Pools may be for pleasure, but keeping them in top working order is a lot of work. The eMod electronic, mode-sensing module, from A.O. Smith Electrical Products Company, Tipp City, Ohio, alleviates some of the headaches that come from pool and hot tub ownership, by detecting problems that could shorten the life of the motor.

With normal wear, a pool motor could last 10-15 years. With clogs, plumbing leaks and other common mishaps, however, a motor’s life expectancy drops to 6-8 years, according to Steve O’Brien, vice president of marketing for A.O. Smith.

"The eMod protects against events, as opposed to normal wear," O’Brien explains. "Something like a voltage spike can ruin a brand new motor quickly."

The eMod automatically calibrates to the specific operating conditions and filtration system of the pool, based on the power requirement of the pumping system.

"Site specific calibration is necessary because many factors can affect flow and power consumption," O’Brien says. Pipe length, pipe diameter and pump position all affect power consumption. "Calibrating to the pump only would not be precise enough, so we invented the site calibration, and to make it easier, we incorporated the self-calibration feature. This allows us to monitor a very tight band and shut off the motor while also reducing nuisance tripping."

Once eMod is calibrated, it uses a current sensor to constantly monitor the input power all the time that the motor is running. "If eMod detects that the input power requirements of the motor change by +/-10 percent, it shuts off the motor," O’Brien says.

The work done by a pump is a measure of how much water mass it is moving, and how much pressure the pump has to add to the fluid. "In other words," says Bill Mehlhorn of A.O. Smith, "the work (or energy consumed) by a pump is the flow rate of the fluid multiplied by the change in head pressure multiplied by the mass of the fluid."

The power into the electrical motor that is moving the pump needs to meet the power to turn the pump, and also any power losses of the motor. Power into an electrical motor is defined as the power line voltage (vac rms) multiplied by the power line current (iac rms) multiplied by the power factor. Power factor is a factor of the phase angle between the input voltage and the input current, and is calculated by the cosine of the angle between the two.

There are several factors that could change input power:

• A locked motor condition: This can result in the pump seizing.
• A dry running pump: A fairly typical example comes from pool cleaners, which run on the bottom of the pool. They can come to the water’s surface, drawing in air instead of water, which can damage the pump seal and motor. A pump can also be dry running if the water level in the pool drops below the skimmer line. This often happens in pools with absentee owners — living part-time in areas like Florida — who aren’t around to keep the water level in check.
• Voltage variations: Both high and low voltage can burn out the motor.
• A plumbing leak: If the water level drops, the flow characteristics of the plumbing system changes.
• A jammed pump: This is a condition that A.O. Smith didn’t expect eMod to detect until a motor on a test pool in Ohio tripped. Technicians found a pebble in the motor’s impeller, which would have ruined the pump.
• Entrapment: A full-suction entrapment, where a body or limb is suctioned or trapped on the drain, will cause a significant change in input power. The idea is like placing a hand over the opening of a vacuum cleaner hose, which would instantly stop the flow. By shutting off the motor, the entrapping force is relieved, allowing the person to get back to the surface.

It’s important to note that entrapment, according to industry definition, can mean hair, limb, object, body or evisceration. eMod is not sensitive enough to detect a hair entrapment, and O’Brien says that no shut-off device is that sensitive. "The only way to protect against hair entanglement in a drain is with an industry-approved drain cover," O’Brien says.

"Any change in input power into the motor is probably something bad going on in the pool system, whether it’s a safety issue, like an entrapment, or something that could eventually harm the pump or motor," O’Brien says.

He adds that a change in a flow in a pool system manifests itself from a motor perspective by a change in input power.

The eMod calibrates when the motor and pump are energized. If eMod shuts off the motor, it will remain off for two minutes and then turn itself back on. This process will repeat five times.

"If something blocks the drain, like a towel or leaves, we don’t want the pump to stay off — we want it to run again," O’Brien says.

If, after five times, the system is unable to start, it will stay off, requiring the power to by cycled, by turning the switch off and on or pulling the plug and then plugging it back in. eMod will then turn on again, still calibrated to the original calibration point. If something changed dramatically while the system was turned off, such as a different pump being installed or the hydraulic system has changed, eMod will have to be recalibrated to keep it from tripping due to the change in power requirements. A button on the outside of the box, held for three seconds, will zero out the calibration and recalibrate to the new system. The eMod technology is available on all A.O. Smith and Century Centurion single-speed and two-speed in-ground pool and spa motors for original equipment pump manufacturers as well as all A.O. Smith replacement motors. A tamperproof compartment made of impact-resistant, high-density plastic protects the load-sensing circuitry. The compartment, mounted directly to the motor, resists the effects of weathering and ultraviolet light.

"The beauty of automatic calibration is that the electronics are basically the same for any motor," O’Brien says. "We could calibrate to a specific motor. A 1/2 HP or 3/4 HP could have different electronics, but that’s not precise enough to do some of the things that we wanted to do."

One of the main features of eMod, which O’Brien says took a while for the company to develop, is the automatic calibration to the total pump and pool environment, as opposed to just being motor specific.

"Motor specific wasn’t sensitive enough," he says.

The software kicks in the first time the pump is energized and that’s when it looks to the baseline of the system and automatically calibrates.

The installation is the same as replacing any motor and requires no special tools or procedures. Though O’Brien advises that a pool service technician replaces the motor, he admits that many consumers do it themselves.

"With motor life expectancy around six to eight years, people who have owned a pool for a while have probably gotten pretty adept at replacing motors," he says.

A.O Smith recognizes that the company has several options for using eMod technology in other applications, and already has one application ready for the HVAC industry.

"We make motors for the HVAC industry, including compressors and fan motors in an HVAC system," O’Brien says. "And HVAC systems have all kinds of sensors built into them."

For example, in the compressor unit, there is a sensor to detect a loss of charge. That loss of charge would manifest itself in less work being required by the motor, just like in a pool motor scenario. So, the company is using eMod in compressor applications.

"We can do it now," O’Brien notes. "We supply on an OEM basis, so it’s just a matter of when our customers may want to integrate it into their product development."

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