Water Well Journal
Issue link: https://read.dmtmag.com/i/767379
Table 1. (continued) Is maximum pump Q < Max. Well Q 3. Preliminary pump and motor selection(s): Review curve(s) and data sheet(s) Maximum bowl diameter = Well Dia.-2 a. Diameter of well I.D./pump O.D. (for bowl and riser pipe/pump cable clearance) Was well graphed? b. Check well alignment and straightness: Obstructions? Minimum submergence = 5 over bowl c. Pumping water level at COS and alternate flow rates: Is pump runout OK? Avoid top feeding installations d. Water feeding level into well: Above or below motor? Minimum V past > 6 motor = .50 FPS 1. Motor cooling requirement (past motor, shroud, or need for cooling line?) 2. Pump hydraulic concerns: (adequate submergence, air draw into pump, cavitation, cascading water, prerotation, etc.) e. Additional concerns? (abrasives, cable or pump rubbing on casing, pipe whipping or unscrewing in well, motor slamming against well?) 4. System parameters: Check impact to existing electrical and piping systems a. Verify system design flow rate and TDH vs. selection-from nos. 1 and 2 Verify weight capacity and rigidity b. Select riser pipe size and joint type: Steel (T&C, welded, flg), PVC, Hose? Recommend V > 3 FPS < 10 FPS c. Select riser pipe/and check valve: Maximum/minimum uphole velocity, C.V. OD/size? Verify adequate room in well exists Auxiliary pipes or devices in well? LWC, sensing/chemical treatment lines, etc.? Will drop cable fit through well seal? d. Wellhead termination: Use tee, ell, or pitless adapter at wellhead-size? First C.V. above pump at 5-20 e. Riser check valve(s): Number? (200 feet maximum spacing); VFD or non-slam rated? Recommend Vd < 3%-NEC < 5% 5. Electrical: Voltage or horsepower drop; NEC considerations? Use 75°/90° rated cable × 4-wire a. Drop cable size and type? Insulation and temperature rating/use 4-wire Rec. secure cable < 10 max. and joint b. Method and spacing of securing cable to riser pipe at maximum 10 intervals c. Submersible motor operating and protection methods Lower motor efficiency = higher current draw 1. Submersible motor unique characteristics = lower motor efficiency Sub motor also has higher inrush amps a. Select starting method: Evaluate inrush KVA/current/voltage drop In some cases: Use cable loss for added Vd (ALS, reduced voltage, VFD, voltage loss via drop/offset cable, etc.) Water to pass by and below motor b. Motor cooling requirements: Velocity (FPS)/volume (GPM) Best P.F. = .95 to 1.0—Desirable > .90 c. Power factor (P.F.) correction (if needed) Current higher than std. HP motor d. Short circuit and O.L. protection methods: Use class 30 Q.T. overloads Use phase protection on 3 phase e. Phase loss, unbalance, and reversal protection means Use line and load reactors on VFD f. High voltage surges and lightning protection Max. L.W.L. cutout at 5 over pump g. Ancillary motor protection means/devices/low water level cutoff? NEC: Single motor amps × 125% h. Impact of motor load to primary electrical system WATER WORKS continues on page 36 Twitter @WaterWellJournl WWJ January 2017 35