5.9.3 Passive Heat Exchanger, uncontrolled (PltHExg22y)
The purpose of energy recovery is to absorb heat/cold from the exhaust air and
transfer it back to the supply air side.
The control of the energy recovery is not possible, the ERC always works with
maximum capacity. With this solution, the outside air cannot be used for heating or
cooling even if the outside air is closer to the setpoint than the exhaust air (e.g. in
rooms with a high internal load or when heating up after cold nights).
5.9.3.1 ERC De-Icing (passive, uncontrolled)
Passive Energy Recovery units are essentially heat exchangers. They receive
warm and humid air on one side and cold on the other which will eventually
cumulate ice on the surfaces when the conditions are suitable for that. Passive
element usually starts to cumulate ice already close to zero Celsius degree.
Detecting ice on the heat exchanger or in the ductwork
Detecting ice on the heat exchanger or in the ductwork is possible:
●
With exhaust air temperature sensor TEh. This is not a real indication, but an
expectation that ice is expected to build up.
–
Deicing with TEh sensor starts when TEh is below the limit.
–
The end of the de-icing phase cannot be detected and is estimated via
timer.
●
With a differential pressure switch over the heat exchanger. This possibility
does not detect ice built up in the ductwork and does not safely work on all
types of heat exchanger. If exhaust air temperature sensor and differential
pressure switch are installed, the differential pressure switch is used to start
de-icing.
–
Deicing is active as long as the differential pressure switch is active.
●
With outside air sensor TOa. This is used when no exhaust air sensor and no
differential pressure switch are available. It is also only an expectation that ice
has built up.
–
Deicing with TOa sensor starts when TOa is below the limit.
–
The end of the de-icing phase cannot be detected and is estimated via
timer.
De-icing the heat exchanger
De-icing is possible by:
1. Reducing the supply fan speed, so that the load of cold air incoming is
reduced, increasing the exhaust air temperature.
2. Preheating the outside air, increasing the exhaust air temperature
De-icing modes
The deicing mode can be configured as:
●
No deicing
●
Reduce fan speed
●
Increase preheating
●
Reduce fan speed and increase preheating
Deicing with fan speed is running in parallel or with 2 stage, see below.
Time based Deicing started by TEh or TOa
The sensor is not suitable for detecting the end of the deicing phase. Therefore, a
fix deicing time is used. After deicing is finished, an off time is started until the next
deicing phase can be started again. The duration of the off time depends on the
measured temperature at the start of a deicing phase. Deicing time, maximum off
time with assigned temperature and minimum off time with assigned temperature
can be configured.
Application functionalities
Energy Recovery
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