Installer - Domestic

- 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.

 

- Which shaft seal do I need for my application?

For further information regarding shaft seals please see WebCAPs, data books and/or I&O information.

 

- How can small UP, UPS pumps be serviced?

No service is required. Should the pump fail while under warranty, it will be replaced.

 

 

- 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.

 

- Grundfos MAGNA: Is it possible to adjust the set point when the pump runs in automatic?

No, the setpoint is pre adjusted.

 

- 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.

 

- 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.

 

- 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.

 





 

 

 

 

 

 





    Facebook Twitter LinkedIn Technorati