VFD Variable Frequency Drive Pumps

Applications & Benefits of VFD Constant Pressure Pumps & Motors

There is a wide range of applications in which VFD pumps are most-suitable, particularly where variable torque is useful such as in centrifugal pumps used in handling wastewater or in supplying varying needs of potable water.

• Economy of operation & water use,
  
  by matching the load on a water pump's motor to the amount of electrical energy it needs to support that load.
• Reduced water tank storage:
  
  domestic water supply applications where tap water is provided by pumping directly from the water well without an intermediate pressure tank, reducing the requirement to store a quantity of water that may become stagnant or non-potable if demand is intermittent or where the water usage rate requirement varies widely over time or season.
• Fountains
  
  using pressure change for decorative purposes ("dancing fountains")
• Geothermal wells
  
  used to provide constant temperature control in buildings, achieved by varying the water flow rate through the heat exchanger
• Groundwater control
  
  in mines or construction projects
• Hydraulic shock and water hammer
  
  in the plumbing system are reduced. Hydraulic shock can cause of annoying water hammer or even of leaks that in turn can cause water damage or may compromise a TPR relief valve
• Increased pump component life:
  
  because the VFD pump ramps up to necessary speed gradually and because during most of its use the pump doesn't run at full speed, the life of its wear-components such as pump and motor bearings, seals, and the impeller assembly are increased.
• Increased pump motor life:
  
  also, because a VFD pump motor is brought up to necessary speed gradually it is subjected to considerably less starting torque and wear than a conventional pump motor that is turned on by an instant supply of full voltage. The VFD pump motor life is increased and its maintenance costs are reduced.
• Water usage rate control
  
  where the supplying aquifer is of limited capacity, limiting the water withdrawal rate to match the aquifer's delivery capacity, thus avoiding over-pumping that can damage the water source; we add that by avoiding over-pumping you also avoid the damage that occurs to a conventional pump if it is run dry after exhausting the water supply.
  
  - Adapted from
  
  Grundfos, "The Advantages of frequency drive operation in submersible pumps", Grundfos Pump Co., retrieved 2022/05/30 original source: https://www.grundfos.com/solutions/learn/ecademy/all-courses/the-sp-submersible-pump/the-advantages-of-frequency-drive-operation-in-submersible-pumps
  
  MPT, "The Benefits of Variable Speed Pumping" Modern Pumping Today Magazine, (2016) retrieved 2022/05/30 original source: https://modernpumpingtoday.com/benefits-of-variable-speed-pumping/

Really? Well in opinion, yes, the above applications and our own use experience with VFD pumps provides ample and economical justification for their use.

But we were stunned to find, in researching this topic, that Cycle Stop Valves, a company producing a device intended to protect pumps from damage from short-cycling, has written what is in our view a highly-opinionated, self-serving Cyclestop article [PDF] claiming that VFD pumps are unnecessary, a scam, and supported by lies and false claims.

It's fair to say that not all plumbers are fans of VFD pumps and some dislike specific brands and models that in their experience were troublesome. However we should not confuse opinion with more-reliable unbiased research.

Our review of that Cyclestop Valve article found it to be factually incorrect. Which in our OPINION is too bad since other than shooting themselves in their own foot by those claims, Cycle Stop valves are a perfectly-legitimate, functional product.

We're disappointed in Cycle Stop whose product we've described in detail

at WATER PUMP SHORT CYCLE STOP VALVE

Watch out: a cycle stop valve is not a proper repair for a well pump that is short cycling - turning on and off rapidly, perhaps every few seconds or four or more times a minute when water is being run. If your well pump is cycling rapidly in that manner, before installing a cycle stop valve, check for a water-logged pressure tank.

Some Pressure Sensitive Water Pumps Omit Water Pressure Tank

Water pressure booster pumps including models that omit the need for a separate water pressure tank are used as building water pressure boosting systems, irrigation system water pressure improvements, agricultural and horticultural applications, and in industrial processes requiring a constant water pressure and flow rate.

Other VFD and pressure booster pumps are designed to work with a small pressure tank (municipal water pressure boosting) or a much larger one (well water systems).

