What is a service disconnect?

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Adamjamma

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Jamaica and london
I will be getting with the utility engineer myself later, but I am fairly certain that they & the city will want fused disconnect at the utility pole before it changes to underground. Thanks
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Now, again, I am a newbie to the codes and trying to learn from those more experienced than I, but, correct me please:
If you have a meter on a pole, just a meter, mind you, and no disconnect into an underground conduit system for a normal home, or even most businesses, there are no fuses to regulate anything until you get to the main panel, where your service disconnect is. This is allowed to be derated, etc and so forth.

There are arguments that a firemans disconnect may be needed, but nothing concrete in most places at this time.

Above there was an argument that if a simple disconnect is used, non-fused, that this would not affect the service rating of the underground feed. This is similar to what has been used forever in Rural Farms and in many apartment complexes, where a pole mounted disconnect that is accessible only by fire poles and utility poles can reach it to disconnect the services at the top of the pole.
Why then would they require it to be fused? Because it is 600 amps rather than 400 or 200 or 100 amps? Just trying to understand not start more fuss... Because I really cannot see the difference here. Personally, would prefer to see a definition in the code to keep it as service until it hits main disconnect at panel, and keep any firefighter or other service related disconnects as service only but having trouble seeing why there is such a difference, or, is it that we are going to be seeing a future shift from three wire service entrance to a four wire service entrance with no derating and they are trying to do it step by step?
 
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Adamjamma

A lot of the items posted here are according to local codes. The AHJ (authority having jurisdiction) whether it be the utility company and/or the local government that inspects it. That is another reason why this is "so much fun", trying to find out what each one wants and in some cases where both of them want different things on the same job.
 
Adamjamma said:
Now, again, I am a newbie to the codes and trying to learn from those more experienced than I, but, correct me please:
If you have a meter on a pole, just a meter, mind you, and no disconnect into an underground conduit system for a normal home, or even most businesses, there are no fuses to regulate anything until you get to the main panel, where your service disconnect is. This is allowed to be derated, etc and so forth.

There are arguments that a firemans disconnect may be needed, but nothing concrete in most places at this time.

Above there was an argument that if a simple disconnect is used, non-fused, that this would not affect the service rating of the underground feed. This is similar to what has been used forever in Rural Farms and in many apartment complexes, where a pole mounted disconnect that is accessible only by fire poles and utility poles can reach it to disconnect the services at the top of the pole.
Why then would they require it to be fused? Because it is 600 amps rather than 400 or 200 or 100 amps? Just trying to understand not start more fuss... Because I really cannot see the difference here. Personally, would prefer to see a definition in the code to keep it as service until it hits main disconnect at panel, and keep any firefighter or other service related disconnects as service only but having trouble seeing why there is such a difference, or, is it that we are going to be seeing a future shift from three wire service entrance to a four wire service entrance with no derating and they are trying to do it step by step?
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A means of disconnect must be provided at or near the closest point of entry to a structure.

Service Conductors are very limited to the length they can travel inside a structure once they get to the structure they are servicing.

Thus you generally see a Meter/Main or Fused Disconnect, Enclosed Circuit Breaker outside by a meter mounted on a house. or a Main Breaker in the panel directly behind the meter.

This, most times serves the purpose of both a disconnect and a means of overcurrent protection.

That 1st means of overcurrent protection is the determining point as to where the service conductors end and where a feeder begins.

If no overcurrent protection exists in the disconnect then the conductors passing through that disconnect from the utility are still Service Conductors.

If there is overcurrent protection in the disconnect, such as fuses, or if the Disconnect happens to be an Enclosed Circuit Breaker then the conductors on the line side of that disconnect are Service Conductors and the conductors on the load side of the overcurrent protections device are considered a feeder.

The rules of installation are different for Service Conductors versus Feeder Conductors.

A Service Rated disconnect has a Neutral terminal in it and a means to bond the neutral to the Grounding Electrode Conductor inside the disconnect.

