What is a water pump inverter and other FAQs

The 3P Technik UK Technical team has a wealth of knowledge about how to move and control water from place to place in different situations from domestic to commercial. In many larger or complex installations a water pump inverter is a key part of the design. “What is a water pump inverter?” and “How does a pump inverter work?” are just a few of the questions we are asked by people new to this realm. We have put together some answers to our most commonly asked questions about water inverters and variable speed pump controllers.

Water Pump Inverter helps maintain pressure not matter how many taps you have open

Water Pump Inverters maintain the same pressure in the water system no matter how many taps or other outlets you have open …

What is a water pump inverter?

A water pump inverter maintains a constant and stable pressure in a water system by varying the speed of the pump motor to deliver the same pre-set pressure at the outlet regardless of how many outlets or appliances are in use, up to the maximum capability of the pump.

How does a pump inverter work?

An inverter converts one voltage and/or frequency to another. In a pump inverter mains power is output at the same voltage as the supply but with variable frequency. The normally fixed speed of a pump motor is determined by the mains frequency, varying this allows the pumps speed and hence flow and pressure to be controlled. Most pump inverters operate at constant pressure. A pressure sensor on the outlet pipework or built into the inverter itself detects any deviation of pressure from the set point and adjusts the pumps speed accordingly.

Pump inverters in the UK and Europe are usually single phase, three phase, or single to three phase allowing a three phase pump to run from a single phase supply.

Some inverters will allow the output frequency to be set above the usual mains frequency and hence above the design speed of the pump to produce greater flow and pressure than could normally be achieved. However, your pump may not be designed to survive this for very long if at all.

What is a pump pressure controller?

A pump pressure controller is any device that operates a pump based on feedback from a pressure sensing component. This could be an inverter, a fixed speed electronic pressure controller (commonly referrred to as a pressure switch), or a simple mechanical pressure switch with a differential between cut-in and cut-out pressure.

What is a variable speed pump controller?

A “variable speed pump controller” is just another way of saying “inverter”.

Are there different inverters for different situation?

Yes, inverters are commonly either general purpose (DIN rail or wall mounted) and designed for a variety of motor applications including fans, conveyors, industrial mixers and machinery, or they’re specifically designed for pump use.

For use with a pump it’s generally better (and cheaper) to purchase an inverter that’s designed for pumps. In addition there are specific inverters for use with solar pumps (Mac3 Hydrocontroller Solar for example) which adjust their speed depending on available power from DC solar panels. There are also inverters for pool use (Mac3 Hydrocontroller Pool) which aren’t pressure controlled and can be scheduled to produce various flow rates on different days/hour schedules.

There are also add-ons such as the Mac3 Multipress4 Irrigation Interface for adjusting pressure to suit different irrigation zones. Also it’s important to choose one with a multi-inverter mode if you might want to connect 2 or more inverters together either to begin with of later on. These are the Advanced versions in the Mac3 range and will talk to each other using a Canbus system allowing them to work together.

Can a submersible pump run on an inverter?

Yes, although for distances exceeding 20m from the pump to inverter a harmonic filter should be installed.

Do I need a pressure vessel with an inverter?

You need to install a pressure vessel in the system when you use an inverter. This is to allow the inverter time to react before falling pressure is lost, and to slow down at the right point without overshooting it’s set pressure. A much smaller pressure vessel is needed than would be required for a fixed speed installation.

How high can a 1hp pump lift water?

The height the pump can lift water depends on the design of the pump. A narrow and closed impeller (faced on both sides) will produce much more pressure than an open vortex design. The trade-off is pressure vs flow. Vortex pumps commonly move several hundred litres per minute at only a few metres lift.  A small borehole pump may lift water 200m at only a few litres per minute.

What is a split phase inverter?

A split phase supply may be generated from an inverter or a transformer, it is basically a single phase with a centre tapped neutral effectively producing 2 phase conductors with 180 degree offset. This is common for domestic electricity in the United States where the drier outlet carries double the voltage of the wall outlets. In UK/Europe this arrangement is not usually supplied and so there is no demand here for inverters to replicate this.

How does a pipe mounted/water cooled inverter work?

A pipe mounted inverter differs from an air-cooled inverter in that it is mounted upon a section of pipe through which the pumped water passes. This gives it the advantage of being able to cool itself with the water it’s pumping with no need for a cooling fan. However, it comes with the potential disadvantages of having to run the pipework to the inverter, and restricting the pipe size to that of the pipe built into the inverter.

The temperature of the water to be pumped is important for a pipe mounted inverter.

Pipe mounted or water cooled inverters are commonly found on pre-built multi-pump booster sets.

When should I choose a pipe mounted inverter instead of a wall mounted inverter?

You should choose a pipe mounted inverter when you know that the inverter will:

  • be mounted in the same room as the pipework
  • that pipework can run vertically through the inverter and,
  • won’t be limited in performance by the size of the pipe in the inverter itself, typically 1” or 1.25”.

Or, when the inverter is going to be situated in a warm temperature and air cooling may not suffice.

You should NOT choose a pipe mounted (water cooled inverter) if:

  • you need to pump warm water,  or
  • the inverter is somewhere where it may freeze.

How do I replace my inverter with another brand, what are the parameters I need to select?

Select an inverter which exceeds the rated maximum Amps and power (Kw or HP) stated on the identification plate of your pump. Be sure to select either single phase for a single phase 230VAC pump, three phase for a 400/415VAC pump, or single to three phase for a three phase 230VAC pump (UK/European voltages assumed).

Is Mac3 a good brand, how do I know that?

Mac3 products are manufactured entirely in Italy to high standards since 1981 and have acquired a reputation for dependability. Mac3 products are a trusted source of OEM level and pressure control components to many high-end global pump manufacturers including Pedrollo, Grundfos and Lowara.