Service Disconnect ?

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augie47

augie47

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State Electrical Inspector (Retired)
This was posed to me in a PM:

"I have been awarded a job to build services in an orange grove. The equipment served are two 200 hp motors 3ph 480v with softstart controllers. Each controller has a 400 amp breaker within enclosure. I was thinking, could I install a non-fused disconnect at the power company point of attachment, then take the feeders to the breaker in the controller enclosure?"

I posted it in the Forum as I don't find the answer to be "clear-cut"because of 230.91.

IF the controllers happen to be rated as service equipment, then I can see no problem bringing the service conductors straight to the controllers, or, if POCO or anyone desires a disconnect ahead of the controllers, the NF service rated disconnect could be added.

If the controllers are not listed as service equipment there is no problem with adding a service-rated NF disconnect, however I don't feel it would be considered the property "service equipment" as 230.91 requires OCP integral with or adjacent to the disconnect.

Add to the mix, this being outdoors, there would be no limit on the length of conductors whether we consider them service or feeders.

Any insight ?
 
Really the only 2 answers that are missing are,
What are the power company requirements for location of the Service Disconnect and
are the Controllers Service Entrance Rated.

If these 2 were known he has probably answered his own questions.
 
Answering the two questions,1) the softstart is Benshaw MX model # RX2E-250-480-12KP, 2) CT type metering. I don't know if the controller is service rated, but for safety's sake I would like to install a non-fused means of disconnect upstream at point of attachment. My AHJ has cited 430.94, which indicated he wants overcurrent protection,what interpretation do you come up with?
 
The 430.94 reference seems a bit odd as in your original PM you mentioned your controller having a circuit breaker and 430.94 allows the protection device to be within the controller.
As a practical matter, if you want disconnects at the POA, I would simply use a fusible disconnect for each controller feed which should resolve any issue.

As a matter of discussion, since your PM mentioned a non-fuse disconnect, I brought the discussion here to see others opinions of having a non-fuse disconnect feeding your controllers being Code compliant without the controllers being service rated themselves.
 
We have about same thing as described on 99.99% of irrigation well installations. The thing that is different is the POCO is installing the non fused disconnect on the pole right below their meter and the load side of this disconnect is essentially the service point. It is their way of providing a convenience disconnect instead of having to call them to disconnect power for most instances when that may be necessary. We treat the supply from there as service conductors, which since there is no overcurrent devices I believe they still are service conductors. When you reach the load end of these conductors you must have 1-6 rated service disconnecting means.
 
That would be my call also. Since there is no OCP at the N/F disconnect, there would need to be a service rated disconnect at the termination point (why I asked if his controllers might be service rated).
I posted his PM so that her could obtain other opinions.
You and I seem to view it the same.
 
kwired said:
We treat the supply from there as service conductors, which since there is no
overcurrent devices I believe they still are service conductors. When you reach the load end of these conductors you must have 1-6 rated service disconnecting means.
Click to expand...

I agree with this also.

It would be my opinion that you could'nt install a "Non Fused" disconnect ahead of a "Non Service Rated"
piece of equipment and be compliant.
 
augie47 said:
...

As a matter of discussion, since your PM mentioned a non-fuse disconnect, I brought the discussion here to see others opinions of having a non-fuse disconnect feeding your controllers being Code compliant without the controllers being service rated themselves.
Click to expand...
I don't think it matters whether the controller is service rated or not, as proposed. 230.82 lists the connections permitted on the line side of the service disconnecting means.

As I see it, the only way the proposed installation could be compliant is if the NF disconnect serves the purpose of a meter disconnect AND the controller is service rated.
 
Smart $ said:
I don't think it matters whether the controller is service rated or not, as proposed. 230.82 lists the connections permitted on the line side of the service disconnecting means.

As I see it, the only way the proposed installation could be compliant is if the NF disconnect serves the purpose of a meter disconnect AND the controller is service rated.
Click to expand...

I think that's a good point.
I didn't think to check that section as it seemed if someone wanted a disconect for safety purposes it would be allowable :D

In addition, in reading T&M's PM again, I also realized we are speaking of large motors and most likely higher available fault currents.
In that regard, as mentioned in 230.82(3), even if non-fuse disconnect were allowed, it would not likely have a high enough rating for the available fault current.

Taking everyone's comments into consideration, it appears a disconnecting means with OCP is the only compliant route.
 
Thank you very much Gentlemen, as my first appearance on this forum I am fortunate to have colleagues with such vast NEC wisdom. Thank you all once more, I'll continue reading and learning form the posts on this forum. As for the fused or non-fused disconnects at point of service I'll opt for fused service rated switch in the design, thanks again for your insight in this important matter.
 
How much distance are we talking between the controller and this disconnect?

There is no limitation on length of service conductors if they are outdoors.

If the loads supplied are not part of same structure, there is no reason each can't be supplied by individual services.