Once that bond is made, the Grounded Conductor and the Equipment Grounding conductor must be kept separated from that point on. Thus a 4 wire feeder would be required.

The fuses, If installed out at the pole in a fused disconnect, are not there to "de rate" the service, they are there to protect the feeder conductors to the structure because an overcurrent protection device was installed making it such.

The decision to place the Overcurrent protection device remote from the structure is what brought the 4 wire feeder into affect.

The NEC is not trying to shift services from 3 wire to 4 wire at all.

The placement of the first means of overcurrent protection and where the first bond from the Grounded Conductor to the Grounding Electrode Conductor on the Customers side is what determines what type of installation you will end up with.

This is just a very non technical overview as if we were sitting on the tailgate trying to hammer this out. :)

JAP>
 
jap said:
That 1st means of overcurrent protection is the determining point as to where the service conductors end and where a feeder begins.

If no overcurrent protection exists in the disconnect then the conductors passing through that disconnect from the utility are still Service Conductors.

If there is overcurrent protection in the disconnect, such as fuses, or if the Disconnect happens to be an Enclosed Circuit Breaker then the conductors on the line side of that disconnect are Service Conductors and the conductors on the load side of the overcurrent protections device are considered a feeder.

The rules of installation are different for Service Conductors versus Feeder Conductors.

A Service Rated disconnect has a Neutral terminal in it and a means to bond the neutral to the Grounding Electrode Conductor inside the disconnect.

Once that bond is made, the Grounded Conductor and the Equipment Grounding conductor must be kept separated from that point on. Thus a 4 wire feeder would be required.

The fuses, If installed out at the pole in a fused disconnect, are not there to "de rate" the service, they are there to protect the feeder conductors to the structure because an overcurrent protection device was installed making it such.

The decision to place the Overcurrent protection device remote from the structure is what brought the 4 wire feeder into affect.

The NEC is not trying to shift services from 3 wire to 4 wire at all.

The placement of the first means of overcurrent protection and where the first bond from the Grounded Conductor to the Grounding Electrode Conductor on the Customers side is what determines what type of installation you will end up with.
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Is it possible to have such a pole-mounted disco/OCP and still have a 3-wire supply and land on a second disco/OCP at the house?
 
LarryFine said:
Is it possible to have such a pole-mounted disco/OCP and still have a 3-wire supply and land on a second disco/OCP at the house?
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You already know the answer to that.

We've been through all of this before in another thread.

The OP mentioned he didn't want to make a fuss out of all this.

JAP>
 
jap said:
You already know the answer to that.

We've been through all of this before in another thread.
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I honestly don't remember, but I have no dog in this fight.

I'm simply asking whether the rule is that the first disco is the service disco, or the one on the structure being served.
 
A few points:

1. Depends where the service point is. If there is something on the utility side, it's not a service disconnect.

2. Note meter disconnect switches are allowed per nec. It's not really clear how/when to differentiate this from a service disconnect.

3. Note the service disconect and OCPD must be the same or immediately adjacent to each other.

4. Nothing wrong (per nec) with hitting a meter only on a pedestal and running hundreds of feet after.

5. You need a fused disconnect for a meter disconnect if the fault current is above 10ka. Otherwise nonfused is fine.
 
perhaps that is what I am having problems with, especially when trying to figure out the so called fireman switches. One of your statements was if a service disconnect is used an ocpd must be used almost immediately. But that then means you must upsize the rest of the wire and switch to a four wire system. No more de rating the feed.

Perhaps this is why so many manufacturers and others are against the fireman switch. Because it takes cost up in wires so how are you going to argue it to a consumer who is looking at the idea that one: it has never been needed before, and Two, their money is already stretched to the breaking point and it just seems to be something not really needed because it hopefully will never be used.

