Yes, absolutely. The installation and operating instructions contain basic instructions which must be followed in connection with the installation, operation, and maintenance of the system. Hence, they must be read by the installer and the relevant personnel/owner prior to installation and commissioning. In addition, they must be available to personnel on site at all times.
The NPSH curve displays the minimum required inlet pressure (expressed in m) allowing the pump to pump in accordance with the performance curve and in order to prevent evaporation of the pumped fluid so as to avoid cavitation inside the pump.
At a given flow rate, the NPSH value available at the pump's suction ports must always be at least 0.5 m greater than the required NPSH value:
NPSHA > NPSHR + 0.5 m safety margin
Cavitation is the formation and abrupt collapse of vapour-filled bubbles. This process takes place at points inside the pump where the pressure falls below the vapour pressure of the pumped medium. The vapour pressure of a liquid is the pressure at which the liquid begins to boil or evaporate. Cavitation, which may damage the pump, occurs when the net positive suction head (NPSHR) needed by the pump is not available.
In order to avoid cavitation, a minimum pressure referred to as the net positive suction head available (NPSHA) must be present at the suction port so that the liquid does not boil or evaporate. It must be ensured that the pressure applied at the suction port is always greater than the vapour pressure of the liquid at a given temperature of the medium.
Note: If a pump cavitates, the control valve on the pressure side should be throttled in order to reduce the flow rate and thus the NPSH value required by the pump. However, it must be ensured that the flow rate remaining is large enough to sufficiently cool and lubricate the pump.
The term "inlet mode" refers to a suction state with positive inlet pressure in which the pumped medium is supplied from a point located above the pump's suction port and which is in contact with the atmosphere (open system). This means that the pressure applied at the pump's suction port is greater than or equal to atmospheric pressure.
The term "suction mode" refers to a suction state with negative inlet pressure at which the pumped medium is supplied from a point located below the pump's suction port and which is in contact with the atmosphere (open system). This means that the pressure applied at the pump's suction port is less than or equal to atmospheric pressure. Centrifugal pumps always require sufficient inlet pressure in order to ensure that pump output is in accordance with the performance curve.
The available NPSH is crucial to proper operation. This is a system parameter that must be greater than the pump's required NPSH value plus a safety margin of at least 0.5 m:
NPSHA > NPSHR + 0.5 m safety margin
When a pump operates too far to the right on the curve, this simply means that the pump is delivering a flow rate greater than that for which it was designed. In other words: The pump is too small for the volume flow needed by the system. Operating the pump in this range may cause damage to the pump and the motor.
The pump must always be operated within the lower and upper flow rate bounds. Ideally, the pump should be operated as close as possible to the point of optimal efficiency in order to ensure a long service life and in order to minimise energy consumption.
If the pump is operating too far to left on the curve, this simply means that the pump is delivering high pressure but at a flow rate that is low or non-existent. High pressure inside the pump stresses the impeller unit and thus increases pressure on the motor bearings. In the extreme case, this will cause damage to the pump and motor. If the flow rate is below the minimum flow rate required for the pump, the pumped medium may also overheat and damage the pump. For this reason, the pump must always be operated inside the lower and upper flow rate bounds. Ideally, the pump should be operated as close as possible to the point of optimal efficiency in order to ensure a long service life and in order to minimise energy consumption.
Solid particles in the pumped medium generate friction, which leads to abrasion of the material. This is a frequently occurring problem in sewerage technology caused by sand in the pumped medium, which destroys pump components like impellers.
The operating instructions provided with every Grundfos product contain relevant troubleshooting information. These instructions describe not only installation, operation and maintenance, but also include a dedicated section to assist in troubleshooting general problems that arise during use. This information is also available via the WebCAPS program.
As an installer, you have the choice of ordering Grundfos customer service from your specialist wholesaler or of contacting us directly.
Please have your customer number ready, should you choose to contact us directly. If you are unsure about whether you have a customer number or not, please send us a copy of your company letterhead.
As a private customer, we ask that you refer to a specialist installation company in your area.
These days, heating systems are designed as hydraulically closed systems. This means that the building height need not be taken into account when designing the pump.
When determining the delivery head for heating pumps, the critical factor is the pipework resistance, including all individual resistances, such as that of e.g. fittings and bends.
De-energise the pump. Remove the screw in the centre of the nameplate. The shaft located beneath this has a groove. Place a screwdriver in the groove and move the shaft in the direction of rotation until you have removed the blockage.
Modern self-regulating heating pumps no longer have a screw in the centre of the nameplate. However, the modern pumps have an anti-block feature. Should a blockage nevertheless occur, the pump head must be removed.
Caution: Hot water may leak out. Please comply with the safety instructions in the installation and operating instructions.
