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IV: VENTING (NATURAL VENT - CHIMNEY) (continued)
1. INSTALL DRAFT REGULATOR following
instructions furnished with Regulator. See Figure
14.
2. Consider the chimney overall. Chimneys that have
a high heat loss may become less suitable as the
heat loss of the home goes down and the efficiency
of the boiler installed goes up. Most homes have
a chimney appropriate for the fuel and the era in
which the home was built. That may have been a
coal fired or an inefficient oil fired boiler built into
a home without insulation or storm windows. With
increasing fuel prices that home probably has been
insulated and fitted with storm windows so that
the heat loss of the home has been reduced. This
requires less fuel to be burned and sends less heat up
the chimney.
A new boiler probably has a higher efficiency than
the boiler being replaced. That probably means
that the stack temperature from the new boiler will
be lower than that from the old boiler and with less
room air being drawn up the chimney to dilute the
stack gases. The combination of a large uninsulated
chimney, reduced firing rate, reduced firing time,
lower stack temperature and less dilution air can, in
some cases, contribute to the condensing of small
amounts of water vapor in the chimney. Such
condensation, when it occurs, can cause chimney
deterioration. In extreme cases, condensed water
Figure 14: Proper and Improper Locations
of Draft Regulator
may be visible on the outside of the breeching or
chimney. In those extreme cases, the chimney
may have to be lined to insulate the chimney and
thus prevent the condensation. The addition of
dilution air into the chimney may assist in drying the
chimney interior surfaces.
3. For the same reasons as in (b) above, heat extractors
mounted into the breeching are not recommended.