Thermal imagers are excellent tools for troubleshooting motor issues and monitoring the motor condition for preventive maintenance for power generation, manufacturing, and commercial plants. Infrared images reveal a motor’s heat signature to tell you about its condition.

What to Scan?

In building your heat profiles, it is best to start capturing good quality infrared images when the motors are running under normal conditions. Doing so will give you baseline measurements of the temperature of components.  Thermal imagers or infrared cameras can capture temperatures of all the crucial components: motor, shaft coupling, motor, shaft bearings, and gearbox.

However, working with loads can be more difficult as the indications of issues are subtler. Thus, a minimum of 40% design load is recommended (National Fire Protection Associate NFPA 70B), and it is better to have a higher load. When you are inspecting in low load situations, take note of all possible issues, be sure to note all possible problems, even if they reflect only a minimal temperature difference. When the load increases, the temperature rises too–and if a problem exists, assume larger temperature differences at higher loads.

What to Look For?

All motors should have the normal operating temperature listed on the nameplate. An infrared camera/thermal imager is unable to see inside the motor, but the exterior surface temperature is an indicator of internal temperature. When the motor is overheating, the windings rapidly deteriorates. As a matter of fact, every increase of 10°C on a motor windings’ designed operating temperature cuts the life of windings’ insulation by half even though the overheating is temporary.

If a temperature reading in the middle of a motor housing comes up abnormally high, an IR image of the motor can tell you where the high temperature is coming from. If a coupling is warm, there may be a misalignment.

There are three primary causes of abnormal thermal patterns:

• High-resistance contact surface, either a connection or switch contact, usually appears warmest at the spot of high-resistance, cooling off the further away from the spot.
• Load imbalances, normal or out of specification, appear to be equally warm throughout the part of the circuit that is overloaded or undersized. Harmonic imbalance also creates the same pattern. If the entire conductor is warm or hot it may be undersized or overloaded. Check on the rating or the actual load to know the cause.
• Failed components may also appear cooler than normally functioning ones. The most common example is a blown fuse. While, in a motor circuit, this can result in a single phase condition and the possibility of costly damage to the motor.

Practicing regular inspection routes including thermal images of all critical motor and/or drive combinations as well as tracking baseline images will help you know if a hotspot is unusual or not. It will also help you verify if the repairs were a success.

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Have you ever wondered how most pipes in buildings get maintained? Or how about some unwanted leaks?

These are just some of the things that thermal imaging can do.

Thermal came from the Greek thermē which means heat. With that said, thermal imaging is done using a thermal camera or thermal imager and is essentially a heat sensor that is capable of detecting any small difference in temperatures in objects. It collects the infrared radiation from the objects then proceeds to create an electronic image based on the information collected.

While it is never a complete guarantee that nothing will be overlooked, thermal inspection is a way to ensure further unforeseen damage can be prevented. The use of thermal imaging has been becoming part of practice when it comes to inspections and for good reason. Thermal imaging is important in the detection of unwanted and excessive moisture in building materials, insulation gaps, heating, and cooling placement, leaks, and unwanted water infiltration to name a few.

Because the purpose of imaging is different for each case depending on what equipment is being inspected, there is no one imaging solution that fits all infrared inspections with the thermal camera. However, there are three commonly used methods that can cover most situations.

Baseline Thermography

This is an easy way to dive into thermal imaging as it can work for almost any application. This is done by first scanning the object or equipment when it is first commissioned or used, which is then turned into the point of reference for future inspections. That is called the baseline. This approach allows you to spot any anomalies down the line of the object’s lifecycle.

Thermal Trending Thermography

Once the baseline has been set, this approach of thermal trending thermography can be used to compare how temperature is distributed in the same components over time. This helps in detecting any change in performance over time and over the object’s lifecycle. This allows you to be one step ahead in scheduling the maintenance for the object before it becomes unable to function.

Comparative Thermography

This approach is based on the idea that you expect similar components under similar loads to have similar temperature profiles. Under this approach, you scan similar components with the thermal camera under the same conditions and compare the results. With three or more components it becomes easier to pick up any deviation or irregularity.

While this approach may seem simple at first, it becomes complex depending on the component being compared. The real difference in temperature that can be considered normal or irregularity will also be different for each component depending on their respective functions.

