residential generator installations

[iwire]

As much as I love to debate with you (and most of the time you are correct) on this issue I will not even attempt a debate due to the fact that in my opinion you are way off base.

I can't help what you think.

If you choose to believe that a disconnect is readily accessible when in a locked cabinet then go for it.

I do.

Mike if a locked door means service disconect is not readily accessible I will have to start pulling the locks of all the electric rooms in commercial buildings.

Let me ask this of you Mike.

If I choose to hang a fused NEMA 3R disconnect on the outside of a building as the service disconnect can I put a lock on it to keep the neighborhood kids from turning it off?

 

[George Stolz]

So then George you would agree that the disconnect required in 440.14 could be in the house and the house locked as long as it was within sight through a window.

I am a bit confused as to how Article 440 was dragged into the discussion? :-?

Sorry for the delayed response, I didn't notice this until just now.

 

[M. D.]

I do.

Mike if a locked door means service disconect is not readily accessible I will have to start pulling the locks of all the electric rooms in commercial buildings.

Bob , ROP 13-123 states that it is the disconect and not the generator that needs to be within sight . I agree that a locked door does not preclude the readily accessible requirement but is the disconect within sight.? or rather a cabinet/housing containing a disconect?

I have used these little disconects for A.C.s there is a 60 amp rated pullout, it is behind a lid / door that can be and many times is locked .Is the disconect/pullout within sight ?nope ,a cabinet/ enclosure is, with a locked lid or door.There is no visible way to tell if it is in the on or off posistion, or whether or not it is a splice box, without opening the door . In my area these things are very common, and never get red tagged.

 

[iwire]

Bob , ROP 13-123 states that it is the disconect and not the generator that needs to be within sight . I agree that a locked door does not preclude the readily accessible requirement but is the disconect within sight.? or rather a cabinet/housing containing a disconect?

I see your point.

Perhaps that is why many of the rental generators we use have the disconect behind a lockable door with a window that allows looking at the controls or why some of the units we install have a break glass E-stop on the outside of the enclosure.

That said when I look at a fused disconect I do not 'see' the disconnecting means I see the enclosure that contains it.

 

[M. D.]

So then George you would agree that the disconnect required in 440.14 could be in the house and the house locked as long as it was within sight through a window.

While I'm not George, I'll respond anyway. If the disconect in the O.P. can be seen from the structure served and is behind a locked door I think it does meet the requirement. Again there are many examples of disconnects behind locked doors that are considered readily accessible for those qulified to have access. A see through door or window could in my opinion meet the minimum requirement.
If any one could find any reputable documentation that concludes a locked door renders a disconect not readily accessible, I would love to see it . I like to think I have an open mind and would like to say that this site works like grease on the hinges.

 

[George Stolz]

While I'm not George....

Are you sure?

 

[M. D.]

Perhaps we are all "George" from time to time.:grin:

 

[iwire]

Perhaps we are all "George" from time to time.:grin:

Thats works out well as I always say let George do it :grin:

 

[Cavie]

A generator with a locked door is not different that a weatherproof panel with a padlock. Think outside the box once in a while. Fire departments have boltcutters.

 

[goldstar]

I don't mean to throw a wrench into things here but if you have a separate line voltage electrical disconnect means (mounted on the building) for the generator and you operate that disconnect (say during a fire) doesn't the generator continue to run ? You would still have power inside the whip between the generator and the disconnect. Also, if the fire dept. shuts off the gas supply during this same condition, doesn't the electronics between the transfer switch and the generator still sense that there is no POCO power and continues to try and start the generator (unless you don't really care) ? If so, (the way I see this) you'll have to open the generator cabinet and remove the fuse that protects the starter circuit so the generator won't continue to try and start. If you're able to get to that point, doesn't the circuit breaker inside the generator cabinet serve as the disconnect means ?

 

[iwire]

I don't mean to throw a wrench into things here but if you have a separate line voltage electrical disconnect means (mounted on the building) for the generator and you operate that disconnect (say during a fire) doesn't the generator continue to run ?

Yes, very likely.

You would still have power inside the whip between the generator and the disconnect.

How is that any different or more dangerous than what happens when you open the service disconnect?

The line side of the service disconnect will be live.

Also, if the fire dept. shuts off the gas supply during this same condition, doesn't the electronics between the transfer switch and the generator still sense that there is no POCO power and continues to try and start the generator

Sure for a bit, it should shut down after a few tries on "Failure to Start"

If so, (the way I see this) you'll have to open the generator cabinet and remove the fuse that protects the starter circuit so the generator won't continue to try and start.

If the house is on fire I don't care if the generator tries to start till the battery is dead....the power will be killed to the building it serves.

 

[iwire]

Mike you still out there?

You should like this from the 2008 ROC 13-259 Log #2122 NEC-P13 Final Action: Accept in Principle
(702.11)

Panel Meeting Action: Accept in Principle

Accept the proposal in principle and revise 702.11 to read:
Outdoor Generator Sets. Where an outdoor housed generator set is equipped
with a readily accessible disconnecting means 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. The disconnecting means shall meet the requirements of 225.36.

Panel Statement: The added sentence clarifies that the disconnecting means must comply with 225.36.

 

[George Stolz]

I just do not understand this service-rated stuff.

 

[LarryFine]

I just do not understand this service-rated stuff.

Allow me.