Above is the Simer Water Pressure Booster pump illustrated by the manufacturer.

Shown above are two water pressure booster pumps that use a pressure-sensitive control and omit the requirement for a water pressure tank

. At above left is a 1 1/2 horsepower pressure booster pump suitable for a whole-house water system pressure boost, while at right in that illustration is the Simer 3/4 HP inline "on demand" pressure booster pump.

Shown above: a Grundfos SCALA2 (aka ScalaII or Scala II or Scala-II) tankless water pressure pump in process of being installed atop a home in San Miguel de Allende, Mexico in March 2017.

• Grundfos Domestic Water Pressure Boosting Pumps, Grundfos CME Plus, BMQE system, and MQ series pumps are designed for pressure boosting systems, Grundfos Pumps Corporation 2001
  
  Butterfield Road, Suite 1700 Downers Grove, IL 60515, Website: https://us.grundfos.com
  
  Grundfos Indianapolis – Peerless Brand: 1-800-879-0182
  
  Grundfos Chicago – Yeomans, Morris, Chicago Brands & Grundfos Wastewater Products: 1-800-921-7867
  
  Grundfos Kansas City – Grundfos Brand: 1-888-237-1960
  
  Grundfos Brookshire – PACO Brand: 1-800-955-5847
  
  The Grundfos SCALA2 pressure pump was installed the property shown in the photograph above in March 2017.
  
  Some important features that we found were that the pump is extremely quiet, and when running at its low speeds is unlikely to be heard outside of a utility or mechanical room at most installations.

Though the pump is very quiet we also mounted it on rubber pads (white arrow) to reduce noise transmission through the concrete roof that also forms the ceiling of an office located immediately-below.

I'm still a fan of this sophisticated pump, though by December 2018 this unit had a main seal leak (yellow arrow) about 20 months after original installation (March 2017).

See its performance discussed at

• WATER PUMP NOISE DIAGNOSIS - noisy Scala 2 improved by mounting on rubber padding
• - noisy Scala 2 pump due to seized, failed motor bearing
• Grundfos Scala 2 PUMP MANUALS [web article] provides details about this pump & a full set of installation & operation manuals, features, service history, warranty replacement information as free PDF downloads.
• GRUNDFOS SCALA2 DATA SHEET [PDF] retrieved 2017/03/26, original source: http://us.grundfos.com/content/dam/GPU/Literature/SCALA2/SCALA2-DATASHEET.pdf

Other VFD pumps and their suppliers are given below on this page.

Water Pressure Booster Pump Installation Notes & Warnings

Generally your pump should be installed in a dry area, protected from the weather and from freezing. Some units like the Scala 2 are also rated for outdoor use.

Check the pump manufacturer's installation instructions for the proper location of check valves in the piping system. Some pressure boosting pump models include a built-in check valve while others require an external valve or if pumping from a well, a foot valve.

Watch out: Check the pump manufacturer's advice about the maximum allowable input water pressure. If you are using the pump to boost building water pressure, for safety you may be required to install a pressure reducer/regulator on the municipal water supply line to limit the water pressure into the pump to a maximum of 20 psi (or other pressure specified by the pump manufacturer.

Watch out: warnings in the installation instructions for some of the pressure booster pumps we examined advise that you should never allow the pump to run "dry" as the pump will be damaged.

The pump body and suction line must be filled with water before the pump is turned on.

Watch out: sand and debris, such as from water obtained from a driven point well can damage the pump.

If there is sand, sediment or debris in the water supply protect the pump with an appropriate filter on the suction side of the pump.

Watch out: for leaks in the plumbing system that can damage the booster pump or that may show up in response to new, higher water pressure levels in the building or due to banging pipes that may occur due to increased water velocity when the tankless water pressure booster pump is installed.

VFD Water Pump Pressure Tank Settings

On constant pressure or VFD water pump systems, some designs use a pressure tank, either a small 2-gallon tank or a larger one.

The small pressure tank smooths out the VFD pump's water deliver at low flow rates and in the factory or default 2-gallon size, is used when the VFD pump system is functioning in an individual home or building as a pressure booster for a municipal water supply system.

