Motor Disconnects At Sewage Aeration Ponds

[Cow]

What does your AHJ say about disconnect location for a submersible well pump? Should you put submersible disconnect within 50 feet of the pump within the well casing?

That isn't logical, besides the exception already covers that scenario...

(a) Where such a location of the disconnecting means
for the motor is impracticable or introduces additional or
increased hazards to persons or property

(b) In industrial installations, with written safety procedures,
where conditions of maintenance and supervision
ensure that only qualified persons service the equipment

Hopefuly they wear the appropriate arc-flash PPE when they disconnect the plugs?!

I don't worry about that, it's not my responsibility to enforce other peoples safety policies....

 

[iwire]

What will happen on the inside of a SS enclosed disconnect? Would you rather be working with a potentially unsafe disconnect or be able to lock out in a safe location? Would you rather be wearing your Mars-suit in the outdoor, or in a controlled indoor environment?

I think a better question is what is the compelling reason not to provide this disconnecting means?

Very doubtful that it would reduce the safety to persons or property.

 

[weressl]

That isn't logical, besides the exception already covers that scenario...


I don't worry about that, it's not my responsibility to enforce other peoples safety policies....

It is NFPA 70E, so if you're the one who starts up or commissions the equipment you better wear the PPE yourself.

Boldened text indicates the applicable issues for this scenario.

The location of the switch in a splashing and humid area presents INCREASED hazards to persons and a sewage treatment facility is under the control either of an industrial establishment, a municipality or a Government Agency and all those are obligated by various laws to service these facilities with qualified persons.

Exception to (1) and (2): The disconnecting means for themotor shall not be required under either condition (a) orcondition (b), provided the controller disconnectingmeans required in accordance with 430.102(A) is individuallycapable of being locked in the open position.The provision for locking or adding a lock to the controllerdisconnecting means shall be installed on or atthe switch or circuit breaker used as the disconnectingmeans and shall remain in place with or without the lockinstalled.(a) Where such a location of the disconnecting meansfor the motor is impracticable or introduces additional orincreased hazards to persons or property(b) In industrial installations, with written safety procedures,where conditions of maintenance and supervision​

ensure that only qualified persons service the equipment.

 

[weressl]

I think a better question is what is the compelling reason not to provide this disconnecting means?

Very doubtful that it would reduce the safety to persons or property.

A disconnect next to a splashing humid location whose internal condition can not be determined is not less safe than the same located/provided in an inside, dedicated electrical room?

 

[weressl]

For reference only.

In 240.90, the NEC talks about 'supervised industrial facilities', and then it goes on to clarify with "exclusively for manufacturing or process control activities".

There is also 240.2 which lists 3 qualifications to be considered a 'supervised industrial facilitiy' and uses the word 'process'.

As it is in Article 240, that definition is only applicable to THAT section, not the entire NFPA 70. It should be in Article 100 to be applicable to the entire Code.

 

[jim dungar]

...that definition is only applicable to THAT section, not the entire NFPA 70.....

So what part of

For reference only.

do you not understand?

 

[iwire]

A disconnect next to a splashing humid location whose internal condition can not be determined is not less safe than the same located/provided in an inside, dedicated electrical room?

Are you suggesting that a proper disconnect for the environment could not be specified?

 

[weressl]

So what part of
do you not understand?

Reference as in relevance. I can quote something out of Roger's Theasurus and be related to the subject, but irrevelant.

 

[weressl]

Are you suggesting that a proper disconnect for the environment could not be specified?

Yes and no.

Yes from the theoretical view point.

No from the practical viewpoint. Specifying a SS enclosure does didly-squat for the components inside. Can't tell you how many of these type installations we'd seen looking pristine on the outside and upon opening one will find the components rotten and corroded, ready to fail upon the FIRST attempt to operate. THAT is where it is more dangetous to have it than not. It is not on the day of installation, but down on the road, in service, when you need it. SO from the installer standpoint of view it is perfectly fine, but from the operational viewpoint it is garbagge. Consequently if we are forced to install any power component or control panels in a wet and corrosive environment, it gets a purge installed on it. http://www.pepperl-fuchs.us/usa/en/classid_2070.htm?tvpv=pa

 

[petersonra]

Are you suggesting that a proper disconnect for the environment could not be specified?

You could pressurize it. My suggestion would be that you seal the conduits first to reduce the amount of air required. All it would take is a relatively inexpensive air regulator, and probably some kind of coalesing filter. But the plant would need to run an air line out there, if there is not one there already.

