250a MLO panel, with 1000A worth of CB's?

[mra1200]

I think I have the answer I've been looking for since this afternoon from this thread, but I want to ask it to be 100% sure.

So long as the total load is less than the rating of the panel/disconnect rating, everything is OK by code, right? I ask because I am a DJ at a club on a weeknight, and we have a Siemens S1 panel (250A, MLO - fed by a disconnect outside the building) that's loaded up with 42 breakers, 2 of which feed another small panel for the storage room (for the icemaker, beer & wine coolers, lights, and a few receptacles).

(30) 1p 20A
(3) 2p 60A
(1) 2p 80A
(2) 2p 100A

I have a gut feeling that this panel has WAY too much stuff connected to it, likely pushing it to the max it can handle, and I will likely recommend to the owner than he pull off everything powering the upstairs and have those circuits put onto the new panel he will have to have installed when he builds a 2nd small bar upstairs (a new panel will obviously be done by someone licensed & insured, as an apprentice I only feel comfortable with replacing a light switch or a receptacle if needed).

The main purpose of this is a real life load calculation & code check, totalling up what is on each circuit to see what (if anything) is pushing the panel or any of the individual breakers to the max. I'm sure this will be a hell of a lot more insightful and interesting than some of the code book work we have to do at the JATC.

 

[360Youth]

I have a gut feeling that this panel has WAY too much stuff connected to it, likely pushing it to the max it can handle, and I will likely recommend to the owner than he pull off everything

I fell for that one when I first started. Adding up the breakers is nowhere close to calculated loads. Each one of those 120v/20a breakers may only be pulling 10 amps at any given time, and even those not all at the same time. Same with HVAC circuits. (non-coincidental loads)

I will likely recommend to the owner than he pull off everything powering the upstairs and have those circuits put onto the new panel he will have to have installed when he builds a 2nd small bar upstairs

Unless he is upgrading the service also, not much is accomplished. Is there another source that the new panels would be fed from and these circuits relocated to??

 

[brantmacga]

I will likely recommend to the owner than he pull off everything powering the upstairs and have those circuits put onto the new panel he will have to have installed when he builds a 2nd small bar upstairs

let us know how that works out for ya

 

[tadavidson]

I bet you could make more money if you would DJ throughout the week and do electrical work on the weekends. GRIN

 

[acrwc10]

Put a little thought on this. The panel is protected by OCPD, fuse,or breaker. Has that tripped ? If you have 42 receptacles with each on its own circuit breaker "say 20 amps each" , with no connected load on 41 of them. Would you need to upgrade the panel? Is that a 840amp load? No it is not. What you need to do is a load calculation. This has more to do with what is the "connected load" then how many circuit breakers are in the box.

 

[tom baker]

The size of an electrical service is determined by the service condutors (except for residential) and not the OCPD. When you do a load calc, you install the conductors sized for the load and then can round up to the next standard size OCD. for example a 501 amp load, you can round up to 600 amp. This is not a 600 amp service, and this is not a practice I recommend.

 

[Rockyd]

It's not as cool as the signatures that say "inspector" or master electrician", but here's mine anyway:

2nd year apprentice at the local JATC

Welcome to the forum.

You don't have to have a cool "handle" to move light years ahead in the industry, just pull up a chair, stay current with the forum, and it's amazing how much can be picked up in here. Good place to get answers to the "scratch the head stuff" too.

 

[LarryFine]

. . . we have a Siemens S1 panel (250A, MLO - fed by a disconnect outside the building)

Are there any fuses or breakers in or adjacent to that disconnect?

 

[mra1200]

I fell for that one when I first started. Adding up the breakers is nowhere close to calculated loads. Each one of those 120v/20a breakers may only be pulling 10 amps at any given time, and even those not all at the same time. Same with HVAC circuits. (non-coincidental loads)

Unless he is upgrading the service also, not much is accomplished. Is there another source that the new panels would be fed from and these circuits relocated to??

I haven't done a thorough check to see what's plugged/wired into what yet (I try to keep my jobs separate), but I know there's a ton of stuff plugged into the receptacle outlets behind the bar and there have been some recent problems, like the breaker on a power strip tripping, a GFCI receptacle melting for the icemaker, and the beer cooler making the CB trip at the panel. The latter two (after a phone call to a electrician friend back home) may be more likely due to corrosion of the plugs from humidity and exposure to various liquids over a long period of time.

