant since the factory charge could result in an over-
charged condition if the line set is relatively short.

16.1 Charging units with R-410A Refrigerant

Charge for all systems should be checked against the Charging Chart inside the
access panel cover.
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