How do VFD’s (variable frequency drives) make a circulation pump slow down and save energy?

There are many options to reduce energy consumption and save electrical expenditures for the pool circulation pumps.  Each option provides a different level of savings, along with different abilities to integrate with the existing circulation, filtration and chemical control systems. These options include:

• Standard Variable Frequency Drive (VFD)
• EkoFlex Smart Pump Control System (SPCS-EF)
• Full-Drive Smart Pump Control System (SPCS-FD)

Each of these approaches to energy savings also requires a different type of installation, with differing costs.  Following is a description of each system, type of required installation, and benefits of each approach.

VFD Overview

A variable-frequency drive (VFD; also termed adjustable-frequency drive, “variable-voltage/variable-frequency (VVVF) drive”, variable speed drive, AC drive, micro drive or inverter drive) is a type of adjustable-speed drive used to control AC motor speed and torque by varying motor input frequency and voltage. 

VFDs are used in applications ranging from small appliances to large compressors. About 25% of the world’s electrical energy is consumed by electric motors in industrial applications, which can be more efficient when using VFDs.

Standard Variable Frequency Drive (VFD)

The simplest and lowest cost system is a standard VFD.  It is not coupled with a flow sensor, so a standard VFD cannot maintain a set flow rate required by the Health Department for a public swimming pool.  Unfortunately, a standard VFD also does not consider many other important parameters required to operate and maintain a pool’s circulation, filtration and chemical control systems.  It is important to remember that all equipment in the pump room works together as a system.  A swimming pool circulation system is a dynamic system, unlike domestic hot water systems, HVAC systems, and other recirculating water systems. The swimming pool system incorporates a filter, which requires a varying amount of pump head to maintain the health department-mandated flow rate as the filter loads with particulate. When a sand filter backwashes, it requires a minimum 15 GPM/square foot of filter surface area flow rate to properly fluidize the media bed.  Without this flow rate during backwashing, the dirt trapped by the filter cannot be properly removed, resulting in failure of the filter.  This is why most aquatic engineers and pool designers recommend against the installation of a standard VFD.  This is also why most standard VFD’s were abandoned soon after they were installed during the last big push for energy efficiency in the 1990’s.  Operators and owners found standard VFD’s are unable to meet the needs of the dynamic swimming pool circulation system, causing problems more expensive to remediate than the savings they provided.

It is possible to install a manually-operated “bypass” to allow the pump to operate at full speed during backwash; however this has many drawbacks. First, it will not allow for an automated backwash.  The manual bypass, which is mounted in a separate enclosure than the VFD, requires that an operator be present to operate the switch.  It is also necessary for the pool operator to remember to engage the bypass not only before backwash, but to manually switch the VFD back to “savings” mode when the backwash is complete.

In addition, most pumps are “oversized” to ensure meeting Health Department flow rates at “worst-case scenario” of having a dirty filter fully loaded to a 15 PSI differential between influent and effluent pressures.  This requires that a “rate-of-flow” valve (built into the filter system) and a butterfly valve be partially closed during normal operation and backwash.  The rate-of-flow valves are completely opened with a VFD (and a SPCS system) to take advantage of maximum energy savings.   The manual bypass, when incorporated with a standard VFD, can allow the pump to operate beyond system design parameters while in bypass mode, which results in cavitation (and expensive damage) to the pump.

A standard VFD also does not allow for the interlocking of the chemical control system (which could result in feeding of chemicals when the circulation pump is off), nor the pool heater “fireman’s” switch (which could result in the sudden shutdown of the circulation pump before the heater cools, damaging the pool heater).

Many standard VFD’s include a simple, “real-time” clock that can allow the circulation pump to switch to an even lower flow rate at a set time every day.  This does not allow any flexibility for the changing programming schedules at an aquatic complex.

A standard VFD will have the lowest initial cost. It will also be the easiest and least expensive to install. True costs of this type of system are hard to estimate, especially when long-term expenses of the incorporation of a standard VFD will mean that the pool circulation, filtration, heating and chemical system will no longer be automated, and it would provide the lowest level of energy savings.

