VSD Centrifugal Chillers
VSD Centrifugal Chillers
(OP)
Guys,
Has anyone had experience with variable speed drive centrifugal chillers? Do they have any significant advantages over normal chillers with inlet guide vane control?
Has anyone had experience with variable speed drive centrifugal chillers? Do they have any significant advantages over normal chillers with inlet guide vane control?





RE: VSD Centrifugal Chillers
At our load conditions and ambient conditions, the VFD chiller was working perfectly. I observed 5-10% savings.
Believe it or not : Goldbach's conjecture says any even number can be written as a sum of two prime numbers. Postulated in 16th century, nobody could, so far, prove it nor disproove it.
RE: VSD Centrifugal Chillers
A typical pay back period would be around 2 to 3 years.
RE: VSD Centrifugal Chillers
RE: VSD Centrifugal Chillers
RE: VSD Centrifugal Chillers
In multiple chiller plants, the chillers are typically fully loaded so there's little advantage for VSDs. Even if you do get low loads and low ambient conditions, chances are if it is a commercial application, you might have an airside economy cycle which limits your chiller operation anyway. No matter how efficient your chillers can be, you cannot beat free cooling!
It all boils down to the return on your investment: would you pay that extra for a chiller to have a VSD or would you use the same money to buy an even more efficient chiller ? e.g would you buy a chiller with VSD with 0.6 kW/ton or a constant speed chiller with 0.5 kW/ton if they were priced the same?
The answer lies in comprehensive analysis/simulation programs, one like VSSriram mentioned. Trane also has one called the System Analyzer which does similar comparisons. The answer is it depends...
RE: VSD Centrifugal Chillers
Caution: I not only have two 750 Ton Carrier Centrifugals with vfd, but also variable primary pumping. Details need to be engineered properly for the vfd portion of the chiller to maintain optimization. Make sure you optimize your cooling towers for low ecwt, or potentially, the chiller will self protect and act like a non-vfd chiller at 60 Hz. Carrier seems to have licked this problem on the larger compressor sizes (>750T). I haven't seen the changes on the Trane or York...just precautions in operation.