Condensation on ceiling registers, potential causes?

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Old 07-31-08, 11:50 AM
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Condensation on ceiling registers, potential causes?

All of the upstairs ceiling registers either show signs of moisture exposure (i.e. rust, staining), or actually have water dripping from them. The worst is in the bathroom, but the bedroom registers are a close second.

This house is located in the upstate of SC, so it's hot and humid all the time. (Just checked and at the time of this post it was around 95 degrees F, and the humidity is around 60%.)

The owners keep the thermostat set lower than is typically recommended for optimum comfort vs. energy usage.

I poked around the attic a bit, not very thoroughly though, and all the ductwork appeared to be insulated properly with no gaps in the insulation. Also, the attic is insulated with a blown-in insulation.

Any ideas about possible causes? I'm not an HVAC specialist, but I have a decent understanding of how it works. I can't be sure without the proper gear, but it felt more humid inside the house than it does in my own.

I'm guessing there's quite a few possibilities, but I don't want to "fix" a bunch of possible problems only to find out the problem was within the system itself.

Any tips, help, and advice would be greatly appreciated. Hopefully this falls under the DIY-fixable category, and not the "call the HVAC guy" category.

Thanks,

~Jeffrey
 
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Old 07-31-08, 12:56 PM
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Could be lots of things but in order for something to "sweat" it needs to be below the dewpoint temp and moisture must be present.
Are you moving enough air across the coil and is the condensate drain pouring water outside? Is the air filter clean and is the coil clean? What is the temp. drop across the coil and what is the relative humidity in the house?
 
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Old 07-31-08, 01:43 PM
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I'm not as equipped for, or knowledgeable about, HVAC to be able to answer all of your questions. I'll do my best though.

The drain is pouring water outside, but where it connects to the attic unit, there is a small (~6") piece of soft, flexible pipe connecting the drain to the unit. This is kinked in two places, restricting the flow, but it doesn't appear to be cutting off the flow enough to be a problem. (Keep in mind that I know very little about what qualifies as "too much," "too little," and "enough," when it comes to HVAC.)

I haven't checked the filter or coil. I'll definitely check the filter, but I probably won't check the coil. I'm confident that, given the proper tools, I could completely disassemble the unit in the attic and then reassemble it from memory without causing any damage. (I used to be one of those kids that would take my dad's power tools apart to see how they worked... the difference was that after I was satisfied, I'd reassemble it and dad would have a tool that was "tuned-up" so to speak, loose screws tightened, bearings lubricated, etc. So I never got in trouble like my friends would. )

But, this isn't my dad's old angle-grinder; so unless it's a simple and obvious task, I'm leaving it to the pros.

I'm not equipped to measure air volume across the coil, nor the temp. drop either.

I don't have a hygrometer either, but you can tell the humidity is higher than it's supposed to be. You can feel it on your skin, and it's not a subtle feeling either. Ever been in a cave? If you have, then that's what the air feels like, though not as extreme.

Thanks for the ideas! Even though they're questions best answered by HVAC pros, at least I'm closer to deciding to tell the owners to call an HVAC service or not.

~Jeffrey
 
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Old 07-31-08, 02:46 PM
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That's OK Jeff. If you could measure the temp. at the register and the temp at the return grill it may be possible to determine if your air temp is too cold and causing the condensate on the registers. Generally, 15-20 degree drop is OK but of course there are variables to that rule of thumb. If you can get those temps and get back here, I'm sure someone can offer more probabilities.
Of course, be sure to check the filters and inspect the duct work the best you can to see if anything is clogged or smashed. It would also be good to know if this is a new problem or if it's been going on since the unit was installed. More info might help.
Bill
 
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