moeller overload not tripping

[spamwize2]

we have a moeller z type overload through a contactor to a single phase motor, it is set to trip at 2.4a but doesnt! the motor is pulling 2.7a anyone any ideas why it isn't tripping

 

[glynnis]

The overload will run at 120% of rated current for 2 hours before it will trip if at room temp.
Look at the following dataView attachment t0033g.pdf
Shown on page 7.

 

[benji]

has the contactor o/l been wired correctly ie. seriesing all 3 poles of contactor/ol

 

[bomjac]

Took some searching, but here you go. All information taken from This Data Sheet.

Assuming you have one of these, Which has a trip curve of

Off the top of my head, the required trip time for a 20% overload on a motor to IEE standard curves is in the region of 50 secs or more. The set up you describe is 1.15 * set current and so will trip on 2 hours or more, perhaps not at all.

As benji says, you should series up the live feed from so that it loops between the left outgoing of the O/L back to the 2nd incoming of the contactor, then from the outgoing 2nd of the O/L back to the 3rd incoming of the contactor. Your outgoing live feed comes from the 3rd outgoing of the O/L. Neutral can either be switched through the 4th set of open contacts on the contactor or linked straight through unswitched.

That will force the O/L to treat it like a 3 phase supply and follow the 3 phase curve. Wire it as a straight L&N through only 2 sets on the contactor O/L set and you will follow the 2 phase curve, with a minimum trip time of ~25 seconds at 2*In.

 

[ringer]

Hope this isn't a silly question, but why do you loop three poles in series? Why not just connect through one pole?

 

[spamwize2]

another question! will the overload work if the neutral is looped through L2 and L3 and the phase through L1?

 

[Knobhead]

another question! will the overload work if the neutral is looped through L2 and L3 and the phase through L1?

It would work but as with any installation the less breaks in the neutral the better