All of these approaches all work to help maintain appliances and ensure that it is running properly. Thermal inspections are a good measure to maintain the objects and also prevent them from further damage. With Fluke’s Thermal Cameras, you are guaranteed to perform thermal inspections with confidence and faster results and better imaging.

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For ages, the temperature has been used to give an indication of a machine’s condition, as machines with unusual temperatures are proven to have potential damages.

Touching the machine with our bare hands can sometimes help determine if the heat is in within limits but it may lead to serious accidents.

According to Westindrives.com, in order to obtain precise machine temperature, thermography or thermal imaging should be used. Other than precision, this technique is also safer.

Thermography – or thermal imaging – allows visualization of heat for maintenance or diagnostic purposes. The application’s infrared radiation is converted by a thermal camera to the visual image.

This thermal camera will speed up troubleshooting and aid in preventive maintenance that can provide a substantial return on investment.

Thermal imagers have also affected the way electricians monitor the operation of electrical systems. These devices gather vital information about electrical components, cooling levels in data centers, backup uninterruptible power supplies, and electrical support equipment. By using infrared (IR) cameras to take noncontact heat measurements of energized equipment, it is possible to diagnose potential problems before they occur.

However, according to Fluke, in order for a thermal imager to serve you right, you must certainly know how it works in different facets of your business. These are:

Electrical and Power Distribution

• Troubleshoots and maintains electrical panels
• Monitors substations and switchgear
• Commissions new installations through the documented condition at the time of acceptance
• Inspects and monitors power generation components

Industrial

• Inspects and troubleshoots motors, drives, and bearings
• Finds pipe blockages or leaks
• Assesses tank levels from a distance
• Identifies circuit board hot spots at the design stage

Energy and Environmental

• Detects heat loss throughout your HVAC
• Locates moisture in your building envelope
• Conducts residential and commercial building energy audits

Thermal imaging technology is very dynamic, and there have been developments in products for over a decade, bringing new products and expanded capabilities.

Thermal imaging may sound so expensive but it is actually a very affordable option for many businesses that need best security, protection solution and a higher return of investment. It, in fact, it costs lower than CCTV. If you are looking for an affordable yet high-quality thermal imaging product, visit https://presidium.ph/ or call +63 2 464 9339 to know more.

Thermal inspection work has now evolved through thermal imaging software that makes our work much easier. Now you can access thermal imaging results through your phone via software/apps. With this software, you can easily create accurate reports concerning mechanical, electrical, building diagnostics, electronic equipment and more.

Just like a professional camera, an infrared camera needs to be paired with thermal imaging software with features that allow you to produce accurate and clear thermal images. A good thermal imaging software also fully utilizes the radiometric data supplied by the camera’s sensor to get the most out of the image or video.

If you’re in the hunt for thermal imaging software, here are some factors to consider:

Multiple Video/Image Formats

It’s important that your software is able to export your images in various formats so it will be compatible with different viewing devices. Formats such as .jpg, .tiff, .bmp, .gif, or .avi are those that can read more advanced data. Fluke Infrared Cameras can in .is2 format, and images can be exported in the most commonly used formats.

Edit and Manipulate Images

You want a software that will allow you to do image enhancements on the software itself. For one, it is more convenient, and second, you can easily mark the important parts of your report.

Live Viewing and Sharing of Infrared Images and Video

Share images in real-time even with team members who are working remotely. The Fluke Connect software allows you to access a live view through an app on your mobile phone.

Remotely Control your Infrared Camera

Your camera must be able to allow you to access and control your device even without having to touch it. This feature would especially be helpful during hazardous situations.

3-Dimensional Analysis

A 3D structure allows for a full and clearer view of what you are working on. You can easily provide solutions and eliminate false positives when you are working with a 3D model.

You must be able to get the most out of your infrared camera so you need to pair it with thermal imaging software that will maximize its capabilities and enhance your results. If you’re looking for an infrared camera and the best thermal imaging software, a wide range of choices await you at www.presidium.ph

Presidium.PH Corporation is an authorized distributor of Fluke– the world’s leader in the manufacture, distribution, and service of electric test tools, biomedical equipment, and networking solutions.

Presidium.PH is a full-time product-based selling business that is focused on test & measurement. They want to bring the latest technology products to the Philippines & cater across multiple industries.

Wanting to give their consumers the best service, Presidium.PH offers Free Onsite Demo for Hi-Touch products with their highly qualified and trained product specialists.

