Looking for the right pump solution can sometimes be a daunting task – especially with the array of pump terminology out and about in the marketplace. To help you make sense of it all, we have tried to further explain what some of the most common pump terms actually mean - and what it means to you.
Non self-priming pumps cannot handle air within their inner workings, and they must constantly have a ‘flooded suction line’, meaning that they operate best below the level of the water source.
Self-priming pumps are able to handle some air within their systems by mixing it with water that is already within their inner workings. These pumps are designed to be able to draw water up from beneath them – and are called self-priming pumps. These pumps can be used for pumping water from a below ground rainwater tank, or from sources of water below the level of the pump. If you have an above ground rainwater tank, and the tank is at the same level as the outlets, you do not need a self-priming pump but it may help with pump priming problems caused by air leaks sometimes found in suction pipes. Many pumps nowadays have self-priming capabilities, but can be used for ‘standard’ installations.
Variable Speed / Variable Frequency / Constant Pressure
Fixed or single speed pumps operate by delivering a band of pressure between a pre-set minimum and maximum pressure. The pressure at the outlets is likely to vary depending on the amount of water being used and the level of the water source (as the water in a tank lowers the pressure at the taps will also drop). Some pumps are able to deliver water at a constant pressure by controlling the speed of the pump. That means that the pump has a controller that automatically adjusts the pumps speed to deliver constant water pressure to the outlets, regardless of the number of outlets open at any one time (up to the pump’s capacity). A variable speed pump changes the speed by the controller adjusting the Frequency (Hz) of the power supplied to the motor. This is why some call constant pressure pumps Variable Frequency pumps.
By using a variable speed pump that adjusts according to water demand, the energy consumption is generally lower, resulting in lower costs. They also provide greater comfort, in that the pressure at the tap is constant, regardless of the demand (up to the pump’s capacity) or the inlet pressure.
Dry Run Protection / Dry Running Protection
You may have also seen the words dry run protection used when looking for information on pumps. Dry run or dry running protection is when a pump is intuitive enough to identify when the water source from which it’s running has run out, for example when the water tank is dry. The pump will automatically switch off upon detecting the lack of supply water, protecting the pump from incurring any damage. Some pumps have an automatic re-start function, which will try to re-start the pump at regular intervals to check whether water has become available.
A ‘pump cycle’ is the start and stop of a pump. Some applications may cause a pump to ‘cycle’ or start and stop repeatedly in a short period. This repetitive starting can cause motor, control or pump failure and can also cause pressure fluctuations that may lead to failure of the pipe or other fittings. Cycling will definitely cause discomfort for the user, especially when the water is used for applications where hot and cold water is mixed. A pump that has an anti-cycling feature will protect it from failure when cycling is detected.
Some pumps an also feature built in thermal protection in the motor or control panel. Thermal protection is incorporated into pumps to protect the motor and components from dangerous overheating that can cause pump failure. Overheating generally occurs when the motor is overloaded, bearings seize up or something locks the motor shaft from turning. When this happens, excessive heat builds up in the motor. Pumps with thermal protection will automatically trip the motor circuit to keep it from burning and damaging the motor.
AS/NZS4020 is an Australian and New Zealand standard awarded to products that comes in contact with drinking water. The standard ensures that products do not affect the taste or appearance of water, do not support the growth of microorganisms and do not release cytotoxic or mutagenic compounds or metals. If your pump is AS/NZS4020 approved you can be sure that it is not affecting the water that passes through it, making it safe to use for pumping water that you plan to drink.
Most pumps available on the market these days are available with a pump controller such as a pressure switch and pressure tank or pressure manager. There are also constant pressure options, which have already been explained above.
A pump controller is used to automatically start or stop the pump when water is required. So, instead of constantly running when you don’t need it, it will only start when it’s required, triggered by a decrease in pressure in the system when an outlet is opened. Some controllers have an adjustable starting pressure, so you can nominate the pressure at which the pump should start.
A pressure tank and switch allows for the pump to start and stop based on system pressure. The tank provides small volume water draw off before the pumps starts. For example, if you use a small amount of water to wash your hands, the water is drawn from the pressure tank without turning the pump on. When more than a small demand is required, the water will be drawn from the tank and the pressure differential will start the system to pump water to the outlet.
A pump without a pump controller, pressure switch or pressure tank is called a bare pump. Bare pumps have no control mechanism, and only run when the power is switched on to them and stop when the power is turned off.
Speak to your local Authorised Grundfos Dealer today or visit www.grundfos.com.au/SCALA2 for more information.