Bosch Heatronic 4000 Installation & Operating Instructions Manual page 9

• STG COND (Staging Mode - Two-Stage, Condensing Boiler
Group)
This setting is applicable for a group of at least two, two-stage
condensing boilers.
• STG NC (Staging Mode - Two-Stage Non-Condensing
Boiler Group)
This setting is applicable for a group of at least two, two-stage
non-condensing boilers.
Lo⁄Hi
If the Lo/Hi staging option is selected the control stages in
sequence all of the stages in a single boiler. Once all of the
stages are turned on, the control then stages in sequence all
of the stages of the next boiler in the rotation sequence.
Lo⁄Lo
If the Lo/Lo staging option is selected, the control stages all of the
Lo stage outputs in all of the boilers first. Once all of the boilers
are operating on their Lo stages, the control then operates the
second stage in each boiler in the same order.
Boiler Group Rotation - - - -------------- --------- --------- -------------------- ---------------
The control has two rotation settings including one for the
condensing boiler group & another for the non-condensing
boiler group.
• ROT COND (Rotation - Condensing Boiler Group)
This setting is applicable for a group of at least two, two-stage
condensing boilers.
• ROT NC (Rotation - Non-Condensing Boiler Group)
This setting is applicable for a group of at least two, two-stage
non-condensing boilers.
The Rotate feature changes the firing order of the boilers
whenever one boiler accumulates 48 hours more run time than
any other boiler. Rotation will be forced if any boiler accumulates
60 hours more run time. After each rotation, the boiler with the
least running hours is the first to fire & the boiler with the most
running hours is the last to fire. This function ensures that all of
the boilers receive equal amounts of use. When the Rotation
setting is set to Off, the firing sequence always begins with
lowest boiler to the highest boiler.
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720 hou rs 672 ho urs
To reset the rotation sequence, clear the Burner Run Time in
the Monitor (#) Menu.
Boiler Run Time Monitoring -------------- ----------- --- -
The running time of each boiler is logged in its respective Monitor
(#) menu. To reset the running time, select the appropriate
BURNER item in the Monitor (#) menu & select CLEAR until
"0" is displayed.
Fixed Lead - - - - - - - - - - - - - - ---- ---------- -------- ---- ------ - - - - - - ----------------------------------------
When the boiler plant includes only one boiler group, either a
condensing or a non-condensing group, a selection must be
made regarding operation of the lead boiler.
ON
In some applications, it may be desirable to have the first boiler
fire first at all times while the firing sequence of the remain-
ing boilers is changed using Equal Run Time Rotation. This
configuration is typical of installations where the boiler plant
BTC461503101C | 6720810369 (2018/03)
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672 hour s 720 ho urs
------------- ----------- -----
includes similar boilers but the first boiler is required to be
the first to fire in order to establish sufficient draft for venting.
With a fixed lead rotation, the lead boiler is always turned on
first & turned off first. The Fixed Lead is always applied to the
boiler 1 output.
OFF
The lead boiler is not fixed to operate first in the firing sequence.
It is included in the rotation sequence with the other boilers.
Fixed Last - -- -- -- -- -- -- -- -- -- -- -- -- - - -- -- -- -- -- -- -- -- --- - - -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- - - -- -- -- -- -- --
When the boiler plant includes only one boiler group, either a
condensing or a non-condensing group, a selection must be
made regarding operation of the last boiler.
ON
In some applications, it may be desirable to have the last
boiler fire last at all times while the firing sequence of the
remaining boilers is changed using Equal Run Time Rotation.
This configuration is typical of installations where the boiler
plant includes higher efficient boilers & a single lesser efficient
boiler. The lesser efficient boiler is only desired to be operated
when all other boilers in the plant are on & the load cannot be
satisfied. With a fixed last rotation, the last boiler is the last to
turn on & the first to turn off. The Fixed Last is always applied
to the boiler 4 output.
OFF
The last boiler is not fixed to operate last in the firing sequence.
It is included in the rotation sequence with the other boilers.
Condensing & Non-Condensing Boiler Groups - -- -- --- -- -
Operating a boiler plant that contains both condensing (high
initial cost) & non-condensing (lower initial cost) boilers allows
the boiler plant to achieve nearly the same operating efficien-
cies as operating all condensing boilers but at a much lower
installed cost to the building owner. High system efficiency can
be achieved as long as the condensing boilers are the first to
operate in the firing sequence. During mild weather, the lead
condensing boilers operate at lower boiler temperatures &
achieve their peak boiler efficiencies while the non-condensing
boilers are rarely operated. During very cold weather, the boiler
target temperature is often above the boiler's condensation
point & the condensing & non-condensing boilers operate
together at roughly the same efficiency level.
When a condensing boiler is operating, it is desirable to operate
the boilers without a boiler minimum temperature being applied
to the boiler target. This allows the condensing boiler to operate
at its maximum efficiency. When a non-condensing boiler is
operating, a boiler minimum temperature should be applied to the
boiler target to prevent damage to the non-condensing boiler's
heat exchanger from sustained flue gas condensation.
The Heatronic 4000 supports operation of a condensing & a
non-condensing boiler group. A condensing boiler group is
created when at least one boiler is selected to be condensing
& a non-condensing boiler group is created when at least
one boiler is selected to be non-condensing. The condensing
boiler group is always sequenced on first, followed by the
non-condensing boiler group.
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Heatronic 4000