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The condensate drain you write of is necessary and provided with a good, standard installation, but that has nothing to do with what I was writing about.
I was referring to condensation on the OUTSIDE of a duct that can occur in moist climates or when the ambient dewpoint is high and the cooler air INSIDE the duct causes the duct temp. to drop. If/When that duct temp. gets below the ambient air's dew point temp., the ambient air in contact with the cooler surface will be cooled. If that cooled air's temp. gets to its dew point temp. moisture will begin to condense out of the air and on to the OUTSIDE of the duct (and just like on a condensate coil - remember the drain you wrote about needing ace ?).
Exterior duct condensation may or may not be a concern depending on the application. For many reasons I believe I know a bit about, it may not need to be addressed by a design consideration or change in the design. Most folks don't bother with it because they are usually ignorant of the possibility as your post seem to serve as a good example. But that doesn't mean it doesn't need to be considered. In the OP's case, I'm assuming he's still in HI, and that seems a pretty warm and more importantly, a fairly moist/humid climate. He also mentioned a warm climate. I raised the duct condensate issue - particularly if ducting might be run through enclosed/inaccessible areas as I mentioned - because it might be something worth considering. And, the OP did ask for comments or further suggestions.
The potential problem also gets a whole lot more insidious when if/when porous insulation such as fiberglass is used without a very good vapor (read VERY tight) barrier on its exterior and subsequently gets condensate on its interior fibers, and that condensate goes unnoticed. Forget the loss of insulating value. Now its a health issue.
The OP can sure take or leave my or any other information as he sees fit., but IMO, you are unaware of potential problems or even what I was writing about.
Even though the state of the cooled air is completely irrelevant to what I was writing about, I must address what I feel is a misleading statement you made about the cooled air's moisture content.
The humidity or moisture content of the air coming out of an operating unit (which, again, has nothing to do with the possible condensation issue I was writing about), has an absolute moisture content will either be the same as it went in - if the ambient air's dew point is < the cooled air's outlet temp., or, if the ambient air's dewpoint is > the air's outlet temp., the outlet air will have a vapor pressure that will have a sat. temp. somewhere between the coil temp. and the air outlet temp. meaning the cooled air will be pretty close to saturation or near ~ 100% rel. humidity. In such cases, the air can't hold any more moisture. I don't think that qualifies as "very dry". At that point, HVAC folks don't think so either. It might be dryer than it went in, and so has a lower absolute humidity, but it won't be very useful at drying much of anything if it's already saturated or close to it - at least not until it's heated in some way.
The OP can sure take or leave my or anyone's information as he sees fit, but IMO only, you are unaware o potential problems or even what I was writing about. I try to keep my yap shut and keep my fingers away from a keyboard if I think I'm ignorant in an area. Something you may want to consider.
I was referring to condensation on the OUTSIDE of a duct that can occur in moist climates or when the ambient dewpoint is high and the cooler air INSIDE the duct causes the duct temp. to drop. If/When that duct temp. gets below the ambient air's dew point temp., the ambient air in contact with the cooler surface will be cooled. If that cooled air's temp. gets to its dew point temp. moisture will begin to condense out of the air and on to the OUTSIDE of the duct (and just like on a condensate coil - remember the drain you wrote about needing ace ?).
Exterior duct condensation may or may not be a concern depending on the application. For many reasons I believe I know a bit about, it may not need to be addressed by a design consideration or change in the design. Most folks don't bother with it because they are usually ignorant of the possibility as your post seem to serve as a good example. But that doesn't mean it doesn't need to be considered. In the OP's case, I'm assuming he's still in HI, and that seems a pretty warm and more importantly, a fairly moist/humid climate. He also mentioned a warm climate. I raised the duct condensate issue - particularly if ducting might be run through enclosed/inaccessible areas as I mentioned - because it might be something worth considering. And, the OP did ask for comments or further suggestions.
The potential problem also gets a whole lot more insidious when if/when porous insulation such as fiberglass is used without a very good vapor (read VERY tight) barrier on its exterior and subsequently gets condensate on its interior fibers, and that condensate goes unnoticed. Forget the loss of insulating value. Now its a health issue.
The OP can sure take or leave my or any other information as he sees fit., but IMO, you are unaware of potential problems or even what I was writing about.
Even though the state of the cooled air is completely irrelevant to what I was writing about, I must address what I feel is a misleading statement you made about the cooled air's moisture content.
The humidity or moisture content of the air coming out of an operating unit (which, again, has nothing to do with the possible condensation issue I was writing about), has an absolute moisture content will either be the same as it went in - if the ambient air's dew point is < the cooled air's outlet temp., or, if the ambient air's dewpoint is > the air's outlet temp., the outlet air will have a vapor pressure that will have a sat. temp. somewhere between the coil temp. and the air outlet temp. meaning the cooled air will be pretty close to saturation or near ~ 100% rel. humidity. In such cases, the air can't hold any more moisture. I don't think that qualifies as "very dry". At that point, HVAC folks don't think so either. It might be dryer than it went in, and so has a lower absolute humidity, but it won't be very useful at drying much of anything if it's already saturated or close to it - at least not until it's heated in some way.
The OP can sure take or leave my or anyone's information as he sees fit, but IMO only, you are unaware o potential problems or even what I was writing about. I try to keep my yap shut and keep my fingers away from a keyboard if I think I'm ignorant in an area. Something you may want to consider.
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