GRUNDFOS · CONSTANT PRESSURE CONTROL UNIT
CU 302
Control and communication unit for Grundfos SQE submersible pumps. Talks to the pump over the existing power leads — no extra wires down the well — and varies pump speed to hold a constant pressure from a trickle to full flow. Pre-set for constant pressure, 20 to 100 PSI, with a 50 PSI factory setpoint.
Constant Pressure 20-100 PSI
50 PSI Factory Setpoint
90-240 VAC, 12.5 A
Type 1 / Type 3R UL
Bluetooth to Grundfos GO
Power Line Communication
Overview
CU 302 is a control and communication unit specially developed for the SQE submersible pumps in constant-pressure applications. It is intended for controlling and monitoring SQE pumps using power line communication, so the control unit communicates with the pump via the power cable and nothing additional is run down the borehole.
The controller operates according to the water pressure measured by a pressure sensor in the installation. When water is consumed, the system detects flow together with pressure change; the controller starts the pump, and pump performance and water flow are controlled by changing the pump speed. The system maintains a constant pressure within the maximum pump performance in spite of varying water consumption.
The factory setup is constant pressure over 2 to 5 bar (20 to 100 PSI) with a setpoint of 3 bar (50 PSI), CIO 1 configured for an analog sensor and CIO 2 for digital outputs; when the pump is running the output changes contact position. Input signals can be analog sensors or digital switches, and the controller can be used in a range of other applications by changing its configuration: level control filling, level control emptying, pressure control on a digital or an analog input, pump out, and pump monitoring.
Operating indication sits on the front of the controller — power on, pump running, and the Grundfos Eye showing pump status — alongside alarm and warning indication. CU 302 reports dry running and service-needed conditions including no contact to the pump, overvoltage, overtemperature and overload. In a constant-pressure installation it works with a 2 gal (8 litre) diaphragm tank rather than a conventional pressure tank, because the pump follows demand instead of cycling between two switch settings.
What Ships and What It Needs to Run
Included: the CU 302 controller with its quick guide and cable-gland accessories; the "With Pressure Sensor" version adds the 0-120 PSI pressure sensor.
Required: a Grundfos SQE pump (the CU 302 runs SQE pumps only, over the power leads), a 2 gal diaphragm tank, and a 90-240 VAC supply. Bought without the sensor, it needs the pressure transducer (0-120 PSI, 92506685).
Setup: factory setpoint 50 PSI, adjustable 20 to 100 PSI in 5 PSI steps at the keypad, or with Grundfos GO and the Grundfos HOME app.
Genuine Grundfos equipment, factory-new in original packaging — sold and supported by Watermain Supply, an independent industrial supplier.
Warranty
24 months from date of installation, but not more than 30 months from date of manufacture. In Grundfos's words, products are “warranted to the original user only to be free of defects in material and workmanship”; the full terms are in the installation and operating instructions on the Data Sheet tab.
Models & Configurations
| Configuration |
Pressure sensor |
Units |
Approval |
Part No. |
| CU 302 UL, complete |
Not included |
PSI |
UL |
92799799 |
| CU 302 UL with PSI sensor |
Included |
PSI |
UL |
92817764 |
Both variants are the North American UL build reading in PSI. Grundfos also lists bar-reading CE variants — 92799797 without sensor and 92817763 with sensor — which are the CE-market builds and are not the ones to order in North America. A constant-pressure installation needs a sensor: order the with-sensor part number, or the without-sensor part number plus a transducer.
Key Features
-
Pre-set for constant pressure — out of the box it holds a setpoint over 20 to 100 PSI, and it also supports level control, pressure control, pump out and pump monitoring by changing the configuration.
-
Power line communication — GENIbus to the SQE over the two existing power leads, so no signal cable runs down the well.
-
Configurable input and output — two CIO channels taking analog sensors or digital switches; analog in 0-10 V, 0-5 V, 0.5-3.5 V, 0-20 mA or 4-20 mA, analog out 0-10 V, 0-20 mA or 4-20 mA.
