I just install circuit breaker 240 v ,but when I use the meter it can only read 120 v on each pole when I check both pole I don't see any thing in the meter,:eek: why is this happen Thanks

Somehow the breaker is only connected to one hot phase, or leg, of the panel. If this is a half size breaker, this mistake is easy to do. Be sure the half size breaker is an actual 2 pole breaker with a one handle and an internal common trip, and is rated for 240 volts. Many half size breakers look like a 2 pole 240 volt breaker.

Be sure to plug any 2 pole breaker onto each of the two hot legs of a panel. This is usually not a problem with a full size breaker.