Grundfos · Split-Coupled End Suction Pump
NBS — 3500 RPM
237 builds in 12 pump sizes: 3 to 125 HP 2-pole motors, up to 448 ft of head and 2,030 GPM.
Up to 448 ft (193 PSI) Head · Up to 2,030 GPM
3-125 HP, 3500 RPM
230/460V 3Ph NEMA Premium Motor, TEFC or ODP
2-6 in Suction x 1-1/4-5 in Discharge
Class 125 ANSI Flanges
DOE PEI 0.88-0.96
175 PSI Working Pressure
-10 to 284°F Liquid
Split Coupling, No Alignment Needed
160-2,277 lb Ship Weight
Overview
The NBS is Grundfos’s split-coupled end suction pump: a single-stage, back-pull-out volute pump on a NEMA Premium efficiency motor, joined by a radially split rigid coupling. The coupling needs no alignment between pump and motor, and it lets the mechanical seal come out without removing the motor. The pump takes up to 35% less floor space than a frame-mounted design, and Grundfos trims and balances every impeller to the duty point.
- No grouting or laser alignment; base frame and spring isolation base available
- Integrally cast diffuser vane reduces turbulence and the need for a suction guide
- Double volute on the larger sizes for longer seal and bearing life
- Two-pole, 3500 RPM motors for higher head; the 1750 RPM range is a separate listing
What Ships and What It Needs to Run
Included: the pump with its NEMA Premium motor, split coupling and coupling guard, assembled on support rails.
Ships by freight: 160 to 2,277 lb shipping weight; plan for a forklift or hoist at delivery.
Sized at install: isolating valves, a motor starter with overload protection, and a base or foundation sized for the pump.
Genuine Grundfos equipment, factory-new in original packaging — sold and supported by Watermain Supply, an independent industrial supplier.
12-Month Grundfos Warranty
Covered for 12 months from the date of purchase under Grundfos’s published warranty terms.
Specifications
| Pump type |
Single-stage, end suction, back-pull-out volute pump, split coupled, mechanical shaft seal |
| Speed |
3500 RPM (2-pole, 60 Hz) |
| Motor |
NEMA Premium efficiency, three-phase, TEFC or ODP by build; shaft grounding ring on builds marked Grounding Ring |
| Flanges |
ASME/ANSI B16.1 Class 125 (cast iron); Class 300 ductile iron loose flanges optional |
| Maximum working pressure |
175 psi (Class 125); 363 psi (Class 300 option) |
| Liquid temperature |
-10 to 284°F, by shaft seal (stamped on the nameplate) |
| Ambient temperature |
104°F and 3,280 ft without motor derating |
| Test |
Hydrostatic test at 1.5 times rated pressure on every pump (HI 14.6:2016) |
Models & Performance — Will It Do What You Need?
Each line below is one pump size: suction x discharge, motor HP, shut-off head from smallest to largest impeller, and the largest impeller’s maximum flow. Open the size that covers your duty point: each row is one impeller Grundfos builds at 3500 RPM, and every figure is the total head in feet the pump adds at that flow. The model number ends in the impeller diameter in inches (NBS 012-070/6.97 = 6.97 in).