-
Manual and automatic control of the pump from the front panel, with a STOP button and keypad lockout.
-
Grundfos Eye status indicator plus alarm and warning indication, including dry running and no contact to the pump.
-
Bluetooth pairing with Grundfos GO for setpoint, control mode, sensor range, scheduling, the installation log and live metrics.
-
Out-of-range sensor detection — a warning or alarm is raised when the input signal falls under or over the configured range, so a failed transducer shows up as a fault rather than a wrong pressure.
-
Field-updatable software and a replaceable battery.
Specifications
| Specification |
Value |
| Supply voltage |
90-240 VAC -10 % / +6 %, PE |
| Frequency |
50/60 Hz |
| Rated current |
Maximum 12.5 A |
| Mains fuses / backup fuse |
Maximum 16 A |
| Power consumption |
Maximum 25 W |
| Overvoltage category |
III |
| Field wiring |
Minimum 20 AWG rated 140 °F or higher. Copper, copper-clad aluminum or aluminum conductors |
| Analog input |
0-10 V, 0-5 V or 0.5-3.5 V at 100 kΩ load; 0-20 mA or 4-20 mA at maximum 2 V drop. Under-range and over-range raise a warning or alarm |
| Analog output |
0-10 V at maximum 20 mA; 0-20 mA or 4-20 mA into 500 Ω or less |
| Default control mode |
Constant pressure, 2-5 bar (20-100 PSI), setpoint 3 bar (50 PSI) |
| Other control modes |
Level control filling, level control emptying, pressure control on digital input, pressure control on analog input, pump out, pump monitoring |
| Pressure sensor range |
0-6 bar (0-120 PSI) analog |
| Transceiver |
RS-485 |
| Protocol |
GENIbus over the pump power cable |
| Wireless |
Bluetooth to the Grundfos GO app |
| Enclosure class |
Type 1 / Type 3R on the UL version (IP55 on the CE version) |
| Ambient temperature, operating |
-4 °F to +122 °F |
| Ambient temperature, storage |
-22 °F to +140 °F |
| Relative air humidity |
5-95 % |
| Dimensions |
9.1 in high x 6.3 in wide x 3.8 in deep |
| Weight |
2.69 lb |
| Marking |
UL |
| Radio noise |
Tested to EN 55014 and EN 55014-2 |
Applications
- Constant-pressure residential water supply from a well, with an SQE pump and a 2 gal diaphragm tank
- Constant-pressure irrigation
- Maintaining a constant water table
- Emptying or filling a tank, and pumping from one tank to another, using level control
- Pump monitoring where speed control is not wanted
CU 302 controls Grundfos SQE pumps only. It will not control an SQ, which has no communication, and it must not be used with any pump outside the SQE range.
Ordering Information
Order by part number. CU 302 UL, complete, without sensor — 92799799. CU 302 UL with PSI sensor — 92817764.
Related parts. CU 302 pressure transducer, 0-120 PSI, 1/2 in NPT — 92506685. SQ, SQE cable kit, 14 AWG 5 ft NSF, motor model C — 97778332. SP, SQ, SQE wrench — 99588350. SQ, SQE flow sleeve, complete — 98148594.
What the installation needs. An SQE pump, a CU 302, a pressure sensor, a 2 gal diaphragm tank and a mains switch. The SQE pump is not included with the controller.
Before You OrderCU 302 is for SQE pumps only — it cannot control an SQ, and an SQE without a CU 302 runs at fixed maximum speed like an SQ. Decide whether you need the sensor: 92817764 ships with the PSI transducer, 92799799 does not, and constant-pressure operation requires one. The controller is a Type 1 / Type 3R enclosure, so it mounts indoors or in a protected location, not in the weather. Wire it with minimum 20 AWG conductors rated 140 °F or higher, on a circuit protected at 16 A or less. Electrical connection should be carried out by a licensed electrician in accordance with local regulations.
