VFD Centrifugal chillers - suitable for locations with very little wet bulb changes
VFD Centrifugal chillers - suitable for locations with very little wet bulb changes
(OP)
Are VFD Centrifugal chillers suitable and/or worth their investment and additional maintenance costs for locations where the wet bulb changes are very less ?
HVAC68





RE: VFD Centrifugal chillers - suitable for locations with very little wet bulb changes
It is not just the outdoor wet bulb that governs load. The sun, which varies from maximum at noon to zero at night, people, equipment, ventilation, and other factors play into the variability of chiller load.
In general, in the US, the investment is a very good one in a new building. Changing an existing chiller to a variable-speed chiller is questionable, though.
Best to you,
Goober Dave
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RE: VFD Centrifugal chillers - suitable for locations with very little wet bulb changes
If you have an unoccupied period in your building operation, with a significant night setback, it could be worthwhile. Ultimately, it will come down to your client and the efficiency target. A vfd chiller will certainly save some energy and not all energy decisions are based on a short term ROI.
RE: VFD Centrifugal chillers - suitable for locations with very little wet bulb changes
RE: VFD Centrifugal chillers - suitable for locations with very little wet bulb changes
variable speed equipment is pretty standard nowadays, not much upcharge anyway.
RE: VFD Centrifugal chillers - suitable for locations with very little wet bulb changes
http://www.turbocor.com/literature/pdfs/casestudie...
Disclaimer: I work for Danfoss, although not for the Turbocor group.
RE: VFD Centrifugal chillers - suitable for locations with very little wet bulb changes
2 schools of thought. One pitching in for VFD regardless of whatever the climate. Second one saying that if the wet bulb differences or delta is not significant, VFD is an additional piece of equipment that has to be maintained.
I am referring to a WATER-cooled centrifugal chiller !
HVAC68
RE: VFD Centrifugal chillers - suitable for locations with very little wet bulb changes
Also, google up this phrase:
variable speed chiller data center
The first BUNCH of hits will be: a) the HP paper I've attached, and b) all the various chiller manufacturers' case studies, technical data, and propaganda.
Best to you,
Goober Dave
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RE: VFD Centrifugal chillers - suitable for locations with very little wet bulb changes
There seems to be little merit in going for VFD chillers in your case.If my memory serves me correctly,the control algorithm for VFD chillers requires a change in lift for the VFD to effect a change in speed.A lift reduction happens eiher by lower condenser temperatures or resetting the chilled water temperatures higher.
Since your wet bulb is stable,there is not much variation in your condenser water temperature . Data centres use a higher than normal chilled water temperature leaving very little room for CHW temeperature reset either.With a fairly constant lift the VFD case is not on in your case.
RE: VFD Centrifugal chillers - suitable for locations with very little wet bulb changes
RE: VFD Centrifugal chillers - suitable for locations with very little wet bulb changes
RE: VFD Centrifugal chillers - suitable for locations with very little wet bulb changes
Don't assume that just because it is a data center that the loads will stay constant. Depending on the applications/services being maintained on those servers/storage, the load can vary wildly or stay pure constant.
One data center processing facility I did had an almost constant load 24 hours/day, 365 days a year. It was processing large amounts of data that was staged.
Other ones I have done, especially if they are support internet apps or office applications, can vary as the demand comes online, as the system grows, etc.
Zuccus
RE: VFD Centrifugal chillers - suitable for locations with very little wet bulb changes
If its a closed drive machine and you have to change the motor it could really be a pain. (VFDs usually need a motor with class F or H insulation) Plus if anything ever happens and the motor goes bad, you could stand to cause a serious problem with you refrigerant in the machine.
As previously stated if the load on the machine varies constatly then it is a good investment. Although it is important to remember that a chiller with a VSD is actually slowing down the motor to save energy, thus reducing the pressure output of the compressor (assuming its a centrifugal compressor) and resulting in teh requirement for raising the CHW temperature or lowering the CW temperature. The alternative to this is you need a compressor outfitted with a Varaible Geometry Diffuser to handle the low load high head conditions. So now you may end up with a new compressor as well.
It is important to consider all these items in your evaluation.
RE: VFD Centrifugal chillers - suitable for locations with very little wet bulb changes
HVAC68
RE: VFD Centrifugal chillers - suitable for locations with very little wet bulb changes
RE: VFD Centrifugal chillers - suitable for locations with very little wet bulb changes
RE: VFD Centrifugal chillers - suitable for locations with very little wet bulb changes