Maximum Inlet Pressure; Minimum Flow Rate; Maximum Starts And Stops; Diaphragm Tank - Grundfos Hydro Multi-E Series Installation And Operating Instructions Manual

Example
pb = 1 bar.
Pump type = CRE 15, 50 Hz.
3
Flow rate = 15 m /h
NPSH = 1.2 metres head.
(from page 46)
Hf = 3.0 metres head.
Liquid = +60 °C.
temperature
Hv = 2.1 metres head.
(from page 47)
H = pb x 10.2 - NPSH - Hf - Hv - Hs [metres
head].
H = 1 x 10.2 - 1.2 - 3.0 - 2.1 - 0.5 equal to 2.8
metres head.
This means that each pump can operate at a suction lift of
maximum 2.8 metres head.
Pressure calculated in bar: 2.8 x 0.0981 equal to 0.27.
Pressure calculated in kPa: 2.8 x 9.81 equal to 27.4.

27.6 Maximum inlet pressure

The maximum inlet pressure must not exceed 8 bar. However, the
actual inlet pressure plus pressure when the pump is operating
against a closed valve must always be lower than the maximum
operating pressure.

27.7 Minimum flow rate

Due to the risk of overheating, the pumps must not be used at
flow rates below 10 % of the rated flow rate of one pump.
The pumps must not run against a closed outlet
valve.

27.8 Maximum starts and stops

The system must not be started and stopped via the power supply
more than four times per hour.
When the system is switched on via the power supply, it will start
after approximately 5 seconds.
If a higher number of starts and stops is desired, use the input for
external start-stop when starting/stopping the system.
When started via an external on/off switch, the system starts
immediately.

27.9 Diaphragm tank

The diaphragm tank precharge pressure must be set to 0.7 x
setpoint.
If the setpoint is changed, the diaphragm tank precharge
pressure must be changed accordingly to ensure optimum
operation.
Measure the precharge pressure while the system is
pressureless.
We recommend that you use nitrogen gas for precharging.
42

28. Inputs and outputs

Ground reference (GND)
All voltages refer to GND.
All currents return to GND.
Absolute maximum voltage and current limits
Exceeding the following electrical limits may result in severely
reduced operating reliability and motor life:
Relay 1:
Maximum contact load: 250 VAC, 2 A or 30 VDC, 2 A.
Relay 2:
Maximum contact load: 30 VDC, 2 A.
GENI terminals: -5.5 to 9.0 VDC or less than 25 mADC.
Other input/output terminals: -0.5 to 26 VDC or less than 15
mADC.
Digital inputs (DI)
Internal pull-up current greater than 10 mA at Vi equal to 0 VDC.
Internal pull-up to 5 VDC (currentless for Vi greater than 5 VDC).
Certain low logic level: Vi less than 1.5 VDC.
Certain high logic level: Vi greater than 3.0 VDC.
Hysteresis: No.
2
Screened cable: 0.5 - 1.5 mm
Maximum cable length: 500 m.
Open-collector digital outputs (OC)
Current sinking capability: 75 mADC, no current sourcing.
Load types: Resistive and/or inductive.
Low-state output voltage at 75 mADC: Max. 1.2 VDC.
Low-state output voltage at 10 mADC: Max. 0.6 VDC.
Overcurrent protection: Yes.
2
Screened cable: 0.5 - 1.5 mm
Maximum cable length: 500 m.
Analog inputs (AI)
Voltage signal ranges:
• 0.5 - 3.5 VDC, AL AU
• 0-5 VDC, AU
• 0-10 VDC, AU.
Voltage signal: Ri is greater than 100 kΩ at +25 °C.
Leak currents may occur at high operating temperatures. Keep
the source impedance low.
Current signal ranges:
• 0-20 mADC, AU
• 4-20 mADC, AL AU.
Current signal: Ri is equal to 292 Ω.
Current overload protection: Yes. Change to voltage signal.
Measurement tolerance: - 0/+ 3 % of full scale (max.-point
coverage).
2
Screened cable: 0.5 - 1.5 mm
Maximum cable length: 500 m (exclusive of potentiometer).
Potentiometer connected to +5 V, GND, any AI:
Use maximum 10 kΩ.
Maximum cable length: 100 m.
/ 28-16 AWG.
/ 28-16 AWG.
/ 28-16 AWG.