The minimum acceptable value for most applications is to have more than 1 megohm (million Ohms) for every 1000 volts of the intended operating voltage. Modern insulation testers have digital readouts and work by applying high voltages to conductors that are insulated.
The rule states that insulation resistance should be approximately one megohm for each 1000 volts of operating voltage, with a one megohm minimum. (By following this rule, a motor rated at 2400 volts should have a minimum insulation resistance of 2.4 megohms).
The rule may be stated: Insulation resistance should be approximately one megohm for each 1,000 volts of operating voltage, with a minimum value of one megohm. For example, a motor rated at 2,400 volts should have a minimum insulation resistance of 2.4 megohms.
Depending on where you live and the part of your home you're insulating (walls, crawlspace, attic, etc.), you'll need a different R-Value. Typical recommendations for exterior walls are R-13 to R-23, while R-30, R-38 and R-49 are common for ceilings and attic spaces.
Readings should be greater than 1MΩ for an Earthed system, or 2MΩ for Class 2 or “floating” systems. Ideally this reading should be as high as possible. PV150 can read up to 19.99MΩ, and the PV200/210 up to 199.99MΩ. A good result would be “>19.99MΩ” on the PV150, and “>199.99MΩ” on the PV200/210.
Insulation resistance can be determined between live, neutral and earth connections with no loads or appliances connected to any sockets or wiring. Any problems would be shown by a lower-than-expected resistance being present between them. In domestic wiring anything above 2 megohms is acceptable.
Thus, the resistance between poles or to earth must never be less than half of one meg ohm (0.5 M Ohms) for the usual supply voltages.
If we wish to label the strength of the association, for absolute values of r, 0-0.19 is regarded as very weak, 0.2-0.39 as weak, 0.40-0.59 as moderate, 0.6-0.79 as strong and 0.8-1 as very strong correlation, but these are rather arbitrary limits, and the context of the results should be considered.
For standard 2x4 walls, which are common in older homes, an R-value of R-15 is considered good, while R-21 is excellent. This can be achieved with high-performance fiberglass batts, dense-packed cellulose, or a combination of cavity insulation and continuous insulation.
The dip from R10 to R4 seems odd, as one would expect more R as you travel further north through the zones. Thicker is not better! Doubling the amount of insulation will double the R-Value, but so what? Doubling the insulation from R-19 to R-38 does NOT cut the heat loss in half (50%) it cuts it by around 3%!
So, when you've conducted your Megger test, you'll want your device to read between 35 and 100 megohms. If your reading is below that range, there's likely an issue with your cable that will negatively affect its performance. Cable insulation can degrade over time due to: Prolonged use.
For domestic installations, according to IEC 60364, the insulation resistance at low voltage must be greater than 1 MOhm, except for voltages lower than 250V. In this case, it must be greater than 500 kOhm.
The minimum insulation resistance allowable is 1 Meg Ohm (1,000,000 Ohms). As detailed above, if a switching device cannot be closed without the appliance being powered then a leakage current test needs to be performed.
BIL testing is an important part of the design and maintenance of electrical equipment. A high-voltage impulse generator is typically used for testing, which applies voltage surges to the equipment and measures the insulation response.
Blanket insulation -- the most common and widely available type of insulation -- comes in the form of batts or rolls. It consists of flexible fibers, most commonly fiberglass. You also can find batts and rolls made from mineral (rock and slag) wool, plastic fibers, and natural fibers, such as cotton and sheep's wool.
Compare your readings to the acceptable range of 20 – 60 ohms. The reading will give you insight into the problem. See the possible outcomes and recommended action below: Acceptable Range: If the measurements are within the acceptable range (20 – 60 ohms) then the electrical circuit for that station is good.
Mineral wool batts are a great choice when it comes to thermal performance. They beat the fiberglass batts with a 22–37% higher R-value per inch.
Aerogel insulation offers the highest R-value of any insulating material at less weight and thickness—ideal for construction, refineries, pipelines, and thin-gap thermal barriers.
The installed insulation R-value for 2x6 fiberglass batt ranges between R-19 and R-21. When blown or sprayed cellulose insulation is used, the R-value is typically R-20 for 2x6 walls.
In some fields, such as the social sciences, even a relatively low R-squared value, such as 0.5, could be considered relatively strong. In other fields, the standards for a good R-squared reading can be much higher, such as 0.9 or above.
According to the U.S. Department of Energy, R-values for exterior walls in colder climates should be at least R-13 to R-23. In milder climates, a lower R-value may be sufficient. For example, in a moderate climate, an R-value of R-13 to R-15 is typically recommended.
The higher the R value, the more your mat resists heat loss and the better it insulates you from the cold ground. As a rule of thumb, an R value of 1.0 to 2.0 is fine for summer use but you'd need a rating of 4.0 to 5.0+ for winter camping.
Following the connection of current using equipment and electronic devices a second insulation resistance test must be carried out. Set the insulation resistance tester to 250V and carry out the test between all live conductors connected together and earth. The insulation resistance value should be at least 1MΩ.
The readout should stay level around one ohm. Two or three ohms is still acceptable, but if one of your cables shows much higher readings than the others (of the same length), you should check that all conductors of that cable really make optimal contact with the terminals in each plug.