Answer by Gil for Measuring AC voltage at the panel - why avoid measuring from neutral?

Measuring from one leg to neutral to check voltage is correct, not a problem. I measure from each leg to neutral, then I measure across the two legs. If the voltage from each leg to neutral is different you probably have a neutral connection problem. The sum of these two voltages should be equal to the phase to phase voltage, all within a volt or so as I do not know your equipment. Do the measurement again with a load turned on, first on one phase and the other and see if you get a voltage change. Do the same thing at the source breaker they should be the same except the voltage with the load may be a volt or two higher. Check the voltage between neutral and ground, it should be about zero. Do this again with a load on only one of the phases then the other. The reading should be the same. Preferably the load is a few amps.