There is no requirement to retest the resistance.
Ground rod resistance tester.
This type of tester is usually available at hardware and home improvement stores as well as from online retailers.
250 54 which requires the resistance to ground of a single made electrode e g ground rod to be 25 ohms or less.
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You are correct that the nec states that if you use one ground rod that the resistance to ground must be 25 ohms.
With this method the resistance of two electrodes in a series is measured by connecting the p1 and c1 terminals to the ground electrode under test.
This is an older type of resistance meter that uses multiple ground probes and wires to assess a ground rod s resistance.
If it is higher then you must place a second ground rod.
Touch one lead to your test wire and the other lead to your test location for example an outlet s third ground plug which is the small round hole at the bottom of the outlet.
In practice for a residential structure most electricians place two ground rods and call it done.
The easiest way for you to measure the resistance of a ground rod is to use a clamp on ground tester.
In areas where driving ground rods may be impractical the two point method can be used.
The remaining ground electrodes are all in parallel and as a group are in series with the ground electrode being measured.
Unfortunately it seems many electrical professionals.
Aemc 6471 multi function ground resistance tester kit 500 ohms resistance 32v voltage 250 ma current by aemc 2 802 50 2 802.
The clamp ground tester is clamped around one of the electrodes and then measures the resistance of the entire loop.
Molded carrying case 9v alkaline battery and calibration verification loop.
Using an earth electrode tester instead of a clamp on tester will take a lot more time and effort.
50 3 358 25 3 358.
P2 and c2 connect to a separate all metallic grounding point like a water pipe or building steel.
Nearly all electricians and electrical inspectors are familiar with the national electrical code requirement in sec.
Built to withstand an entire spectrum of ground testing methods fluke s family of earth ground testers have been designed to be accurate safe and easy to use.
Fully auto ranging with data hold to capture readings.
This is a different tool from the clamp on multimeter which only reads ac current.
Reads ground resistance down to 0 10 ω.
