Nowadays, you’d think that pretty much everything anyone needs to know is on the web somewhere. Sure, it’s mixed in with misinformation and may be buried, but if you persist, you’re sure to find it, right?
When I woke up on Friday, June 30, to a warming house, a dead central air conditioner, impending deadlines and the imminent July 4 holiday, I could only spend about 30 minutes checking breakers and the presence of power before I thought it would be prudent to call for service.
Our house isn't big, but it’s tall, with two floors and a walkout basement. The stairwells are open, and it has a sunroom on the southern exposure. The heating and cooling demands vary a lot, so when we had the current HVAC system installed almost 20 years ago, the engineer in me chose to upgrade to a Trane high-efficiency, two-stage furnace and condenser set with a variable-speed blower. We also retrofitted a zoning system (Arzel) that uses pneumatic dampers and four thermostats to direct conditioned air to the three floors and/or the sunroom. It normally works very well.
Since the problem seemed to be in the condenser unit or its controls, and the Arzel installer (“George”) is 40 miles away, I called an excellent local shop I knew from other work. Their technicians are familiar with the equipment but knew nothing about the pneumatics—they use and prefer Honeywell electric damper systems. Over the course of three man-hours, they honed in on the zoning controller, read the manual and made some phone calls, and declared that the board was bad. They flipped two switches to bypass the controller and open all the dampers, and wired the HVAC directly to the second-floor thermostat.
(They also showed me my condenser coils were filthy. If you don’t know when yours were last cleaned, just go do it. Do it now, I’ll wait. And the dryer duct and its blower, too, while you’re at it.)
With our “advanced control system” bypassed, cooling resumed and we got by for several weeks while I learned more about the zoning system. It can control a broad range of systems, and has many interlocks and failsafes to protect the equipment from overpressure, over- or under-temperature, short cycling and more. It was obviously designed by engineers with a lot of experience in how different HVAC systems work, and fail.
I contacted Arzel, which understandably won’t bypass its distributors and sell direct, so I called George, who offered me a board ($800, no warranty) or a new controller ($1,400, now with lifetime warranty). I researched the possibility of using a Honeywell controller to run the air valves on the Arzel system, and I decided that could work.
But first, I asked George how likely it was that the board was really the problem. He said, “Oh, I’ve installed hundreds of systems over the years, and I think two boards have gone bad. It’s usually something else, like a loose wire or a hose leak.”
The pneumatic dampers are connected using color-coded rubber tubing (like automotive vacuum hose) to hose barbs at the top of the controller. Twenty years ago, George’s technicians had plumbed and wired the controller, leaving a mess of tubes and wires around the box. I insisted that they tidy it up, and they bundled it all up with zip ties, leaving the hoses making sharp turns onto the barbs. Over the years, the tubing kinked and loosened, causing leaks and restrictions.
I recut the tube ends, reconnected and supported the tubing, then put the switches and wiring back where they belong. The system has been working now for about a week.
The rep at Arzel doesn’t know how a hose leak could lock out the condenser unit, but he wouldn’t say it was impossible. The real problem may be an intermittent board ground or bad wire connection. They problem may come back and if it does, I’m ready to diagnose it.
Or it may be a feature that never made it into the documentation. I’ve since scoured Google looking for any reference to a similar situation and haven’t found it. I’m glad I talked with George.