NBS 012-070: 2 x 1-1/4 in, 3-15 HP, 88-209 ft, 195 GPM
| Impeller |
0 GPM |
100 |
145 |
195 (Max) |
| /6.97 |
209 |
202 |
186 |
151 |
| /6.42 |
188 |
180 |
164 |
— |
| /6.10 |
171 |
159 |
137 |
— |
| /5.87 |
158 |
144 |
119 |
— |
| /5.71 |
149 |
134 |
106 |
— |
| /4.92 |
116 |
94 |
— |
— |
| /4.29 |
88 |
56 |
— |
— |
NBS 015-070: 2-1/2 x 1-1/2 in, 5-20 HP, 92-218 ft, 379 GPM
| Impeller |
0 GPM |
190 |
285 |
379 (Max) |
| /6.93 |
218 |
210 |
185 |
149 |
| /6.30 |
185 |
169 |
145 |
— |
| /5.59 |
143 |
126 |
104 |
— |
| /5.04 |
116 |
100 |
— |
— |
| /4.49 |
92 |
73 |
— |
— |
NBS 015-090: 2-1/2 x 1-1/2 in, 15-40 HP, 228-448 ft, 306 GPM
| Impeller |
0 GPM |
155 |
230 |
306 (Max) |
| /9.84 |
448 |
422 |
369 |
296 |
| /8.82 |
361 |
324 |
287 |
— |
| /8.27 |
316 |
284 |
250 |
— |
| /7.80 |
275 |
243 |
206 |
— |
| /7.09 |
228 |
195 |
— |
— |
NBS 015-095: 2-1/2 x 1-1/2 in, 15-50 HP, 184-437 ft, 451 GPM
| Impeller |
0 GPM |
230 |
340 |
457 (Max) |
| /9.69 |
437 |
420 |
377 |
— |
| /8.82 |
362 |
340 |
306 |
255 |
| /7.87 |
286 |
263 |
236 |
— |
| /7.48 |
256 |
231 |
202 |
— |
| /7.01 |
222 |
197 |
162 |
— |
| /6.46 |
184 |
159 |
— |
— |
NBS 020-095: 2-1/2 x 2 in, 15-60 HP, 149-383 ft, 577 GPM
| Impeller |
0 GPM |
290 |
430 |
577 (Max) |
| /8.90 |
383 |
362 |
329 |
258 |
| /8.58 |
354 |
334 |
305 |
— |
| /8.03 |
306 |
287 |
258 |
— |
| /7.17 |
242 |
223 |
194 |
— |
| /6.77 |
214 |
196 |
163 |
— |
| /6.30 |
184 |
165 |
— |
— |
| /5.75 |
149 |
127 |
— |
— |
NBS 025-070: 3 x 2-1/2 in, 7 1/2-30 HP, 92-212 ft, 619 GPM
| Impeller |
0 GPM |
310 |
460 |
619 (Max) |
| /6.77 |
212 |
200 |
176 |
139 |
| /6.61 |
203 |
186 |
161 |
— |
| /6.30 |
182 |
162 |
137 |
— |
| /5.67 |
143 |
124 |
98 |
— |
| /4.96 |
108 |
88 |
— |
— |
| /4.57 |
92 |
67 |
— |
— |
NBS 025-095: 3 x 2-1/2 in, 25-75 HP, 156-382 ft, 770 GPM
| Impeller |
0 GPM |
380 |
580 |
770 (Max) |
| /9.37 |
382 |
373 |
344 |
291 |
| /8.43 |
314 |
305 |
275 |
234 |
| /7.80 |
267 |
259 |
233 |
— |
| /7.17 |
227 |
218 |
196 |
— |
| /6.30 |
173 |
165 |
140 |
— |
| /5.98 |
156 |
147 |
117 |
— |
NBS 030-070: 4 x 3 in, 15-40 HP, 108-209 ft, 932 GPM
| Impeller |
0 GPM |
470 |
700 |
932 (Max) |
| /6.85 |
209 |
194 |
168 |
123 |
| /6.30 |
175 |
160 |
136 |
— |
| /5.83 |
148 |
130 |
106 |
— |
| /5.59 |
135 |
114 |
91 |
— |
| /5.04 |
108 |
82 |
— |
— |
NBS 030-095: 4 x 3 in, 40-125 HP, 160-357 ft, 1,401 GPM
| Impeller |
0 GPM |
700 |
1,050 |
1,401 (Max) |
| /8.86 |
357 |
355 |
334 |
293 |
| /8.07 |
299 |
297 |
276 |
— |
| /7.36 |
242 |
237 |
210 |
— |
| /6.89 |
204 |
196 |
171 |
— |
| /6.50 |
181 |
171 |
140 |
— |
| /6.10 |
160 |
146 |
111 |
— |
NBS 040-070: 5 x 4 in, 20-50 HP, 99-193 ft, 1,453 GPM
| Impeller |
0 GPM |
730 |
1,100 |
1,453 (Max) |
| /6.77 |
193 |
177 |
149 |
102 |
| /6.30 |
165 |
147 |
121 |
— |
| /5.75 |
132 |
107 |