Where a VFD pump system is used with a large water storage tank as a re-pressurizing system or with well water supply, often a larger water pressure tank will be installed as well, configured as shown below.

Our examples here make use of Gould's 13159RB115, ResiBoost Series, BOOSTER SYSTEM with TANK for which the IO manual is given from Xylem below on this page.

What's the correct pressure tank setting for use with a VFD water pump / controller?

Our reader asked:

What pressure should I set my expansion tank bladder at on a Constant Pressure Well System? My VFD is set at 60 PSI on the controller.

I have a 2 gallon Well-X-Trol expansion tank. On 2023-05-08 by Larry Grotenhuis -

Answer by InspectApedia Editor (mod) - pressure tank is set to 20 psi below the VFD pump pressure setpoint

@Larry Grotenhuis,

Thanks, that's a really helpful constant pressure pump + pressure tank settings question.

Why is there a little pressure tank at all on a VFD constant pressure water pump system?

The answer is that at very low flow rates, such as a single toilet flush tank re-filling, the pressure tank can let the VFD pump rest - at use rates that are so low that they're below the low-end of the pump's intended/expected delivery rate.

This is avoiding what can be more of a problem than one might think. For example, at the variable flow Scala 2 pump we use for lots of examples in this article series,

see
https://inspectapedia.com/water/Water_Pump_Pressure_Sensitive.php VARIABLE FREQUENCY / VARIABLE SPEED DRIVE WELL PUMPS (VFDs)

we found that when the water softener system is running in regeneration mode the flow rate can be so long and so slow that the VFD pump thinks that there is a water leak somewhere. That can cause the VFD pump's protection circuit to actually shut the pump off entirely, fouling up the softener's regeneration process.

What is the proper pressure tank setting for a VFD water pump system?

- an example answer, using the Xylem Goulds 13159RB115, ResiBoost Series, Booster System with Tank IO MANUAL

the company says

Set the air pressure (pre-charge) in the tank with the tank empty of water.

Pre-charge must be adjusted to be 20 psi below the Pressure Setpoint (SP) based on 5 psi pressure drop.

Notice that this is significantly-different than the "2 psi below pressure switch cut-in" for conventional pump and tank systems.

So you set the required operating pressure of your water system (that's the SP given above) using the pump's set-up instructions, then set the tank pre-charge as we just indicated, to 20 psi below the setpoint.

I think that for your system running at 60 psi that means your little 2 gallon expansion tank air pre-charge, set with the system EMPTY of water and pressure - would be set to

40 psi.

Thanks for really helpful question, let me know what you think.

- the "right" answer depends on the brand and model of VFD pump and tank that you have installed, so please give us that information so that together we can see what the IO manual wants us to do

Pressure sensitive water pump sources & IO Manuals

• AMTROL Inc. Corporate Office 1400 Division Road West Warwick, R.I. 02893 Phone: (401) 884-6300 Email: info@amtrol.com, Website: http://www.amtrol.com/, Amtrol RP-HP
  
  Pressureiser water pressure booster systems include a pressure boosting pump integrated with an Amtrol water pressure tank. The system is designed to boost building water pressure 50-50 psi above the incoming municipal-supplied water.
  
  Amtrol has offices world wide including Canada, Central America, Europe, Puerto Rico, Mexico, South America, United States
• AQUASUB ENGINEERING (Corporate Office) Thudiyalur (post) Coimbatore - 641 034. Tamilnadu, India Phone: 0422-2642484 Fax : 0422-2642128 Email : aquasub@vsnl.com
• Aquatec 8800 Series Booster Pumps, Aquatec International, 17422 Pullman St., Irvine CA 92614, Tel: 800-975-9995, Website: www.aquatec.com
• Bell & Gossett: commercial grade and sized inline pumps, http://bellgossett.com/pumps-circulators/in-line-pumps/
• B&G / XYLEM ECOCIRC XL PUMP INSTALLATION & OPERATION MANUAL [PDF] (2018) Xylem / Bell & Gossett - retrieved 2022/11/17 original source: https://www.nationalpumpsupply.com/content/pdf/bell-&-gossett-ecocirc-xl-installation-guide.pdf
  
