View Full Version : Mcquay Chlr Mechanics ? VFD Cent CWS-T
10-24-2007, 02:30 AM
10-24-2007, 04:38 AM
10-24-2007, 06:57 AM
I won't put any imput in since I only work on chillers but not for McQuay. JMHNO
10-24-2007, 08:56 AM
Like any other chiller, to get energy effeciency, as the load goes up, you want to lower the tower water to keep the "lift" down on the impeller. If lift goes down, required horse power goes down, therefore a savings in $$$. But, on the other hand, cold tower water can have some adverse affects on some chillers. Oil loss problems and motor cooling on hermetic motors. I have personally run McQuay chillers in the low 70's and not had a problem. Although, what will mess them up is fluxuating tower water. McQuay uses a pilot operated TXV to control main valve. I 'm sure if you have had any basic refrigeration, you know a TXV has to have a solid column of liquid to it operate correctly. One question I have is your header says VFD -CWT. Is the chiller a VFD machine?
10-24-2007, 07:41 PM
licensed to chill
10-24-2007, 08:35 PM
How about just getting the product data and installation manual for the machine and see what mcquay designed the machines to run at.
5 minutes of reading and you will probably answer your own question
p.s. mcquay sucks
10-24-2007, 09:24 PM
You or your customer should be able to get the cut sheets for the machines from Mcquay or the local rep. It will give you full and part load performance data including design entering cond. water at various loads. For sure it will be designed for cond water relief. Colder tower water will reduce lift and allow VFD to back off at lower loads and increase efficiency. I've been told (and read somewhere) entering cond water should not be less than 20*f above leaving chilled water setpoint. Control guys we usually deal with will maintain tower water temp at 5*f above outdoor wetbulb with minimum and max temps. Seems to work well. But again get the cut sheets.
10-25-2007, 05:45 PM
We need to know more about your unit. Depending on the tonnage you will have either a EXV below 300 tons and above 300 tons you will have an TXV. They have different equations to determine the min entering condenser water temps. Go to McQuay website and look for WSCWDC-5 IMM on page six you will find what your looking for.
10-26-2007, 10:02 AM
I would say you are having a very good day.
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