The Grundfos CRE is a vertical multistage centrifugal pump with a variable-speed drive built into the motor. It is a clean-water pump: Grundfos lists it for industrial and municipal water supply, distribution from waterworks, pressure boosting in mains and in high-rise buildings, washing and cleaning, water treatment, boiler feed and condensate, cooling and air-conditioning, machine tools and irrigation. The pump head and base are cast iron and every other wetted part is EN 1.4301 stainless steel, which is the AISI 304 grade. Non-corrosive liquids only.

Sizes run CRE 1 to CRE 155, where the number is roughly the rated flow in m³/h, and each size carries a range of stage counts. Ports are in line, at the same level, so the pump drops into a horizontal pipe run. That is the CR layout and the CRE inherits it, along with the chamber stack, the staybolts and the cartridge shaft seal. It sits in our centrifugal pump category and comes from Grundfos.

What the integrated converter actually buys you

Grundfos is blunt about the difference: "The difference between the CR and CRE pump ranges is the motor." The hydraulics, the materials and the seal are the same. What changes is that the motor is an MGE, and the MGE has a frequency converter inside its terminal box.

Read that as a list of things you no longer buy and no longer commission. The inverter, its enclosure, its cooling and the cable run between panel and pump all disappear into the motor. So does the motor-protective circuit breaker. The pump arrives tested and pre-configured, and the person commissioning it types in a pressure.

When a plain CR is the better buy

Grundfos names three reasons to select an E-pump: the consumption fluctuates, you want constant pressure, or you want to communicate with the pump. If none of those is true, a CRE is money spent on control you will not use. A transfer duty that runs flat out into a tank does not vary, and a fixed-speed CR with a starter is the cheaper pump with less to go wrong.

The other check is where the pump lives. Putting the drive on the motor puts the electronics in the plant room, at whatever temperature and altitude the plant room happens to be. Grundfos calls for an oversize motor above 50 °C ambient or above 1000 metres, which is the sort of derate that turns a straightforward selection into a bigger frame size. Tell us the ambient and the site altitude when you enquire.

A stack of impellers, each in its own chamber, adds pressure to the same flow. That is how a tall, narrow pump reaches 262 m of head. The CRE is not self-priming, so the inlet has to be flooded.

The E-motor is what makes it a CRE. Grundfos builds the MGE as a totally enclosed, fan-cooled motor with a frequency converter in the terminal box and a PI controller behind it. On a pump ordered with the integrated pressure sensor, the sensor on the outlet feeds pressure back to the controller, the controller compares it with the setpoint and the converter trims motor speed until the two agree. Because that runs continuously, the pressure in the pipework stays put while the draw on it changes. Two control modes ship on the pump: constant pressure, which is the factory setting, and constant curve.

Order a CRE without the sensor and you get open-loop speed control, or a pump ready for a sensor you fit later. That variant covers flow, level, temperature, differential pressure and differential temperature control, and it is also the one to specify when a remote analogue signal sets the speed from a building management system.

Protection is inside the converter rather than the panel. The MGE carries thermal protection against slow overload and blocking, and Grundfos states that E-pump installations do not require a motor-protective circuit breaker, only normal short-circuit protection for the cable. Motors from 3 to 26 kW include a Bluetooth module that talks to Grundfos GO at up to 10 metres; pumps from 0.37 to 2.2 kW are factory-fitted with the FM300 functional module, which brings three analogue inputs, two Pt100/1000 inputs, two LiqTec sensor inputs and two signal relays for anyone wiring the pump into a wider control scheme.

On efficiency, Grundfos rates the MGE motor at IE5 level from 0.37 to 26 kW, and states that the product complies with the ecodesign requirements for water pumps in the ErP Directive, Commission Regulation (EC) No 547/2012. The hydraulic side is measured by the Minimum Efficiency Index, and the benchmark Grundfos quotes for the most efficient water pumps is MEI ≥ 0.70.