They also offer special discounts on their products with free delivery within Metro Manila to ease their clients from the hassle of traveling and transporting their purchased tools.

And unlike other retailers, Presidium.PH values and really care for their customers and does not stop accommodating them once the receipt is printed. In fact, Presidium.PH provides them information and all the help they need after purchasing their products with their immediate and impressive after-sales service.

And to assure the protection of their valued clientele, there is a product warranty guarantee for every product.

Make sure you are getting every cent’s worth of your money by buying your tools and equipment from authorized distributors like Presidium.PH itself.

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The “run to failure” maintenance strategy is still prevalent among many plants nowadays. This means that no maintenance will be done for machinery until it fails while the maintenance staff will run from one disaster to another one. This can induce a much higher maintenance cost and lesser productivity.

Some companies have transitioned to preventive, or calendar-based, maintenance. Actions are scheduled regardless of the actual condition of the equipment. With this approach, fault-free machines can be repaired unnecessarily, leading to higher program costs.

Over the past 30 years, the US Navy and many Fortune 500 companies transitioned from preventive maintenance to condition-based maintenance. With condition-based maintenance, machines are measured with methods such as vibration analysis, which don’t require tearing a machine down to find out its condition. When a machine condition fault comes up, a repair is scheduled when it’s needed – not before and not too late.

Early indicators of machine health

Several technologies are used to measure and diagnose machine health. Two of the most important are vibration testing and infrared thermography. The graph shows how you can detect changes first with vibration testing, then with infrared thermography. Only later on – shortly before machine failure – can you hear audible noise and feel the heat.

Benefits of early vibration testing include:

• Give maintenance staff time to schedule the required repairs and acquire needed parts.
• Take faulty equipment offline before a hazardous condition occurs.
• Incur fewer unexpected and serious failures, helping to prevent production stoppages that cut into the bottom line.
• Increased maintenance intervals. Extend the life of equipment and schedule maintenance by need.
• Incur fewer unexpected or catastrophic failures because problem areas can be anticipated before failure.
• Peace of mind. Build confidence in maintenance schedules, budgeting, and productivity estimates.

Mechanics of vibration testing

A transducer picks up vibration signals from bearing locations and transmits these signals to a data collection device. Here are a few important things to note about the mechanics of vibration testing:

• All rotating equipment generates a unique vibration signal or signature.
• These unique signals are usually captured in series, with the signal’s amplitude (y-axis) depicted over time (x-axis). This is called a time waveform.
• The waveform contains information about the machine at the point of measurement. Vibration comes from the rotating shaft, adjacent machines, foundation, noise, rotating components, structural resonances, flow turbulences, and other sources.
• However, the patterns of different events are overlapped and jumbled together. Separating and isolating one vibration signal from another is complicated.
• Frequency analysis performed in the data collector simplifies the waveform into certain repetitive patterns. Fast Fourier Transform (FFT) is a mathematical algorithm performed by the vibration testing tool to separate individual vibration signals.
• Spectrum is the plot of each of these individual signals on a simple plot of amplitude (y axis) against frequency (x axis).

We can simplify it down to a three-step process.

1. Identify vibration peaks as they relate to a source component on the machine.
2. Look for patterns in the data based on vibration rules.
3. Measure the amplitude of the vibration peak to determine the severity of the fault.

Once the fault and severity are determined, you can recommend a repair and generate a work order.

Bearing faults and failures

A study conducted by the SKF Group tracked the life of 30 identical bearings and found that there is a wide variation in bearing life. This precludes the use of an effective calendar-based maintenance program.

Another study found that bearing faults can account for over 60 percent of mechanical faults. Although bearings are a major contributor to mechanical problems, sometimes bearing faults are the result of a separate underlying problem, such as unbalance. Some customers replace bearings every few months until they learn to balance and align the machine – then bearings will last for years. Bearings fail because of:

• poor insulation
• poor lubrication
• contamination
• wear fatigue
• other faults

A roller bearing – also called a rolling-element bearing – carries a load by placing round elements between the two pieces. Most machines today have roller bearings.