EkoFlex Smart Pump Control System (SPCS-EF)

The EkoFlex Smart Pump Control System (SPCS-EF) is a much better option than a standard VFD.  The SPCS-EF has a standard VFD as one of its components, along with an overload block, bypass and output contactors to provide additional protection to the pump motor. The manual bypass in the EkoFlex will allow the operation of the pump even if the VFD is not operating.  In addition, it includes a 5% line reactor to protect the VFD and other internal components.  The SPCS-EF interlocks with the chemical control system, preventing chemical feed if the circulation pump is shut off, and the SPCS-EF is enclosed in a NEMA 12 wall-mounted enclosure.  It comes standard with a manual potentiometer, but the EkoFlex can be provided with a 4-20mA flow sensor, or incorporated with a BECSys5 or BECSys7 controller to ensure that Health Department-required flow rates are maintained.  The SPCS-EF has a manual switch for off, bypass, and normal filtration (energy-savings mode), and is programmed for easy switching between the different modes.  Unlike a standard VFD, the EkoFlex also incorporates an interlock to the pool heater’s fireman switch.  The SPCS-EF EkoFlex has easy-to-see mode indicator lights in its front panel.

It is important to note that the SPCS-EF, when incorporated with a 4-20 mA flow sensor or BECSys controller, will provide for proper backwash flow rates of 15 GPM/sq. ft. of filter area, as long as the flow sensor is placed after the filter.

Installation of the SPCS-EF is more involved than a standard VFD, and will be more expensive to purchase and install.  The SPCS-EF system integrates better with the circulation, filtration, heating and chemical systems than a standard VFD.

Full-Drive Smart Pump Control System (SPCS-FD)

The greatest energy savings for pool circulation pumps will be provided by the full-drive Smart Pump Control System (SPCS-FD). It is a fully automated system, and communicates with every piece of equipment in the pump room necessary to have automation.  It also provides the greatest reduction of electrical costs.  The SPCS has all the features of the SPCS-EF, along with many more functions that make it the best choice for aquatic facilities.

The SPCS-FD communicates with the filter controller to know when the filter is backwashing.  There is no need for a pool operator to flip a switch on the motor control to insure correct flow rates for backwash, nor does the operator need to remember to switch back to “normal filtration” at the end of the backwash process.  The SPCS-FD has a VFD as one of its many components, along with a line reactor to insure only “clean” current is transmitted to the pump motor.  It also incorporates a main circuit breaker, a magnetic contactor, motor overload protection, over and under voltage protection  (sustained low voltage is the #1 destroyer of VFD’s), an emergency shut-off relay, a power block with easy-to-land connectors for interlocks.  All of these components are mounted in a NEMA 12 enclosure, with a cooling fan to protect against overheating.  The SPCS-FD has five separate modes, with an easy-to-use selector switch.  All of this results in a true automated system that integrates with the existing pool equipment in the pump room.

The SPCS-FD’s exceptional energy savings is enhanced by its “Plus” mode.  The SPCS-FD has a PLC communicating with an easy-to-program multi-day, multi-event timeclock.  This allows the SPCS to automatically switch from the “normal” flow rate to a reduced “Plus” flow rate whenever desired, thus taking advantage of down-time whenever it may occur.  The “Plus” mode flow rate is selected to ensure that there is enough water circulating to allow water chemistry and heater flow switches to work, but at a rate lower than “normal” flows.

Installation of the SPCS-FD requires a contractor familiar with pool automation, and capable of wiring the interlocks from the pool chemistry controller and filter backwash controller.  The SPCS-FD requires an investment greater than the other energy options, but the savings provided by the SPCS-FD very rapidly compensate for initial higher cost.

The SPCS-FD is chosen by aquatic engineers and designers for new and existing facilities because it is the only completely automated system available, incorporating a VFD with all the other components required to automatically respond to all the changing situations encountered in a highly-used aquatic facility. The SPCS-FD will provide the greatest savings on electrical costs, day-after-day, year-after-year.

Vacuuming, manual or robotic, what makes sense?

Automatic (or robotic to some) vacuums have been around for many years now, but most recently in the last 3-5 years the quality and functionality have definitely improved.

Historically robotic vacuums have been expensive to purchase and repair making end users question the viability of the purchase. To a much lesser extent both of those concerns still exist and are real but like many products the evolution has cured many of the older problems, if you care for it properly it will return long hours of service.

How the automatic concept pays us by allowing the pool technician to use their skills more effectively throughout the day and letting the machine do the vacuuming as needed in the off hours. Think of it as best time utilization. You will still need to manually vacuum your pool occasionally but it will be minimal. If you are a first time user consider requesting a demo for your pool to ensure it will meet your particular configuration and expectations, also a service agreement if there will be multiple users of the vacuum. Yes automatic vacuums are well worth it.