As I said in my original post, I thought it would be a great learning experience to total up what is on each circuit, to see what the loads are. A real life example would be more interesting than what the NJATC books/prints could offer up.

let us know how that works out for ya

Actually, doing so wouldn't be so bad since (AFAIK) most of the circuits are run up through the floor to several junction boxes. Piping/MC'ing to the lighting would be cake since all the dimmer switches are surface mounted in one spot.

I bet you could make more money if you would DJ throughout the week and do electrical work on the weekends. GRIN

my hourly rate for DJ'ing is indeed higher than what JW's get paid here, and I'm only a 2nd year apprentice. :grin:

if only I could find 36 more hours a week to DJ to make a full 40...

Put a little thought on this. The panel is protected by OCPD, fuse,or breaker. Has that tripped ? If you have 42 receptacles with each on its own circuit breaker "say 20 amps each" , with no connected load on 41 of them. Would you need to upgrade the panel? Is that a 840amp load? No it is not. What you need to do is a load calculation. This has more to do with what is the "connected load" then how many circuit breakers are in the box.

Having just noticed this TODAY, I didn't have time to really think it through, but yeah it makes much more sense. I was thinking about how the code says the maximum load is 80% of the receptacle rating (ok, 210.21(B)(2) doesn't explicitly say 80%, but the math on that table comes out to 80%) and I was calculating that same percentage from the 1000A total (800A). The phone call to the friend earlier alerted me to the fact that some of the appliances we have there don't draw as much current as I thought, so the panel and certain CB's aren't as loaded down as I feared (well one circuit is, but that's trivial to run the cords to another receptacle on a circuit that's not so loaded down).

 

[mra1200]

Are there any fuses or breakers in or adjacent to that disconnect?

To be honest I have no idea, it's not something I've ever needed to look at or touch, I just know it's there (and it's big). I'd be absolutely shocked that the EC who installed everything would NOT put in a fusible/breaker'ed disconnect. I'd be more shocked that an inspector would sign off without having it fused/CB'ed.

 

[Smart $]

my hourly rate for DJ'ing is indeed higher than what JW's get paid here, and I'm only a 2nd year apprentice.

Don't forget to add in bene's in making that determination. If you are DJ'ing as an independent contractor, you have no bene's from this source of income and any out-of-pocket expense you incur is deducted from said income.

Having just noticed this TODAY, I didn't have time to really think it through, but yeah it makes much more sense. I was thinking about how the code says the maximum load is 80% of the receptacle rating (ok, 210.21(B)(2) doesn't explicitly say 80%, but the math on that table comes out to 80%) and I was calculating that same percentage from the 1000A total (800A). The phone call to the friend earlier alerted me to the fact that some of the appliances we have there don't draw as much current as I thought, so the panel and certain CB's aren't as loaded down as I feared (well one circuit is, but that's trivial to run the cords to another receptacle on a circuit that's not so loaded down).

The 80% goes the other way. 800A of CB ratings would be 640A of continuous load... and you are adding up CB ratings and amperage incorrectly. On this matter, you failed to mention whether this panel/service is split phase (120/240, 1?, 3W) or polyphase (208Y/120 or 240/120, 3?, 4W). This will make a difference on how you add up single pole and two pole loads. In either case, the single pole CB's will draw a maximum of only 1/2 (split 1? system) or 1/3 (3? system) of their rating on the service or feeder when they are balanced and operating concurrently.

For example, on a 120/240 system, a single pole 20 has an available (non-continuous) limit of 20A @ 120V. That is 240VA. Put two single poles together, each on a different line and you get 480VA. This balancing on the lines puts just a 480VA ? 240V = 20A draw limit on the service (not 20A + 20A = 40A).

So in the case being discussed, if the panel is served by a 120/240 system, the 30 20A-1P CB's are likely placing only a 300A draw limit on the service instead of 600A by the way you are making it appear. If the panel is being served by a 208Y/120, 3? system, those CB's place only a 200A draw limit on the service. And if they all happen to be serving continuous-rated loads, we electricians (et al) have to ascertain the circuits place no more than a 240A or 160A burden, respectively, on the service.

Additionally, distribution systems are designed, among other things, to dissipate heat so as to not degrade conductor insulation. If a panel is overloaded, it and several CB's are likely to be quite warm to the touch.

 

[mra1200]

Don't forget to add in bene's in making that determination. If you are DJ'ing as an independent contractor, you have no bene's from this source of income and any out-of-pocket expense you incur is deducted from said income.

