1.800.627.4499
36
PA-Series
ERV
OPERATION
NOTE: System
blowers are not
provided with the
PA-Series and are provided
by others.
NOTE: The precise
determination of
energy exchange
effectiveness in the field
is quite difficult. Accurate
determination of the supply
and return mass airflow
volumes is required. Also,
temperatures must be very
carefully measured. The
leaving airstreams display
significant temperature
distribution
3.0 OPERATION
3.1 BASIC FUNCTION OF PA-SERIES ERV
The PA-Series ERV transfers heating or cooling energy from an exhaust airstream to a fresh
airstream.
The energy-recovery cores operate with no moving parts. The energy-recovery cores will
transfer energy between the two airstreams as long as airflow is maintained.
Filters are provided with the unit so that the faces of the evergy-recovery cores need not be
cleaned more often than annually. Filters must be maintained, see Section 4.0 Maintenance.
3.2 CHECKING OPERATION OF THE PA-SERIES
3.2.1 Airflow
Energy recovery will not occur unless airflow is occuring in both airstreams. One place to
confirm that air is moving is at the weatherhoods where air is exhausted and brought in.
If close control of the airflow vollume is critical, it may be desirable to permanently install flow
measuring stations in the ductwork connected to the unit. These also can be used to determine
when filters should be cleaned or changed.
3.2.2 Energy Exchange
When there is significant temperature difference between the inside and outside air, it should
be possible to measure a change in temperature (in either airstream) before it enters and after
it leaves the unit.
The temperature increase or decrease in each airstream is a function of:
1. the number of cores in the system;
2. the flow rates of the two airstreams;
3. temperature difference between the two airstreams.
See the product specification sheets to determine the expected energy exchange effectiveness
under specific conditions.
The accuracy of temperature exchange effectiveness calculations can be improved by
calculating effectiveness separately for each airstream, then averaging the results. Accuracy
is also better (uncertainty is lower) when the temperature difference between the entering
airstreams is at least 20˚F. Nonetheless, it is generally impossible to measure effectiveness in
the field with an uncertainty less than 10%.
3.2.3 Operating Controls
The operating controls are not supplied with the PA-Series. A wide variety of control schemes
may be selected by the engineer, installer, or owner to meet the ventilation needs of the facility.
3.2.4 Continuous Operation
Continuous operation is acceptable in virtually all conditions. With continuous operation in very
cold weather, some frost may accumulate on the outside of the case. If the system is cycled off
periodically, this frost will re-evaporate. Frost on the outside of the case does not necessarily
indicate any frost inside the Energy Recovery Core.
3.2.5 Operation in Extreme Cold Weather
The unit is capable of operating at outside temperatures down to -10˚F, with indoor humidities
below 40%. Units can operate at more severe conditions occasionally with brief or no impact
on its performance. At lower humidities, it can operate at lower outside temperatures without
freezing the energy-exchange core.
