- What is/causes water hammer?
Water hammer is a pressure surge caused by a rapid change of water velocity in a piping system. Water hammer is often accompanied by a sound comparable to a hammer hitting a pipe, hence the name. In water well systems, water hammer is typically caused when
a) the check valve installed in the drop pipe nearest the pump is more than 9 m above the standing water level, or
b) the check valve installed in the drop pipe leaks while the next check valve above holds.
In both situations a partial vacuum is created in the drop pipe. On the next pump start, water moving at very high velocity fills the vacuum and strikes the closed check valve and the stationary water in the pipe above it, causing a pressure surge and hydraulic shock. This shock can split pipes, break joints and damage the pump and/or motor. When discovered, the system should be shut down and the pump installer contacted to correct the problem.
- What is the NPSHR curve and the relevance of it?
The NPSHR curve (Net Positive Suction Head Required) shows the amount of suction head for a given flow, the NPSH available at the inlet of the pump must exceed the value shown on the NPSHR curve by 0.6 m: NPSHA > NPSHR + 0.6 m for safety.
- What happens when you run a pump beyond the right-hand side of the curve?
Operating a pump beyond the right-hand side of the performance curve is another way of saying that the pump is producing more flow than it is designed for. It means the pump is undersized for what the system actually requires, and operating a pump in this way can damage both the motor and pump end.
A pump must be operated within its minimum and maximum flow limits at all times, and ideally the pump should be operated as closely as possible to the best efficiency point to ensure long life of the product and minimise energy consumption.
- What happens when you run a pump on the left-hand side of the curve?
Running the pump on the left hand side of the curve means that the pump is running at a high pressure and at a low or no flow condition.
High pressure in the pump drives down the impeller stack and increases pressure on the motor bearings. In extreme conditions this will cause failure of both the motor and pump end. If the flow is less than the pump's minimum flow requirement, the fluid in the pump may overheat and damage the pump.
A pump must be operated within its minimum and maximum flow limits at all times, and ideally the pump should be operated as close as possible to the best efficiency point to ensure long life of the product and minimize energy consumption.
- What is the maximum allowable fluid temperature?
The maximum operating temperature for a sump/sewage or effluent pump is determined by whether the pump is run in continuous or intermittent operation under fully submerged conditions.
Please refer to the Installation & Operating instructions (I&O) for your product.
Consult Grundfos regarding high temperature applications.
- What is the maximum inlet pressure?
Please refer to the Installation & Operating instructions (I&O) for your product.
- Can Grundfos Commercial/Industrial pumps be safely operated outdoors with no weather protection?
In order to maximize the life of the motor and pump, some form of weather protection should be used.
Examples range from a simple rain shield to protect the pump from direct rain, or an insulated housing with space heaters to protect from freezing temperatures.
- What will happen if the pump is not emptied correctly in case of frost?
In the worst case the intermediate part of the pump, which includes pump foot and discharge, will burst.
- What is the importance of the proper design of bypass lines?
Sufficient flow through a pump is required to ensure that adequate cooling and lubrication of the pump is maintained at all times.
Inadequate cooling and lubrication will result in overheating, bearing wear, friction between the seal faces, seal leakage, and ultimately cause premature pump failure. A bypass line should be installed if there is any possibility that the pump may operate under its minimum flow requirements. The bypass line should run from the pump vent or discharge pipe back upstream of the pump as far as practical or into a tank to allow sufficient cooling of the liquid. The liquid from the bypass line must have the opportunity to cool down before re-entering the pump in order to prevent overheating of the pump. For this reason, never run the bypass line directly back to the pump inlet.
A properly sized bypass is one that satisfies the pump's minimum flow requirement, as stated in the data booklet for each pump.
Grundfos offers bypass orifices, sized for each pump model. Please note that during periods of full demand the combined flow through the system and bypass must not exceed the maximum flow rate of the pump.
- Which shaft seal do I need for my application?
Grundfos offers bellows and O-ring style mechanical shaft seals in its commercial/industrial products. The standard shaft seal in each pump has been designed and selected to meet the needs of typical water applications and some chemical applications.
However, some specialty applications may require different seal-face materials and different O-ring or bellows materials than in the standard seal. Grundfos offers a wide variety of seal-face material combinations such as carbon/tungsten carbide, tungsten carbide/tungsten carbide, carbon/ceramic, and silicon carbide/silicon carbide. O-rings are available in EPDM, FPM (FPM is similar in properties to Viton®), Chemraz, and Kalrez while the bellows material choices are limited to EPDM and FPM.
Shaft seal selection is based on several factors such as pressure, temperature, chemical compatibility, presence of abrasives, and viscosity. If you need help selecting a shaft seal for a specialty application, please contact a Grundfos Service Centre for assistance.
Viton® and Kalrez are registered trademarks of DuPont Dow Elastomers, and Chemraz is a registered trademark of Green, Tweed & Co.
For further information regarding shaft seals please see the Grundfos Product Center, data books and/or I&O information.
- My circulator is noisy (humming or chattering). Is it normal? What can I do?