• BurCam Pressure Booster pumps, e.g. Burcam Model 506532SS dual application pressure booster pump can be used as a water pressure booster pump or as a shallow well single-line jet pump; Bur-Cam Company, 2190 Boul, Dagenais West, Laval, Quebec, Canada H7L 5X9, Tel: 514-337-4415, Website: www.burcam.com, also sold through re-sellers such as Northern Tool, Sears, Walmart
• Dayton 4HFA8 booster Pumps sold through Grainger, Zoro, other retailers
• e-LNE in-line pumps, capable of higher flow rates than the small systems we discussed in the article above,Xylem Water Solutions UK Limited Main Office Millwey Rise Industrial Estate Axminster Devon EX13 5HU – UK Tel: (+44) 01297 630210 Fax: (+44) 01297 630295 E-mail: lowaraukservice@xyleminc.com http://www.lowara.co.uk/
• ESYBOX AC VFD PUMP INSTRUCTION MANUAL [PDF] DAB PUMPS S.p.A. Via M. Polo, 14 - 35035 Mestrino (PD) - Italy Tel. +39 049 5125000 - Fax +39 049 5125950 www.dabpumps.com
  Excerpt:
  The product is an integrated system composed of a vertical multi-stage centrifugal electric pump, an electronic circuit that controls it and an expansion vessel.
  
  The pump also has WiFi and Bluetooth connection systems for remote control via DConnect Cloud and for a better user experience with mobile devices via the dedicated app, see chapter 12.
  
  The APP and DConnect Cloud also allow the use of additional features not present directly on the display (e.g. energy and flow meters).
  
  DAB Pumps and Grundfos both distribute VFD pumps world-wide.
• Flexcon, SMART TANK INSTALLATION INSTRUCTIONS [PDF], Flexcon Industries, 300 Pond St., Randolph MA 02368, www.flexconind.com, Tel: 800-527-0030 - web search 07/24/2010, original source: http://www.flexconind.com/pdf/st_install.pdf
  
  Excerpt:
  The Smart Tank pressure system provides constant pressure over abroad range of flows, and the storage that every water system needs.
  
  The unique Smart Tee valve is connected to the Online tank with a union.
  
  Every Smart Tank system includes a relief valve and a manifold that provides ports for the system’s pressure switch, pressure gauge, drain valve and relief valve.
  
  This puts the controls right where they belong - at the tank. The Smart Tee valve and Online tank have been engineered to work together for optimum system performance.
• FRANKLIN ELECTRIC INLINE SYSTEM CONSTANT PRESSURE SYSTEM OWNERS MANUAL [PDF] link as above, retrieved 2018/10/30, original source: http://littlegiant.com/media/130617/225883101.pdf
• Grundfos Pumps Corporation 2001 Butterfield Road, Suite 1700 Downers Grove, IL 60515 USA, E.g. the Grundfos CU 301 control and communication unit developed for SQE well pumps used in constant-pressure applications and the
• Grundfos Scala 2 PUMP MANUALS [web article] provides details about this pump & a full set of installation & operation manuals, features, service history, warranty replacement information.
• GRUNDFOS SCALA2 DATA SHEET [PDF] example of a Variable Freque3ncy VFD pressure sensitive water pump - retrieved 2017/03/26, original source: us.grundfos.com/content/dam/GPU/Literature/SCALA2/SCALA2-DATASHEET.pdf
• Grundfos CU331SP VFD PUMP CONTROLLER MANUAL [ PDF] is a constant pressure, variable frequency drive controller programmed with parameter settings optimized for submersible pump applications, and the
  
