Check Valves; Temperature Rise; Electrical Connection; Motors - Grundfos CR Serie Instrucciones De Instalación Y Operación

8.9 Check valves

A check valve may be required on the discharge side of the pump
to prevent the pump inlet pressure from being exceeded.
When a pump with no check valve is stopped because there is no
demand on the system (all valves are closed), the high system
pressure on the discharge side of the pump will "find" its way
back to the inlet of the pump.
This is especially critical for CRN-SF applications because of the
very high discharge pressures involved. As a result, most CRN-
SF installations require a check valve on the discharge piping.

8.10 Temperature rise

It may sometimes be necessary to stop the flow through a pump
during operation.
When the flow is stopped, the power to the pump is transferred to
the pumped liquid as heat, causing a temperature rise in the
liquid.
The result is risk of overheating and consequent damage to the
pump. The risk depends on the temperature of the pumped liquid
and for how long the pump is operating without flow. See the
following temperature rise table.
Time for temperature rise of 18 °F (10 °C)
Pump type
Seconds
210
CR 1s, 1, 3
240
CR 5
210
CR 10
150
CR 15
120
CR 20
CR 32, 45, 64,
60
90, 120, 150
Conditions/reservations
The listed times are subject to the following conditions/
reservations:
• No exchange of heat with the surroundings.
• The pumped liquid is water with a specific heat capacity of
Btu kJ
1.0 / °F (4.18 / °C).
lb. kg
• Pump parts (chambers, impellers and shaft) have the same
heat capacity as water.
• The water in the base and the pump head is not included.
These reservations should give sufficient safety margin against
excessive temperature rise.
The maximum temperature must not exceed the pump maximum
temperature rating.
16

8.11 Electrical connection

8.12 Motors

Grundfos CR pumps are supplied with heavy-duty, 2-pole
(3600 rpm), ODP (open drip-proof) or TEFC (totally enclosed fan
cooled), NEMA C frame motors selected to our rigid
specifications.
Motors with other enclosure types and for other voltages and
frequencies are available on a special-order basis.
CRN-SF pumps are supplied with an IEC (metric) type motor with
a reverse thrust bearing.
If you replace the pump, but keep a motor previously used on
another CR pump, be sure to read
Minutes
proper adjustment of the coupling height.
3.5

8.13 Position of terminal box

4.0
The motor terminal box can be turned to any of four positions in
steps of 90 °.
3.5
To rotate the terminal box, remove the four bolts securing the
2.5
motor to the pump but do not remove the coupling. Turn the motor
to the desired position; replace and securely tighten the four
2.0
bolts. See fig. 11.
1.0
Position 9:00
Fig. 11 Motor terminal box positions (top view)

8.14 Field wiring

Lead sizes should be based on the current carrying properties of
conductors required by the latest edition of the National Electrical
Code or local regulations. Direct-on-line (DOL) starting is
approved due to the extremely short run-up time of the motor and
the low moment of inertia of the pump and motor. If DOL starting
is not acceptable and reduced starting current is required, use an
auto transformer, resistance starter or soft starter. We suggest to
use a fused disconnect for each pump in case standby pumps are
installed.
Warning
The safe operation of this pump requires that it is
grounded in accordance with the National
Electrical Code and local codes and regulations.
Connect the ground conductor to the grounding
screw in the terminal box and then to the
ACCEPTABLE grounding point. All electrical
work must be performed by a qualified electrician
in accordance with the latest edition of the
National Electrical Code and local codes and
regulations.
12. Maintaining the motor
Discharge
Position 12:00
Standard terminal
box position (6:00)
Suction
for
Position 3:00