- 1. Air in the system is causing noise. Air must be purged from entire system.
- 2. Pump may be oversized for system. Remedy is to throttle back valves until noise quiets down, or replace the pump to a proper size.
- 3. System may be boiling due to an undersized pump. Remedy is to re-size pump for the system
- 4. Excessive bearing wear (chattering). Pump must be replaced.
- 5. System may be clogged (old system). A remedy is to clean the system.
- What does it mean when my circulator feels hot to touch?
- 1. Circulators are typically used to pump hot water, so a warm or even a hot circulator is normal.
- 2. Pump may be dry running. Check flow.
- 3. Pump may have locked rotor due to worn bearings or dirty system. Clean or replace pump and clean system.
- Why is my motor running hot?
Because of modern design and manufacturing techniques, it is typical for many of today's motors to run hotter than those in the past. In fact, it is not uncommon for the surface temperatures of some newer motors to reach as high as 90°C (194°F) while maintaining and even exceeding the life of motors made in the past.
This means that a "hot" motor is not necessarily an indication that something is wrong. However, if the motor in your pump application seems to be running uncharacteristically hot, there are several situations that may be causing this condition:
- Electrical: Under or over voltage, unbalanced three-phase power, and a loss of insulation resistance;
- Environmental: High ambient temperatures, lack of ventilation, and high altitudes (thin air);
- Mechanical: Excessive cycling, too low or too high a flow rate, high rotating resistance by a damaged pump, high viscosity or specific gravity liquid, or obstruction in the pump.
- What should I do if my pump motor is exceeding full load amperage?
There are several reasons why the pump may be exceeding full load amperage:
Low supply voltage, three-phase current is imbalanced, motor is shorted or grounded, wiring or connections are faulty, viscosity or specific gravity too great, and pump is bound or worn.
All of these possibilities and their solutions are discussed in the "Troubleshooting" section of the Installation and Operating Instructions (I&O) that comes with the product.
The pump might also be undersized for the application and operating beyond its rated flow. In this case try throttling the discharge valve on the system back toward the closed position until pump motor amps are within limits. Also, in some cases it is normal for a Grundfos pump to exceed the motor's rated full load amperage.
- The overloads on my motor starter are tripping (or fuses are blowing). What’s wrong?
There are several possible reasons for tripping overloads or blowing fuses. These possibilities and their solutions are discussed in the "Troubleshooting" section of the Installation and Operating Instructions (I&O).
The pump might also be undersized for the application and operating beyond its rated flow. In this case try throttling the discharge valve on the system back toward the closed position until motor amps are within limits.
- What happens in case of under-voltage? (below std. voltage - 10%)
1. Std. motor: The surface temperature will increase. The motor will be overloaded, and will cut off by means of the thermal contact or the thermal relay.
2. E-motor: The built in motor protection stops the motor, and restarts when normal conditions are available.
- What happens in case of over-voltage? (above std. voltage + 6%)
- 1. Std. motor: The surface temperature will increase. The motor/pump will turn faster and therefore the power requirement will increase. This results in increased current and the motor will cut off by means of the thermal contact or the thermal relay.
- 2. E-motor: The built in motor protection stops the motor, and restarts when normal conditions are available.
- What are the symptoms a circulator exhibits if it's only a "bad capacitor"? Can it be replaced?
Pump may be slow or sluggish to start, or may not start at all. Remedy is to replace the capacitor or the pump.
- Does Grundfos offer a thermal protection module for the UPS series 200 pump?
Yes, a terminal box/module replacement is available to retrofit the UPS single and three-phase units.
- Is it really necessary that I use the built-in thermal protection for my UPS series 200 pump?
Yes, the warranty on the pump is void unless thermal protection is wired in at all times, and permanent damage can occur to the pump if the thermal protection is bypassed.
- Can I run the pump with a variable frequency drive (VFD)?
Grundfos currently offers a wide variety of "E-pumps"... pumps with the Grundfos MGE integrated variable frequency drive motors.
MGE motors eliminate the higher cost of labour and materials and potential technical problems associated with stand-alone VFD installation. MGE motors also offer an impressive list of features and benefits. In addition to the E-pumps, all three-phase industrial motors offered by Grundfos are suitable for use with variable frequency drives.
- What is minimal rotation speed of motor during the operation with frequency converter?
The recommended minimal rotation speed of motor has to be not less than 25 % of maximal rotation speed.
- Where can I find instructions of installation and operation for a pump/device?
The Installation & Operating instructions (I&O) is enclosed in the pump/device box. They can also be located on the Grundfos Product Center.
- Where can I find troubleshooting information for my Grundfos Product?
The Installation and Operating instructions (I&O) that was supplied with your Grundfos product is an excellent resource for troubleshooting information.
The I&O explains proper installation, operation and maintenance procedures and also contains a troubleshooting section that covers common application problems.
If after you have reviewed the I&O and still need help, please go back to your original point of sale.
- How do I contact Grundfos Service?
Visit http://www.grundfosservice.co.uk/ or telephone 01942 263628