  This switch is also discussed
  
  at WATER PUMP PROTECTION SWITCH
• LITTLE GIANT INLINE SYSTEM CONSTANT PRESSURE SYSTEM OWNERS MANUAL [PDF] link as above, retrieved 2018/10/30, original source: http://littlegiant.com/media/130617/225883101.pdf
• Pacific Hydrostar pressure boosting pump, sold by Harbor Freight and at Amazon.com, a brand trademarked by Harbor Freight, is shown just below. 90 day warranty. Pacific Hydrostar also makes pressure washers, sewage pumps, fountain pumps and utility pumps. We haven't found the actual manufacturer of this pump.
• Pentair INTELLIFLO VARIABLE SPEED PUMP INSTALLATION & USERS GUIDE [PDF] (2020) Pentair, retrieved 2022/11/17, original source: https://www.pentair.com/content/dam/extranet/nam/pentair-pool/residential/manuals/pool-pumps/intelliflo-vs/intelliflo-vs-pump-manual-english.pdf
• PENTEK INTELLIKIT HOME WATER MANAGEMENT SYSTEM CHOICES [PDF] (2012) Pentair, 293 Wright Street, Delavan, Wi 53115 USA Website: www.pentair.com Tel: 866-9 PenteK retrieved 2020/10/19, original source: https://www.pentair.com/content/dam/extranet/pentek/sell-sheets/intellikit-choices-well-system-sell-sheet.pdf#page=1
  
  Described further at
  
  WATER PRESSURE BOOSTER PUMP [web article]
• Rowa water pumps - Bombas Rowa, http://www.bombasrowa.com/ are distributed throughout Latin America and provide instructions in English, Spanish, or Portugese. Rua Benedito Campos de Moraes, 177 - Vila Anastácio - São Paulo – SP – CEP: 05094-010 - Tel: 55(11) 3648-9294 www.bombasrowa.com / diretoria@bombasrowa.com.br
• Simer Water Pressure Booster Pumps, Simer Pump 293 Wright Street Delavan, WI 53115, Tel: (800)468-7867, Website: http://www.simerpumps.com/
• ShurFlo industrial pumps, Pentair Food Service, 1040 MUIRFIELD DRIVE HANOVER PARK, IL 60133 USA T 630.307.3000 / 800.942.1153 (US ONLY) Website: http://foodservice.pentair.com/
• TQ Booster Pumps, Walrus Corporation, e.g. TQ400, TQ800, or TQ1500 electronic control water pressure boosting pumps
• Xylem HYDROVAR PUMP CONTROL INSTALLATION, OPERATION, MAINTENANCE MANUAL [PDF] (2015) Hydrovar variable speed drive pump control from Xylem
• Xylem Goulds 13159RB115, ResiBoost Series, BOOSTER SYSTEM with TANK IO MANUAL [PDF] (2022) Xylem Inc. 1 Goulds Drive Auburn, NY 13021 USA Tel: +1 (866) 325-4210 Web: www.xylem.com/goulds - Retrieved 2023/05/08, original source: xylem.com /siteassets/brand/g oulds-water-technology/resources/manual/r esiboost-installation-manual---im325.pdf
  
  This is the Variable Frequency Controller for VFD Goulds/Xylem water pump systems.
  
  Overview:
  
  ResiBoost™ is a variable frequency drive (controller) intended to be used with an electric pump for constant pressure systems. Not suitable for drainage systems with/without level control.
  
  A water system is only occasionally required to run at maximum capacity and the amount of water withdrawn varies over time.
  
  ResiBoost™ automatically controls the speed of the electric pump while keeping the pressure in the system constant in relation to the signal of the pressure transducer (sensor) which is integral to the drive.

InspectAPedia is an independent publisher of building, environmental, and forensic inspection, diagnosis, and repair information provided free to the public - we have no business nor financial connection with any manufacturer or service provider discussed at our website. We do not sell products nor services.

Pressure Sensitive Pump & VFD Variable Frequency Drive Pumps Research

A look at some relevant patents, books and other documents can help us understand how pressure sensitive water pump controls work.

• Arnette, Henry K. "System for protecting a liquid pump." U.S. Patent 5,244,351, issued September 14, 1993.
• Bynum, J. "Pressure sensitive control for pump regulator." U.S. Patent 3,794,789, issued February 26, 1974. Abstract:
  
  The specification discloses a water pumping system including an electric motor driven pump coupled to an underground water reservoir by way of conduits and to an uphold storage tank for storing water
  
  and having a pressure regulator for completing an electrical circuit to the pump motor from an electrical energy source when the water pressure falls below a preset low pressure level and for disconnecting the electrical circuit when the water pressure rises above a preset upper pressure level.
  
