need feedback mcquay chiller 3

[johnhjo]

my client asking for mcquay because of its lowest price.
Does anybody had experience with McQuay screw WSC 079 - 087 and/or centrif AGS 400. I need opinion about them; How reliable?, is it good or bad.

 

[Cooky]

I can't comment on the specific chiller you mention. However, I can tell you that with chillers, you get what you pay for.

The lowest priced chiller will probably suffer with a greater number of breakdowns. The noise level may be higher, and the chiller COP will almost certainly be lower.

My advice, is to calculate the operating cost (based on the chiller COP over the expected chiller life) and add this to the initial purchase price. This is a much better indication of true chiller cost.

Hope this helps,

Cooky

 

[cme]

I wouldn't touch a mcquay screw chiller with a 10' pole

 

[tombmech]

"Cookie" has very good advice. Without naming names, I have seen multiple oil pump failures (during factory witness testing) and chillers flash-flooded with rain midway up their shells on the truck dock awaiting shipment.

As for air-cooled recips and screws, I've seen shells fracture because of inadequate freeze protection (internal to the chiller), multiple compressor failures within the first 2-3 years, and plastic condenser fan blades separate and slice through the coil bundle on their way to impaling the building structure.

"Cme" also has an interesting comment. I wonder why he limited it with the word "screw"? Perhaps that was just becuase of the specificity requested with this thread. ;-)

 

[tombmech]

P.S. Just to be clear, I have no actual experience with the specific model chillers you mention. Yet, the experiences I relate are true. Whether they are anomalies or a general trend, is something you should decide on your own.

For many property owners, a chiller is the most expensive and most complicated piece of equipment they will ever own. Cost cutting and a possible sacrifice in quality results in diminishing returns - very quickly.

Even with the experiences I related, the decisions were based on supposed added capability, not lower cost. It was thought that the price was an added benefit. However, even the "added capability" was not enough to make up for the eventual problems.

 

[johnhjo]

Thank you guys for all the comment.

Yes, previous centrif mcquay had a sound pitch as loud as jet engine. But new design implementing 'liquid injecton' method in order to reduce pitchy sound. The compressor discharge area is injected with liquid (refrigerant) droplet from condenser. The idea is to absorb compressor' sound energy while droplet evaporate and reduce discharge superheat.... nice thought!

But what struk me the most is the size of centrif impeler 6" diameter only and rotating more than 20.000 /minute. High rotation does mean lower component lifetime. McQuay also implementing extra oil lubricant reservoir + piston + compressed spring in case power outage. Does this employ with other centrifugal chiller as well? What I see is McQuay has different design compare to others... Well, I guess that unique design really make the price differ... (-:

 

[tombmech]

The primary difference in centrifugal chiller design is the choice of motor drive: open vs. semi-hermetic, and refrigerant: low pressure vs. high-pressure. Both decisions impact lubrication issues, noise, efficiencies, and reliability.

The 6" diameter and 20,000 rpm impeller is no cause for concern itself. Rather, it is a measure of the ratio between volume and pressure dictated by the refrigerant (higher pressure). The McQuay centrifugal compressor design is essentially the same Westinghouse design invented 50+ years ago. Even so, there is no inherent advantage/disadvantage with the compressor that outweighs all others. There are preferences.

As for the oil pump/reservoir system changes, or other issues ... well - you saw my previous comments.

The attributes of that chiller design compared with Carrier's newer R-134a designs, Trane's low-pressure R-123 designs, or York's open-drives are too numerous and complicated to discuss on a forum format.

 

[HVAC68]

Higher speed does not necessarily mean higher wear and tear or problems. It all depends on how the product and the component is designed. Aircraft engines run at very high speeds - are we scared to fly ???

The best way forward would be to do a cost-benefit analysis including a life cycle cost calculation and arrive at the right product for you. Don't forget to ensure that you have local service back-ups by whichever manufacturer you choose.

Good luck

HVAC68

 

[chillergeek]

The WSC079/087 are a very sound centrifugaldesign. Its design has been around for years and a very popular model for McQuay. Every chiller manufacturer has sweet spots for both efficiency and price so saying that the least expensive(which the majority of the time is NOT McQuay)is not a good reason to buy just doesnt make good business sense.

The biggest thing to look for is local service capabilities and knowledge of their respective equipment which McQuay is limited in certain areas of the world.

The AGS is a top of the line air cooled screw chiller which
is very reliable. It will freeze up as any flooded chiller will do if proper installation instructions are not followed. The same cannot be said for the model ALS in its early years (up to 2001). It was way too touchy for most customers in the "run it to it breaks" mode