Incident with a motor pump

[Integrator741]

Good evening.

Today at work one of my mate had an incident with a motor pump - he tripped over the motor supply cable (Probably the cable wasn't that good in the first place) and it just blew. That bang took out the motor's lid and all three phases apart.

Now the interesting part is that a breaker in our panel didn't trip, I've been told that the breaker is tested and it's working 100% - if that's the case, why it didn't trip?

thanks

 

[Minder]

Probabally one reason is breakers are time delayed devices, in order to avoid nuisance tripping on spikes etc.
The short was too brief for the breaker to react, this is why some equipment is fitted locally/internally with fast blow or even semi conductor fuses, which are super fast.
M.

 

[Integrator741]

So is there something that needs to be done about it?

 

[Tha fios agaibh]

Inverse time circuit breakers are sized from 150% to 300% of the motors full load current. (Usually 250%) here in the States anyway. Instantaneous breakers are sized even higher.
So the breaker did not have a chance to see the current at levels where it would trip. Low peak Fuses are preferred for motor circuits because of their ability to respond faster.

 

[Tha fios agaibh]

The real problem is why the motor cable was laying on the ground where someone could trip on it.
It also should have been properly secured where the ends of the cable wouldn't rip out by someone's foot.

John

 

[Integrator741]

The real problem is why the motor cable was laying on the ground where someone could trip on it.
It also should have been properly secured where the ends of the cable wouldn't rip out by someone's foot.

John

I couldn't agree more.

Thank you.

 

[Minder]

Ah yes OSHA does not extend to the UK!
M.

 

[hevans1944]

When you replace the motor, you might consider wiring a Cinch-Jones male connector with spade prongs on a short lead to the motor and a female Cinch-Jones connector to the power cord. Then, when Bozo trips over the cord again, it will simply disconnect from the motor.

 

[Tha fios agaibh]

Ah yes OSHA does not extend to the UK!
M.

No? Thought they'd be under;
https://osha.europa.eu/en/legislation/directives/council-directive-2006-95

 

[Tha fios agaibh]

Better still have an electrician run ridgid conduit and transition to liquid tight flexible metal metal conduit the last few feet.

 

[Minder]

No? Thought they'd be under;
https://osha.europa.eu/en/legislation/directives/council-directive-2006-95

I have been out of the electrical industry in the UK for some decades and do not remember it then, but it looks like it was something formed after the EU.
M.

 

[Tha fios agaibh]

I hear you!
Codes and standards are constantly changing and a struggle to keep up with.
As a master electrician one of the hardest things for me is to try and forget older codes and adapt to new ones.