dew

JohnWood1

But one thing to keep in mind that the author is talking (i think) about a static system..... In actual application, we have fresh vapor entering on a regular basis and on a condensing appliance, we run the gamut of temps, percentages etc all the way thru the system. In the old days, we did not want the vapor to condense. Now we want that 970btu/lb that used to go up the stack (on purpose)

bob_44

Dew Point

Thought this was intresting, you can see from this that every time a drop of condensate forms you lower the dew point and thus you have to lower the return temp to keep the process going. If your return is 90F you have only condensed 70% of whats available. bob

bob_44

True John

but I wonder what % of the gases are actually cooled to the dew point. I would think that the heat-x in a boiler would be similar to a air cond coil and have a by-pass factor not ALL the gases come in contact with the heat-x/fins. bob

Bob Harper

more to it

High sulfur heating oil has a higher dewpoint than low sulfur oil. Just another factor to consider...

bob_44

Humidity

Someone in another thread expressed concern about the relative humidity of the combustion air. The amount of water in the amount of air required to burn 1 therm of nat. gas if the air is 70F @ 50% RH is .06 gal approximately. If air 20F@100%RH .02 gal. bob