This gets worse when trying to figure out how to do a fireman switch for solar or other supplies in a home, where you then start looking at relays or external conduits before bringing the power inside the home. About the only way I can figure is to use a group of relays on one disconnect, so you do nut run into the six disconnect rule as well.

Just wondering if either the rules need clarified or a whole section needs written so the fireman switches can be put into place without costing homeowners a fortune in such a way that they decide to hire handymen to wire their homes because electricians have to follow expensive rules. Personally, I do not see the need to have to switch the feeders from a fireman switch to a four wire system just because we are trying to allow firemen a way to cut power to a building before they enter it, especially when utility power can be cut by simply pulling the meter, thus the main power systems we are trying to group with the fireman main utility switch are those that supply alternate energy modes to the property.

But again, I am a student, looking at this as if I am trying to convince a person they should add this switching system to their property for safety sake in case of fire, when no one else in a neighborhood has it on their homes, which were built earlier. It is like selling people on surge protection devices...

Does not make it any easier when it looks in catalogues like such a switch is between 500 and 1000 dollars yet the main breaker panel can be bought for less than two hundred...
 
Adamjamma said:
trying to figure out the so called fireman switches.

No more de rating the feed.

many manufacturers and others are against the fireman switch.

Just wondering if either the rules need clarified or a whole section needs written so the fireman switches can be put into place without costing homeowners a fortune in such a way that they decide to hire handymen to wire their homes because electricians have to follow expensive rules.

Personally, I do not see the need to have to switch the feeders from a fireman switch to a four wire system just because we are trying to allow firemen a way to cut power to a building before they enter it, especially when utility power can be cut by simply pulling the meter, thus the main power systems we are trying to group with the fireman main utility switch are those that supply alternate energy modes to the property.
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I'm not sure what your meaning when you refer to "De rating the Feed" ?

What are you considering a "Firemans Switch" and why are you so much against it ?

I've never seen a manufacturer that was against selling product.

The owner cannot hire a "Handy Man" that is not licensed as an electrician to do the install.

If your local authority requires the Service Disconnect to be located on the outside of a structure, like ours does, You either put it in or your project doesn't pass inspection to get the power turned on at all.

The utility meter does not meet the definition of a disconnect and cannot be used as one.

The NEC does not need to be re-written.

It would be better to take the necessary steps needed to obtain a better understanding of it.

JAP>
 
It is more a question of why am I considering a firemans switch. The requirement for the neutral and four wire feeds and full ratings are fairly new in some ways. Well, guess it may go back to 90's but... residences were able to run 200 amp services on cables capable of running less than 200 amps from the meter to the main panel inside, whether overhead or underground. Suddenly, if a disconnect goes in between the meter and the main panel, so it can be turned off from outside the home, or from near the road on a long run like in the rural areas or places like I deal with in Jamaica, where the POCO wants meters visible from property line so they do not have to enter the property, the wiring from that disconnect must be four wire now. and at fill amps not the reduced amps. Which can add a lot more cost, especially when one adds in voltage drop. I have dealt with a property before where the customer had a meter at the driveway entrance from the road, with a disconnect on their post, and then had a half mile run along the driveway to a post in the center of their yard before splitting to feed 4 separate buildings, each treated as a main panel. To me a typical farm system. Disconnect at the meter post and disconnect at the central post in the main yard could both be used to disconnect the utility from the buildings in case of a fire. All of it run on three wires from the meter until you got to the buildings, with two disconnects that had no fuses in them. System at least thirty years old when I last saw it and worked fine.

To do a similar system would require heavier wire and a four wire system from what many are saying... between voltage drop and the requirement now to, at least from what I am reading, create a grounded and bonded system from the meter location along the half mile driveway to the buildings.. four wire from road to buildings as well. But is it actually any safer? Or is it just adding cost? The main reason for the disconnects at the road to the main post was so if a storm blew a tree down that took the wires down, one could disconnect the power, fix the wire, and turn the power back on. Main reason for disconnect at pole in yard was so one could change services at the various buildings or even add extra buildings to the services.

