I received this comment from Bruce Porter, Manager UPG Field Service. Bruce has written many application bulletins for UPG and is well-respected for his expertise in the HVACR field. He also teaches HVACR at Metro Technologies Center HVAC. I felt it was important enough to use as a second post on this subject. Here is what Bruce has said about voltage imbalance. As most of you know, I always promote analog meters and this is just another reason to carry one.
“The thing that must be considered when checking for voltage imbalance is the meter you are using. In the above post is is mentioned to use a digital meter. This is not a good practice for this type of test. An analog meter should be used because overwhelming majority of digital meters average. In my working life I have found very few technicians that really understand what a digital meter is telling them, sure it reads voltage but at what part of the sine wave? If you have an averaging volt meter most technicians do not even know how to turn that feature off in their meter. This can and will lead to a very different outcome when doing this type of test. If you have a phase imbalance and you are going use capacitance to correct it you will be totally off the ranch if you use a averaging digital voltmeter. I would ALWAYS recommend an analog meter such as the old Simpson or one like it that most have in their truck. I realize its like carting around a brick, but its accurate and for doing calculations and capacitance calculations in particular there is no substitute. This type of meter should always be in your service truck anyway because of its megging capabilities.The technician that is prepared and knows how to use his arsenal of tools will be the successful technician and the customer gains the benefit. Be that technician today.”
Thanks to Bruce for this additional information.