Enzymes, another needless chemical for your pool….. or not?

What is an enzyme and why should you care?
Enzymes are everywhere. We even have enzymes in our mouths and they work as the first stage of digestion by breaking down food into smaller molecular components to get this process going.

Pool enzymes aren’t much different. A common view is that enzymes “eat” whatever they are designated to treat but what really happens is a process of separation. Enzymes break things down to smaller pieces to better eliminate detrimental chemical.

Pool enzymes are “built” to remove the annoying things that are difficult for chlorine to attack. You’re familiar with these; oils from cosmetics, sunscreen, deodorants, hair products, nitrogen from perspiration and urine and other organics.

The use of enzymes can help your pools or spas in many ways. They can:

• Lessen the frequency of required breakpoint chlorination
• Eliminate scum lines on walls in skimmer pools, wave pools and spas
• Lower the use of chlorine by “pretreating” organics
• Prevent oil contamination of all filter media
• Eliminate biofilm in piping and filtration tanks that require the “attention” of chlorine
• Help keep UV quartz tubes and UV intensity sensor clean and operating more efficiently between services

It is important to know that while they can be a benefit, not all are created equally. Enzymes are chemically designed for certain tasks and selecting the product that best meets your needs can sometimes be tricky.

The answer to the initial question is that yes, enzymes do have value and are a useful pool water treatment when applied properly by experienced personnel.

Why does your chemical tubing explode?

Because it can’t take it anymore!  In short, because of material fatigue.  Plastic material will become brittle over time as a result of UV, heat and chemical exposure.

Tubing should be inspected routinely for abrasions (is it rubbing against anything?), nicks or cuts.  If tubing becomes kinked during installation or tight radius bends it will “bruise” and eventually leak.  Tubing exposed to sunlight must be UV rated (often black).  You should use the highest pressure rated tubing appropriate for your system.

Chemical leaks are bad.  Chemical leaks are unsafe.  Chemical leaks can be expensive.

Only love lasts forever.  Change tubing before it puts you on notice.

Control your pool from your phone

Did you know that you can manage one pool or thousands of pools from all over your City, State, or even around the world from your laptop, iPad or Smartphone? The communication is basically free, the implementation cost is relatively low, but the impact on your pool operations is tremendous. Combined with good on-site water testing and maintenance basics, remote e-based water management programs are providing many organizations with high quality and streamlined pool operations.

Compared to earlier controllers that were limited to pH, ORP, and temperature parameters, the new controllers include digital GPM flow as a standard feature, so you can monitor your precise Health Department-required flow at any time day or night. You can also can monitor pump vacuum (hair & lint strainer soiling), influent pressure (pre-filter), effluent pressure (post filter), pool water level, chemical tank levels, direct reading of water clarity, direct PPM reading, direct chloramine readings, and much more.

Vital information about your pump room that is easily accessible on your Smartphone helps you manage your overall operation easier and better, and can help prevent a wider variety of pool room issues. With expanded information you can now be alerted with:

• Flow below required GPM,
• VFD operating at a higher than normal level (not saving energy due to site conditions),
• Dirty strainer (which can cause damage to pumps),
• Dirty filters (reducing pool flow or decreasing water clarity),
• Tampering or pump operating outside its recommended amperage (prevent from burning out),
• Low or empty chemical containers,
• Chloramine levels that can cause eye and lung irritation,
• Clarity levels that fall below Health Department guidelines

CO² pH control, why bubble up your pool?

When CO² is added to water it creates carbonic acid which we can utilize to lower pH in our pools. The residual side-effect is that it will promote Total Alkalinity (TA) rise. CO² alone will require the additional maintenance procedure of column poring acid directly into the pool. This is undesirable for a few reasons we won’t discuss at this time.

The combined use of CO² and acid has both chemicals feeding at the same time when you need to lower pH. With this method, both lower pH and they counteract the TA side effects created by the other. You use less sodium bicarbonate for TA adjustment and less acid as well. Win win.

What does UV do?

Ultraviolet light (UV) provides a non-chemical, environmentally friendly treatment option for a wide range of processes. Most microorganisms, even cryptosporidium, are inactivated in less than a second by high doses of UV light, leaving no undesirable chemical residues. Due to their compact size, low ownership costs and simple maintenance requirements, UV-disinfection units have been installed by many of the world’s multi-national soft drink companies, breweries, pharmaceutical giants, municipal waterworks, and wastewater treatment plants.

