Grundfos CRE 3 Variable-Speed Pump, 1 in NPT, 3600 rpm

CRE 3 is the CR platform with the drive built into the motor. The MLE motor carries its own frequency converter and a graphical control panel, so the pump varies its own speed to hold a setpoint instead of running flat out and throttling. There is no separate VFD to buy, mount, wire or commission.

Hydraulically it is a vertical multistage pump with suction and discharge on the same centreline, so it drops into a straight pipe run. Wetted parts are AISI 304 stainless with a cast iron pump head and base — the same material grade as CR.

This listing is the 3600 rpm, 1 in NPT build. Grundfos publishes the 3600 rpm and 4000 rpm variants as separate part numbers with different duty points, so they are listed separately rather than mixed. At 3465-3526 rpm the CRE 3 frame is rated 15.5 GPM, and 10 stage counts cover 48 ft to 404 ft of rated head on 1/2 to 3 HP motors.

Speed is the whole point. The motor runs anywhere from 360 rpm up to its rated speed, so one pump covers a wide duty band and holds constant pressure as demand changes. That also means the published duty point below is the full-speed figure — at part load the pump sits lower on its curve and draws proportionally less power.

Drawing from a tank, cistern or well. Nothing arrives with pressure, so what the pump adds is what you get. Read the table straight through: a CRE 3-9 gives you about 93 psi at 15.9 GPM.

Fed by a city main. The pump adds on top of what already arrives, and the controller holds the total. On a 40 psi main asking for 133 psi at the fixture, the pump only has to add 93 — and because it is variable speed it will do exactly that and no more. Incoming pressure buys you more flow, not more pressure.

With sensor. The pump ships with a factory pressure sensor and the wiring to it. Out of the box it holds a constant discharge pressure: set the pressure you want on the control panel and the pump varies its speed to maintain it. This is the version to order unless you already know otherwise.

Without sensor. The pump is the same machine with the same drive and panel, but no pressure sensor is supplied. It cannot hold constant pressure until a sensor is connected, or it is driven by an external signal or a building management system. Order this version only when the sensor already exists, is supplied by others, or the pump runs in constant-speed or externally-controlled mode.

The sensor range against each part number is the sensor’s measuring span — on this listing, 145 psi to 362 psi depending on model. That span is the ceiling on what the controller can be told to hold; it is not a claim about what the pump can produce. Read it together with the rated head table and the maximum operating pressure.

• Frequency converter built into the motor — no separate drive to buy, mount, wire or commission, and no drive panel to find space for.
• 360-4000 rpm speed range — the pump throttles itself by slowing down rather than by closing a valve, which is where the energy saving comes from.
• Graphical control panel with the FM300 - Advanced function module — setpoint, control mode and alarms are set on the pump itself.
• IE5 motor efficiency class, enclosure IP55, with built-in electronic motor protection.
• In-line ports — suction and discharge on the same level, so the pump installs in a straight run without an elbow or offset.
• Cartridge shaft seal — HQQE, silicon-carbide faces, replaced as a complete unit without setting faces by hand.
• NSF/ANSI 61 certified for drinking water contact.
• 1 in NPT connection — Grundfos type Oval / NPT(F), rated PN 16.

• Constant-pressure boosting in commercial buildings and multi-unit residential
• Pressure boosting where demand swings through the day and a fixed-speed pump would cycle
• Water treatment, filtration and reverse osmosis feed
• HVAC heating, chilled water and condenser water circulation
• Industrial process transfer where flow or pressure has to be held to a setpoint
• Retrofits replacing a fixed-speed pump plus external VFD with one machine

Best operating range. Grundfos does not publish an efficiency curve for this range in the product data, and a range cannot honestly be derived from a single published duty point, so we do not print one here. Send us the duty and we will read it off the curve for the exact model.

This is where the pump turns the most electricity into water pressure. Ask for more flow than it can deliver at your setting and it runs at full speed continuously, which is where motors and seals wear out. Sizing a booster to the building rather than to the headline numbers is what makes it last.

Each part number is a complete pump: pump end, MLE variable-speed motor with its built-in frequency converter and control panel, coupling, coupling guard and HQQE cartridge shaft seal, factory assembled and tested.

The pressure sensor is supplied only on the with-sensor part numbers. Check the Sensor column above against the part number you are ordering.

Oval flanges are included with this connection style. Expansion tanks, isolation valves, external sensors, foundation bolts and building-management interfaces are not included.

Select the HP and voltage, then the model, then whether you want the factory pressure sensor. Each combination is a distinct Grundfos part number, listed in the table above and shown in the SKU of the selected variant.

The picker shows only the combinations Grundfos publishes for the 1 in NPT, 3600 rpm build.