I had a company install an A/C evaporator unit on my existing heating system. A plugged drain caused the plastic pan inside the evaporator to overflow with water, which then ran out through the metal housing into the safety catch pan underneath. But the insulation inside the evaporator underneath the catch tray is soaking wet now.

There is no drain hole in the bottom panel, so water trapped with the insulation can only leave via evaporation. I am worried that the insulation will become moldy before it dries out, causing health issues. Currently there is no smell or any other problems.

In order to inspect/replace the insulation, the entire evaporator unit needs to be removed, which would take a considerable amount of time and effort.

Does the insulation need to be replaced or will it evaporate dry before it becomes moldy?

I would appreciate any help.

  • I think you have your terminology confused. The condenser is the part outside. The evaporator is the inside part attached to your air handler. – longneck Jun 30 '13 at 23:27
  • Thanks. I have adjusted the question to mention the problem is the evaporator unit, attached to the air handler. I had my terminology wrong. – Wayne Piekarski Jun 30 '13 at 23:32

Insulation can get wet as almost anything can. If you can take the insulation out and dry it properly it will be fine - fan and moderate heat.

Insulation itself does not harbor mold quickly. It is associated with mold because insulation (fiberglass/rock wool) holds water and makes things around it moldy. As long as you get the insulation thoroughly dry within a few days it does not need to be replaced.

  • +1 for "fan and moderate heat". Heat helps but moving air is the key!. – Jason Jul 1 '13 at 1:27
  • One thing you can do to help is to set you air handler's fan switch to on. The constant moving air will help to dry the insulation. – longneck Jul 1 '13 at 3:43
  • My problem is that the insulation seems to be sandwiched in between the plastic catch tray and the metal outer housing of the unit. It is not possible to remove the insulation, and it is hard to tell if air can actually flow over it to dry it out. Most of the insulation is well hidden and inaccessible to check it either. – Wayne Piekarski Jul 1 '13 at 4:27
  • It should be removed. The limited airflow will guarantee mold/mildew. Can a couple slits be cut to allow you to bend up a large enough flap? The flap can be sealed down with the aluminum HVAC tape. – HerrBag Jul 1 '13 at 14:15
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    If you can't at least check it out it should be replaced. – DMoore Jul 1 '13 at 14:43

I was eventually able to convince the contractor that the unit needed to be replaced. After they removed it, I inspected the insulation in the old unit and it was still saturated, as I suspected, but no mold yet. The water had nowhere to go, and could never evaporate away. They then replaced the evaporator another (twice!) because it was leaking water out the bottom, eventually they realized they were never installing the catch pan correctly. But now the unit is working, almost 2 years later. What a disaster ... never using this company ever again, but I learned a lot about A/C units along the way.

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