I found this statement （3rd paragraph), can you share your opinion about handle tie? thanks!
“The National Electrical Code, NEC, is written as a restrictive document. What this means is that unless something is prohibited, or directed to be done a certain way, it is permitted. You aren't going to find a paragraph that says it's OK to put 2 circuits on a 2 pole breaker, only a paragraph that says it's not OK if it isn't (and there isn't one, by the way)
Multi wire branch circuits save copper. 2 separate circuits require 2 hots, 2 neutrals, and 2 grounds and a multi wire requires 2 hots, 1 neutral, and 1 ground. Multi wire circuits also help limit voltage drop. The savings are even more pronounced in 3 phase applications.
While 2 pole breakers are acceptable on multi wire branch circuits, 2 singles with handle ties are a better option if there are no line to line (hot to hot) loads. The handle ties are designed so the handle on a tripped breaker can move without shutting off the other breaker but when operating the handles manually both breakers shut off per NEC rules. Note that APPROVED handle ties are required.
Jerry mis-spoke on the testing of multiwire circuit voltage. You should have ~240 volts betweel the 2 hot wires on a correctly wired one and will have ~0 volts between hot wires on an incorrectly wired one. Assuming you get 120 volts between the 2 hot wires a different kind of wiring issue is at hand where one hot wire has been wired as a neutral rather than just having the 2 hot wires on the same line circuit. The line to neutral voltage should always be ~120 volts, even if the hots are on the same line circuit. Any other voltages indicate the neutral is open somewhere”.
“The National Electrical Code, NEC, is written as a restrictive document. What this means is that unless something is prohibited, or directed to be done a certain way, it is permitted. You aren't going to find a paragraph that says it's OK to put 2 circuits on a 2 pole breaker, only a paragraph that says it's not OK if it isn't (and there isn't one, by the way)
Multi wire branch circuits save copper. 2 separate circuits require 2 hots, 2 neutrals, and 2 grounds and a multi wire requires 2 hots, 1 neutral, and 1 ground. Multi wire circuits also help limit voltage drop. The savings are even more pronounced in 3 phase applications.
While 2 pole breakers are acceptable on multi wire branch circuits, 2 singles with handle ties are a better option if there are no line to line (hot to hot) loads. The handle ties are designed so the handle on a tripped breaker can move without shutting off the other breaker but when operating the handles manually both breakers shut off per NEC rules. Note that APPROVED handle ties are required.
Jerry mis-spoke on the testing of multiwire circuit voltage. You should have ~240 volts betweel the 2 hot wires on a correctly wired one and will have ~0 volts between hot wires on an incorrectly wired one. Assuming you get 120 volts between the 2 hot wires a different kind of wiring issue is at hand where one hot wire has been wired as a neutral rather than just having the 2 hot wires on the same line circuit. The line to neutral voltage should always be ~120 volts, even if the hots are on the same line circuit. Any other voltages indicate the neutral is open somewhere”.
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