Of Course, now some farms have major three phase services supplying milk systems etc, but, most farms in Jamaica are not so advanced and with customs fees at the wharf may never get that advanced. However, fire department in Jamaica has asked if in future codes it could somehow be written to require a disconnect on the outside of all structures. Placed at no higher than 2.7 meters from either grade or sidewalk or pavement.
 
I think basically I am trying to figure out if we can get a consensus or a reason for not requesting the following: If a disconnect is requested by local authorities on the outside of a building or at a meter ( the fire fighters disconnect) then this can be a non fused disconnect. This would not replace the main fused disconnect at the main panel, and can thus be fed from the meter to its position, and from it to the main panel and/or main OCPD under the regular single residence rules of feeding the main panel.
If a fused disconnect is used, this must become the main OCPD and the feeder rules then are in place from this position to the main panel and an OCPD may not be required at the main panel.

Of course, idiots like myself probably will put an OCPD at this position and at the main panel as well, just because it does protect the wire, and in Jamaica wire is very expensive, but...

Main reason I am looking at this is the island is looking at adopting the NEC as the majority of its code regulations. There will be a few modifications due to the closeness to UK and Canada, but hopefully pulling the better and not the worst parts of them in regards to the styles of building construction and weather problems on the island. Not trying to make anyone angry, just trying to understand more of the safety concerns of such systems, as the main difference comes down to the requirement that one, the meter be located on a pole constructed at the property line so the meter reader does not need to enter the property, two, that there be a panel on each floor in an accessible location that is not in a closet or behind a closed door, with OCPD on each panel, and the first panel from the meter being wired as the main panel, with the neutral and grounds separated after that panel in all other panels, but they must be fed from this panel, and now with the possible requirement to include an outside disconnect, that is grouped with disconnects for any solar, wind or other generation means, is able to be disconnected by fire fighters in case of emergency, but is lockable so as to keep vandalism at a minimum. The exact codes are not yet actually written to give us the basics but are only the suggested after the fire departments requested such switches after having some problems with certain house fires.
But, I am not sure how good such switches would be in a country that the average time of response for the fire department is two to three hours... yes, hours...
Already stated in the possible amendments to the NEC if adopted are the color codes of wires, the number of outlets per circuit in a kitchen, which they will not raise from three..lol... even with many of us asking for five... and the requirement that each floor have its own panel box, including any basement if accessible and having any outlets. Oh, and no panel box may be on an outside wall if the wall is concrete construction... laughed when I saw that one...
 
Adamjamma said:
It is more a question of why am I considering a firemans switch. The requirement for the neutral and four wire feeds and full ratings are fairly new in some ways. Well, guess it may go back to 90's but... residences were able to run 200 amp services on cables capable of running less than 200 amps from the meter to the main panel inside, whether overhead or underground. Suddenly, if a disconnect goes in between the meter and the main panel, so it can be turned off from outside the home, or from near the road on a long run like in the rural areas or places like I deal with in Jamaica, where the POCO wants meters visible from property line so they do not have to enter the property, the wiring from that disconnect must be four wire now. and at fill amps not the reduced amps. Which can add a lot more cost, especially when one adds in voltage drop. I have dealt with a property before where the customer had a meter at the driveway entrance from the road, with a disconnect on their post, and then had a half mile run along the driveway to a post in the center of their yard before splitting to feed 4 separate buildings, each treated as a main panel. To me a typical farm system. Disconnect at the meter post and disconnect at the central post in the main yard could both be used to disconnect the utility from the buildings in case of a fire. All of it run on three wires from the meter until you got to the buildings, with two disconnects that had no fuses in them. System at least thirty years old when I last saw it and worked fine.

