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mcquay air cooled rotary problems

mcquay air cooled rotary problems

mcquay air cooled rotary problems

We have a client experiencing some problems with McQuay ALS series chillers (air cooled screws). The problems are repeated compressor failures, particularly the gate rotors. I'm told they are a composite material and pieces are shearing off. This is happening on multiple chillers (ALS-195, 285; year is 1996). Some are on the second or third failure. Has anyone heard of, or had experience with similar problems? Is this somehow isolated to these 2 machines or is it symptomatic of this series?
The same client is having another problem on a 1999 ALS-220 with the phenolic coil coating literally flaking off. Any thoughts would be appreciated.

RE: mcquay air cooled rotary problems

We are experiencing gate failures on our Als Screw drive units as well,Mcquay is offering a Soft Start kit as an upgrade to older ALS units. Their newest screw drives  includes this soft start kit. Word we got from Mcquay technicians is the compressors slug liquid, tearing up the gates, normally after a power bump or outage. They tried curbing the problem with software upgrade but have had to resort to this "kit" It's expensive and some of their customers are changing out their chillers with that of other manufacturers, we have put constant pressure on Mcquay international and their pricing is coming down.We have experienced this problem on three of our four ALS chillers. We also believe the other problem with our compressor failures is inadequate lubrication, a design flaw.

RE: mcquay air cooled rotary problems

The problem is the liquid line solenoid, feeding the injection to the compressor, can leak by in some cases. This is possibly caused from liquid being trapped betweeen the main liquid line solenoid and the injection solenoid during a shutdown period; a warming ambient condition may cause the seat on the injection solenoid to distort and leak. This causes liquid slugging on starting of the compressor. After a compressor pumpdown, get the pressure rate of rise to determine if the solenoid is or isn't fully closed.


RE: mcquay air cooled rotary problems

I am familiar with a client company that has 9 ALS 380A units of 1996 vintage.  Of the original 36 compressors, none remain.  In addition, several of the warranty replacements have subsequently failed and have been replaced.  The "kit" has also been marketed to this client by McQuay.  Cost is in excess of 30% of the original purchase price of the chillers. I am interested in ballen's discussion of the phenolic coating flaking off.  What does this material look like?  On the same site, a material similar to aluminum shavings has appeared in some of the filter driers and appears to be causing condensor coil blockages.  Have always suspected that this might be gate material, but have gotten contrary information from McQuay.   

RE: mcquay air cooled rotary problems

The phenolic coating referred to is a protective coating applied to the condenser coil & fins to inhibit corrosion. For example, these units are along the seacoast, where salt air causes unprotected coils/fins to corrode before their time. The coating was bubbling, or losing its adhesion to the coils. This problem was totally separate from the compressor failure problem (i.e. the flaked coating is external to the refrig. circuit).

RE: mcquay air cooled rotary problems

A client company is looking into purchasing McQuay ALS chillers. Whats the latest on their screw compressor failures? Is their current offering reliable?

RE: mcquay air cooled rotary problems

Regarding the phenolic coating on the condenser coils, I have seen air dryed phenolic coating bubbling and peeling within months of application on the exterior and interior of rooftop makeup air units. Either it was improperly applied or improperly cured or both. If you have an air dryed phenolic coating, i'm not surprised it's peeling. It tends to be brittle, and can flake. Heresite Protective Coatings makes a high quality baking phenolic for heat transfer coils (or other equipment such as fan wheels and housings), but it must be applied by a licensed applicator (maybe only at Heresite's factory), and is therefore quite expensive. Suggest you check out an epoxy modified phenolic coating which is supposed to be superior and far more flexible than straight phenolic. Manufacturers seem to prefer supplying this coating based upon submittals i've received over the years. I think the finish is black, and effect on heat transfer is negligible. TechniCoat 10-1 by Aero-Marine Engineering. www.ame-technicoat.com
Regards, Yeldud

RE: mcquay air cooled rotary problems

I work for a company that frequently provides these McQuay ALS screw chiller parts to customers for their repairs.  We do not provide these chillers themselves, but I have noticed that these do tend to frequently require replacement or work in this area.  I have not had any failures reported on the latest vintage of units (built within the last 3 years) so if your question is about whether they have changed, they seem to have.  The older units do tend to have serious problems (especially with the gates) as noted before, but I do know that McQuay has been offering a training seminar at their Staunton, Virginia plant the last few years that helped many of my field techs to answer questions about how to correct some of their problems with minor field adjustments rather than waiting for total collapse of the units and giving it a major overhaul.

RE: mcquay air cooled rotary problems

Yes it was symtomatic of this series and more specifically during this time frame.  The problems have gone away with the newer machines.  Poor lubrication to the outbourd bearings was a problem.  Liquid slugging went away when the compressor changed its design from the original stargate design to the slic design. (screw liquid injection compressor.)  The factory had a vendor spray the coating on the coils instead of diping them in a vat.  McQuay has replaced the coils under warranty in some cases.  The labor was not included but the coils were warrantied.  The composite material wears or breaks off when alignment is out of tolerence (damage to the outboard bearings - poor lube).  When a compressor is changed you must install a strainer in the suction line.  Due to the pressure differential from suction to discharge the composite materials gets flushed into the evaporator.  This does plug up the subcooler on the condenser coil.  

RE: mcquay air cooled rotary problems

I'm considering a McQuay Energyplus chiller system for an application. This of course is now Oct 2005. The chiller in question employs the McQuay Stargate Single-Screw Compressor (Frame 3200).

I'm aware of much anecdotal evidence that suggests I exclude their chiller on account of the compressor's poor reputation for reliability. Is anyone willing to comment?

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