Analyzing roller bearing faults

Bearing frequencies are non-synchronous. The geometry of the balls, cage, and races show up at different speeds; these speeds are not a multiple of shaft speed. In most cases, non-synchronous peaks are roller bearings. Most vibration programs use the following bearing frequencies:

• inner race
• outer race
• cage
• ball spin

Vibration pens, meters, and testers

When you move up to a vibration meter, you have the capability to measure overall vibration in addition to specific variables. The Fluke 805 Vibration Meter has a combination vibration and force sensor tip that compensates for user variance (force or angle) – yielding accurate, repeatable readings. This meter has a four-level severity scale and an onboard processor that calculate bearing condition and overall vibration using easy-to-understand textual alerts (Good, Satisfactory, Unsatisfactory, Unacceptable). Its sensors can read a wide range of frequencies (10 to 1,000 Hz and 4,000 to 20,000 Hz), covering most machine and component types. The 805’s straightforward user interface minimizes user inputs to RPM range and equipment type. This gives frontline maintenance personnel and operators a screening tool to determine which equipment is healthy and which needs further troubleshooting.

As described previously, an advanced vibration testing tool, the Fluke 810 Vibration Tester, has a diagnostic engine that combines algorithms with a database of real-world measurement experience. You can also get this product for A SPECIAL DISCOUNT so make sure to CONTACT US NOW or email us at info@presidium.ph!

Lockout or Tag-out procedures indicates steps that electricians must follow to remove power from an electrical circuit or panel to lock out and tag the circuit panel, for no one to re-energize it while there is a work in progress.

This is especially important for the increasing number of specialty contracts, ranging from health inspectors to thermographers that we have today. These contracts must work around electrical panels and exposed circuits, which exposes them to various safety risks. With this, contractors or anyone else who may be exposed to live voltages should, therefore:

• Have a full understanding of lockout/tag-out procedures
• Learn how to verify that power has been removed before they begin any form of work, especially if live circuits may be nearby

Additionally, contractors should also always carry a non-contact voltage detector to confirm and check if their work environment is safe from exposure to live circuits or conductors. Non-contact detectors are relatively affordable and industrial models such as the Fluke 1AC are safety rated up to 1000 volts AC.

About lockout/tag-out

Industry standards like the NFPA 70E, Standard for Electrical Safety in the Workplace, published by the National Fire Protection Association sites Lockout/Tag-out electrical disconnect principles and procedures. Specifically, NFPA 70E requires everyone working on exposed conductors and circuit components operating at 50 volts and up to be properly trained in using lockout/tag-out devices and procedures to ensure their safety. The document also indicates specific circumstances when working on live circuits is permitted and also sets approach boundaries for both qualified and unqualified personnel.

Standard lockout/tag-out process (Conducted by the electrician)

• Open disconnecting device(s) for each source of power supply.
• Visually verify that all blades of the disconnecting devices are fully open or that circuit breaker is in the fully disconnected position
• Use a voltage detector to verify that the circuit/panel is de-energized

Verifying lockout/tag out (Conducted by the non-electrician)

• Visually verify that applied lockout/tag-out devices were applied by the electrician in accordance with a documented and established policy and that he/she has declared the area or equipment electrically safe.
• Test your voltage detector on a known live circuit to make sure that it’s working
• Use your voltage detector to test the surrounding equipment cabinets and circuit panels (covers, not wiring) to ensure that everything is de-energized or grounded

Only after the area has been declared electrically safe should you:

Test each phase conductor or circuit breaker for the absence of voltage. The wand should read no live electricity on each test.

After each test, re-check the voltage detector wand on the known live circuit. It is essential to note that you can only begin work once you’ve completely verified the absence of voltage in the area to ensure safety.

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Motor drives are commonly found technology that is used to transform constant voltage from the main AC power supply into a voltage that varies to control motor torque and speed. Motor drives have higher efficiency and have a degree of control that is not available on simple directly driven motors. These features result in energy cost saving, better production performance, and extended life of the motor.

Motor systems are vital to the operations of almost every plant. It accounts for 60% to 70% of all electricity used [according to the US Department of Energy]. Unsurprisingly, motor drives are frequently used in many industries and facilities. Make troubleshooting and maintenance a priority to ensure that motor drives are working efficiently.

CHALLENGES IN TESTING MOTOR DRIVES

Variable Frequency Drives (VFD), Variable Speed Drives (VSD), or Adjustable Speed Drives (ASD) are often performed by specialists. They use several test instruments like oscilloscopes, digital multimeters, and other test tools. The said testing may involve trial and error using elimination. Testing typically occurs annually, unless, there is a system malfunction. Due to a lack or incomplete history of the equipment, identifying where to begin such a test becomes problematic. Equipment history includes documentation of specified tests and previous measurements performed, completed work or as-left condition of individual components.

