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Steve3948

3 Phase Motor 2.5mm 30A Mcb

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Steve3948

So today had a call from another contractor asking if a 3 Phase Lift Motor wired in 2.5mm on a 30A Mcb was a Code 2.

Cable undersized for fuse rating, should be 20A or cable size increased.

 

Now I replied it's ok from memory, having dealt with this before many moons ago, as across 2 phases 400V its 2 X 2.5mm and not a problem on 30A TP Mcb.

 

He felt this was incorrect.

 

 

 

 

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Tony S

I would be very wary with that. 2.5mm² may be OK for a normal motor. Lifts have their own set of rules regarding protection and duty cycle.

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Steve3948

Yes, I'm now thinking I may be wrong having thought about it, but for some reason I felt I had come across this in the past, still felt Code 3 more appropriate though.

 

I gather it's a small hydraulic single lift installed some 20 years ago, 3 phase  motor, wired with 2.5mm SWA to a 30A Mcb.

 

 

 

 

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Tony S

Goods or passenger lift? Each have different regulations as far as I remember. Goods lifts aren’t quite as stringent as passenger lifts. Both come under “lifting mechanisms”

 

 

 

This is totally off topic, I was called to a 10 person passenger lift with 1.25t of refractory cement in it. I isolated it and walked away laughing, “you got it in there, you get it out!”

 

 

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Rob.

What size is the motor?

 

Does it have overload protection? 

 

A 30A TP MCB will allow 30 amp to flow through each phase. So the following statement is incorrect. 

 

Quote

Now I replied it's ok from memory, having dealt with this before many moons ago, as across 2 phases 400V its 2 X 2.5mm and not a problem on 30A TP Mcb.

 

 

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Zotek
On 11/2/2017 at 02:38, Steve3948 said:

So today had a call from another contractor asking if a 3 Phase Lift Motor wired in 2.5mm on a 30A Mcb was a Code 2.

Cable undersized for fuse rating, should be 20A or cable size increased.

 

Now I replied it's ok from memory, having dealt with this before many moons ago, as across 2 phases 400V its 2 X 2.5mm and not a problem on 30A TP Mcb.

 

He felt this was incorrect.

 

 

 

 

I second his opinion. This was not correct. You need to increase wire size.

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Rob.
28 minutes ago, Zotek said:

I second his opinion. This was not correct. You need to increase wire size.

 

Please read up on fixed load applications, and how motor circuits use thermal protection to cover the cables and motor. 

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Sidewinder

As has been suggested above, this, may, be acceptable and may not even be within the scope of BS 7671.

 

110.2 EXCLUSIONS FROM SCOPE

The Regulations do not apply to the following installations:

(i) ...

(x) Those aspects of lift installations covered by relevant parts of BS 5655 and BS EN 81

(xi) Electrical equipment of machines covered by BS EN 60204...

 

BS EN 81-2 Hydraulic lifts sounds the right standard to be looking at for the specifications then out from there.

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Evans Electric

Sidey , what applies to overhead cranes ?     I used to do a lot of work for a crane maintenance  company ,  remove old controls , build and fit new panels to control crane by radio from the ground .   

 

First time with them I couldn't come to terms with the small cable size they used  for the hoist motor , which would be a large slip ring motor   ( Can't remember the HPs now)   .   But I was thinking in terms of constant running  when really the hoist motor only ran for 30 seconds  when it lifted    .   I think , where I would be thinking of  16mm   they used nothing larger than 6mm   or 10mm .   

 

We also removed the driver's cab , by request ,  to prevent the return of the driver sitting up there all day . 

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Sidewinder

EN 60204-32 for electrical systems of hoisting equipment 

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