Actually they are available to me if I wanted them, but the only bene that is useful to me is a gym membership. The bene's from the local here are pretty good (health, dental, & vision), though the family plan doesn't kick in until after the 3rd year in the apprenticeship (as a single guy that matters little to me).

The 80% goes the other way. 800A of CB ratings would be 640A of continuous load... and you are adding up CB ratings and amperage incorrectly. On this matter, you failed to mention whether this panel/service is split phase (120/240, 1?, 3W) or polyphase (208Y/120 or 240/120, 3?, 4W). This will make a difference on how you add up single pole and two pole loads. In either case, the single pole CB's will draw a maximum of only 1/2 (split 1? system) or 1/3 (3? system) of their rating on the service or feeder when they are balanced and operating concurrently.

For example, on a 120/240 system, a single pole 20 has an available (non-continuous) limit of 20A @ 120V. That is 240VA. Put two single poles together, each on a different line and you get 480VA. This balancing on the lines puts just a 480VA ? 240V = 20A draw limit on the service (not 20A + 20A = 40A).

So in the case being discussed, if the panel is served by a 120/240 system, the 30 20A-1P CB's are likely placing only a 300A draw limit on the service instead of 600A by the way you are making it appear. If the panel is being served by a 208Y/120, 3? system, those CB's place only a 200A draw limit on the service. And if they all happen to be serving continuous-rated loads, we electricians (et al) have to ascertain the circuits place no more than a 240A or 160A burden, respectively, on the service.

Additionally, distribution systems are designed, among other things, to dissipate heat so as to not degrade conductor insulation. If a panel is overloaded, it and several CB's are likely to be quite warm to the touch.

The S1 panel is a 208Y 3 phase board, and I'm not sure if things are balanced out properly (another interesting thing to study as a real life example), but everything is definitely working. I'm finding that MANY of the circuits have very little if anything on them (e.g. separate circuits for each bathroom, with only 2 60w bulbs) or some with nothing at all on it (an outlet we found that no one knew was there on it's own breaker).

 

[K2500]

The 80% goes the other way. 800A of CB ratings would be 640A of continuous load...

I was talking with my journeyman the other day, and he tells me that the springloaded switches (the kind with the charging handles) are good for the full 100%, continuous load or not. This was a 2000A disconnect. Before, as I understood it, the 80% applys to all continuous loads. Are there exeptions for this kind of thing?

 

[jim dungar]

I was talking with my journeyman the other day, and he tells me that the springloaded switches (the kind with the charging handles) are good for the full 100%, continuous load or not. This was a 2000A disconnect. Before, as I understood it, the 80% applys to all continuous loads. Are there exeptions for this kind of thing?

All standard UL listed enclosed overcurrent protective devices (fusible switches and breakers) are only rated for 80%. Special (highly ventilated) enclosures are required to get a UL 100% rating.

ANSI switchgear (most but not all drawout breakers) is typically 100%.

 

[mra1200]

Are there any fuses or breakers in or adjacent to that disconnect?

I hate to say it, but it looks like there are NO fuses or breakers between the disconnect and the panel

There could be something inside the disconnect, but there was nothing on it indicating what size fuses or breaker it was...

 

[paul]

Sounds like everything is okay to me. Whatever you do, don't recommend that the owner turn off circuits upstairs. He hasn't had any problems with his system and it sounds like it's on the up and up. In other words...if it ain't broke...don't fix it.

The guys here are going to give you a little bit of a ribbing and chuckle. However, each one of us was in your shoes at one time or another. I like your eagerness to learn, but settle down there a bit on this building.

You also may want to be careful doing the side-jobs of fixing certain items at this establishment. There are liabilities that can be incurred by trying to help out the owner. Even as small as changing out a receptacle or switch. When you do this while working for a shop, your work is insured. Going at it alone, it is not and neither are you. You can then be held 100% liable for anything that happens and you'd be hung out to dry.

 

[Smart $]

There could be something inside the disconnect...

It is most likely a fused disconnect.

The S1 panel is a 208Y 3 phase board, and I'm not sure if things are balanced out properly...

Being balanced properly can be misleading if you use actual measurements. For instance, a receptacle circuit may be calculated at 180VA per yoke, but in use there may be nothing plugged into any of the receptacles on that circuit. Yet it is the calculated load that is used to balance the panel's load distribution. I suppose it can be said it is also balanced between what can happen and what is likely to happen.