But newer instruments like the Fluke Motor Drive Analyzers MDA-510 and MDA-550, makes drive testing more efficient and insightful with the capability to document the process every step along the way. These reports can be stored and compared against subsequent tests to get a bigger picture of motor drive maintenance history.

AN EASIER WAT TO TROUBLESHOOT VFDs

Advanced motor drive analyzers combine the functions of a meter, handheld oscilloscope and recorded along with the guidance of a skilled instructor to employ on-screen prompts, clear setup diagrams, and step by step instructions written by motor drive experts to help you through the needed tests.

To get to the root cause of a motor drive system failure or when doing a preventive maintenance check is best done with a set of standard tests and measurements at key points within the system. Starting with the power input, key tests with different measurement techniques and evaluation criteria are completed throughout the system, ending at the output.

Here are the essentials tests for troubleshooting motor drives:

Safety notes: read the product safety information before you start. Comply with local and national safety codes. Use personal protective equipment to prevent shock and arc blast injury where hazardous live conductors are exposed.

To begin each test with a Fluke Motor Drive Analyzer simply connect the test probes according to the diagram, then select Next.

Drive Input

An effective first step in determining if a feeder circuit to the drive has a distortion/disturbance/noise that may be affecting power ground is to analyze the power going into the motor drive

• Differentiate the measured frequency against specified frequency. Exceeding 0.5Hz difference could cause problems
• Observe if whether the harmonic distortion is within an acceptable level. Look at the waveform shape or view the harmonics spectrum screen that shows both the total harmonic distortion and individual distortion. Flat-top waveforms can indicate a nonlinear load connected to the same feeder circuit. If total Harmonic Distortion exceeds 6% there is a potential problem
• Check the voltage unbalance at the input terminals to make sure that the phase unbalance is not too high (less than 6-8%) and that the phase rotation is correct. High voltage unbalance reading can indicate phase failure. Over 2% reading can lead to voltage notching and cause a trip of the drive’s overload fault protection or disturb other equipment.
• Check for current unbalance. Excessive unbalance may indicate a drive rectifier problem. A current unbalance reading over 6% may point to a problem within the motor drive and become problematic.

DC Bus

The conversion of AC to DC inside the drive is critical. It is required to have the correct voltage and adequate smoothing with low ripple to have the best drive performance. High ripple voltage may indicate failed capacitors or incorrect sizing of the connected motor. You can use Fluke MDA-500’s record function to check DC bus performance dynamically in the operating mode while a load is applied.

• Determine if the DC bus voltage is proportional to the peak of the input line voltage. The voltage should be about 1.31 to 1.41 times the RMS line voltage (except controlled rectifiers)
• Check for any distortion or error in peak amplitude of the line voltage. A DC voltage reading +/- 10% from the nominal voltage can be a sign of a problem.
• Identify if the peaks of the AC ripple have a different repetition level. Ripple voltages above 40V can be due to malfunctioning capacitors or a drive rating too small for the connected motor or load.

Drive Input

It is important to check the drive output. It can show clues to problems within the drive circuits.

• Check if the voltage and current are within limits. High output current decreases stator insulation life.
• Ensure that the voltage/frequency ratio is in specified limits. A high ratio may make the motor overheat; a low ratio will make the motor lose torque. Unstable frequency and voltage indicate potential issues with the speed control circuits
• Observe the voltage modulation using phase to phase measurements. Voltage peaks higher than 50% can be problematic.
• Check the steepness of the switching impulses as shown by the drive reading. It is the rate of the voltage over time. Compare it to the motor’s specified insulation.
• Measure voltage unbalances at full load. It shouldn’t exceed 2% as it can cause excessive heat in the motor winding.
• Measure current unbalance, which should not exceed 10% for three-phase motors. Large unbalance with low voltage can be caused by shorted motor windings or phases shorted to ground.

Motor Input

The voltage supplied at the motor input terminals = key. Cable selection from drive to motor = critical.

Improper cabling selection can result in both drive and motor damage due to excessive reflected voltage peaks.

