[Editor's note: This installment of "System Mysteries" is a collaborative creative endeavor betweenThe NEWSand Emerson Climate Technologies. These articles are designed to help clear up some diagnosis misconceptions. This installment invites readers to solve a no-cooling call for a home's R-410A system. Do you have the correct answer to this troubleshooting question? If so, visit the contractor connection found at www.emersonclimatecontractor.com to submit your answers to the latest System Mysteries.]

It was the tail end of the 2005 cooling season in Missouri. Kelly and Marcus had been living in their home about 12 years, and last year they had to replace their heat pump. It was the end of the season, but the timing was right for their budget. Besides, it was hot and neither of them tolerates the heat very well.

They had hoped to be able to fix the old unit, but it was an old heat pump (20-plus years) in a very old house - almost 100 years old. It seemed smarter to replace the unit with one that was more efficient. The new unit also used R-410A, and the information they had read online about the refrigerant resonated in their ecological consciences, which had slumbered since the 1970s.

Yes, Kelly and Marcus are baby boomers.

With this late heat wave, the contractor they called was rushed for time. But they had done their research online, they knew what they wanted, and were able to be flexible about their schedules to accommodate the installers. The new unit (plus indoor coil) was installed, charged, and operating quicker than they would have imagined. It was the same size as their old R-22 unit, 2.5 ton.

The heat wave didn't last too long. Still, Kelly and Marcus felt good about the purchase, felt secure that next year they would not only be comfortable, they would also save money and help the environment.

Fast forward to the start of the 2006 cooling season. Temperatures are starting to climb into the upper 80s, so Kelly switches the thermostat over to cooling while she works in her home office. She anticipates that the new heat pump will cool better than the old one. It seems to be ... but soon she notices that the fan always seems to be running. It's always there as background noise.

As the outdoor temperatures get even hotter, she and Marcus both notice that the unit seems to run nonstop, never shutting off. "That won't save much money," grumbles Marcus. "We're using so much energy," adds Kelly. "How is that helping the environment?"

Eventually the new air conditioner runs all day long and the house doesn't cool down. They call the contractor who installed it. Because the unit is still under warranty, their call is given priority status.


Tom is not one of the installers of this unit; he's a service tech, and he's new to this contracting company. The owners hired him to replace a tech who was let go due to an unusually high number of callbacks. Tom has had to deal with a lot of dissatisfied customers. People had also been let go from the installation side of the business. Tom has dealt with their customers too.

Based on the information he got from the dispatcher, this sounds like another case of a poor installation. But you never know; with the late-season install, it could be that a manufacturer's part just got around to failing.

Kelly is waiting there for Tom. The outdoor ambient is 85°F, and the house is hot and humid since she decided it wasn't a good idea to keep running a heat pump that just wasn't working. For all her discomfort, she is a relatively easy customer to work with, and Tom is grateful for that. "Gotta love those laid-back boomers," he says to himself.

He goes to the thermostat (a programmable model) and turns on the system, so he can check the operating characteristics. "Is it the thermostat?" asks Kelly. "Nope," replies Tom. "The thermostat would shut off if the temperature ever got low enough. I have to look into the way the system is running."

He goes into the backyard and takes the cover off the condensing unit. He checks the temperature and pressure at the suction line, just where it enters the compressor and records 64 psig and 70°. He also checks the compressor amperage and finds it to be low.

Then he goes inside to the evaporator, again checking pressure and temperature, this time at the outlet. The values here are 65 psig and 60°.

Tom goes back inside the 1,600 square-foot house and shuts off the system at the thermostat. He has a few ideas, based on what he has seen in other homes. He makes a quick note on the invoice and mentally curses the system's installers. Then he looks at Kelly's calm face and reminds himself not to jump to conclusions. "It shouldn't be too hard to fix," he says, and smiles.

What did Tom look at next? What did he find? Emerson Climate Technologies will award prizes to the winner and participants. The winner's answer will be published in an upcoming issue of The NEWS. All entries must be received no later than June 5.

Publication date: 05/22/2006