Not sure if you can help me or not but I recently purchased the Extech CT80 to test/diagnose wiring issues inside my home and there’s something I confused about regarding the neutral and hot impedance tests. The main reason I purchased this equipment is because the wire I specifically wanted to test was 14 awg and I suspect it to be probably somewhere around ~100 ft long (and about 18 duplex outlets on it). When you calculate the impedance of the cable at that awg and length with a resistance of 2.525 per 1000 ft at 68 degrees, my assumption is with the wire length itself in the best case scenario wouldn’t fall below 0.2525 Ohms at the end of the run (thus setting the floor threshold number).

In the manual under

**Test 5: (Impedance Measurements)**It states that if the voltage drop measurements are too high (greater than 5%) is then to test the hot and neutral impedance to determine the problem (In my case it was 13%). In the suggestions chart it states a limit of 0.048 ohm /ft of 14 awg wire. At 100ft, the limit (correct me if I’m wrong) is 4.8 ohms max (0.048 x Length of Wire) and the likely cause is excessive loading (I understand these are just troubleshooting suggestions). This is where I’m confused.

Since the branch circuit I’m testing has nothing plugged in and the only draw would be from the load test with CT80, what would be the ceiling limit (max safe threshold value) be on a 14awg branch circuit per foot? (I spent days researching this and still can’t find anything useful for hot/neutral impedance testing) The reason I ask is because if I use the resistance of the wire and set the “best possible scenario” @ 0.2525 ohms and my testing results show 0.50 ohms (which is close to double the resistance of the wire), I’m not sure if this is great or really bad. If I use the 10 awg number of 0.01 ohm/ft, then the limit is stating that it’s ok to be up to 1.0 ohm (which is well below what I’m currently seeing but that’s on 10 awg and I would assume 14 awg would be much higher)

Is there any reference on what would min and max should be in best case/worst case scenarios? Right now my assumption is the min value is the resistance of the cable itself without any splices/cuts/etc and the maximum value is 0.048ohms/ft (or 4.8ohms at 100 ft)? Or am I just completely misunderstanding something?

I appreciate any support you can provide!