Hidden Home Danger: Can you trust your HVAC tech?

I'm like many homeowners. I am a complete novice. A n00b. That being the case, you do your best to protect your family, by hiring trained, or even licensed professionals to stay on top of "all the things." However, sometimes, if you want something done right, you have to do it yourself.

As for the professionals involved, they should be embarrassed.

🤖 The Machine

1979 built house. My HVAC is what came with my home: a 2010 vintage Rheem Air Handler, upright unit, heat pump system with aux heating strips. The condenser system is a 1998, somehow.

Since I moved in, in 2020, I've hired actual HVAC techs to inspect the system.

🔎 The 2024 Cleaning and Inspection

The last time I had my HVAC system inspected and cleaned, was a Home Depot associated/branded contractor. The are guys that were in store, offering their services as Home Depot subcontractors. This seemed legit, because it was a Coolray van that pulled into our driveway.

Ultimately, the HVAC tech's suggestions were to replace a wobbly breaker, and to replace the system because it's old. Breaker replacement was a good call, one side of it had melted wire, corrosion.
Hey, isn't that what most HVAC guys tell you?

As it turned out, we originally hired them to do a cleaning, not just an inspection, of the inside and outside units. The Coolray guy gave me a bit of guff, saying I didn't pay for cleaning, so I paid them another extra fee to do the cleaning.

I ended up finding out they didn't clean the outside unit at all, so I ended up cleaning that up myself.

🌡️Late December 2025 - Bye-bye Google Net, Hello Ecobee... and a revelation.

You might have heard, Google Net Gen1 & 2 thermostats were rug-pulled by Google, changing the terms of the sale after the sale, breaking the devices and offering a repair for a fee.

I replaced the Nest with the Ecobee Premium thermostat, with the remote sensors with presence sensing. It's a no-brainer for my old home, since my son's room takes priority at night.

⚡Get the wiring right!

Buying a home used, it behooves us to make sure things are code-adherent, and wiring is correct. Thermostat wires are among the most confusing, so the best way to figure that out, is to go and open the air handler cover. It is there, where you can see the labels on the circuit board, which would go to the thermostat. Noted those, and the colors that are connected to them.

🦠Surprise!!! (Not a good surprise)

When I opened the air handler, I was greeted with a classic ash-tray / musty smell, coughing, and the sight of a known nemesis. Black mold. That did NOT get there overnight. Evidently, neither the inside nor outside unit was cleaned, and I had paid twice for that service.

I have a particular sensitivity to mold, having been exposed in my childhood term over a long period of time. Every season like clockwork, it doesn't take much to send me to sinus-infection sick land.
🤧 Predictably, yes, I am sick currently, after that face full of mold.

It's at this time that I realize, I hired the wrong people. Home Depot's name is on this, and I trusted that brand's recommendation. That's on you, Home Depot.

The only thing Home Depot would do if I complained, would be to refer me off to their "adjuster," another contractor called Sedgwick (delightful human beings to deal with - yes that's sarcasm). I'm not going to waste my time on that.

🛠️ Mold Mitigation

Everything out there says, hire a professional. Well, that didn't work. It's still a good idea to hire a pro, that you trust and know personally. I just don't know anyone.

I performed the same exact mitigations that the professionals would have had to perform. Saving money and cutting corners is not the objective, but was a side effect. Your family's health is what is important here. If you have or know a pro, use them.

What I did:

1. ⚠️ Turn off the power. The advice is to not turn on heat strips, or the system, because it just would atomize and distribute the mold elsewhere.
2. Clean out the crud/buildup that you can see... carefully...
   ⚠️ Wear PPE, this microbial junk is nasty and sometimes quite dangerous. Don't breathe it, don't touch it, don't eat it, and wear eye protection. It can float. Ventilate the area well. Exhaust fan if you have one.
   ⚠️ Soft surfaces, like insulation, has to be replaced if it has mold in it. You can chemically treat, but it's usually not effective.
3. ❓Check for and address WHY the excess moisture/growth conditions created an issue in the first place.
   Mine was a clogged drain line, from the crud that built up over time. There's going to be moisture there, and it's by design. Cleaned that out.
4. EPA approved for HVAC: Chemical mold neutralizer/inhibitor aerosol. Carpet bomb the microbes! Bleach free, safe for indoor spaces.
   ⚠️ Let it dry completely. Be sure to read the chemical safety information. Be safe.
5. 💡Install a UVC light.
   ℹ️ Placement matters! Install preferably on the return side in the handler, exposing the pan (if it is not plastic), and the underside of the condenser coil.
   Don't expose heating strip kits, or ceramics to UVC. Allowing heat from heating strips to get to your light may shorten the life span, since those heating strips can get to temperatures of > 1000F.
   ⚠️ Warning: Don't turn it on, and don't expose your eyes, skin, or any part of you to it! The goal is to give the evil microbes sunburn, not yourself.
   ⚠️ Design consideration: Shield PVC-jacketed wires, if any, from the UVC light. PVC is not UV resistant.
6. 🌬️ Run the system for a bit while people aren't inside the house. Leave windows open for a bit. Air it out.

✅Result: SUCCESS... for now.

After sitting on the front porch for a bit with my Milo's tea and a box of tissues, it was time to test the air. I re-entered the house, immediately I notice that the musty smell was GONE. Took a whiff of the air out of a vent register. CLEAN. Ecobee air quality monitor status: CLEAN.

Note that you have reduced the mold drastically, but it's probably still there in your ductwork and home. Having mold testing/monitoring is a good idea at this point.

There is maintenance that must be done.
Let it slip, and you might face the same issue.

1. The EPA certified chemical I used is a mold inhibitor and mold killer, but it has to be reapplied once every 3 months. I have plenty in the $11 can that I purchased, for one or two more treatments. SET A REMINDER.
2. The UVC lamp has a lifetime: about 6 months. Just replace it. It won't buzz or send you a message when it fails, so when it does fail, you won't know it. The one I have is 8000 hour rated, and designed to be on 24/7.
3. Replace filters religiously. Keep the outside equipment clean, free of debris. Check on the inside unit (turn that lamp off first) periodically for any missed spots.