To do a similar system would require heavier wire and a four wire system from what many are saying... between voltage drop and the requirement now to, at least from what I am reading, create a grounded and bonded system from the meter location along the half mile driveway to the buildings.. four wire from road to buildings as well. But is it actually any safer? Or is it just adding cost? The main reason for the disconnects at the road to the main post was so if a storm blew a tree down that took the wires down, one could disconnect the power, fix the wire, and turn the power back on. Main reason for disconnect at pole in yard was so one could change services at the various buildings or even add extra buildings to the services.

Of Course, now some farms have major three phase services supplying milk systems etc, but, most farms in Jamaica are not so advanced and with customs fees at the wharf may never get that advanced. However, fire department in Jamaica has asked if in future codes it could somehow be written to require a disconnect on the outside of all structures. Placed at no higher than 2.7 meters from either grade or sidewalk or pavement.
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We too are required to have a disconnecting means on all of our structures being fed by electricity.
whether it ends up on the inside or outside is usually up to what the project allows and what is required by local ordinances.

Sometimes that disconnect can be as simple as a single pole light switch.

As far as in your scenario, the service disconnect they are talking about may be just that. A Non Fused disconnect for the 3 wire service conductors that they can seal off themselves to limit it's use.

Have you asked them, or, are you speculating that this is where the 4 wire feeder will have to begin ?


JAP>
 
After the service point, the first disconnecting means and OCPD, which must be together, is the Service Equipment by NEC description/definition. The grounding electrode system must also be located here, which means everything past this is a feeder, requiring an equipment ground, thus the "4-wire feed".

If fire safety rules are incorporated into the local code, it is possible to require the Service Equipment to be located outside at a location accessible to emergency responders. In areas of the country where basements and crappy weather are rare, service equipment and main loadcenters are often outdoors. But even if the home has an indoor panel the service equipment with disconnect can be located outside.
 
The power company here requires a disconnect ahead of the meter on 480v services so they don't have to bypass and pull the meter under a load.

They put their seal on it.

This is not considered our service disconnect where the overcurrent and bonding takes place.

I don't see this as being much different than what the OP's up against.

Jap>
 
jap said:
The power company here requires a disconnect ahead of the meter on 480v services so they don't have to bypass and pull the meter under a load.

They put their seal on it.

This is not considered our service disconnect where the overcurrent and bonding takes place.

I don't see this as being much different than what the OP's up against.

Jap>
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They don't trust that a disconnect on the other side is equally capable of opening any closed circuits?

Must be PP&L......Paranoid Power & Light :D
 
jap said:
Have you asked them, or, are you speculating that this is where the 4 wire feeder will have to begin ?


JAP>
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Currently they are still arguing over the need to use the NEC or to just write their own codes or to leave it as it has been for twenty years plus... but the fire department is asking them to do something and no one has any great idea because of electricity thefts and such. Fire department says putting it at certain height is within reach of the pole carried on fire truck, so the fire department could flip it off yet your normal burglar etc would need ladders to reach it. Current argument is not just an is it needed but how does the average person in the island who already is having trouble with new rules and costs of importing supplies afford something that costs so much when they have never needed it before.
But, this is a bunch of politicians arguing over wether or not there is a need for taxicabs to pay for their permits or have they been charged improperly..lol
A group of us who actually want to make sane safe rules for the industr are trying to find efficient ways to do this and find wether or not it is acceptable... under the codes most likely to be adopted and upgraded on a regular basis.
Since it has shown up in arguments in the USA, especially concerning solar installations, a few of us are trying to understand how the switches would relate to the feeder and service feeder rules, and also trying to find other ideas out, such as:
Would it be better to require installations to include the switch based upon the maximum allowable bus panel installed in the residence or based upon the service applied for when applying to the POCO.. so far all of us are in agreement that even if a person only applies for a 60 amp electricity service, if the panels installed are up to 125 amp, then this disconnect must be capable of the same 125 amp, and if the panels are 200 amp capable, then the switch must be 200 amp capable... a 60 amp switch should not be installed. But, are we right to require such a disconnect switch if installed to be bigger than the main OCPD?
In our groups mind, one of the most common reasons for electrical fires is overloading of services as installed so making the fireman switch be a minimum size of the maximum OCPD that can be installed in the panel boards just makes more sense than having a 60 amp switch on the outside of the home, the owner adds an AC unit and changes the main breaker to 90 or 100 amps because the panel can handle 125 amp breakers... but switch is incorrect. We had even considered asking the government to require the service cables from the meters to be set for the maximum bus rating regardless of the main OCPD. But that is recieving a lot of flak concerning costs, etc.
Our groups position is that you size feeders from one panel to another based on breaker at second panel but, hwo do you make sure there is enough main entrance cable?
Of course, the the arguments come in about well, it was sized for the needs, and if the need is now greater then we should replace the cables anyway...
 
