Resi. 240v center tapped transformer 2

[WhyDoYouAsk]

Would you say that,
if the 120v on one side of the neutral connection increases by any amount,
because of a sudden 120v load (let's say 10A) on the other side of the neutral,
the neutral connection is necessarily bad (high resistance connection)?

 

[waross]

Hi Lionel;
A "normal" voltage drop or voltage rise will depend on both the unbalanced current on the neutral all te way back to the transformer and on the resistance of the conductors all the way back to the transformer.
Although voltage drops due to high resistance issues are usually many times greater than voltage drops due to normal conductor resistance, in extreme cases there may be some overlap or ambiguity. The test that I suggested compares the resistance (by means of the voltage drop) of the line and the neutral. It is a little more involved but it removes much of the ambiguity that may result from a simple voltage drop measurement.
If the opposite line is not available, The voltage may be checked from the hot to a good ground. With a good ground the voltage drop to ground should be 1/2 of the total voltage drop at the load.
If I was on-site, doing the measurements myself I would probably use the test that you have suggested, and take into account the age of the installation and probable length of the runs and apply some judgement to the results.
But, To set a test that will be preformed by a variety of technicians with varying degrees of ability and experience and set a definite Go-No-Go point we would probably both want a test that leaves less to the judjement of the technician.

Bill
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"Why not the best?"
Jimmy Carter

 

[LionelHutz]

Yes, the test is good. I'd hope the technician has some intelligence to be capable of making a good judgement call since any test might still require some interpretation.