HVAC Condensation Question

Happy New Year everyone! Here is my first, of no doubt many, questions for the new year.

I checked my HVAC filter today and noticed the right side was wet along the cardboard edge. The system was installed new in Feb. 2021.

I opened the front cover and saw some condensation (see pic).

Also, there is another cover hiding the coils (see pic). As inspectors, would you remove this also to get a look or would you disclaim it as not visible?

I thought I would get some trustworthy opinions before reaching out to a repairman.
For some more background, I am in central FL, in the past month I have been running both the AC and the heat pump, and the unit is in the garage. It is electric.

Any idea what the condensation may be from and any maintenance or repair advice?


Hello Matt,
If the filter was very dirty could cause the unit to freeze enough on the evap coil and this will cause condensation this could be one of the possibilities. Also, check the insulation in the panel because if there is not enough insulation can cause condensation as well and last but not least any gaps that hot air can find the way in when the unit is off will be an issue for this.

Our humidity this week has been very high, and the AHU cabinet is in your garage.
The water appears to be near a seam, likely air leakage.
Cold metal + moist garage air = condensation.

The filter being wet is from water forming on the coil, and dripping on the filter or not reaching the drain pan under the coil completely.

Have the tech check for air flow as well as sealing the unit better.


Anytime I see condensation that is not “contained” I consider this a defect in need of evaluation or repair.

You may not have to disclaim it. Removing covers or dismantling equipment is outside NACHI sop, but check your state sop.

I do not remove these covers on heat-pumps and I have no requirement to do so. Others might depending on their level of comfort or understanding of these units.


Thanks Nestor. I’m thinking it is an insulation issue.

Thanks Dominic. Yes, the condensation is at a seam. The insulation there wasn’t even wet.
Thanks for the info.

Hi Brian,
Thank you. Our state SOP doesn’t require inspecting coils so I guess I wouldn’t/shouldn’t.

Welcome to our forum, Nestor!..Enjoy participating. :grinning_face_with_smiling_eyes:

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Would you remove the interior cover during your inspection even though it is outside the Fl. SOP? (I see you are in Altamonte Springs. I am in Ocoee.)

I wouldn’t remove that as part of my inspection. Also, condensation is a tough one since it can take hours (or longer) for it to start to leak and we just don’t run equipment for that long.

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Let me ask some questions to help you understand that your asking.

What does an A/C do to make cool air?
It removes heat.
There are two types of heat; latent, and sensible.
Latent pertains to moisture.
Before the A/C can lower temp (sensible), it must remove Moisture (latent heat). There is 970 Btu/lb,h2o.

What temperature does the coil operate at?
Generally 40F, if unit is designed and maintained properly. This is just above freezing, so it is always operating below the dew-point of the air (especially in Fla). So we expect moisture to happen. If not, it’s probably not working right.

Where are you seeing moisture?
Is it leaking all over the floor or just sweat on the unit?
In your case it is on the unit. Whoever mentioned insulation, insulation is not to prevent freezing or condensation. It just slows it down. Under hot, and especially humid conditions the unit runs a long time and the unit will cool down below the dew-point temp often, thus condensation.

You have a small air leak where you see the moisture in your pic. This leak cools the cabinet faster as it is bypassing the insulated panel.
When the unit shuts off, condensation forms. It does not condense water while running because it evaporates faster than it condenses with the fan blowing.

You saw wet insulation. This is not a problem (it is simply water leaking back into the unit). Water does increase heat transfer and will make the wet spot bigger, but is not significant in this case.

Calling for service is up to you, but $75 for a piece of tape (to stop the air leak) is not cost effective as you have the tools (seeing you took this thing apart).

As for water leaks, there are only three sources of water issues; plumbing, building envelope leakage, and condensation. If you suspect condensation when diagnosing water issues, what is the dew-point and where is the source of cool that is below that dew-point?
For your case, any time the a/c runs in Fla, it’s operating below the dew-point of the ambient air, thus the source of temps below dew-point.

Insulation installed exterior of the unit (air duct, suction refrigeration lines, condensate drain pipes etc.) is preventing the ambient air from contacting the component, not stop heat transfer. This insulation should be a closed cell type as air can flow through fiberglass ect due to pressure differentials created in the operation of the unit. Use the wrong type and the insulation will be saturated with condensation creating a bigger problem than if it wasn’t ever there.

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Wow David,
Thanks so much for that detailed explanation! Your answer is like an abbreviated master class, at least for me. When is InterNACHI going to get you to contribute to the online course material?