Motor Control Push Button

[Elekk]

This refers to the situation when an outdoor motor is controlled by an indoor starter.

Is it required by BS/IEC code that in addition to starter, a local stop/start or hand/off/test push button is needed near the motor? Or is it enough to control the motor only from the starter in the switchboard?

 

[Sidewinder]

Two things, Risk Assessment, and what the motor does immediately spring to mind.

The motor will really require a local isolator always provided it is a normal 1/3ph DOL / Y/D motor.

Need some more info really...

 

[Elekk]

This is a 22kW 400V 3-Phase squirrel cage DOL (direct on line start) motor which drives a centrifugal pump in industrial plant.

It makes sense to put a local isolator but the main question is whether it is required by code or not. Because if not, then it is hard to justify the installtion of the local isolator to the client.

 

[Sidewinder]

PUWER98 & EAWR89 (BOTH STATUTORY) can be interpreted to require local isolator, as does 7671.

Are you sure that it is 22kW DOL!!!!!!!!!!!!!!!!!!!!!!

 

[Elekk]

It looks that all motors which can give rise to hazard need an isolator installed adjacent to the motor. But what is the definition of motor being a hazard? Does it have to do something with the maintenance of motor? I'd appreciate any explanation!

 

[Sidewinder]

If you can get electrocuted whilst working on the motor or its supply terminals should it be switched on from a remote location then you need a means of isolation under your control local to the motor.

If the motor can give rise to a hazard of any kind, anywhere if started from a location remote to itself or its "action" location then there are other considerations....

 

[Riggy]

You really don't want to be starting a 22Kw Pump on Direct On Line, total madness

In every situation?

 

[Sidewinder]

Pretty much Riggy, work out the LRC on a 22kW motor for DOL starting!

 

[Elekk]

Schneider and others have direct online startes for motors 22kW and even larger upto 250kW.

 

[Sidewinder]

Yes they are available, however, do you have the incoming supply to allow this.

As I said above work out the LRC and see what you are drawing!!!

 

[revjames]

You really don't want to be starting a 22Kw Pump on Direct On Line, total madnessIsolator Required as above

At the Aluminium smelter (where I worked until oct 09) we started everything DOL including 3.3KV 1850HP ID Fans, large compressors, overhead cranes the lot. And NOTHING had a local isolator. It was a site standard that everything was isolated in the MCC (motor control centre) rooms and locked off. Supply was verified as dead at the equipment before commencing work.

 

[Riggy]

Pretty much Riggy, work out the LRC on a 22kW motor for DOL starting!

I spent the first 25 years of my working life at a factory where we started everything below 100hp (and quite a few above) DOL The bigger stuff had soft starts or DOL start with fluid couplings. I agree this is unusual but statements like "total madness" pee me off with no knowledge of the context.

 

[Sidewinder]

Rev,

You has SSW to allow this in a controlled environment, however, this does NOT meet the heirarchy of control in current H&S legislation.

You may have been given a waiver as you were a controlled site, however, this cannot be taken carte blanche.

Riggy,

Fluid couplings have unique characteristics which will allow DOL starts with significant external loads.

In this day and age to stat a motor DOL at 22kW is unnescessary, and unlesss you have a sufficiently robust supply and have liaised with the DNO, then you will have other legal issues to deal with.

Things move on, just because it was OK, it is not necesarrily now.

ALA 7671.

There are other LAWS of the LAND which require certain things which are not covered in 7671 one must be aware of these to comply with them.

 

[Riggy]

I understand all of this, the point that I was trying (and obviously failing) to make was that jumping on the OP's comment about DOL starting a 22kW centrifugal pump wasn't all that helpful.

I also failed to clearly explain the use of fluid couplings by my former employer. They were used only on big stuff (250kW upwards) and only on loads with long run-up times (centrifugal fans, etc)

 

[revjames]

The smelter had its own 132KV sub and used 250MW so werent too bothered about things like MD. Was an experience to stand by the ID fans and manually start them. Some newer parts of the plant had inverter starts but the cost of modifying 4 motors of this size was prohibitive.

 

[Sidewinder]

Riggy,

I did not jump on the OP merely questioned the DOL of a 22kW motor at 400V a.c. IMHO.

The reason being that few posters on here asking questions of this sort are working with such systems as you descrive else they would be working for an ellectrical engineer who would explain the situation or design the system for them, as I would.

Rev,

Were the ID fans 400V a.c.?

I stand by my commet to Riggy in this post.

One has to remember that both of you almost certainly had electrical engineers overseeing your site.

Questions like this to me smack of no engineering input what so ever.

Sorry.

 

[Riggy]

!!!!!!!!!!!!!!!!!!!! = ?

I'll remember that conversion!

 

[Sidewinder]

What did I miss?...

 

[revjames]

Riggy,Rev,

Were the ID fans 400V a.c.?

I stand by my commet to Riggy in this post.

One has to remember that both of you almost certainly had electrical engineers overseeing your site.

Questions like this to me smack of no engineering input what so ever.

Sorry.

Quite right, there were engineers everywhere. Senior engineers, area engineers, improvement engineers, reliability engineers, planning engineers (me)

The ID fans were 3.3KV and ran 24/7 so didnt have to stop start very often, just for maintenance and power failure etc. still a large inrush current even at that voltage. The electricity savings of inverters were worked out into 7 figure sum but the cost of doing was something like

 

[Riggy]

What did I miss?...

Sorry, I was being naughty, you merely questioned the OP's suggestion of 22kW DOL by using 20 exclamation marks. I couldn't resist!