Before someone brings up anything about one service for the facility, remember what we are talking about here - an orange grove. This could be something on hundreds of acres and to supply everything on the site is just not that feasible to do with a single service of 600 volts or less. A manufacturing plant with multiple buildings on only 10 acres is a lot different.
 
It would help me if I could see a drawing of the proposed installation.

But from what I understand;

For long runs, it would be HV to a pole mounted transformer. Service down to a meter, with a fused disconnect supplying (and protecting) short feeders to the motor controller. The fuse selection would provide required AIR and possibly short curcuit and ground fault coordination with controller OCD.

Also, we have to address Grounding and bonding at the service and equipment.

Then how is the motor controlled and monitored? Wireless communication?

How do we route signalling and control conductors in relation to power conductors?
 
MarineTech said:
It would help me if I could see a drawing of the proposed installation.

But from what I understand;

For long runs, it would be HV to a pole mounted transformer. Service down to a meter, with a fused disconnect supplying (and protecting) short feeders to the motor controller. The fuse selection would provide required AIR and possibly short curcuit and ground fault coordination with controller OCD.

Also, we have to address Grounding and bonding at the service and equipment.

Then how is the motor controlled and monitored? Wireless communication?

How do we route signalling and control conductors in relation to power conductors?
Click to expand...
I know little about orange groves, but for a typical irrigation system around here, HV is POCO owned equipment, they typically install a transformer (bank of transformers) on a pole at the edge of the field, with meter at this pole. A disconnect is not necessarily required but POCO often puts one on the pole just below the meter. It is unfused and they typically do this so the owner has a convenient way to disconnect the usual nearly 1/4 mile of conductor that will be run to the center pivot location instead of having to call POCO to disconnect the transformers to work on these conductors. I suppose if the disconnect were supplied by contractor maybe available fault current could be a reason to require a fused disconnect, but since it is POCO supplied inspector does not even look at it, and from there we have customer owned and maintained service conductors to the first disconnect(s) often about 1/4 mile away.
 
kwired said:
I know little about orange groves, but for a typical irrigation system around here, HV is POCO owned equipment, they typically install a transformer (bank of transformers) on a pole at the edge of the field, with meter at this pole. A disconnect is not necessarily required but POCO often puts one on the pole just below the meter. It is unfused and they typically do this so the owner has a convenient way to disconnect the usual nearly 1/4 mile of conductor that will be run to the center pivot location instead of having to call POCO to disconnect the transformers to work on these conductors. I suppose if the disconnect were supplied by contractor maybe available fault current could be a reason to require a fused disconnect, but since it is POCO supplied inspector does not even look at it, and from there we have customer owned and maintained service conductors to the first disconnect(s) often about 1/4 mile away.
Click to expand...

Thanks for the description.

It would be interesting to calculate the 1/4 mile loss (heating) expense per year in power usage in relation to paying for upfront HV underground lines to the center pivot. Also, the OC device AIR at the controller must somehow handle the increased inductance in this long feeder.
 
MarineTech said:
Thanks for the description.

It would be interesting to calculate the 1/4 mile loss (heating) expense per year in power usage in relation to paying for upfront HV underground lines to the center pivot. Also, the OC device AIR at the controller must somehow handle the increased inductance in this long feeder.
Click to expand...

That is something to consider. I have often wondered why the HV is not run to the center pivot. I was once told the HV cables don't have the life expectancy that the LV cables would have. I would also guess POCO does not want to have the added infrastructure to maintain, and if they did, would have to consider maintaining those lines in distribution charges.

As far as losses, these are seasonal loads, heaviest loading is typically in July and August, as crops are more mature and require more water at that stage. If we were to have some help from mother nature, the demand for water is less.

I don't know what the difference in operating costs are, but for the past 20 years or so there has been pretty good demand for farmers wanting electric wells for irrigation (majority of them being 60 to 100 HP). The power companies will only let so many on their system each year as they need to have their distribution updated to handle the additional load. Most common alternative power source is diesel engine, and some propane or natural gas units are scattered around also. I would guess even with any line losses it is considered overall a better deal than using fossil fuels. With an electric motor you not only have energy cost to consider, you also get rid of oil changes and other maintenance, new and used oil handling, storage, disposal, fuel delivery, and other items that you have with internal combustion engines. Electric motor requires little maintenance in comparison.
 
Gentlemen, The POCO will be suppyling 501 KVA at pole mount transformers, secondary will be 480/277Y. The service may seem doubled because, at each well and retention pond which are within close proximity to each other we will have two 200 hp motors. My intention is to build two 400 amp services, rather than have one 800 amp disconnect, and nipple into softstart controller. The distance from HV is about 1/4 mile all pole distribution, the size of project is 2,200 acres (this phase) there will be 3 retention pond/well locations. The POCO Supervising Engineer told me they would be using CT's at each service and added that they would be in a 36"X36" enclosure, I don't know what that means maybe tap thru, I'll talk to his meter tech and get more info this week. There is alot of design work before can apply for a permit, it's not that though with everyone on the same page the job should go smooth. Later, Tom
 
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