Contactor/overload wiring help pls...

[Colin33]

Hi all, never had to wire a domestic sewerage pump before so not my usual line of work. Was told I need a thermal overload for the pump (1.1kw) and this came with a contactor (not sure why it needs a contactor, but it appears that the overload unit need one to plug into. Can anyone please advise on how to wire this? The enclosure has an earth and Neutral link inside.

 

[Colin33]

You are asking for advice here not sure this is the way to achieve that.

Sorry Westward but all too often on these forums people get put down or belittled for asking for help. I don't wish or need to be told to 'get an electrician' I just want some help from someone who is able to do so and if they can't help, why waste their time getting involved?

 

[Colin33]

Thank's guys, becoming clearer now So live feed to T1 at top of contactor, Live to pump to 2T1 of overload. Neutral in to T2 of contactor, Neutral to pump from 4T2 on overload. Red flying lead shown in photo to 95NC on overload. And link T3 of contactor to 6T3 of overload?

 

[davesparks]

Thank's guys, becoming clearer now So live feed to T1 at top of contactor, Live to pump to 2T1 of overload. Neutral in to T2 of contactor, Neutral to pump from 4T2 on overload. Red flying lead shown in photo to 95NC on overload. And link T3 of contactor to 6T3 of overload?

Nope you've missed out the start and hold in contacts, along with looping through the third set of contacts on the overload to give it a balanced load.

 

[davesparks]

Sorry Westward but all too often on these forums people get put down or belittled for asking for help. I don't wish or need to be told to 'get an electrician' I just want some help from someone who is able to do so and if they can't help, why waste their time getting involved?

The reason I said get an electrician is that every electrician will have learned this basic DOL starter circuit whilst at technical college doing the theory side of their apprenticeship. Therefore any electrician will know the circuit and be able to connect it up.

 

[sam400]

Without trying to confuse things you normally have a start float and a stop float otherwise the pump will bounce

 

[westward10]

Surely it is not a good idea to have the contactor permanently energised.

 

[Andy-1960]

Surely it is not a good idea to have the contactor permanently energised.

Should not be a problem, many sites (hospitals for example) have essential sides of switchboards powered via contactors that are permanently energised until power failure then the essential side is fed via a generator.

A better alternative for this pump application would be to select a manual motor stater (Such as Schneider GV2-ME) which will provide thermal magnetic protection but without the need for any control wiring.
Thermal-Magnetic motor circuit breakers - TeSys GV2 | Schneider Electric - http://www.schneider-electric.com/en/product-range/684-tesys-gv2/

 

[Colin33]

The reason I said get an electrician is that every electrician will have learned this basic DOL starter circuit whilst at technical college doing the theory side of their apprenticeship. Therefore any electrician will know the circuit and be able to connect it up.

Yes, I'm sure this was briefly covered during my college days but having never had to wire one in over 20 years it's not something I'm familiar with. I certainly don't recall being taught how to couple a thermal overload with one. Well done Dave if you can remember everything you learnt, I'm afraid I'm not that good

 

[Rocboni]

I wouldn't wire it with a start button surely it's bad design that after a power failure you have to go out and start your sewage pump, could get a bit messy if someone forgets?

This must be a basic system or it would have come with a purpose built panel. The blue button on the front is a reset button to reset the overload if it trips,

 

[Ollie Barwick]

Hi Colin33 not sure if you have resolved issue but if it was me I'd recommend Changing the protective device to a Motor mcb Such as below. If this is not possible let me know and I will try and help with Contactor O/L. I work in water industry and would use a motor mcb in this situation.

 

[Colin33]

Thanks Ollie, yes it would've been better to use one of those, but unfortunately I was ill advised and now have to use what I have. If there's a simple way to wire up the existing unit to achieve thermal overload protection then that's the way to go.... don't really need the start/stop options, there's a simple reset button on the overload unit to press in the unlikely event of motor overload. The pump is serving a single property of just one occupant so unlikely to be any issues

 

[davesparks]

Yes, I'm sure this was briefly covered during my college days but having never had to wire one in over 20 years it's not something I'm familiar with. I certainly don't recall being taught how to couple a thermal overload with one. Well done Dave if you can remember everything you learnt, I'm afraid I'm not that good

I don't remember everything I've learned, but I do have all of my textbooks and notes from when I was at a college which I regularly refer to for this sort of thing.

 

[ruston]

It's amazing what triggers the memory back into action .

 

[Rocboni]

Just take a live to A1 via 95 and 96 (N/C) of the overload and Neutral to A2.

Loop the live for the motor round the contactor as previously illustrated.

 

[garygoth]

Sewage pumps are prone to blockages which result in windings burning out, so the overload is installed to protect the motor.This should be set to the full load current as stated on the motor data plate.
Terminations as follows...
L1 is incoming live and L2 is incoming neutral.loop a wire from T2 to L3. Pump wires are now terminated live inT1 and neutral inT3
Next supply neutral to A2 and a live to 95NC and loop a wire from 96NC to A1.Terminate earths. Press reset on overload.Due to high start currents being in excess of 8X full load current on start up you might consider a C curve breaker.