Which Starter Contactor

[Mark Whitehouse]

Hi all I have a 3 hp single phase motor that only runs when you hold the button and stops when you release it. I am struggling to get my head around which contactor to get for it. Any help would be great.

 

[westward10]

Has it only just started doing this or did it previously carry on running once the start button was released.

 

[Mark Whitehouse]

Has it only just started doing this or did it previously carry on running once the start button was released.

No this is how it should run for safety. The whole thing got ripped out before I got to it. So starting on the back foot. I've got a new motor but need to get a starter contactor. There is a separate button to run the motor, not on the contactor.

 

[Spoon]

Lads on the comp so i cant check regs.
Dont you need a thermal overload for a 3hp motor?

 

[westward10]

It is single phase 3hp.

 

[Mark Whitehouse]

It is single phase 3hp.

No single phase

 

[Mark Whitehouse]

Sorry yes single 3hp

 

[Spoon]

 

[Mark Whitehouse]

Just got the paperwork out for the motor and it has an overload built in .

 

[westward10]

The control contactor will need to incorporate an overload relay.

 

[Andy-1960]

Just got the paperwork out for the motor and it has an overload built in .

Can you post this paperwork?
Do you have the full load current of the motor?
Also what does this motor drive as this may affect the duty rating of the contactor and also may determine if a safety circuit may need to be incorporated.

 

[ipf]

Can you post this paperwork?
Do you have the full load current of the motor?

Well you know it's 3hp....

 

[Andy-1960]

Well you know it's 3hp....

Yes, but full load currents do vary depending on efficiency and number of poles. Always best to rate control gear from information on the motor plate.

 

[Darkwood]

I take it this is a deadmans operation method, you just need a suitably rated starter that you can remove the retaining link wire out of the circuit to give this operation method, the majority of motor DOL starters out there allow you to do this, as mentioned though you will need overload protection fitted, I also would like to see this paperwork for the motor, motors can come with integral thermal devices but they normally require external monitoring but this alone may not satisfy the requirements for overload detection as they are usually a secondary backup as motors can overheat without running in overload.
You are the designer of the control circuit regardless if your copying the old method therefore you should be complying to BS 60204 (2018), this falls outside of the BS7671 although you do find the odd relevant regulation that is reflected in the BS7671.

 

[Mark Whitehouse]

Thank you all I have found a DOL with overload to do the job