  Coupled between the source and the pump motor is a pressure switch sensitive to the water pressure of the system for disconnecting the electrical circuit in the event that the water pressure falls to a given lower pressure level below the preset low pressure level of the pressure regulator.
• Gray, John. "Pressure control for water systems." U.S. Patent 3,135,282, issued June 2, 1964.
  Excerpt:
  
  This invention relates to a pressure control for water systems, and is particularly concerned with apparatus for delivering water or other liquid at a constant pressure when the system demand and the supply source are both variable.
• Grundfos, THE ADVANTAGES OF FREQUENCY DRIVE OPERATION IN SUBMERSIBLE PUMPS [PDF] Grundfos Pump Co., retrieved 2022/05/30 original source: https://www.grundfos.com/solutions/learn/ecademy/all-courses/the-sp-submersible-pump/the-advantages-of-frequency-drive-operation-in-submersible-pumps
• Grundfos Pumps, Australia, vGrundfos Pumps Pty. Ltd Mail: P. O. Box 2040, Regency Park, South Australia 5942 Delivery: 515 South Road, Regency Park, South Australia 5010 Web: http://au.grundfos.com/
  
  
• Herrmann, Thilo, and Uwe Schmida. "Rainwater utilisation in Germany: efficiency, dimensioning, hydraulic and environmental aspects." Urban water 1, no. 4 (2000): 307-316.
• Hollinshead, William H., "Pump control." U.S. Patent 2,765,743, issued October 9, 1956. Earlier and more traditional pump pressure control switch design for rotary pumps.
• Jones, Matthew P., and William F. Hunt. "Performance of rainwater harvesting systems in the southeastern United States." Resources, Conservation and Recycling 54, no. 10 (2010): 623-629.
• Kulkarni, Sunil Jayant. FACTORS AFFECTING PUMP PERFORMANCE-AN INSIGHT INTO RESEARCH AND INVESTIGATION [PDF] International Journal of Research & Review 4, no. 8 (2017).
  Abstract:
  
  Different geometrical parameters such as slot radial position (Rs), slot height (hs) and slot inclination angle (θs) affects pump performance.
  
  Many investigators have carried out experiments and simulation studies to optimize the parameters affecting pump performance. Current review summarizes research and investigation on pumps and factors affecting pump performance.
  
  Studies by various researchers confirm that with increasing the slot height, the impeller head decreased. For proper selection of a pump, it is important to have proper understanding of design restrictions, operating conditions of the irrigation system, and required flexibility in system operation.
  
  Series configurations are used for very high heads and parallel are used in high flow rate applications.
  
  Also studies indicated that that the friction effect on centrifugal pump can be reduced by properly studying the impeller friction losses, volute friction losses and disk friction losses.
• LaValley Sr, Ronnie L. "Pressure responsive fluid pump shut off and alarm system." U.S. Patent 5,064,347, issued November 12, 1991. Abstract:
  
  A pump supply system for furnishing well water or the like which is sensitive to and operates within a range defined by a pressure switch to supply water when pressure in the system falls below a preset minimum pressure and shut off the pump when the pressure reaches a predetermined value.
  
  Timing means is employed in the system and preset to time out after a predesignated interval of operation of the pump.
  
  The system will retime the next pumping cycle, if that interval of operation is not exceeded. If the pump seeks to operate beyond the predesingated time period, the timing circuit is disabled, the pump is shut down, and an alarm is activated.
• Lancaster, Brad, and Joe Marshall. Rainwater harvesting for drylands and beyond. Vol. 1. Rainsource Press, 2008.
• Merritt, Herbert E. Hydraulic control systems. John Wiley & Sons, 1967.
• McIntosh, Todd. "Gray-water reclamation and reuse system." U.S. Patent 5,106,493, issued April 21, 1992.
• MPD & SWPA, THE BENEFITS OF VARIABLE SPEED PUMPING [PDF] (2016) Modern Pumping Today Magazine, Web: modernpumpingtoday.com - retrieved 2022/05/30 original source: https://modernpumpingtoday.com/benefits-of-variable-speed-pumping/
  
  This article was written by authors at the SWPA, Submersible Pump Wastewater Association, Tel: 847.681.1868 Email: swpaexdir@sbcglobal.net Website: www.swpa.org
  
  Excerpts:
  Combining the strength of submersible pumps with the efficiency of variable frequency drives (VFDs) creates a tremendous opportunity for pump users to reduce energy costs, improve performance, and extend equipment life.
  
