Dunkirk Excelsior EXB Series - Manual (Page 36)

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14.2 Vent and Vent Connector
1. Vent connector should be kept as short as possible.
Horizontal length of vent connector should not be
greater than 10 feet.
2. Type L Vent pipe or other suitable material may be
used for vent connector if flue temperature is less than
570° F.
3. 4,5 & 6 section boilers have sheet metal flue collar
spacer included in accessory carton for attaching 5”
diameter vent connector to cast iron flue collar. For
7 section boiler, 6” diameter vent connector attaches
directly to cast iron flue collar.
4. Attach vent connector and flue adaptor ring to cast
iron flue collar with three screws. Pre-drill cast iron flue
collar to prevent cracking.
5. Canadian versions have vent spill switch kit included.
6. Inspect chimney and connector annually for signs of
debris and corrosion. Loose mortar at base of chimney
may be sign of condensate damage to chimney.
7. Inspect base of chimney for any signs of seepage.
Discoloration may be a sign of chimney damage. Have
repaired immediately.
8. Contact qualified service agent immediately to examine
damage and correct. Operation of damaged chimney
may cause venting failure and force flue gases into
living space.
9. If chimney is to be re-lined, use recommendations in
NFPA31, Appendix E or CSA B139.
14.3 Draft
• Natural draft generated through chimney is dependent
on several factors including, chimney height,
temperature of flue gases, cross section area of
chimney, chimney wall insulation value, dilution air and
total volume of flue gases. Operate boiler for at least 5
minutes before measuring draft.
• Minimum Draft at Breech – Draft induced by the
chimney must create at least a neutral pressure of 0
(zero) inches water column (INWC) at breech. Slightly
negative (i.e. suction) pressure is preferred. Pressure
at breech cannot be positive since this could create
condition that allows flue gas by-products to escape
from draft regulator. Draft is to be measured up stream
of draft regulator. See Burner Specifications.
• Over-fire Draft - Measure pressure at 1/4” NPT test port.
Three pass boilers have higher pressure drop than single
pass. Table 8A shows expected pressure drop between
over-fire and breech. Total pressure drop is difference
between over-fire draft and breech draft. For example,
if over-fire draft = 0.05 INWC and breech draft = - 0.05,
total pressure drop = 0.05 - (-0.05) = 0.10 INWC. See
Figure 33, Page 37.
Table 9 - Pressure Drop Between
Over-Fire & Breech
Sections Inches WC
4 0.03-0.05
5 0.05-0.08
6 0.09-0.16
7 0.07-0.16
14.4 Stack Temperature
1. Higher stack temperature, greater amount of draft
generated. Lower stack temperature not only reduces
amount of draft created but also increases possibility
flue gases could condense in chimney connector or
stack.
2. Consult NFPA 31 and CSA B139 for information for
appropriate choice of venting materials. Chimney may
have to be lined to create sufficient draft, or chimney
may have to be lined to prevent corrosion of masonry
chimney. Consult qualified service agency for chimney
requirements in your area.
3. Baffles – Efficiency of boiler is based on insertion of
flue baffles supplied with 4,5 & 6 section units. Baffles
are installed in 3rd pass (two inner flueways). Refer to
“8 - Boiler Assembly” on page 13 for baffle installation.
Remove baffles to increase stack temperature.
4. Remove baffles if any signs of condensation in chimney
or chimney connector. Removing baffles may not
address condensation.
14 - CHIMNEY AND VENTING CONNECTIONS