I am a homeowner that basically has a commercial building with 5 separate HVAC zones, with 3 1997 Ruud 90's installed in a large equipment room in my basement. I have been dealing with health problems that have substantially wrecked my life starting in about 2002. It began with fall sinus infections and soon became non-stop. In the last year I discovered a way to keep the infections at bay but still started feeling a worse as soon as fall hits. I would feel better when out of house for a few days and then sick within a day of getting home. Allergy tests, Mayo Clinic, specialists; all no help. No mold problems. Seems like a sick home with no explanation. This last couple of weeks when it finally got cold in the NW, I was getting headaches that lasted all day and started searching for answers, looking primarily in the equipment room.

The first thing I noticed was a huge white mass in the drain opening that the 3 units flu condensate drip into. 2 units were discharging and draining through a small opening in the mass and the 3rd didn't drain even after running for quite a while. I poured a few pitchers of hot water down the drain and washed out most of the buildup but soon had a huge headache. I also pulled the hoses from the built-in traps and verified water was draining through them. A few hours later I had a tech out that gave a cursory check that the units were running right and said not too worry about the lack of condensate because different rooms have different moisture content. Now that I understand how the furnaces work much better than I did a few days ago I realize how stupid that comment was. He had a sales guy with him because we are exploring replacing my 2 90 cfm ERVs that I think provide maybe half the fresh air I need in the house. Within 10 minutes they were both tearing up and the tech was having a breathing reaction and wanted to get the heck out. It was a weird smell, almost like a cleaning product, but they hadn't smelled it before. The room is served by two large fresh air ducts for the 2 water heaters so it seemed strange the odor wouldn't clear quicker.

The company's solution was to send a top tech with pressure gauges to see if there was a negative pressure situation and back drafting or something similar. I said I thought we would find something much simpler but did the test and found no problem. I'm was still having problems at certain times of day, seeming to get worse with heat cycles. We started thinking CO problems even though my home monitor didn't show anything. I rented a handheld sniffer and verified no problem. Today, I decided to check the furnace myself and inspected the cooling pan, took the inducer fan off, and pulled the bottom of flu and all hoses off. The flu drain hose was full of wasps and wouldn't pass water until I flushed it hard. Seems like a big problem but the system still runs fine and that is a sealed system so it didn't make sense have the vapor could get in the house even if it was evaporating. Study the install manual more. Ruud had a warning not to connect air conditioner condenser drain to the flu condensate drain because of problems if those drains plugged. Look at my install and that's exactly what they did to save short PVC runs. But why the warning, what could be the problem?? I'm not totally sure but have a theory that may not even require drainage problems. The first problem is the acidic water cooking off and not draining and somehow entering the circulating airflow. The second is the venturi effect sucking air up the condenser drain that sucks condensate vapor into the airflow. I just cut the PVC drain and capped it and will reroute before summer and am anxious to see health improves over time.
I'm curious if anyone has seen similar installations or the health issues from condensate. Thanks for reading my novel.