In March 2005, I had a 12 year old central heat pump replaced with a brand new unit. At the same time, I replaced the main ducting from the heat pump with brand new ducting. The H&A guys said the branch ducting was fine and didn't need to be replaced so it wasn't.

Over the past couple of months (since Mid June) I have noticed a little higher humidity level in the house (I haven't measured the humidity with any instruments, I can just feel more sticky at times). Additionally, we have noticed that on the wall of *some* of the vents a black 'mildew' looking substance has started forming on the wall. When we clean it, it takes a couple of weeks but the stuff reappears again gradually. Keep in mind that this doesn't happen at all of the vents, just 3 of 12 vents located through out the house.

I went out side the heat pump and felt the drain to see if water was being drained from the unit but to me, being a laymen, I'm not sure how much water should be draining. It wasn't a constant drip but you could feel inside the drain and feel water was present.

Is this something I should be concerned about or am I being paranoid? If it is something I should be concerned about, what steps should I take?

Thanks,

Ray.

labman

If I remember correctly, failure to dehumidify correctly is a consequence of oversizing the A/C. If you tightened the house up over the years, an older system may have lost some capacity and continued to do OK. A new, the same or larger system, with the new ducts, could now be oversized.

Even so, you don't want to tear it out and put in a slightly smaller one. Make sure the drain is running freely. blow it out with air if you can, or poke a wire down it. The drains are often small and have too many elbows. Open up the unit and clean the A-coil and pan with bleach. Try to reduce moisture in the house. Make sure the dryer vent is working right. Consider adding a vent in the bathroom, or turning on the fan when you shower. Deal with any water problems in the basement or crawl space. Make sure the ground slopes away from the house so water drains away from it. Moisture can even work its way up into the house through a slab.