Is it necessary to upgrade to a bypass meter socket before installing solar and tapping into it?
Also what is the difference between a 4, a 5, or a 7 terminal socket?
I am trying to spec out a milbank socket that would work with the K4977 tap connectors and would appreciate any advice or help out there
Your utility will need to answer whether it is necessary to upgrade to a bypass lever.
The terminal number indicates how many terminals there are in the meter enclosure, that feed a measurable circuit to the meter globe. Generally, 4-terminal is what you need for standard 120/240V single phase, and 7-terminal is for 3-phase. The 5-terminal meter sockets are for single phase, when it originates off of a 3-phase system, such as 120/208V like you might see for the service to each dwelling unit in an apartment building. This application would need the 5th-terminal, so the meter can measure that the two live lines are 120 degrees out of phase, instead of directly opposite.
Each line that has its current metered, has a line and load terminal. The neutral has a combined busbar that has a terminal on each side (which don't count toward this number), and isn't current-metered. If there is an odd number in the terminal number, that means there is a voltage tap onto the neutral bar, which is then measured by the globe.
As for tap connectors, it is common for utilities to not allow these inside the meter enclosure. Not an NEC issue, mainly a POCO rule. So unless you know that you can do this, plan on a separate enclosure for making your tap.
