AC makes very loud noise upon start up - http://www.hvacmechanic.com/ Forums

Original message

mstarr

198.146.69.107

"AC makes very loud noise upon start up" , posted Tue 20 May 10:05

Help! I just had a technician out two days ago for a regular system check. I have two units, upstairs and downstairs. He added a 1/2 pound of freon to the upstairs unit, did the general maintenance and other than adding the freon, all systems checked out fine. We had a cold spell so the unit did not go on for a couple of days after he left. When it turned on it made a very loud vibration sound (almost like air in a water line) that came from the attic down into the outside unit. The sound went away after 5 seconds, and ran and cooled fine. I then started it again after 15 minutes and no noise. After letting it sit for 3 hours, I turned it on again and it made the same loud vibration noise and then ran normal. Could the freon line be getting air into the line if it was not tightened correctly? System worked fine prior to tech being there. In fact he was the first person to turn on the unit for the season. Any suggestions on what it could be?

Replies:

Jojo98

68.53.201.185

"Re(1):AC makes very loud noise upon start up" , posted Tue 20 May 22:54:

Sounds like liquid slugging. If it is liquid slugging it will ruin the compressor. If he added refrigerant, did he repair the leak? He might have overcharged the system, if the weater and house wasn't very warm. Get it checked out.

[this message was edited by Jojo98 on Tue 20 May 22:55]

yuri

205.200.197.252

"Re(1):AC makes very loud noise upon start up" , posted Tue 20 May 11:28

Air cannot get into the line as it is under a positive pressure. You have a vibration which may or may not have happened due to the tech being there. S**t happens. Don't blame the tech but nicely call him back and have him check it again to see if something came loose/got moved.

Yuri

mstarr

198.146.69.107

"Re(2):AC makes very loud noise upon start up" , posted Tue 20 May 11:40

I'm not blaming the tech at all, in fact, they have been one of the most pleasant companies to work with. I am just trying to figure out what it might be. Thanks for your input.

theduke03

24.250.18.179

"Re(3):AC makes very loud noise upon start up" , posted Tue 20 May 17:20

That sound is probably liquid refrigerant flashing off as it enters the evaporator coil, which is completely normal.

"My dad was the most feared furnace fighter in Northern Indiana."