Millenium Compressor Problems

[hvac-alan]

Recently did a service on several Carrier heat pumps at a small commercial building (38YCC models). The 5 ton versions (three phase 230v)had Millenium Compressors by Carlyle. When the unit disconnect was shut off, a loud burping sound occured followed by about a minute of loud metallic clicking. Sounded like sticking a metal rod in some bicycle spokes. The noise came from the compressor. The pressures, etc were normal. The unit is only a year old. Has anyone ever experienced this. Called Carrier--they say they have had no problems and that it is new to them???

[jemawalton]

I remember having the same issue in some ref cond units with Millenium Scrolls. Was told by a factory rep that the internal check valve in the discharge of the compressor wasn't seating fast enough, causing the compressor to run backwards. Don't know how much stock to put into it and I don't think they offered any kind of fix for it, but it sounded plausible.

[jo-hvac]

Put a copeland in it. I know the unit is still under warranty, but the millenium will fail,and when it does
you will have a mess on your hands.I think carrier replaces it with a copeland when it fails.it's been awhile.
(snowball is dead!)
Question:can a srcoll run backwards if it has on time delay?

[Edited by jo-hvac on 06-01-2005 at 06:57 PM]

[hvac-alan]

Thanks for your replies. Carrier rep called me today and told me essentially what you guys said that when the unit shuts off the discharge valve is not closing so as refrigerant equalizes the pressure backflows through the compressor to the low side which makes the scroll turn in reverse, thus making the awful noise. Apparently, Milleniums sound very loud when they run in reverse. Alot louder than other scrolls.

Apparently, their fix is to put a check valve into the discharge line. The valve will be comp'ed but no labor. The unit is not even a year old--told the owner to get in touch with the company that installed the unit. They will cover the labor under their warranty.

I will certainly steer our company away from putting in a bunch of units with these compressors--having to go back recover refrigerant, re-evacuate the system, and sweat in a check valve, then re-charge the until will sure shave off the profit off of install margins. May be cheaper to just put a Copeland in from the start.

Thanks again.