86 |
— |
| /5.51 |
121 |
95 |
70 |
— |
| /5.43-4.80 |
99 |
71 |
— |
— |
NBS 040-095: 5 x 4 in, 60-125 HP, 175-308 ft, 2,030 GPM
| Impeller |
0 GPM |
1,000 |
1,500 |
2,030 (Max) |
| /8.35 |
308 |
287 |
249 |
185 |
| /7.72 |
262 |
238 |
200 |
— |
| /6.93 |
204 |
174 |
143 |
— |
| /6.46 |
175 |
142 |
115 |
— |
NBS 050-070: 6 x 5 in, 25-75 HP, 89-198 ft, 1,960 GPM
| Impeller |
0 GPM |
980 |
1,450 |
1,960 (Max) |
| /6.93 |
198 |
171 |
147 |
97 |
| /6.77 |
185 |
154 |
132 |
— |
| /6.46 |
167 |
132 |
110 |
— |
| /6.06 |
146 |
107 |
86 |
— |
| /5.98-4.88 |
107 |
70 |
56 |
— |
| /5.59-4.49 |
89 |
52 |
43 |
— |
Head in feet at the flow in GPM heading each column: 50% and 75% of the largest impeller’s curve, then its end. Bold = the last column that impeller reaches; — = beyond its curve. Digitized from the 3500 RPM curves in the Grundfos data booklet NBS, NBSE, 60 Hz ANSI (Data Sheet tab) and rounded down; the curves are in the image gallery. PSI = feet ÷ 2.31.
Before You Buy — The Limits That Decide the Fit
| Liquid |
Clean, thin, non-explosive liquids with no solids or fibers: water, water-glycol, condensate, process water |
| Minimum flow |
At least 10% of the rated flow at all times; never run against a closed valve |
| Pressure |
175 psi working pressure with Class 125 flanges |
| Power |
3 x 230/460V, 60 Hz (a few builds 460V only) |
| Priming |
Non-self-priming: the pump and suction pipe must be full of liquid before start |
| Speed control |
Fixed speed; for variable flow see the NBSE with built-in drive |
Installation Notes
- Mount on a level base or foundation; no grouting is needed when the pump is supplied on a base frame.
- Fit isolating valves on both sides and support the pipework so it puts no load on the pump flanges.
- Fill and vent the pump and suction pipe before starting, and check the direction of rotation.
- On a variable frequency drive, Grundfos recommends a shaft grounding ring and an insulated bearing from 100 HP.
From the Grundfos data booklet NBS, NBSE, 60 Hz ANSI.
Applications
Hot water heating and chilled water, cooling towers and condenser water, data center cooling, boiler feed and condensate, district heating, water supply and pressure boosting, industrial washing and liquid transfer.
Materials of Construction
| Pump housing |
Gray cast iron ASTM Class 35 (ductile iron 70-50-05 optional) |
| Impeller |
Stainless steel ASTM A351 CF8 (316 optional) |
| Shaft |
Stainless steel AISI 420 (304, 316 or duplex optional) |
| Motor stool |
Gray cast iron ASTM Class 35 |
| Coupling |
Ductile iron, split design |
| Coupling guard |
Stainless steel AISI 430 |
| Cover and seal cover |
Ductile iron 70-50-05 |
| O-rings |
EPDM (Viton or NSF EPDM optional) |
Standard materials from the Grundfos data booklet NBS, NBSE, 60 Hz ANSI, pp. 33-34.
