I live in a two-story house with 2 zone central air. It has a air handler/cooling coil in the attic and the compressor(s) outside. A similar set-up is for the downstairs. My problem is with a loud gurgling noise on start-up on the upstairs unit only that I can hear run up the wall (in my bedroom). This repeats at least 2 times until the system comes up to pressure.
My HVAC guy tested the system for leaks and found none. He then drained the whole system down (with a vacuum pump) and refilled the system with fresh freon. The noise returned !
New HVAC guy…. same checks, same refill, the noise remains.
Any ideas?
Replies
That sound is the freon changing from a liquid to a gas or in other words expanding from one state to another. No way to 'repair it". I can hardly believe any body went to the trouble to bring the system down and then recharge. A check of the charge with gages and the charging chart would have told him this was correctly charged. If you must, you could include additional sound insulation around the line set to mitigate the problem.
Sounds more like a system design problem, i.e. line set to long and not properly sized. He should call the mfg and ask what the lenght limit is for that size unit with the size line set he has in place.
Dave
That too might be a possibility. The one that gave me the most problem was a condo which had the condensing unit on the roof and the air handler in the garage on the bottom, garage, level of three story townhouse. The line set ran up the wall directly behind where the people sat when they watched tv. Everytime the unit turned on, the refrigerant changed state and boiled in the line set as it was going back to the compressor through the suction line set. Since the line set was in a common wall and not accessible for its entire length, we overinsulated it with Rubatex and high density material. I think we used sheet lead. It helped a lot, but never completely eliminated the problem. The line set was properly sized for the distance in this instance though. It even had the necessary traps in the suction line.
Virtually all my experience (limited) is with larger commercial RTUs and chiller systems. On some the larger split system we have the line set from condenser/ compressor to the air handler can be several stories apart. We always have the equipment manufacture engineer the line set and traps for each application. My limited exposure to residential HVAC has led me to believe that most of the engineering in that market is by ROT, and "it worked on the last job."
Dave
In my example, we actually had an engineer to design the sizing along with the suction traps as it was a new construction project. Unfortunately the routing was changed by the field installation team because of a load beam and this was not directed back to the engineer. The sound issue only became evident to "us" once the units were fired up. By then it was too late to reroute. Both of the lines followed the same routing. You are right about the engineering in general though. Most of the line sets I used to see were at the absolute minimum sizing for the install and customer be dammed. Typical track work type construction. We however used to get involved in correcting lots of poor installs and that is where I received some valuable training on what not to do.