Applications for UV light treatment continue to grow. In addition to inactivation of microorganisms, UV will break down inorganic and organic pollutants in water. This is particularly true in the swimming pool industry, where, in addition to the disinfection benefits, a significant reduction in combined chlorine levels can be achieved.

Using the proper UV product for each specific application insures that you are getting the right equipment to meet your needs. There are two major “classes” of UV for aquatic applications- low pressure UV and medium pressure UV.

Medium Pressure UV systems emit a “wide” spectrum of UV light (200 nm- 315 nm).  This wide UV spectrum not only effectively deactivates pathogens (such as Cryptosporidium, Giardia, E- coli, and Pseudomonas), but also destroys all three chloramine compounds.  This type of chloramine control is vital- not just for the safety of the bather and the comfort for those both swimming in the pool and those on the pool deck.

By emitting most of its UV energy at 254 nm, Low Pressure Amalgam UV is excellent at deactivating pathogens.   Low Pressure UV uses much less electricity to operate and is more user-friendly for the typical spray park customer.

What does total alkalinity (TA) and dominoes have in common?

Like the first tipped domino in a line-up, total alkalinity has reaching influences on pH, corrosion indices, ORP and chlorine levels controlled by ORP.

• When TA is out of range, <50 PPM or >150 PPM, pH becomes unstable and control can be very difficult.
• The amount of chlorine required to yield target ORP set point is dependent upon stable pH. This can result in either lower or higher than desired chlorine levels in the pool.
• The stability of TA produces a stable pH which is the cornerstone of all corrosion water balance indices.

The lesson here is that when TA levels are a problem, so are pH levels. When pH is in trouble, often so are chlorine levels.

Always fix TA first and pH is likely to tall in place as will chlorine.

Do you have too much chlorine in the pool?

Perhaps you are swimming in a heavily used pool; or maybe you are in the bleachers at the natatorium watching the big swim meet. You notice the smell of “chlorine” in the air. And – it’s bad – really bad. If you are in the pool, your eyes may be stinging and swelling. Even if you are up in the bleachers, you realize that your eyes are becoming red and irritated. Either place, you smell “the smell.” “Too much chlorine, again!” you think. “I told them last week that they were using too much chlorine, and they obviously weren’t listening.” You resolve to go talk to the pool manager again, and make sure that she hears you – loud and clear – this time.

You find the pool manager in her office, and you begin reading her the riot act. Fortunately, she is a patient person, and lets you say your piece. Her response, though, is not what you expected.

She explains to you that the smell, eyeburn, and irritation weren’t a result of having too much chlorine in the pool water, but from not having enough! And she tells you why:

Swimmers’ sweat and other organic pool water contaminants contain nitrogen-rich ammonia. As long as the pool water maintains at least ten times as much molecular weight of chlorine than nitrogen, the nitrogen off-gasses to the atmosphere. Outdoors, it blows away; indoors, it must be evacuated from the natatorium (and it usually doesn’t get all evacuated, which leads to big problems). But if there is less that ten times as much chlorine in the water than the nitrogen being introduced, then the nitrogen combines with the chlorine, making chloramine.

A pool can be “heavily” chlorinated (20 ppm+) and, as long as there are no chloramines, the water will not have “the smell” and it will not cause irritation. But just a little bit of chloramine (0.4 ppm and higher) leads to eyeburn, irritation, “the smell”, and contributes to respiratory damage. Chloramines are created when the chlorine residual in the pool water is lower than what is required to treat the nitrogen load. Chloramines can be destroyed by adding enough chlorine to the water to overcome the molecular weight imbalance and restore the 10:1 chlorine/nitrogen ratio.

“So” the pool manger says “I need to do some water testing when the pool closes, and calculate how much chlorine I need to add to destroy the chloramines. I will multiply my chloramine level by ten, then add this much chlorine directly to the water. I’m going to add it tonight, and the pool will be closed tomorrow until the chloramines are gone and the free chlorine residual drops to an acceptable level.”

You ponder this as you drive home: The red eyes, irritation, and smell are not caused by too much chlorine, but from actually having too little chlorine during a high organic load. And – even stranger – more chlorine, in the right amount, needs to be added to the pool water to get rid of the smell and other problems.