Danfoss OBC 85B.10 Data sheet

Data sheet

Electronic Oil Burner Control OBC 85B.10

Description

Function

The microprocessor based control OBC 85B.10
offers stable and precise timings independent of
variations in supply voltage and ambient
temperature.
The control is undervoltage protected in
accordance with EN 298:2012. In case of

The OBC 85B.10 controls the cut-in and cut-out of
the oil burner’s components and monitors that
the combustion cycle is performed safely.
When the boiler thermostat (TR) cuts in, heating
of the oil in the oil preheater (OFV) will begin.
Once the release temperature is reached and the
oil preheater’s thermostat (OTR) cuts in, the
burner motor will start the pre-purge and power
will simultaneously be applied to the ignition
(TT). Following the pre-ignition and pre-purge
time, the oil will be released by valve V1 being
opened and subsequently V2 will be opened.
When the boiler thermostat opens after the
heating period power is not cut off when the
boiler thermostat opens, as power is still needed
for the burner motor so that post-purge can
occur. Instead, a timer function ensures that the
burner motor continues to run until the end
of the postpurge time. If the thermostat cuts
in before the end of the post-purge time, the
control will interrupt the post-purge and start a
new cycle with pre-heating.

Note: On the OBC 85 the boiler thermostat
(TR) must always be connected to terminal 7,
and the high temperature cutout (TB) must
always be connected to terminal 1.

Operating information

OBC 85B.10 is equipped with a two-coloured LED
which displays both the operating status and can
indicate the causes of errors leading to lockout.
In the event of operating lockout, the cause of
error can be read out as a flash code by holding
down the reset button for at least 5 seconds and

undervoltage the control will prevent the burner
from starting and simultaneously show a flash
code. Besides this, up to five other fault types can
be read out as flash codes when the control is in
lockout.
The design complies with the requirements of
the RoHS and WEEE directive.

Application and features

• For 2 stage burners up to 30 kg/h

• For burners with or without preheater

• Precise and reproducible timings

• Limitation at 3 restarts by flame failure within
the same operating period

• Limitation of 10 min. on preheating time

• Remote reset and alarm output

• Post-purge

• Indication of reason for lockout

• Indication of preheating and operation

then releasing it. Undervoltage will, however, be
displayed automatically. Reset can be performed
directly in alarm mode (constant red light) or in
flash code mode by pressing the reset button for
at least 0.5 seconds but no more than 3 seconds.

In flash code mode it is possible to return to
alarm mode by holding down the reset button
again for at least 5 seconds.

Normal operation

When the boiler thermostat (TR) cuts in, the reset
button flashes green. As soon as the preheater
thermostat (OTR) cuts in, the reset button lights
up constant green. When the boiler thermostat
cuts out, the green light does not turn off until
the post-purge period ends.

Errors during operation (flash codes):

• If the mains voltage falls below 185 V before
start-up, the control will be blocked from
starting. If the mains voltage falls below 170
V during operation, the oil supply and burner
will be stopped. In both cases, the reset
button will automatically flash 8 times.
When the mains voltages reaches 185 V, the

control will restart as normal. Please note
that the control cannot be reset if the mains
voltage is below 170 V.

© Danfoss | 2019.09

VD.HN.B3.02 | 1

Data sheet Electronic Oil Burner Control OBC 85B.10

• If the mains voltage exceeds 264 V, the control
will automatically enter alarm mode. The

purpose of the overvoltage cut out is not
simply to protect the electronics in the
control, but also the other components in

the burner.

• If light is registered in the final stage of the
pre-purge time, the control will not release
oil and will enter alarm mode.

• If no flame is established at the start, i.e. by
the end of the safety time, the control will
enter alarm mode.

• In the event of a flame failure during
operation, the oil supply will be cut off after
no more than 1 second and the control will
restart the burner. If flame failure occurs more

than three times in the same operating period
(TR connected), the control will enter alarm

mode.

• If the release temperature in the preheater is

not reached within 10 minutes, the control
will enter alarm mode.

The OBC 85B.10 processor also monitors the
outputs at TT, V1 and V2. If errors like electrical
noise (EMC) are registered at the outputs, the
control will enter alarm mode.

Note:

OBC 85B.10 can only be reset while t he supply voltage is
connected.

Flash codes

Event Code

False light 2 flashes

No flame when safety time elapses 3 flashes

More than three restar ts in the same
cycle

Max. waiting time on preheater overrun
(10 mi n)

Supply voltage above 264 V a.c. 6 flashes

Undervoltage <170 V (automatic) 8 flashes

Application failure (EMC)

4 flashes

5 flashes

constant

flashes

2 | © Danfoss | 2019.09

VD.HN.B3.02