I think the best bet is if it is that bad is to avoid putting anything there that you do not absolutely have to put there.

 

[weressl]

You could pressurize it. My suggestion would be that you seal the conduits first to reduce the amount of air required. All it would take is a relatively inexpensive air regulator, and probably some kind of coalesing filter. But the plant would need to run an air line out there, if there is not one there already.

How much air are you going to loose through the breaker/disconnect handle connection?

Do you know the cost of air?

I think the best bet is if it is that bad is to avoid putting anything there that you do not absolutely have to put there.

Now, yer talking....

 

[jim dungar]

Reference as in relevance. I can quote something out of Roger's Theasurus and be related to the subject, but irrevelant.

How is a limited NEC reference not relevant to a general discussion of possible interpretations of a related, but undefined, NEC reference? It has as much relevance as your assumption that the environment, under discussion, will be splashing and humid.

 

[weressl]

How is a limited NEC reference not relevant to a general discussion of possible interpretations of a related, but undefined, NEC reference? It has as much relevance as your assumption that the environment, under discussion, will be splashing and humid.

The discussion is not general, it is about a specific requirement in 430.

The "splashing and humid" is not an assumption but my personal and direct expereince with the specific - here is that word again - equipment, namely: aerators.

 

[iwire]

You could pressurize it. My suggestion would be that you seal the conduits first to reduce the amount of air required. All it would take is a relatively inexpensive air regulator, and probably some kind of coalesing filter. But the plant would need to run an air line out there, if there is not one there already.

I think the best bet is if it is that bad is to avoid putting anything there that you do not absolutely have to put there.

Maybe we all have different areas in mind, but this is pretty much what I visualize when I think of a water treatment plant. I don't mean exactly like this, but generally outdoors and the switches are not being sprayed with water.

The picture below pops up on a search for sewage aeration pond, again I see no problem locating a disconnect at the equipment, there is one there.

 

[jim dungar]

The discussion is not general, it is about a specific requirement in 430.

But the definition of 'supervised industrial location' is not defined in 430, so other NEC specific interpratations my be relevant in passing judgement of intent.

The "splashing and humid" is not an assumption but my personal and direct expereince with the specific - here is that word again - equipment, namely: aerators.

The OP said the aerators could only be reached by boat or by 'pullin them in', this means the pumps are floating in the middle of a pond. While some wind blown mist may occasionally occur, my personal experience has been the shoreline is not normally subject to splashing by the process liquid.

 

[weressl]

Maybe we all have different areas in mind, but this is pretty much what I visualize when I think of a water treatment plant. I don't mean exactly like this, but generally outdoors and the switches are not being sprayed with water.




The picture below pops up on a search for sewage aeration pond, again I see no problem locating a disconnect at the equipment, there is one there.

Lets look at these in motion:

 

[petersonra]

How much air are you going to loose through the breaker/disconnect handle connection?

Do you know the cost of air?

I did not say it was a good idea. but if you are forced to put in a disconnect switch in an area that is somewhat corrosive in nature it might be the only real answer.

 

[iwire]

Lets look at these in motion:

Uh huh, I understand, but none of us have a clue if the OPs pond looks like your link or if it looks like glass.

Again I ask the question can't you spec a disconnecting means for the designed environment? Obviously the motor is in that environment and survives.

I am baffled why are you insisting on putting the longevity of electrical equipment ahead of the safety of personal.

I know our AHJs do not feel like you do and I am glad of that.

 

[kwired]

Uh huh, I understand, but none of us have a clue if the OPs pond looks like your link or if it looks like glass.

Again I ask the question can't you spec a disconnecting means for the designed environment? Obviously the motor is in that environment and survives.

I am baffled why are you insisting on putting the longevity of electrical equipment ahead of the safety of personal.

I know our AHJs do not feel like you do and I am glad of that.

Doesn't longevity of the equipment have an impact on how safe it is when it starts to deteriorate - not trying to argue against using the disconnect but it is reality. A few code cycles ago a lockable disconnect at the controller was suitable disconnect for the motor, some jurisdictions still allow that as it once was worded.

 

[iwire]

Doesn't longevity of the equipment have an impact on how safe it is when it starts to deteriorate

Of course, and just like the motor it serves, the disconnect may need replacement sooner due to the environment.

but it is reality.

And so is people taking shortcuts when the disconnect is not right at the equipment.

A few code cycles ago a lockable disconnect at the controller was suitable disconnect for the motor,

I do not remember that, what code cycle allowed that?

The substantiation may prove very interesting and on point in this thread.