Product Overview

26
103859-12 - 8/19
MPO-IQ
Installation & Service Manual
B. CHIMNEY CONNECTOR
1. A chimney connector (vent pipe) is used to connect
the boiler to the base of the chimney. The chimney
connector should be kept as short as possible. The
horizontal length of the chimney connector shall not
be greater than 10 feet.
NOTE: Secure chimney connector to cast iron
smokebox collar with three (3) #10 x ½" self drilling
hex head TEK screws provided in miscellaneous
parts carton. Locate screws around perimeter of
connector as shown in Figure 15 and approximately
½" in from edge. Use drill with 5/16" hex bit to drive
screws through connector and smokebox collar.
DANGER
The chimney and connector shall be inspected
annually for signs of debris and corrosion. Loose
mortar at the base of the chimney may be a sign
of condensate damage to the chimney. A chimney
professional shall be contacted immediately to
examine the damage and recommend a solution.
Long term operation while in this condition may
cause a venting failure and force flue gases into
the living space. If the chimney is to be re-lined
use the recommendations in NFPA 31, Appendix E
or CSA B139.
2. Vent Connector shall be any of the following and
of the same size as the outlet of boiler.
a. Type L or a factory built chimney material that
complies with the Type HT requirements of
ANSI/UL 103. Install in accordance with listing
and manufacturer’s instructions.
b. Steel pipe having resistance to corrosion
and heat with a minimum wall thickness of 24
Gauge (0.024”).
DANGER
Any signs of condensate seepage at the base of
the chimney shall be inspected immediately. The
discoloration may be a sign of chimney damage
and must be remedied immediately.
C. DRAFT
1. The natural draft generated through a 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, to name a few.
Make sure that the boiler has been running for at
least 5 minutes before measuring the draft.
2. Minimum Draft at Breech (Canopy) – The draft
induced by a chimney must create at least a
pressure of 0 (zero) inches water column (“ w.c.)
at the pressure tapping on the canopy mounted on
rear of boiler (see Figure 15). The pressure at the
canopy cannot be positive since this could create a
condition that allows flue gas by-products to escape
from the draft regulator. A negative pressure reading
up to -.03 inches water column is acceptable for
proper operation. (See Tables 15A thru 15C and
16) Burner Specifications at the rear of this manual
for more details)
3. Minimum Overfire Pressure – The overfire
pressure is another piece of information that is
often measured, however this should be done for
observation purposes only! The breech pressure
must be used to qualify the draft condition. See
Tables 15A thru 15C and 16 for more details
as a guide. Actual draft and temperature
measurements may be different then those values
in the table.
D. STACK TEMPERATURE
1. The temperature of the flue gases has a significant
effect on the amount of draft created in a vertical
chimney as well as the propensity to create
condensate. The higher the stack temperature, the
greater the amount of draft that can be generated.
A lower stack temperature not only reduces the
amount of draft that can be created but it also
increases the possibility that the flue gases could
condense in the chimney connector or stack.
2. NFPA 31 and CSA B139 have information to help
the installer make an appropriate choice of venting
materials. In some cases a chimney may have to
be lined to create sufficient draft. In other cases,
the chimney may have to be lined to prevent
the corrosion of a masonry chimney. Consult
with a chimney specialist knowledgeable on the
requirements for chimney requirements in your area.
Figure 15: Smokebox Pressure Tapping
for Checking Draft at Breech
4 Natural Draft Venting (continued)
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