When a 'standard' whole-house automatic transfer switch (ATS) is installed, it is wired between the meter and the service panel, and switches the entire normal service current (which is why it must be sized for the service and not just the generator.)

Unless you happened to already have a main disconnect at, or adjacent to, the meter, and wire the ATS after this main disconnect, the ATS will be ahead of the panel's main breaker, which is (or was) the main disconnect. You now have equipment that cannot be disconnected from the utility.

To get around this, you either must install a new main disconnect between the meter and the ATS, or use a 'service-rated' ATS, which merely indicates that the ATS contains its own built-in disconnect, typically a circuit breaker.

Every service-rated ATS I've seen contains both a utility disconnect and a generator disconnect, each wired between the input terminals and the actual transfer switch itself. This way, the ATS can be isolated from the two supplies, in compliance with the requirements for service disconnects.

In other words, if the only way to de-energize an ATS is to pull the utility meter, you do not have a compliant installation. This installation required the new meter-main (or a stand-alone main disconnect), as well as the wall-mounted generator disconnect, because the ATS is not the service-rated type:

Meanwhile, a service-rated ATS could have been used, which would have allowed the original meter to remain, and neither added disconnect would have been required. In my opinion, using the service-rated ATS more than pays for itself in material and labor savings.

 

[iwire]

Larry I am all but certain that George is confused about the same thing I am.

Why does the code require a service rated disconnect for a separate building or structure when that disconnect is supplied by a feeder.

Example.

Building one has a service.

I run a 100 amp feeder across building one to a panel mounted on the outside wall of building one.

No disconect required and if I choose to install one it need not be service rated.

Now I change my mind and move the panel to Building two just 10' away.

Now it requires a disconnecting means per 225.31. This I understand and agree with.

However that disconnecting means is required to be service rated by 225.36.

Why?

 

[LarryFine]

However that disconnecting means is required to be service rated by 225.36. Why?

I believe it has to do with the availability of a means for bonding the service grounded conductor to the disconnect enclosure. Interrupting capacity may also be a factor.

The 30a, 3-pole fusible switch I removed from the building I'm working on indicates (to paraphrase) "suitable for use as service equipment when the bonding screw is installed."

Interestingly, even though it was used this way, and a "service disconnect" label was added, the bonding screw was still clamped under one of the bus screws with the little cardboard tag intact.

Since there was no grounded conductor run to the switch, I guess there's no complaint. The EMT effectively bonded the enclosure, but I would have run a #10 to the bus and used the screw anyway.

 

[iwire]

I believe it has to do with the availability of a means for bonding the service grounded conductor to the disconnect enclosure.

That would make sense if one was to use the grounded conductor as the grounding means as allowed by 250.32(B)(2). However that option is being taken away and bonding at this switch would be a violation with an EGC run.

Interrupting capacity may also be a factor.

The available fault current increased when I jumped the 10' to building two?

 

[volt102]

Bob, thanks for posting that ROC....That was the change I was talking about.

For the 2005

With 90.3

Chapters 1 through 4 apply except as amended by Chapters 5, 6, and 7 for the particular conditions.

Amend- to alter formally by modification, deletion, or addition

Chapter 7 would need to say something like this in order to amend the requirements to get rid of the service rating requirements.

Where an outdoor housed generator set is equipped with a readily accessible disconnecting means that complies with 225.36 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.

Being able to bond the Grounded to the Grounding is not the only difference between a service rated disconnect and a non-service rated disconnect.
Check out the Panelboard Marking Guide. Besides that, one of them has an extra label applied.

Jim

 

[jwelectric]

Mike you still out there?

You should like this from the 2008 ROC 13-259 Log #2122 NEC-P13 Final Action: Accept in Principle
(702.11)

Yes I have been checking in for a few minutes over the past couple of nights. Have a job that had to be done this weekend and have devoted all my time to work. Still haven?t finished but can get done in the morning before the inspector arrives I do hope.

Thanks Bob for the link. In the classes that are being taught here in NC on generators the instructors have been very adamant about the disconnect being rated as service equipment. They are also very adamant about the disconnect being visible not the generator.
I have sent an email about the lock and readily accessible and should here something latter this week.

Larry if the ATS is service rated it must comply with 230.91.
In the picture I posted the service was changed for other reasons than the installation of the generator but the picture is good for showing 230.91.
One of the common problems around here is the electrician sitting a ATS beside the meter base that doesn?t have overcurrent protection which is a violation of 230.91

Please don?t give up on me as I need all the help I can get but please understand I have to pay the light bill or they will cut my power off and then I might be faced with this dilemma with my generator. (this is meant to be funny so please laugh)

 

[LarryFine]

Larry if the ATS is service rated it must comply with 230.91.
In the picture I posted the service was changed for other reasons than the installation of the generator but the picture is good for showing 230.91.
One of the common problems around here is the electrician sitting a ATS beside the meter base that doesn’t have overcurrent protection which is a violation of 230.91

Please don’t give up on me as I need all the help I can get but please understand I have to pay the light bill or they will cut my power off and then I might be faced with this dilemma with my generator. (this is meant to be funny so please laugh)

Ha-ha!

Mike, I wasn't picking. The ATS I'm talking about is the service-rated version of what you used. Notice there are two breakers; the upper is the utility breaker, which is the disconnect that makes this ATS servcie-rated to begin with.

All that would have been necessary to do would be to nipple from the meter to the ATS, bring the generator feeder into the same enclosure, and land your grounds. I'll get a pic of the one I installed recently.