I have always known that the design of the Grundfos impeller stack has a much better drop in horsepower than most other brands of pumps. The new software that Grundfos has for sizing pumps is excellent. (seen here http://product-selection.grundfos.com/catalogue.html)
I have wanted to see the horsepower requirements for these small pumps for years. This information has always been available for larger pumps, just not the small ones. Many of Goulds larger pumps have a good drop in horsepower, but not all of them. However, the design of their small plastic pumps doesn’t allow the impellers to unload as easily as the fixed stack design with the Stainless Steel impellers of the small Grundfos pumps.
Actually Grundfos pumps are so good at reducing the amp draw when simply restricting the pump with a valve, that it is almost impossible to beat it even when using a Variable Speed Drive. The 3” SQ pumps don’t have nearly as good a drop in horsepower as the 4” S series pumps.
With the new software I haven’t figured out how to show the horsepower when using the CU301 box to make the SQ a variable speed design. But my guess is that it will not be much different from what their 4” pumps will do naturally by just restricting the flow with a valve. This maybe the reason this kind of information has not been available before, because it shows the natural drop in horsepower to be about the same as could be done with a variable speed drive attached.
I have always known that if this kind of information were available, people would realize VFD’s do not save energy on these kinds of systems. I am going to make some copies of all these pump curves, because once Grundfos realizes what we can do with this information, it maybe quickly taken off line.
I have wanted to see the horsepower requirements for these small pumps for years. This information has always been available for larger pumps, just not the small ones. Many of Goulds larger pumps have a good drop in horsepower, but not all of them. However, the design of their small plastic pumps doesn’t allow the impellers to unload as easily as the fixed stack design with the Stainless Steel impellers of the small Grundfos pumps.
Actually Grundfos pumps are so good at reducing the amp draw when simply restricting the pump with a valve, that it is almost impossible to beat it even when using a Variable Speed Drive. The 3” SQ pumps don’t have nearly as good a drop in horsepower as the 4” S series pumps.
With the new software I haven’t figured out how to show the horsepower when using the CU301 box to make the SQ a variable speed design. But my guess is that it will not be much different from what their 4” pumps will do naturally by just restricting the flow with a valve. This maybe the reason this kind of information has not been available before, because it shows the natural drop in horsepower to be about the same as could be done with a variable speed drive attached.
I have always known that if this kind of information were available, people would realize VFD’s do not save energy on these kinds of systems. I am going to make some copies of all these pump curves, because once Grundfos realizes what we can do with this information, it maybe quickly taken off line.