electrofelon said:
Most meter sockets have bypass capability, either horn, block, or lever, so I don't think it's a load interrupting issue. I think they just want to be able to kill power to the meter socket.
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They can do as they please up to the service point. But there's a lack of logic to them wanting to shut off power to the last two feet of their system...they pretty much work live everywhere else. But again, their circus, their monkeys....
 
Adamjamma said:
Currently they are still arguing over the need to use the NEC or to just write their own codes or to leave it as it has been for twenty years plus... but the fire department is asking them to do something and no one has any great idea because of electricity thefts and such. Fire department says putting it at certain height is within reach of the pole carried on fire truck, so the fire department could flip it off yet your normal burglar etc would need ladders to reach it. Current argument is not just an is it needed but how does the average person in the island who already is having trouble with new rules and costs of importing supplies afford something that costs so much when they have never needed it before.
But, this is a bunch of politicians arguing over wether or not there is a need for taxicabs to pay for their permits or have they been charged improperly..lol
A group of us who actually want to make sane safe rules for the industr are trying to find efficient ways to do this and find wether or not it is acceptable... under the codes most likely to be adopted and upgraded on a regular basis.
Since it has shown up in arguments in the USA, especially concerning solar installations, a few of us are trying to understand how the switches would relate to the feeder and service feeder rules, and also trying to find other ideas out, such as:
Would it be better to require installations to include the switch based upon the maximum allowable bus panel installed in the residence or based upon the service applied for when applying to the POCO.. so far all of us are in agreement that even if a person only applies for a 60 amp electricity service, if the panels installed are up to 125 amp, then this disconnect must be capable of the same 125 amp, and if the panels are 200 amp capable, then the switch must be 200 amp capable... a 60 amp switch should not be installed. But, are we right to require such a disconnect switch if installed to be bigger than the main OCPD?
In our groups mind, one of the most common reasons for electrical fires is overloading of services as installed so making the fireman switch be a minimum size of the maximum OCPD that can be installed in the panel boards just makes more sense than having a 60 amp switch on the outside of the home, the owner adds an AC unit and changes the main breaker to 90 or 100 amps because the panel can handle 125 amp breakers... but switch is incorrect. We had even considered asking the government to require the service cables from the meters to be set for the maximum bus rating regardless of the main OCPD. But that is recieving a lot of flak concerning costs, etc.
Our groups position is that you size feeders from one panel to another based on breaker at second panel but, hwo do you make sure there is enough main entrance cable?
Of course, the the arguments come in about well, it was sized for the needs, and if the need is now greater then we should replace the cables anyway...
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Wow. Sounds like analysis paralysis. NEC is a model code, it's flawed and certainly not written in stone. Use it and if needed modify whatever doesn't work in your situation.

Undersizing any component below the maximum load is foolish on the service side. The cost differences shouldn't be all that dramatic considering if the customer can afford the power bill and the goodies that consume it, they should be able to afford the gear to make it happen. Before the meter is usually before the service point, and undersized cable there really isn't the problem you might assume. It certainly isn't going to start a house on fire.
 
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