double pole MCBs

  • Thread starter Srinivas, Hari (IE03)
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Thread Starter

Srinivas, Hari (IE03)

Can somebody tell me the advantages of using Double pole MCBs, with respect to safety.

Trevor Ousey

It all depends on where and what you are supplying. In hazardous locations you have to, the potential between neutral and earth is a problem. With floating supplies it should be done. Another advantage is that the circuit opens with each pole and in effect you have two in series. But on the other hand with the average installation it can be painful and a possibly hazard if it fails to only open the neutral.

Trevor Ousey
2-pole circuit protection of any kind, breaker or fuse, applies for line -to- line voltages. Here in the states this is most commonly 208 and
480Vac. There are instances allowed(?) by the NEC whereby the neutral circuit can be opened in a line -to- neutral config.
Double pole MCBs is a secure way to shut off the power to your machine. You always know that your machine is isolalted from your powerdistribution.

Met vriendelijke groeten,

Onno Moret

Imtech Projects West
Control Systems
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Where load is connected between 2 phases of a 3-Phase supply, it is essential to protect it with a 2 pole CB so that both "hot" lines are opened under fault condition or fully isolated when switched off, (As when maintenance is to be
performed on the load.) On a 1-phase supply where there is any possibility of line reversal, e.g. where supplied from a non polarized two pin plug, both lines must be protected - even when one line is Neutral, as, in that case it is not known which line is "hot". It could also be argued that, as there are 2 poles in series, the circuit may be broken more effectively, (i.e. 2 arc paths now in series), but this is not a normal consideration in practice.

Tony Firth, Electrical Eng.,
Quester Technology Inc., Fremont,CA
hi hari:
our clients ask for 2 pole MCB for total isolation pf control and power circuit for

futura electronics
system house of GE-Fanuc

Srinivas, Hari

For normal applications using 110Vac/220Vac is it really required to go for Double pole MCBs..