• Check that the current present at the terminals is within the motor rating. Over-current conditions can cause the motor to get hot and lessen the life of the stator insulation.
• Voltage modulation can help identify possible problematic high voltage peaks to ground
• Voltage unbalance that affects the life of the motor can be a sign of damaged inverter.

Motor Shaft Voltage

When the rotor shaft exceeds the insulating capacity of the bearing grease, flashover currents or sparks can occur. It can result in pitting and fluting of the motor bearing race that can damage motor permanently.

• Measure the voltage between the motor chassis and the drive shaft. The Fluke MDA-550 provides a carbon fiber brush probe for this purpose. This test can detect the presence of destructive sparks and the impulse amplitude can help you prevent future failures.

Interested in Fluke MDA-550 Motor Drive Analyzer? Order it at Presidium.PH to get a discount!

Throughout the years, many companies have transitioned from “run-to-fail” maintenance strategies to preventive maintenance strategies. This is because as many companies found, have allowed lower maintenance costs and lower production costs.

However, over the past couple of years, many of the biggest companies have transitioned from preventive maintenance to condition-based maintenance. With this new type of maintenance, machines are measured through vibration analysis. Vibration analysis is a non-invasive, non-machine tearing technique that allows engineers to find out the condition of a machine not before and not too late. Through vibration analysis, when a machine condition fault comes up, a repair is automatically scheduled as needed.

What are the benefits of vibration testing?

1. This allows predictability, in that it allows you time to schedule repairs and to acquire the parts that you need ahead of time.
2. Vibration testing makes the work environment more safe as it allows you to pull out equipment before it becomes hazardous for everyone.
3. This process allows for fewer unexpected failures, which helps to keep production from stopping unexpectedly, which could thereby cut into the bottom line.
4. Vibration analysis also allows increased intervals in maintenance. This then extends the life of the equipment and allows you to schedule maintenance only when needed.
5. When you use vibration testing, this makes equipment more reliable as it incurs fewer unexpected failures because you will be able to identify problem areas before they fail.
6. Finally, this gives engineers the peace of mind they need when coming up with maintenance schedules, budgeting and estimating equipment productivity.

All in all, having an advanced vibration tool on hand allows for higher productivity and lesser machine failures.

The mechanics of vibration testing can be summarized into three simple steps:

• First, by identifying the vibration peaks relating to the source components on the machine.
• Second, by then looking for patterns in the data based on vibration rules.
• Lastly, by measuring the amplitude of the vibration peak to determine the severity of the fault.

Once you’ve determined the fault and severity, you’ll be able to recommend a repair and create a specific work order needed.

Learn more about the various industry-related articles here at Presidium.PH! Contact us to know more about our products. You may call us at +63 2 464 9339 or email us at info@presidium.ph!

Have you ever seen that tiny pen with a glowing tip? Do you know that it is called capacitive voltage sensors and it’s one of the technological breakthroughs in the metrology industry?

Wondering how it works? Here’s how:

AC voltage detectors work based on the principle of capacitive coupling. According to Fluke, to understand this, let’s return momentarily to electrical circuit theory and recall how a capacitor works. A capacitor has two conductors or “plates” that are separated by a non-conductor called a dielectric. If we connect an ac voltage across the two conductors, an ac current will flow as the electrons are alternately attracted or repelled by the voltage on the opposite plate. There’s a complete ac circuit even though there’s no “hard-wired” circuit connection. The electrical “field” inside the capacitor, between the two plates, is what completes the AC circuit.

We are actually missing the fact that our world is full of small “stray” capacitors. We always think that these are just individual circuit components like motor starting caps.

Here’s an example from the Fluke website:

Suppose you are standing on a carpeted concrete floor directly under a 120 V light fixture and the light is on. Your body is conducting a very small ac current because it is part of a circuit consisting of two capacitors in series. The two conductors or plates for the first capacitor are the live element in the light bulb and your body. The dielectric is the air (and maybe your hat) between them. The two conductors for the second capacitor are your body and the concrete floor (remember that concrete is a good conductor, as is shown by the use of concrete-encased electrodes as earth grounds).

The dielectric for the second capacitor is the carpet plus your shoes and socks. This second capacitor is much larger than the first. A very small ac current will flow because there is 120 V across the series combination. (As an aside, this current must be way below the shock threshold or we wouldn’t be living in a world of ac power-we definitely would not be turning on lights in the bathroom.)

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