What is the effect of bringing dilution air into the draft diverter of a natural draft furnace?

Bringing dilution air into the draft diverter of a natural draft furnace decreases the dewpoint temperature. This occurs because dilution air, which is at ambient temperature, mixes with the flue gases that exit the furnace. The introduction of cooler air effectively reduces the overall temperature of the exhaust gases.

The dewpoint temperature is the temperature at which water vapor in the flue gases begins to condense into liquid water. When the flue gases are cooled through the mixing of dilution air, the gases can reach this dewpoint at a lower temperature than they would without the dilution air. Therefore, by reducing the temperature of the flue gases, bringing in dilution air helps prevent condensation within the venting system, which is important for maintaining efficiency and preventing corrosion within the furnace and flue system.

In summary, the dilution air aids in controlling the temperature of the flue gases, thereby decreasing the dewpoint temperature and protecting the system from the potential damages associated with condensation.