DOL Starter Wring

[Jimmyb]

Hello, Can someone please tell me the reason why you always loop back the netural wire from T2 to L3, I was always told 'its because we do' , I have one to replace and would like to know the reason i assumed it was so all the poles are covered and it may help pick up on overloads better.

Many Thanks

 

[Darkwood]

Assuming.... you are switching single phase L1 - live, L2 - Neutral and T2 looped to L3 thus giving ......
T1 line out and T3 Neutral out. ???

 

[Jimmyb]

yes wiring single phase, why is it looped back i thought today what happens if you just wire 2 poles up ?

 

[Darkwood]

If contactor is on its own then you dont really gain anything but if overload fitted its possible that it will sense single phasing in the empty phase especially if its an electronic one which monitor load and voltage of each channel, so wiring as you said has its functional uses but ive seen it done with L1 looped to L2 and N in L3. Most ppl dont really know why they do it but, i think its just been passed down so much so its always done regardless of overload fitted or not, and also i prefer using live through 2 channels for extra isolation on drop out, i come across contactors fail closed on one phase a few times but still its rare.

 

[silva.foxx]

(diagram shown only for relevance with 1ph and 3ph overload)


You only need to use the third pole if you're using a 3ph overload, so that the overload doesn't 'suppose' that the unused pole is a missing phase.

If you're not using a 3ph overload, then you can just use two poles.

regards
s.f

 

[Darkwood]

Hey silva .... although your answer the same i have to admit yours is prettier lol

 

[silva.foxx]

Prettier...maybe...but speed rules and you are king!