Distribution Panel Size

Status
Not open for further replies.
lookin2pass said:
I don't see how having 6 breakers in this panel can possibly be considered overcurrent protection.
Click to expand...

But it is code compliant and the installation you have is very common.

It's great you care about your work but what you have is correct, safe, compliant and common.

If you try to change this set up you will be looked at like you have 2 heads.


By the way, the first time I ran into it I was surprised as well, in that case I had 1600 amp switchgear 'protected' with over 3000 amps of breakers.
 
Last edited:
I just wish that it made sense. It seems more than a little strange that the NEC goes to such great lengths to make everything as safe as possible by protecting everything (a lot of times redundantly) only to leave the main feeders and panel unprotected.
 
lookin2pass said:
I just wish that it made sense. It seems more than a little strange that the NEC goes to such great lengths to make everything as safe as possible by protecting everything (a lot of times redundantly) only to leave the main feeders and panel unprotected.
Click to expand...

I fully understand how you feel, it had to be about 10 years ago I wrote into one of these electrical forum questioning the service I ran into for the same reasons you have.

Once I was shown the NEC rules regarding this it hit home to me.

The NEC requires that the existing load be determined before adding any new load to a building.

Now is that how it really happens? Heck no, but the NEC assumes we are doing load calculations for every load we add.

I also started noticing how often this exception is used. I see it used on multi-dwelling unit services, I see it used often to avoid installing GFP main breakers which are expensive.
 
The second problem that I'm having is that I think I'm addicted to this website. I can't even tell you how many hours I've spent reading posts and replies in the last 2 days. I belive my wife thinks I'm having an affair! Sorry. didn't mean to get off topic.
 
lookin2pass said:
The second problem that I'm having is that I think I'm addicted to this website. I can't even tell you how many hours I've spent reading posts and replies in the last 2 days. I belive my wife thinks I'm having an affair! Sorry. didn't mean to get off topic.
Click to expand...


:D


It happens, like I said it was about 10 years ago that I asked my question and now I am a moderator here with at least two of the guys that answered my questions back then.

I have learned a ton about this trade from the many members on these forums. :cool:
 
lookin2pass said:
I don't see how having 6 breakers in this panel can possibly be considered overcurrent protection. If we use the line of reasoning that it can't be overloaded because we did the load calculation and it is less than the panel and conductor rating, then that can be said for every panel. You have to know the load calculation to size the panel and the conductors feeding it. By that reasoning we don't need a main on any panel because we already know that it pulls less than what it is rated for. We coud just start bolting lugs onto the busses in every switchgear and distribution panel without fear of ever going high enough for it to be a problem. Add to that. the fact that there is no way to shut the DP down to do any type of service work and you have a major flaw in the electrical system. Now if I have a breaker that quits working properly, I can't just turn the main off and replace it, I have to call the power company to send a bucket truck out to pull the fuses on the pole to kill the power to the primary on their transformer. Every reason for having a main breaker or disconnect on any other panel would apply to the distribution panel for the same reason. I can't figure out any good reason why this exception exsists. It's driving me crazy thinking about it. I noticed a quote that somebody has at the bottom of their post and couldn't hep thinking how well it fit this rule. "just because you can do something, doesn't mean that you should" Thanks Smart $, i'm glad I'm not alone on this.
Click to expand...

You can overload it, Smart$ gave a good example of it possibly happening. In most cases load diversities are enough that it does not get overloaded.
In most of those installations you run into - look at the rating of the gear, take current readings at any random time, look at what size of transformer the POCO has provided, the true load is most often less than the calculated load.

If you are adding some significant load it is important to determine if existing equipment can handle the added load.

Unless you have large individual loads like 200+ HP motors, most loads do have enough diversity to complicate the actual load they demand at a given time.
 
Think of it this way Lookin2pass. This is no different than having a service gutter fed from the transformer with parallel 600MCM coppers with (1) 400A, (1) 200A, (2) 150A, and (2) 60A disconnects tapped from them.
 
I am not trying to argue

I am not trying to argue

I agree that it is leagal, and I'm not trying to say that we need to make provisions for future loads. I'm only saying that it does not make sense to allow the capacity for more loading than the panel or conductors feeding it are rated for. In the example of a 200A panel with a 200A main, that is loaded with (42) 20A breakers, it makes sense because no mater what the amount of load is, the panel and wire is protected by the 200A main. There should either be a main OCPD that protects the panel and wire at its rating, or the 6 or less breakers that somehow qualify as the OCP should not be allowed to add up to more than the panel and wire feeding it are rated for. Either option would work to to protect the wire from overcurrent. Like I said a couple of posts back, every reason that you would have OCP in any panel would apply to the DP as well (whether its protecting it from overloading due to added loads, equipment malfunction, variable loads not accounted for in the load calc., Etc., does not matter). I just don't see why It's alright to do it in this situation but not anywhere else. The "we know the load calc. is lower that the panel and wire rating so it's not possible to overload it" doesn't make sense. If it did we could do it on every panel we install because we always know the load before we even order the wire and panel.
I guess it just boils down to the fact that I don't like it because I can't see the logic behind it. Sorry to ramble on, I'm going to install it the way the NEC says is acceptable, but I won't be happy about it. LOL!;)
 
In smart $ example in post #19 there was no load added (other than the customer plugging more stuff into the general use receptacles)
There is more than one way to to pull more amps than what the load calc. is figured at.
The thing I can't figure out is why this would be OK in this situation, but not in any other situation?
If you make the 400A breaker into (2) 200A breakers it is an illegal installation.
Why? What has changed?
 
One more thing that will help prevent the panel from being overloaded....the capacity of the utility transfomer probably be less than the calculated load.
 
Something I do with this type of install is to ask if the electrician would be willing to placard the ampacity of the service conductors. Especially if only four or five of the allowable six disconnects are being utilized.

To make it clear there is NO code requirement for such labeling and I will not even attempt to defect the job if the electrician doesn't want to apply the additional label. I think it just gives a "heads-up" to anyone in the future that may look at adding additional load to this type of set-up.

Pete
 
pete m. said:
Something I do with this type of install is to ask if the electrician would be willing to placard the ampacity of the service conductors. Especially if only four or five of the allowable six disconnects are being utilized.
Click to expand...

I would actually be for an NEC section requiring that.

To have to show up on a job and try to determine the ampacity of the service can be easy or it could be very difficult.
 
As we know this practice of using a panel as service equipment with 1-6 breakers as service disconnects (assuming it is SUSE rated) is code compliant and in fact has been allowed pretty much forever. I'm not sure if I agree with it, but it is what it is.
But I can't help but notice an opposite philosophy in Art 430.120. As some will recall I have mentioned this before, so please forgive me. IMHO Art 430.120 does not pass the common sense test for the opposite of this practice. Isn't 430.120 basically saying, you never know what size motor will be installed at a later date? That seems absurd to me unless that is a design choice. Now I realize that that the drive power consumption has to be taken into account, but it seems that 430.120 could be modified to accomadate this. The way 430.120 is now written in many situations you end up with feeders that are wildly oversized.
 
texie said:
As we know this practice of using a panel as service equipment with 1-6 breakers as service disconnects (assuming it is SUSE rated) is code compliant and in fact has been allowed pretty much forever. I'm not sure if I agree with it, but it is what it is.....
.
Click to expand...
I see where you and the OP are coming from, but I am of the opinion that any time the NEC rules on the side of practicality it is a time to rejoice, not criticize.
 
Status
Not open for further replies.
Top