A: Circulator pumps are generally used to circulate hot water. The temperature of the pumped medium is transferred to the pump, and it is normal for the pump's surface to be warm or even hot.
B: The pump's rotor may have become blocked by worn bearings or dirt. Replace the pump and clean the system.
A: Air in the system leads to noise. The entire system must be inspected and bled.
B: The pumps may be oversized for the system in question. To fix this, throttle the pressure-side valves until the noises are eliminated.
C: The water in the system is boiling because the pump is undersized. This can be remedied by installing a larger pump.
D Excessive wear of bearings (rattling). The pump needs to be replaced.
S: A system that has already been entered into operation has become clogged. The system needs to be cleaned.
Circuit breakers and fuses trip for numerous reasons: Undervoltage, incorrectly designed circuit breaker or fuses, too low a setting for the motor-protective circuit breaker, asymmetric three-phase current, a short circuit on the motor, incorrect wiring or faulty electrical connections, a worn or blocked pump, a defective capacitor for single-phase motors, a motor-protective circuit breaker exposed to a higher ambient temperature than the motor.
However, the pump may also be undersized for the application in question, and may be operating in excess of its nominal flow rate.
The pump is running sluggishly or not at all. This can be remedied by replacing the capacitor.
(only on some types the capacitor can be replaced).
The pump curve of a heating pump displays the feed rate on the x-axis and the delivery head on the y-axis. The pump curve shown in the graph is curved, dropping off from left to right.
Every possible duty point of the pump is shown on the pump curve where the dependencies are as follows: High feed rate = low delivery head; low feed rate = high delivery head.
In a heating system, a system curve emerges as a function of the system hydraulics. This curve intersects with the pump curve at a point representing the duty point of the pump.
The dynamic total delivery head is also referred to as the "delivery head" or simply as the "total delivery head". In the technical literature, the total delivery head is defined as the work that needs to be performed by the pump to pump the medium with reference to a defined unit of weight. Expressed more simply, the delivery head is equal to the pressure measured at the discharge port minus the inlet pressure applied at the suction port. The delivery head is generally specified in m. Generally speaking, the delivery head is represented together with the flow rate in the form of the QH curve.
Flanges and seals need to be ordered separately. The type and size of the flanges and seals must be specified when ordering.
In the case of non-regulated fixed speed pumps, an overflow valve limits rising pressure when closing the radiator thermostat by moving the medium from the flow pipe to the return pipe.
When installing differential pressure-regulated pumps, you should remove or block overflow valves, as two control loops might have a disruptive influence on one another. It is possible that the safety guidelines issued by the manufacturers of heat generators will advise against so doing. Please observe the manufacturer's instructions.
The pump reacts to changing volume flows in the system by changing the speed. When thermostat valves and control valves are opening, the volume flow rises and the pump increases the speed. When valves are closing, the pump reduces the speed. This also reduces power consumption. In order for this type of control to function reliably, it is necessary to perform a hydraulic balancing of the pipe network.
Hydraulic balancing of the pipe network is required in order to avoid oversupply/undersupply of individual pipe trains and consumers. This ensures optimal, low-noise heat distribution.
Hydraulic balancing is performed using pipe train regulating valves and thermostat valves with preset or adjustable lockshield valves.
No, this is not possible, since the housing and the heads are designed to fit together.
Flow noise is caused by the friction of the medium at bottlenecks in the pipe network, e.g. at the valve openings of thermostat valves. This can be remedied by reducing pump output.
In order to ensure even, low-noise heat distribution without oversupply or undersupply to any pipe trains or consumers, hydraulic balancing of the pipe network is required.
No, this is not permitted, as pump components that have come into contact with pumped media are not suitable for use in drinking water systems.
In this pump design, all rotating parts (shaft, rotor, impeller) are located within the can in the pumped medium. Cooling and lubrication is provided by the pumped medium.
Dry running, also referred to as inadequate lubrication, occurs when there is air in the rotor chamber, meaning that rotating parts are not cooled and lubricated as they should be. Dry running leads very rapidly to destruction of the pump.
Reasons may include inadequate ventilation of the pump. In the event of installation at the highest point of the heating system, incorrect pre-pressure in the expansion vessel may cause air to enter. Vapour formation in the pump due to excessive temperatures.
In a dry-running pump, the component that comes into contact with the medium (the wetted part) is separate from the motor. The seal of the pump shaft in the wetted part is provided in the form of a mechanical seal. The pump is driven by a motor connected to the pump shaft by a coupling.
Yes, that is possible. To do so, connect one phase and the neutral conductor. The voltage between phase and neutral is 230 V.
If there is no neutral conductor, a new cable must be routed. Such work must only be performed by a qualified electrician.
If excess temperature protection is not properly connected or bridged, the pump may be permanently damaged. In addition, this will also void the pump's warranty.
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