Danfoss EPU 2370, Instructions Manual, Page: 34 / 48

34 VI.72.M4.02

Danfoss 11/97
BC-HM
System type 3 - Hot air blower (unit heater)
System 3 - Unit heater system with constant room temperature
Control principle
PI flow temperature control (S1) and P
room temperature control (S2). Flow
temperature is held constant by motor
valve control M. Fans P1 controlled by
relay R1, circulation pump P2 by relay
R2.
Notes
- Frost protection can be obtained at
any point in the system by connecting
a separate S3 sensor. A frost signal
stops the fans, starts the circulation
pump and fully opens the valve.
- Sliding frost protection is possible
when return sensor S4 is connected.
When the return temperature is 10°C
or less, the reference for S1 is
increased and thereby the valve
opens. If it is not possible to reach
6°C in the return, the fans stop.
- Warm-start function. Relay R1 cut-in
is delayed in order to counter cold
supply air at the changeover from
reduced to normal temperature. The
R1 closes under the following
conditions:
with S4 installed:
when P4.0 is larger than P1.1
and the delay in P4.3 has
elapsed.
without S4 installed:
when the delay in P4.3 has
elapsed.
- Load-dependent compensation is
possible by connecting sensor S6.
Two independent compensation
curves can be set. Curves must be
set in P6.2 and P6.3 in P7.2 and P7.3
respectively.