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5 Functional Description
5 Functional Description
5.1 Sequence of Functions
(Heaters with Electronic Control Units
SG
1561,
SG
1561
GT
and
SG
1561
GS)
(see also Functional Diagram)
The description below refers
to
wiring diagram B 8014-
3000-0008/-0009, see "Wiring Diagram", see pp.
39
5.1.1 Switching the Heater
On
Positive voltage
is
continuously supplied to electronic
control unit connector
A2
via
fuse
F1,
and
to
control
unit connector A 1 via fuse
F2.
Upon switching on, posi-
tive control voltage is also supplied to the electronic
system
of
the control unit via control unit connector
A6.
- Operation indicator light
is
illuminated.
- Closing relay
is
energized
- Glow-plug operation is activated via relay
K1
- TRS: The solenoid value
in
the combustion air line
opens.
- After preheating (approx.
25
sec.
for
SG
1561
GS,
approx.
30
sec. for
SG
1561
GT),
positive pulsed
voltage
is
applied to control unit connector D3 (ap-
plies
to
control unit
1561
and
1561
GT), or C10
(control unit
1561
GS) via transistor
v101rr
(no
pulse-control relay
exists
in
control unit
SG
1561
).
Control unit connector D3/C10 supplies metering
pump Y
via
temperature limiter
B2
and
safety switch
S3/S6.
- Safety time (max. 90 sec.)
and
fuel inlet flow time
(approx. 5 sec.) commence.
- After the fuel inlet flow time has elapsed, motor
Mis
switched
on
via relay
K2
and electronic control unit
connector D1/C4.
NOTE:
In
the case
of
Air
Top
24/32 equipped with
SG
1561
GS the motor starts at partial load after overcoming a
breaking-off torque and after
20
seconds switches over
to full load.
If flames have formed during the safety time, flame
de-
tector
B1
signals "light" and relay
K1
is released.
Safety time
is
reset and the glow plug/pencil-type glow
plug (SG
1561
GS)
is
switched
off.
In
the case of
proper ignition this procedure lasts approx. 15 seconds.
Restarting:
If
no flame has materialized during the
safety time, a second start-up attempt is carried out
automatically.
5.1.2 Combustion
The
heater, which
is
now operating, continues to run
until the control voltage is interrupted
at
control unit
connector
A6.
This occurs either when the heater
is
switched off manually or when the preset operating
time
has elapsed,
or
by the room thermostat.
Depending on the amount of heat required, the heater
can
remain in the "combustion mode" or "part load
mode" (i.e. heating operation at reduced heat output)
for
an
extended period of time.
5.1.2.1 Start of Part
Load
Operation
If
the system is equipped with a room thermostat B3.
the
latter closes as soon as the preset room tempera-
ture
has
been reached. Positive control voltage
reaches plug
A3.
During part load operation, metering
pump Y cycles
at
a lower frequency. After 20 sec. (HL
24/32) or
85
sec.
(Air
Top 24/32), motor M also oper-
ates
at
the lower part-load speed. The heater now oper-
ates
at
reduced output until the room temperature is
at
a level where the lower switching point
of
room thermo-
stat 83
is
reached.
During the entire part load phase the operation indica-
tor remains on.
5.1.2.2 Start of Full Load Operation
When
the
room temperature has reached the lower
switching point
of
room thermostat 83, the latter
opens. The positive control voltage
is
removed from
plug
A3
and metering pump Y resumes operation at the
higher full load frequency. After
10
sec. also motor M
switches to the higher full load speed.
NOTE:
If
a room thermostat with On/Off switch is used, this
control operation can also
be
effected between part
load mode and the Off state (control idle), depending
on
the switch position.
5.1.3 Start-Up Following Control Idle Period
After the room temperature has fallen to a certain level,
the
HL 24/32 heaters (fitted with glow plug) always
start
up
at
full load.
The
Air
Top
24/32 heaters (fitted with pencil-type glow
plug) start up at part load after overcoming a
break-
away torque and change over to full load after 20 sec-
onds.
Depending on the switch position, change-over to part
load operation is effected after a minimum of
60
sec-
onds operating at full load.
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