Generator feeder disconnect location

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olc

Senior Member
Quick question - do I need to treat the feed from a emergency generator like a service? A disconnect where it enters the building?
 
OK, not a quick question.
The stand-by feed from the generator is a "service". The disconnect for this "service" can be outside the building and is the circuit breaker at the generator (which is outside).
The disconnects and over current protection for the transfer switch are 1. A circuit breaker in the MDP. and 2. The circuit breaker at the generator. Nether are with-in sight of the transfer switch.

OK?
 
I don't know what you mean by "service" in relation to the generator.

You have a back up generator and utility power feeding a transfer switch and the common on the transfer switch feeds a main breaker in the MDP. Is that correct? If so, that's fine.
 
I am pretty sure the feed from a generator is defined as a service. See 230.2(A).
A circuit breaker in the MDP feeds the normal side of the transfer switch.
The transfer switch (common) feeds a subpanelboard.
 
olc said:
I am pretty sure the feed from a generator is defined as a service. See 230.2(A).
A circuit breaker in the MDP feeds the normal side of the transfer switch.
The transfer switch (common) feeds a subpanelboard.
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Nothing, other than a supply from the utility, is a service.
Service. The conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premises served.
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230.2(A) (1) - (5) act as exceptions to the main rule that says a building is only permitted to have a single service. It has nothing to do with a feeder from a generator.
 
If this is actually an emergency generator (Article 700 installation) and the generator is outside of the building, see 700.12(B)(6) for the rules that cover the generator disconnect. Note that the "within sight" part of that rule applies to the disconnect itself. It is not good enough for the generator or the generator enclosure to be "within sight". That actual physical device the opens the power circuit must be "within sight".

There are similar rules for legally required standby systems and optional standby systems in 701.12(B)(5) and 702.12(A).
 
OK Don. So if I have an NEMA 3R breaker enclosure as an outside feeder disconnect, because the handle of the breaker is not visible, I need another disconnect?
 
RB1 said:
OK Don. So if I have an NEMA 3R breaker enclosure as an outside feeder disconnect, because the handle of the breaker is not visible, I need another disconnect?
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Well if your Enclosed Breaker does not have an external means to operate it then your probably right.

JAP>
 
RB1 said:
OK Don. So if I have an NEMA 3R breaker enclosure as an outside feeder disconnect, because the handle of the breaker is not visible, I need another disconnect?
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You have feeders from the generator not a service. They fall under article 225 for out door feeders ( unless the generator is installed indoors ) If the breaker is labeled from the factory as "suitable for service equipment " and the generator is with in sight then you do not need the disconnect. If the generator doesn't comply with the definition
In Sight From (Within Sight From, Within Sight).
Where this
Code specifies that one equipment shall be ?in
sight from,? ?within sight from,? or ?within sight of,? and
so forth, another equipment, the specified equipment is to be
visible and not more than 15 m (50 ft) distant from the other
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.

Then you must follow 225.32




225.32 Location.
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The disconnecting means shall be installed

either inside or outside of the building or structure
served or where the conductors pass through the building or
structure. The disconnecting means shall be at a readily
accessible location nearest the point of entrance of the conductors.
For the purposes of this section, the requirements
in 230.6 shall be utilized.
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RB1 said:
OK Don. So if I have an NEMA 3R breaker enclosure as an outside feeder disconnect, because the handle of the breaker is not visible, I need another disconnect?
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I would say no because when you get into larger gen sets, the OCPD gets into the 1200, 2000, and 2500 amp range and this is usually in the breaker form located in nema 3R or 4X enclosures.
 
CEB,

I understand that it is not a service that is why I called it a feeder disconnect. I am disagreeing with the interpretation that the disconnecting means itself must be within sight and is not permitted to be located behind a cabinet or enclosure door. Many inspectors have interpreted "within sight" to preclude the generator disconnecting means from being located within the generator enclosure. I disagree with this interpretation.
 
