Grundfos CR 20-5 5.5 kW Vertical Multistage Pump

Grundfos CR 20-5: vertical CR multistage pump explained

The Grundfos CR 20-5 is a vertical, multistage, in-line centrifugal pump with 5 impellers, paired with a 5.5 kW two-pole motor. In the CR 20-5 type code, 20 stands for the size (rated flow 20 m³/h) and the number after the hyphen, 5, is the count of impellers stacked inside the sleeve. More stages add head at the same flow, which is why the CR 20-5 sits at the lower end of its size family. Seven Star LLC supplies the CR 20-5 in Oman and the GCC as an independent supplier in Muscat, not affiliated with the manufacturer.

The data booklet describes the CR family as pumps for non-explosive liquids that do not attack the pump materials. The CR version combines cast-iron head and base with stainless steel hydraulics and suits clean, non-corrosive liquids such as potable, process and cooling water.

Reading the type code

• CR: product family and material grade (cast iron head and base, stainless steel EN 1.4301 / AISI 304 hydraulics).
• 20: size, equal to the rated flow in m³/h at the best efficiency point.
• 5: number of impellers. A second number after another hyphen, such as -2, would mark reduced-diameter impellers.
• The full order code continues with letters for pump version, pipe connection, materials, rubber parts and shaft seal, for example A-F-A-E-HQQE, where F means DIN flange and HQQE is a silicon carbide / silicon carbide seal with EPDM.

CR 20-5 technical specifications

Values for flow range, efficiency and maximum pressure describe the whole size 20 family, while the inlet pressure, motor, dimensions and weight are specific to 5 stages. Hydraulic curves for each stage count are published in the data booklet; ask us for the curve pages when you need to read head at your own flow.

How the CR 20-5 works

Water enters the base, is routed to the first impeller and then passes through the chambers in series. Each chamber turns velocity into pressure and hands the liquid to the next impeller, so the discharge pressure is built up stage by stage. In this pump the chamber stack and sleeve are clamped between the base and the pump head by staybolts, and a cartridge-type mechanical shaft seal sits at the head. The cartridge format lets maintenance staff swap the seal without dismantling the hydraulic stack.

Inlet and outlet ports are at the same level and have the same diameter, so the pump can be dropped into a horizontal one-pipe layout. The motor drives the shaft through a coupling inside the pump head, and the motor stool carries the load, which keeps the footprint small compared with horizontal pumps of similar duty.

Where the CR 20-5 fits in the CR range

The CR 20 size spans 11 to 29 m³/h and shares the DN 50 connection with CR 15. The decision between the two is made at the duty point: if the required flow sits above about 22 m³/h, the CR 20 hydraulic keeps the pump nearer to its best efficiency point. Related models in the same size include CR 20-1, CR 20-3, CR 20-7, CR 20-10, CR 20-17. Their power, length and weight grow with the stage count, as the family table below shows. For variable-speed control, the same hydraulics are available with an integrated frequency converter as CRE or CRNE pumps; those are separate ordering references.

Construction materials

Selecting and ordering a CR 20-5

• Duty point: required flow in m³/h and required differential pressure; confirm that 5 stages cover the head with a margin of at least a few per cent.
• Liquid: water quality, chloride content, pH, temperature, density and viscosity. Dense or viscous liquids can need an oversized motor.
• Pressure: inlet pressure at the suction flange plus the pump differential pressure must stay below the maximum operating pressure of the flange class.
• Connection: DN 50 DIN flange here; confirm counter-flange standard and PN rating on site.
• Motor: 5.5 kW, 50 Hz, three-phase; confirm supply voltage, start method and any ATEX or thermal-protection requirement.
• Shaft seal and rubber parts: the seal code (for example HQQE or HQQV) and the EPDM or FKM rubber follow the liquid and temperature; check the shaft-seal operating range in the data booklet.

Installation, commissioning and maintenance of the CR 20-5

Set the pump on a level, rigid foundation and fit the base-plate bolts evenly; at 966 mm overall height it is tall, so leave headroom for motor removal. Fill and vent the pump completely before starting, because it is not self-priming and a dry run damages the seal faces. Check rotation direction at the motor, then open the discharge valve gradually and compare line pressure with the duty point.

In service, watch for seal weeping, bearing noise at the motor and drifting differential pressure. The data booklet advises keeping inlet pressure plus pump differential pressure below the stated maximum, and notes that starting at the limit can exceed it; at zero flow the pump develops its shut-off head. Keep a spare cartridge seal and sleeve O-rings on the shelf for pumps in continuous duty.

Typical applications in Oman and the GCC

In the Gulf, this pump is typically specified for larger booster sets, central chilled-water and cooling-water circuits, process-water supply, irrigation and landscaping mains, and boiler feed on mid-size steam plant. High ambient temperature, dust and humidity push motors hard, so many buyers choose a motor with a generous thermal margin and shade the unit from direct sun. Water chemistry on the coast, especially chloride, drives the choice between CR and CRN materials; treated or low-chloride water suits the CR construction, while seawater-influenced circuits should be checked for CRN.

Oil and gas facilities use pumps of this type on utility water and firewater-support lines, power stations on cooling and demineralised-water make-up, and desalination plants on brackish-water feed and chemical-free utility duties. Always confirm the liquid is clean and non-explosive before using a standard pump.

CR 20 family overview: stage counts, motors and weights

The table is taken from the dimension tables for the 20 size and shows how a longer stack needs a bigger motor. It corresponds to the 5-stage, 5.5 kW entry.

Information to send with an RFQ for the CR 20-5

• Required flow, differential pressure and the number of duty points.
• Liquid, temperature, chloride level and solids content.
• Inlet pressure and available NPSH at the site.
• Supply voltage, frequency, start method and ambient temperature.
• Flange standard and PN rating of the mating pipework.
• Quantity, whether a spare seal kit is wanted, and delivery location.

Documents and quotation

The Grundfos data booklet covering the CR, CRI and CRN range, including the CR 20-5, is attached on this page. Please read the curve pages for your stage count before confirming the duty.

Send the part number CR 20-5 with your duty data and we will prepare a quotation. Seven Star LLC is an independent supplier in Muscat and is not affiliated with the manufacturer.