Bosch Buderus SB625WS, Installation Instructions Manual, Page: 26 / 52

26 | Installation
SB625WS/SB745WS 6 720 805 218 (2013/02)
The free area of the openings must be taken into account restrictions
from the louvers and screens. The louver manufacturer should be
consulted for the percentage of free area available. When free area is not
known, metal louvers typically have 60-70% of free area, wooden
louvers have between 20-25% of free area. Louvers should be in a fixed
position or interlocked with equipment so that they open automatically
during equipment operation.The combustion air damper opening shall
be located as follows: top louver shall began within 12” of the ceiling and
the bottom louver within 12” of the floor as prescribed in NFPA 54.
Direct intake method - If outside combustion air is required, air may be
drawn from the outdoors via a duct connected directly to the burner
intake. The duct shall be constructed of galvanized steel or a material
having equivalent strength and rigidity. Refer to the burner
manufacturer's recommendations and installation instructions for
additional guidelines and application requirements.
5.9 Combustion Air from an adjacent room
Where combustion air is to be used from within the building, air must be
provided into the equipment room through two permanent openings
into the inferior building. Each opening must have a minimum free area
of 1 square inch for each 1,000 Btuh of the total input rating of all fuel
burning equipment in the space. The louvers shall be located as follows:
top louver shall start within 12” of the ceiling and the bottom louver
within 12” of the floor as prescribed in NFPA 54.
5.10 Condensate Removal
The exhaust vent pipe must be pitched at least ¼ “ per foot of length back
to the boiler. This will allow condensate to drain back to the unit to be
disposed. Low spots in the venting where condensate may collect
should be avoided. A plastic hose or PVC drain pipe may be used to
condensate discharge to the neutralization system. Care should be
taken to avoid kinks and from raising the drain line above the trap
assembly.
5.11 Condensate
5.11.1 Draining the condensate
Condensing boilers produce a flow of condensate that varies according
to operating conditions. The maximum hourly production of condensate
is shown in the technical specifications table for each individual model.
The condensate drain system must be suitably dimensioned to cope with
the flow produced. Also, pipe and hose diameter must not be less than
1” at any point. This diameter corresponds to that of the boiler’s
condensate drain fitting [1].
The connection to the waste water drain pit must be made in compliance
with national and local legislation and standards.
To prevent combustion fumes from leaking into the air of the boiler
room, the condensate drain pipe must incorporate a siphon creating a
minimum head equivalent to the fireside pressure drop (

Tab. 5,
page 9) plus 1 inch W.C. The connecting pipes between the boiler,
siphon and waste water drain pit must be laid at a minimum down slope
of 3° and must be installed in such a way as to prevent any build-up of
condensate.
Fig. 23 Draining the condensate
[1] Condensate drain fitting
EX: (SB625WS/290)
• Boiler pressure = 1.284 inches W.C.
• Siphon head = 1.284 1 inch = 2.28 inches (approx.)
5.11.2 Neutralizing the condensate
Neutralization unit types NB-5LP, NB-6
The NB neutralization unit is designed for systems with boiler
condensate drain pits located at a lower level than the boiler condensate
drain fitting. These neutralization units do not require any electrical
connections.
The inlet fitting of the NB neutralization unit (the lower fitting) must be
connected to the boiler condensate drain fitting.
The outlet fitting of the neutralization unit (the top fitting) must be
connected to the boiler room’s waste water drain pit using a section of
flexible hose or PVC pipe (not supplied).
Type
Dimensions
inch [mm] Fitting
Ø
NB-5LP 9x36 1/4x7 5/16 (228x921x192) 1”
NB-6 12x12x12 3/16 (305x305x306) 1”1/4
Table 11 Neutralization unit types NB-5LP, NB-6
≥3°
≥3°
6 720 805 218-22.1T
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