  VFDs work on “Affinity Laws” where BHP of the pump is related to the cube of operating speed, with reduction in speed leads to lower resultant pressure on the fluid and hence less consumption of centrifugal energy.
• Rahman, Ataur, Joseph Keane, and Monzur Alam Imteaz. "Rainwater harvesting in Greater Sydney: Water savings, reliability and economic benefits." Resources, Conservation and Recycling 61 (2012): 16-21.

• Rainwater harvesting pumps: HydroForce™ Pumps Ltd Contact Details HydroForce Pumps Ltd Unit A Harrier Park, Southgate Way Peterborough Cambridgeshire PE2 6YQ +44(0) 1733 405 107 info@hydroforcepumps.co.uk
• Rainwater Harvesting Ltd Unit A Harrier Park Southgate Way Peterborough Cambridgeshire PE2 6YQ General enquiries call +44 (0) 1733 405 111 Fax: 01733 230 996 info@rainwaterharvesting.co.uk

• Schaub, Robert F., "Tankless water pressure system." U.S. Patent 3,198,121, issued August 3, 1965. Abstract excerpts:
  
  This invention relates to a tankless water pressure system and more particularly to a system for boosting water supply pressure for multi-story buildings and the like. ... One system heretofore used is a hydro-pneumatic tank system
  
  . Such systems have the disadvantage of requiring large expensive tanks occupying a large amount of space, normally require a separate air compressor, involve substantial fluctuations in the pressure of the water supplied, and increase the air content in the water thereby increasing its corrosive action on the plumbing.
  
  Tankless systems have also been proposed utilizing one or more continuously operating pumps driven through variable speed driving mechanisms which are controlled in response to the demand to vary the pump speed.
  
  While such systems maintain the pressure within closer limits than a tank system and eliminate the need for the tank and air compressor, they are expensive to install and are difficult and expensive to maintain, due to the complexities of the variable speed driving mechanisms and the controls therefor.
  
  Systems of this type, however, occupy a substantial amount of space.
  
  It is accordingly an object of the present invention to provide a tankless Water pressure system which is simple and inexpensive to install and maintain, which occupies a minimum amount of space and which maintains the pressure within very close limits.

• Shen, Der-Fan. "Flow regulator for water pump." U.S. Patent 6,564,826, issued May 20, 2003.
  Abstract:
  
  A flow regulator for a water pump, comprising a valve body, a piston block, a spring, a connecting pipe, and a rod.
  
  The valve body is roughly shaped like a cross, having a passageway in a vertical direction and a first tube and a second tube in a horizontal direction. The piston block is glidingly movable in the horizontal direction in the first tube.
  
  The spring is disposed in the second tube, having ends that are fastened to inner and outer holding plates.
  The connecting pipe is connected with the first tube, transmitting water pressure from a supply pipe to the first tube.
  
  The rod connects the inner holding plate and the piston block to allow the water pressure and the elastic force to balance each other.
  
  The piston block is pushed inward by the water pressure, narrowing the passageway, while being pressed outward by the elastic force, so that controlled water flow and pressure in the supply pipe are achieved....
  
  The present invention relates to a flow regulator for a water pump, particularly to a flow regulator for a water pump, which controls water outflow of a water pump by a differential pressure method, achieving smooth delivery of water by the water pump.
• Shen, Der-Fan. "Flow regulator for water pump." U.S. Patent 6,309,185, issued October 30, 2001.
• Smith, Dresden G. "Air and water volume control apparatus for hydropneumatic tanks." U.S. Patent 4,576,552, issued March 18, 1986.
• Speed, Russell H. "Water well pump control assembly." U.S. Patent 4,462,758, issued July 31, 1984.
  This patent describes a more traditional pump pressure control switch design. Abstract Excerpt:
  
  The control assembly includes a mounting plate, a pressure switch that responds to the pressure of the liquid in the tank, the pressure switch being mounted on the plate, a terminal board and a printed circuit board.
• Triezenberg, David M. "Variable-speed motor drive controller for a pump-motor assembly." U.S. Patent 6,264,431, issued July 24, 2001. Abstract:
  
  A liquid pump system for providing liquid to a tank includes a variable-speed motor drive and a control circuit coupling the variable-speed motor drive to a power source.
  
