Dual-Circuit System

By John West
Chester, VA

My question involves a dual-circuit packaged air-cooled chiller with four scroll compressors. One circuit looked fine. The other circuit sight glass was black on the moisture indicator. Rust could be seen inside the sight glass.

My first impression was that the system had contaminants and there was moisture in it. This is a new system that has not been started. I called the manufacturer’s representative and was informed that sunlight can cause this. The protective covers were on each sight glass.

Would you start this system? I was informed that it would be safe to run.

From Dan Kramer
Patent Attorney and Specialist Grade Member of RSES

In my opinion, your problem is not one that you alone should solve.

You should inform your supervisor or boss of all the facts and let him resolve it between the supplier, the manufacturer, and the owner of the equipment.

Oral advice that the system “is safe to run” merely means that no one will be hurt if it runs.

A manufacturer’s representative who says that such a problem could be caused by sunlight is trying to keep you in the dark. It is well known that the new HFC refrigerants and POE lubricants have highly detergent properties and can cause rust and other contaminants to move around the system. Also, both POE and the HFCs can hold many times more water than the old refrigerants and minerals.

I, as owner, would be much more confident if the situation were personally observed by the manufacturer’s service manager who authorized removal and moisture concentration tests of the refrigerant and lubricants of each system by a qualified lab. If the system proved dry, I would still want a letter on the manufacturer’s letterhead that the observed condition would affect neither the system’s performance nor life, nor cause abnormal maintenance and that operating the system would resolve the observations in the sight glass.

On the other hand, if one or both systems were wet, I would want the manufacturer to approve removal of the refrigerant and lubricant. This would be followed by an evacuation of the system to a condition where it would hold below 500 microns with the vacuum pump off. Then I would recharge with fresh new refrigerant and oil.

Barring such steps, I, as owner, would want the system returned and replaced with one that is in proper operating condition. Yes you, as contractor, would probably have to bear the expense of removal and reinstallation, but that, in my opinion, is what a responsible contractor should do.

Removing Oil

By George Mitchell
Baltimore, MD

What is the recommended procedure for removing the oil from an R-123 chiller?

From John Lawler
St. Louis, MO

We researched the question with Trane service reps who directed us to page 68 of the company’s operations maintenance manual CVHE-0M-8C, dealing with the CenTraVac equipment. Among other things, it was recommended:

  • Oil needs to be analyzed after the first six months.

  • After 1,000 hours and one year of operation, it is recommended to change the oil and filter and have the removed waste oil analyzed.

  • Subscribe to an annual oil analysis program rather than automatically changing the oil every year.

    Beyond that, here is the procedure for changing the oil as outlined on the previously stated page 68. (And, remember, this is for a Trane CenTraVac.)

    Caution: Be sure to open the control panel disconnect switch before draining the sump. Failure to do so could possibly burn out the oil sump heater.

  • Draw the oil from the chiller through the oil charging valve on the chiller oil pump into an approved, evacuation tank; or

  • Pump the oil from the chiller through the oil charging valve into an airtight, resealable container, using a magnetically driven auxiliary pump.

    Forcing the oil from the oil sump by pressuring the chiller (i.e., by raising chiller temperature or adding nitrogen) is not recommended.

    Refrigerant dissolved in the oil can be removed and returned to the chiller by using an appropriate deep-vacuum recovery unit and heating/ agitating the oil container. Follow all federal, state, and local regulations with regard to disposal of waste oil.

    Replace the oil filter (1) annually, (2) at each oil change, or (3) if erratic oil pressure is experienced during chiller operation.

    Publication date: 04/01/2002