Evaluating Relative Humidity: Factors and Measurements

There are a lot of factors affecting the cooling performance of an air conditioning unit, such as the relationship between dry bulb temperature, wet bulb temperature, relative humidity, and dem point temperature. Making sure that these facets are good to add to the overall performance of the unit and, essentially, occupant comfort.

To make sure that an air conditioning unit is running at maximum capacity, HVAC technicians usually use a sling psychrometer and psychrometric chart. These devices are also called “humidity” meters, and in order to make sure that your unit is still working great, you need measuring devices that are accurate, more convenient to use and can be used in various locations even unsuitable for sling psychrometers.

If you want to do an HVAC evaluation and diagnostics on your unit, you need a device, such as the Fluke 971- a measuring device that can calculate wet bulb temperature and dew point temperature.

To better understand how to properly measure and evaluate your air conditioning unit, here are key terms you need to be familiar with:

Wet Bulb

Closely related to enthalpy or the total heat in the air (dry bulb and wet bulb). In a psychrometric chart, the wet-bulb lines are nearly parallel to the enthalpy scale and values.

Dew Point

This is critical in both hot and cold weather evaluations. Duct surface temperature must be maintained above the dew point to prevent condensation whether inside or outside of the conditioned space.

Relative Humidity

This must be kept low enough to ensure inside wall and window surface temperatures do not approach dew point. If condensation appears on window or wall surfaces, condensation hidden within envelope walls will be likely.

If you want to do an HVAC evaluation and diagnostics on your unit, you need a device, such as the Fluke 971- a measuring device that can calculate wet bulb temperature and dew point temperature. Visit www.presidium.ph and view our wide range of measurement devices that will suit your needs.

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How to Choose the Best Insulation Resistance Tester

No idea what kind of insulation resistance tester to use? Not sure which model is working with the best efficiency? We have conked-out our answers to your queries when it comes to deciding which is the best insulation resistance tester to use.

Make A List of Equipment for Testing

First things first, make a list of all the equipment you will need with their nominal voltage rating (seen on the equipment’s nameplate) for an insulation resistance testing. It is necessary to identify the nominal voltage rating so you could determine what test voltage is needed from the tester. Also, you will also need to indicate the number of insulation resistance tests you plan to perform in a year. As you go along the process, you will surely be surprised of how features of the tester work, the quality, and durability it brings as how it is designed to be, especially how relevant it is for everyone.

Identify Voltage Requirements

It is important to know that the output test voltage applied to equipment has to be based on the manufacturer’s recommended DC insulation resistance test voltage. However, if the test voltage is not indicated, you may refer to the International Electrical Testing Association’s table of recommendations. It is important to note down the most suitable insulation resistance tester that can supply the output test voltage needed. Also, not all insulation resistance testers are the same – some testers can only support somewhere between 5000 V dc – 10,000 V dc. Please refer to the table of recommended test voltages and minimum insulation values below.

insulation resistance

Know Where Will the Testing Take Place

Knowing the testing environment and the other uses of your insulation resistance tester can greatly benefit you in choosing other additional features. A digital multimeter and the ability to use one instrument for both insulation resistance tests can also add convenience to the process.

Some insulation resistance testers can be very large and not portable, so there is a need for circuits and equipment to be verified as electrically de-energized first before an insulation resistance tester is connected to the equipment so it wouldn’t be a hassle for you to carry the insulation resistance tester to various locations.

What You Learn from an Insulation Resistance Test

Insulation Resistance Testing puts a qualitative value on both conductor insulation and internal insulation. It is done by applying a dc voltage to the conductor equipment under test.

There are a couple of things to remember as you go along the test and it’s essential to always be guided by these. First, as the charging current begins to build, it is normal to see a low value on the meter face. With more current flowing out of the test, the lower the megaohm reading.  A higher megaohm is directly associated with good insulation quality.

Absorption or polarization is the next current flowing towards the equipment. The amount of absorption is dependent on the contamination of the insulation. When there’s moisture in the insulation, the absorption value will be high and the resistance is low.

Experience Level

The ability of the test instrument will be as good as the person’s experience level on reading it. You must consider your expertise in selecting the insulation resistance tester that you must use. Though, insulation resistance testing training needs not to be extensive.

Also, make sure the insulation resistance tester that you will purchase must support the output test voltage and other functions.

If you having trouble choosing the correct resistance insulation tester, you must choose the ones that provide troubleshooting efficiency and complete maintenance records over time.

Learn more about the various products of Fluke Industrial Group and Fluke Calibration, check them out at Presidium.PH!

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What Does Infrared Mean?

Infrared means “beyond red.” Thermography then pertains to a “thermal picture.” Put together, infrared thermography then means beyond a red temperature picture, which is taken by thermal cameras. This explains why in thermal imaging, we can see a gradient of red and purple captured in a photo.

 

Infrared, just like visible light is part of the electromagnetic spectrum. Infrared just has a longer wavelength and lower frequency compared to visible light. Infrared thermography is the science of detecting infrared energy emitted from an object, which is then converted into apparent temperature, then displayed as an infrared image. This is what the thermal camera takes.

 

Any presence of anomalies is often an indicator of potential problems.

 

This is very helpful in detecting things not otherwise visible to the naked eye such as heat patterns and the infrared wave spectrum. It aids in identifying components that are going bad before they get even worse.

 

infrared camera

 

How does thermal camera work? Instead of giving a numerical test result with various test meters, a thermal camera (also known as a thermal imager) captures the image that you can enhance using different color palettes and highlighting tools in order to point out a problem. An advantage of the thermal camera is that you can capture an object when it is under load and is used as it allows you to take a picture without making direct contact.

 

Most of these thermal cameras are able to capture “radiometric” data which means you can see the temperate for each pixel within the range. Very useful in detecting an anomaly, you can drill down and see the temperature of the exact points in question and see if it is in the normal range or not.

 

Infrared thermography can be useful in seeing beyond what is visible the data that is found all around us. Get to see in infrared with Fluke’s Thermal cameras, the world leader in the manufacturing and distribution of electronic test tools.

 

Learn more about our products here at Presidium.PH or contact info@presidium.ph!

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Using Thermal Imaging to Troubleshoot Motors and Drives

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.

 

Interested in getting an Infrared Camera or Thermal Imager? Get it now at www.presidium.ph!

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