  The control circuit has a switch that may be disposed in a state according to the amount of liquid in the tank.
  
  The control circuit provides for supplying power to the variable-speed motor drive from the power source regardless of the state of the switch.
  
  The control circuit may include a transmitter that generates a high frequency signal representative of the state of the switch. In that embodiment, a detector coupled to the variable-speed motor drive receives the high frequency signal to control operation of the liquid pump system.
• Triezenberg, David M. "Motor drive circuit for pressure control of a pumping system." U.S. Patent 5,580,221, issued December 3, 1996.
• US DOE WHEN SHOULD INVERTER-DUTY MOTORS BE SPECIFIED? [PDF] U.S. Department of Energy, Advanced Manufacturing Office, Motor Systems Tip Sheet #14, retrieved 2017/11/17, original source: http://energy.gov/sites/prod/files/2014/04/f15/motor_tip_sheet14.pdf
  
  Excerpt: Electronic adjustable speed drives, known as variable frequency drives (VFD), used to be marketed as “usable with any standard motor.” However, premature failures of motor insulation systems began to occur as fast-switching, pulse-width-modulated (PWM) VFDs were introduced.
  
  The switching rates of modern power semiconductors can lead to voltage overshoots. These voltage spikes can rapidly damage a motor’s insulation system, resulting in premature motor failure.
• Vishwanath, S. "Domestic Rainwater Harvesting–Some applications in Bangalore, India." In Rain Water Harvesting Conference. H2-1, p. 5. 2001.
• Walski, Thomas, Kyle Zimmerman, Mark Dudinyak, and Preethy Dileepkumar. "Some surprises in estimating the efficiency of variable-speed pumps with the pump affinity laws." In World Water & Environmental Resources Congress 2003, pp. 1-10. 2003.
  
  Abstract:
  The pump affinity laws are widely used in adjusting pump performance curves from one pump or speed to another.
  
  In most cases, they work fairly well and can be reliably used in modeling studies. This paper describes an experiment undertaken to determine how well these laws apply to a variable speed pump, in which the speed is controlled by a variable-frequency drive, the most common technology used today.
  
  The pump speed was varied from full speed to roughly 30 percent of full speed. Over that range, the affinity laws worked quite well for adjusting the pump head characteristic curves.
  
  However, the pump efficiency curves fell significantly lower than those predicted by the affinity laws.
  
  The explanation for this is most likely the loss of efficiency in the variable-frequency drive itself.
  
  Since energy costs are the largest component of pump life-cycle costs, the implications for pump selection are significant.
  
  With variable-speed drives costing almost as much as the pumps themselves, it becomes essential for life-cycle cost estimates, whether done manually or with models, to accurately account for the loss of efficiency.
• Walters, William. "Pump protector apparatus." U.S. Patent 4,329,120, issued May 11, 1982.
• Ward, S., F. A. Memon, and D. Butler. "Performance of a large building rainwater harvesting system." Water research 46, no. 16 (2012): 5127-5134.
• Ward, Sarah. "Rainwater harvesting in the UK: a strategic framework to enable transition from novel to mainstream." (2010).
• Whitesides, Randall W. BASIC PUMP PARAMETERS AND THE AFFINITY LAWS [PDF] PDH Center, Fairfax, VA (2012). Contact: 5272 Meadow Estates Drive Fairfax, VA 22030- 6658 USA, Phone & Fax: 703-988-0088 www.PDHonline.org www.PDHcenter.com
  
  Excerpt: A brief discussion of the mathematics of variables and constants is undertaken to support the introduction and understanding of the Affinity Laws. The Affinity Laws allow Engineers to estimate the resulting changes to certain hydraulic parameters caused by the manipulation of a single centrifugal pump variable.
• Worm, Janette. AD43E Rainwater harvesting for domestic use. Agromisa Foundation, 2006.