HVAC mystery that needs solving

**fosterfest** · 03-10-2009, 10:47 PM

will apologize in advance if I am violating any rules by being a non-pro who needs some help but my AC guy (whom I really like alot and respect) isnt coming up with any answers. Also I posted this in "general discussion" before seeing this board which seems more appropriate so I am double posting, so sorry for that too.

I have a 1 year Central AC and heat system with a gas heater and blower in the attic. Whenever I turn the heater on, it snows flat, dandruff-like flakes.

It only happens when the heater is turned on after the A/C has been running for a while. If the heater runs for a few days, it eventually clears up. But then if you turn the A/C on, it seems to reactivate the problem and the next time the heat is activated again, it snows again.

This logically would seem to me to be water related somehow. Like there is something the A/C water is wetting which prevents the snow, but once the heat is turned on, whatever it is dries out and begins flaking

My AC guy first told me it was the fact that my ceilings in this old house are layered sheet rock on top of plaster and thus the supply grilles arent getting a good seal and the dust Im seeing is either sheet rock or plaster. He sealed one of them with foam just to test but that did not solve it.

Also the doest really doesnt seem like either of those things as I would expect it to be either powdery or granular while these are very clearly flat flakes like dandruff.

I went up there myself to poke around. I pulled off a duct from the plenum and found the white flakes throughout the duct which I thought might disprove the supply-grill-bad-ceiling-seal theory.

I also noticed that the 1" PVC drain out of the A/C actually travels gradually up for about 2 feet before draining out of the house which I thught might somehow relate to my water-based theory.

Hes coming over for a third time next week. Any ideas I could suggest to him?

thank you.

**BamaCool** · 03-10-2009, 10:53 PM

Easy fix....place a bottle of Head & Shoulders in the return!

**klove** · 03-10-2009, 11:01 PM

Originally Posted by BamaCool

Easy fix....place a bottle of Head & Shoulders in the return!

You're gonna have all these nice folks thinkin' that we from the Southern areas have no manners and civility............

And Foster, always remember the 5 rules of plumbing:
1) Hots on left
2) Colds on right
3) >____ DON'T FLOW UPHILL(****!!!!)<
4) Paydays on Friday
5) I'm not gonna say this one, cause the boss would get his feelin's hurt

**james80031** · 03-10-2009, 11:03 PM

Originally Posted by BamaCool

Easy fix....place a bottle of Head & Shoulders in the return!

LOL.

**GREGHVACGUY** · 03-10-2009, 11:46 PM

Just thinking is there a humidfier that is puting water build up that is leaving white deposits in duct work.AC fan moving more air and breaking the flakes up very small that you cant see.Heat in moving air slow and not breaking them up so you see it.one last thing is it mold from ac staying wet when ac is on and when heat is on drys it and then it snows.Try running ac and befor you turn heat on put fan to on and see if it happens. good luck and keep us posted on what you find.

**fosterfest** · 03-11-2009, 12:03 AM

yeah, I was thinking possibly something mold-related. It sure does smell bad. Will try the fan idea. Thanks

**GREGHVACGUY** · 03-11-2009, 12:31 AM

What is your location.That may help.I wish i was putting on my ac its still cold here 50 today now 37 and dropping.

**james80031** · 03-11-2009, 12:31 AM

Get a service performed that includes cleaning the evap coil.

**fosterfest** · 03-11-2009, 12:39 AM

South Louisiana. 80 degrees today.

will have evap coil checked. Thanks.

**Daltex** · 03-11-2009, 02:42 PM

Originally Posted by fosterfest

I also noticed that the 1" PVC drain out of the A/C actually travels gradually up for about 2 feet before draining out of the house which I thught might somehow relate to my water-based theory.

Have him correct this asap.

**smstooge** · 03-11-2009, 07:54 PM

Maybe you should have your indoor air quality checked! That could be white mold and could affect your breathing!!! Also have him pitch the drain 1/4 inch per foot to the out side. and last check air filter use a good quality filter it is not worth usin cheap filters in my opinion

**hvac-learning** · 03-12-2009, 11:09 AM

good hvac guy drain goes up hill? nice sounds like water created scaling effect in a/c coil pan or over flowed pan and acitic water is breaking down galvanized ductwork, or ductwork was already whiting effect and he installed it anyway

**motoguy128** · 03-12-2009, 12:25 PM

Originally Posted by smstooge

Maybe you should have your indoor air quality checked! That could be white mold and could affect your breathing!!! Also have him pitch the drain 1/4 inch per foot to the out side. and last check air filter use a good quality filter it is not worth usin cheap filters in my opinion

Air filter won't make much difference if the problem is occuring downstream of the filter. It sounds like the source is at or near the indoor coil. Too "good" or expensive of an indoor filter can cause too much airflow restriction as well.

Definitely need to fix the drain. Drains, won't drain uphill. With exception to capillary effect or other pumping action, gravity always wins.

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