Grundfos Hydro Multi-E Duplex Constant Pressure Booster - CRE 3 and CRE 5

Hydro Multi-E Duplex with CRE 3 or CRE 5 pumps is a factory-built constant-pressure booster: two Grundfos CRE vertical multistage pumps piped in parallel on a common stainless steel base frame, with AISI 316 inlet and outlet manifolds, isolating and check valves on every pump, pressure gauges, two outlet-pressure sensors, dry-running protection and a breaker cabinet. It is pre-piped, pre-wired and pressure- and function-tested at the factory.

There is no separate control panel. Each pump carries a Grundfos MLE permanent-magnet motor with its own frequency converter and PI controller, and the pumps talk to each other. The system holds one outlet pressure by varying speed, cuts pumps in and out as demand changes, and alternates duty so run hours even out. Any pump with an outlet-pressure sensor can take over as master, so the system keeps running if one pump or one sensor drops out. Optional CIM modules connect it to BACnet, Modbus, PROFINET or EtherNet/IP building management systems.

CRE 3 and CRE 5 are the small-flow builds: up to 89 GPM with 2 pumps and the highest heads in the Hydro Multi-E range, for apartment buildings, hotels, schools, offices and process boosting. They sit outside the DOE Pump Energy Index scope, so they carry no PEI rating; for the DOE PEI-rated CRE 10, 15 and 20 builds see Hydro Multi-E Duplex (DOE PEI rated).

Standard hydraulics expect a flooded or pressurized inlet. For suction lift, Grundfos moves the check valve to the inlet side as a factory option, specified at order. The system is rated for indoor installation only. Systems built with CRE 3-15 and CRE 5-16 pumps are not NSF/ANSI 61 and 372 approved.

Hydro Multi-E ships as a factory-built duplex or triplex, chosen at purchase. Each added pump adds flow at the same pressure, and the system cascades pumps in and out on demand. The triplex version is listed separately: Hydro Multi-E Triplex with CRE 3 and CRE 5.

More pumps hold more pressure at the flow the building actually draws. Each pump carries a share of the water, so each sits higher on its own curve: at 80 GPM a CRE 5-9 system adds 162 ft (70 psi) on two pumps and 232 ft (100 psi) on three. The shut-off pressure at zero flow is the one figure that does not rise, because it is set by the pump build.

Figures read from the Grundfos CRE 5 curve chart, Data Booklet 99347082, printed page 34.

Every build comes in two dry-running protection versions with different part numbers. Inlet pressure switch versions (part numbers beginning 99334 and 99445) use a normally open switch on the inlet manifold that stops the pumps at 3 psi and resets above 5 psi. Inlet pressure sensor versions (part numbers beginning 99761) carry two inlet-pressure transducers, one to each master motor, with the trip level set in the operating panel or Grundfos GO. The sensor version also reads the actual inlet pressure.

* Not NSF/ANSI 61 and 372 approved. Max boost is the peak of the curve near zero flow, a ceiling rather than a working point; max flow is the end of the duplex curve; both read from the Grundfos curve charts (Data Booklet pages 33 and 34). HP is rated motor power per pump. Part numbers from the Grundfos price list effective January 1, 2026; HP, weights and connections from the Data Booklet, printed pages 43 to 44.

Voltage is fixed per part number. Single-phase and three-phase units, and 200-240V and 440-480V units, are not interchangeable. Confirm the service before ordering.

From the Grundfos dimensional drawing: A is pump height, A1 breaker cabinet height, B length, C depth; overall height is the taller of A and A1. Dimensions may vary by plus or minus 0.5 in. Net weight is the system; gross includes packing. Grundfos asks for 3 ft of clearance on all sides. Source: Data Booklet 99347082, printed pages 43 to 44.

Sources: Data Booklet 99347082 (10.2025) pages 3 to 13; Installation and Operating Instructions 98419766 pages 26 to 29; Grundfos price list (NSF note and PEI scope).

Maximum feeder overcurrent protective device rating for the whole system, as printed by Grundfos for Hydro Multi-E. Supply tolerance plus or minus 10%. Motors of 5 to 7.5 HP need an especially reliable earth connection because leakage current exceeds 3.5 mA. Source: Installation and Operating Instructions 98419766, page 28.

A pump curve plots what the system adds to whatever pressure arrives at the inlet — never the discharge pressure and never the setpoint. Each cell reads feet of head added (psi added). The one-pump row is what the system delivers at low demand, before the next pump cuts in.

CRE 3 builds — flow in US GPM across the top

CRE 5 builds — flow in US GPM across the top

Drawing from a tank, cistern or well — nothing arrives with pressure, so what the system adds is what you get. Read the table straight through: a duplex CRE 5-9 at 60 GPM comes out at 218 ft (94 psi).

Fed by a city main — the system adds on top of what already arrives, and the controller holds the total at the setpoint. With 134 psi wanted at the outlet on a 40 psi main, the duplex CRE 5-9 only has to add 94 psi and delivers about 60 GPM; with 110 psi wanted, it adds 70 psi and delivers about 80 GPM. Incoming pressure buys you more flow, not more pressure — and inlet pressure plus the closed-valve pressure must stay under the 232 psi system rating.

Ask the system for more than it can deliver at your setpoint and all pumps run at full speed continuously, which is where motors and seals wear out. Grundfos also sets a floor: do not run below 10% of one pump's rated flow. Sizing to the building rather than to the headline maximums is what makes it last. Send us the peak flow, the setpoint and the inlet pressure and we will return the build with the manufacturer's curve for it.

Grundfos publishes these systems' performance as curve charts, not tables. The figures above are read from those charts (Data Booklet 99347082, 10.2025, printed pages 33 and 34; the charts are also in the image gallery), heads rounded down to the whole foot and psi = ft x 0.433 rounded down; a blank cell means Grundfos does not draw that curve at that flow. The first column is the ceiling at or near zero flow, not a working point. Curves are at a fixed 3,480 rpm, 60 Hz, airless water at 68 °F, ISO 9906:2012 Grade 3B; fitting and valve losses are not included. Grundfos does not publish a best operating range for these systems.

Source: Data Booklet 99347082, printed page 13.

CIM modules fit in the pump terminal box and must be fitted by authorized persons. Tank sizes from the Grundfos price list effective January 1, 2026 (recommended minimum sizes); CIM part numbers from Data Booklet 99347082, printed page 53.

The system is set up and run from the operating panel on the master pump, with no app required. Grundfos GO adds guided commissioning, live operating data, alarm troubleshooting and PDF reports on a smartphone. Grundfos lists the MI 301 mobile interface as the accessory for this: it pairs with the phone by Bluetooth and reaches the pumps by radio or infrared. It is sold separately.