A company I deal with recommended a 1.5 hp Berkeley horizontal multi-stage jet/centrifugal pump (cat. no. 15LT2). They sent along a data sheet showing the performance of this pump in different configurations. Matching the well I plan to install this pump in, I selected, from the data sheet, 20' of suction with a delivered pressure of 40 psi. The tables showed the following performance in GPM.

Shallow well single pipe, 20' of suction, 40 psi = 9.4 gpm

Deep well double pipe, 20' suction, 40 psi = 21.7 gpm

Centrifugal application, single pipe, 20' suction, 40 psi = 39 gpm???

First, what would you do to this pump to operate it in "centrifugal application" as opposed to running it as a "shallow well" single line jet pump?
Second, WHY would anyone run this pump as a shallow well jet pump when you can deliver more than four times as much water running it as a centrifugal pump? I feel I must be missing something here, as I thought centrifugal pumps could not touch the performance of jet pumps drawing from a depth of 20'.

I tried phoning the 1-800 number for this company but spent two hours patiently waiting for a technician while a recording told me how important my business was to them so, I'm hoping someone on the forum can explain this puzzle to me.