Loyal readers may recall that I’ve been fighting high humidity in our house for a while (see ChatGPT is almost as bad at home maintenance as I am for a discussion about how window replacement resulted in our A/C being oversized).
I decided to splurge on the top-of-the-line Trane/American Standard TAM9 air handler and a variable-speed condenser for one of the three systems in our house. Once installed, the humidity did go down from about 55-60 percent to 45-50 percent. Mission accomplished, as George W. Bush might say? No. The thermostat raised dire warnings about “Err 166.00”. This is something to do with the Electronic Expansion Valve (EEV) and “superheat”, two terms that I can’t understand. After the error was raised, power consumption for the air handler dropped to about 20 watts, i.e., less than a small window fan. How could this possibly work even if the compressor was running at only 50 percent? That would be 1.5 tons (out of 3) spread into 5 rooms with 20 watts of fan power? After a week in this state, the system failed completely.
The dealer said that he had no idea what was wrong, but was planning to swap components out until the problem went away. “Maybe it is a sensor. Maybe it is the fan motor,” he guessed. Why not call the manufacturer’s tech support line? “They’re useless.”
He was over at the house the other day (Visit #5?) and I had him call tech support on speaker just to humor me. After learning that the 166.00 errors typically happen between 4 and 8 am, American Standard’s tech support expert attributed the problem to the thermostat being set at 72 degrees. “There is no cooling load in the middle of the night and nothing for the system to do, so it shuts the EEV valve to protect the compressor,” he said. What was his recommended fix? “Set the thermostat to 75, which is what air conditioners are designed for.” If this kind of protection was necessary, how had the previous single-stage system managed to survive more than 6 years, at least 1.5 of those years with the thermostat set to 72? “They don’t have as many sensors as the latest equipment.”
(He is correct that the Manual J calculation for sizing air conditioning typically assumes an indoor setting of 75F and an outdoor temp that is supposed to be the 99th percentile of hotness. In Palm Beach County, that’s 91 degrees, though if sizing a variable-speed system maybe it should be bumped to 95 to allow for the possibility that Professor Dr. Greta Thunberg, Ph.D.is a true prophetess.)
In short, what had caused the problem with our $12,000+ air conditioner was that we had tried to use it as an air conditioner and it wasn’t smart enough simply to turn itself off when the room temperature reached the thermostat set temperature.
(Everyone likes Lennox better, but their fancy “communicating” gear requires 4 wires between air handler and condenser and our existing systems had either 3 wires or 2 wires run between indoor and outdoor units. Trane’s communicating gear requires only 2 wires, so we’re stuck with Trane unless we want to start opening up walls and ceilings to run new wires. Florida houses have no basements and no attics, which makes retrofitting problematic, but nobody seems to care because the standard practice is to gut-rehab or bulldoze after 20-30 years (or 6, if you’re an elite New York-based environmentalist and sustainability expert).)