Minimum Inlet Pressure; Maximum Inlet Pressure; Electrical Data; Frequency Of Starts And Stops - Grundfos CR 2 Instrucciones De Instalación Y Funcionamiento

4.4 Minimum inlet pressure

Fig. 3
H
The maximum suction lift "H" in metres head can be calculated as
follows:
H = p x 10.2 – NPSH – H – H
b f
p = Barometric pressure in bar.
b
(Barometric pressure can be set to 1 bar).
In closed systems, p
in bar.
NPSH = Net Positive Suction Head in metres head
(to be read from the NPSH curve on page 69 at the
highest flow the pump will be delivering).
H = Friction loss in suction pipe in metres head at the
f
highest flow the pump will be delivering.
H = Vapour pressure in metres head, see fig. E on page
v
66. t = Liquid temperature.
m
H = Safety margin = minimum 0.5 metres head.
s
If the calculated "H" is positive, the pump can operate at a suction
lift of maximum "H" metres head.
If the calculated "H" is negative, an inlet pressure of minimum
"H" metres head is required. There must be a pressure equal to
the calculated "H" during operation.
Example:
p = 1 bar.
b
Pump type: CR 16, 50 Hz.
3
Flow rate: 16 m /h.
NPSH (from page 69): 1.5 metres head.
H = 3.0 metres head.
f
Liquid temperature: +60°C.
H (from fig. E, page 66): 2.1 metres head.
v
H = p x 10.2 – NPSH – H – H
b f
H = 1 x 10.2 – 1.5 – 3.0 – 2.1 – 0.5 = 3.1 metres head.
This means that the pump can operate at a suction lift of maxi-
mum 3.1 metres head.
Pressure calculated in bar: 3.1 x 0.0981 = 0.30 bar.
Pressure calculated in kPa: 3.1 x 9.81 = 30.4 kPa.

4.5 Maximum inlet pressure

Figure B, page 64, shows the maximum permissible inlet pres-
sure. However, the actual inlet pressure + pressure when the
pump is running against a closed valve must always be lower
than the "maximum permissible operating pressure".
If the system and the pumps are to be pressure-tested at a pres-
sure higher than that stated in fig. B, page 64, the pump shaft
must be locked to prevent axial movement.

4.6 Electrical data

See motor nameplate.

4.7 Frequency of starts and stops

Motors up to 4 kW: Maximum 100 times per hour.
Other motors: Maximum 20 times per hour.
Hf
NPSH
Pb
Hv
– H
v s
indicates the system pressure
b
– H [metres head].
v s

4.8 Dimensions and weights

Dimensions: See fig. C, page 65.
Weights: See label on the packing.

4.9 Sound level

See fig. D, page 66.

5. Installation

The pump can be installed vertically or horizontally, see fig. 4.
Ensure that an adequate supply of cool air reaches the motor
cooling fan. However, the motor must never fall below the hori-
zontal plane.
Fig. 4
Arrows on the pump base show the direction of flow of liquid
through the pump.
Figure C, page 65, shows the dimensions of the base as well as
the diameter and the position of the foundation bolt holes.
To minimize possible noise from the pump, it is advisable to fit ex-
pansion joints either side of the pump and anti-vibration mount-
ings between foundation and pump.
Port-to-port lengths and pipework connections appear from fig. C,
page 65.
Isolating valves should be fitted either side of the pump to avoid
draining the system if the pump needs to be cleaned, repaired or
replaced.
Install the pipes so that air locks are avoided, especially on the
suction side of the pump. Correct pipework shown in fig. 5.
Fig. 5
Pos.
Description Function
no.
Expansion Reduces noise and absorbs vibra-
1
joint tions and expansion.
Isolating valve Enables easy service of the
2
pump.
Pipe hanger Supports pipe and absorbs distor-
3
tion and strain.
Note: The pump must always be protected against backflow by
means of a non-return valve (foot valve).
1 2 3
3
1 2
5