RB1 said:
OK Don. So if I have an NEMA 3R breaker enclosure as an outside feeder disconnect, because the handle of the breaker is not visible, I need another disconnect?
Click to expand...
If you can see the actual disconnect enclosure, I think you are in compliance. Many generators have a generator enclosure and the disconnect is inside that enclosure and that would not be within sight.
 
RB1 said:
CEB,

I understand that it is not a service that is why I called it a feeder disconnect. I am disagreeing with the interpretation that the disconnecting means itself must be within sight and is not permitted to be located behind a cabinet or enclosure door. Many inspectors have interpreted "within sight" to preclude the generator disconnecting means from being located within the generator enclosure. I disagree with this interpretation.
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It would make more sense to me if I knew why they want it to be within site.

Being within site of the building does no good if you take that as meaning you can see it while your working on something inside.
Unless you keep someone posted at a window to report to you while your working on the transfer switch that someone's messing around at the generator that would be pointless.

Or is it that
Maybe, I'm a fireman and Lightning strikes, Power goes out, building on fire, generator starts, supplies backup power to the building, I need to shut the electric off, generator enclosure locked, cant get to disconnect.

JAP>
 
RB1 said:
CEB,

I understand that it is not a service that is why I called it a feeder disconnect. I am disagreeing with the interpretation that the disconnecting means itself must be within sight and is not permitted to be located behind a cabinet or enclosure door. Many inspectors have interpreted "within sight" to preclude the generator disconnecting means from being located within the generator enclosure. I disagree with this interpretation.
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If the disconnect is outside of the building, and is serving as the required building disconnect, the disconnect itself must be within sight from the building. I think the code is clear on this issue.
700.12(B)(6) Outdoor Generator Sets. Where an outdoor housed generator set is equipped with a readily accessible disconnecting
means in accordance with 445.18, and the disconnecting means is located within sight of the building or structure supplied, an additional disconnecting means shall not be required where ungrounded conductors serve or pass through the building or structure. Where the generator supply conductors terminate at a disconnecting means in or on a building or structure, the disconnecting means shall meet the requirements of 225.36.
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The wording in 701 and 702 for legally required standby systems and optional standby systems is the same. They all clearly require the disconnect at the generator, where that disconnect is being used as the building disconnect, to be within sight from the building.
 
I disagree Don. If I have a NEMA 3R switchboard serving as the disconnecting means for a building, the actual disconnect device is located behind cabinet doors. The same is true for large NEMA 3R service entrance rated transfer switches.
 
Don,

You have to open the doors of an enclosure to access the disconnecting device on a NEMA 3R switchboard. The same is true for larger service-entrance-rated NEMA 3R transfer switches, the disconnect device is located behind latched cabinet doors. The only difference for the generator is that the enclosure is not dedicated solely to the disconnect device. The definition of within sight states that the specified equipment is to be visible. I would think that the general term "disconnecting means" would include the equipment enclosure as part of the equipment.
 
I think more emphasis needs to be placed on the reasoning for the rule rather than beating up this generator disconnect "Within Sight" rule that keeps coming up time after time that will never seem to be resolved.

Long story short the only reason I can see for the "Within Sight" rule would be for an emergency situation, and even then if you didn't know where to look for it to begin with you'd have to run around the building to try and find it anyway.

Its not like a disconnect for a motor or something like that. "Within Sight of the Building" doesn't make it "Within Sight" of whatever your working on like a motor or air conditioning unit or the like.

If it is for Emergency Shutdown Purpose and the reasoning is to be able to find it quickly the rule should read "Within Sight of the Buildings Service Disconnecting Means".

So what is the reasoning behind having to be able to see the disconnect or even the Enclosure for the disconnect on a generator installation?
If its for servicing purposes, why doesn't the Lockout Capability of the Disconnecting means come into Play?

If its for convienience in case of an emergency, then why is it not "Within Sight of the Service Disconnecting Means" instead of the building in general?

JAP>
 
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