I went to check some lights in a Pediatric Clinic. Normally just have to replace a ballast. This one had a dual-lite emergency ballast in it, with 2 hot feeds. Lights would not work on emergency ballast. The regular ballast feeds through the emergency ballast(bunch of wires). There was no diagram for the wiring on the emergency ballast, so before I did anything I took voltage readings on the 2 hot feeds feeding the ballast. I had around 115 volts on one, and only 90 volts on the other one. I traced the conduit a little in the hallway above the ceiling and find that the wire that only has 90 volts is feeding other lights in the hallway with regular ballast, and the lights are working:D I wouldn't think they would work on that low voltage, but obviously there's a bunch of them working on it. I'm suppose to go back on a Saturday and try to trace the problem. I'm thinking that this may be the reason the emergency ballast is not working. Either the low voltage has burned the ballast up or it just won't "kick in" with that low voltage. Plus I'm sure the low voltage is not good for the rest of the lights. Any thoughts on what would make the voltage be low? Loose neutral somewhere maybe? It's looks like it's going to be a job trying to find it. This place is pretty big. I'll probably have to check some j boxes at random, starting close to the panel. Thanks for your input...

sparkync:

The 'E' ballast has an internal battery that provides reduced illuination from 1 or possibly 2 fluorescent lamps in the fixture, and should be on a 'nite lite (24/7) circuit, usually with any exit or other egress lighting.

Are you sure you were not 'reading' the 90 volts on the output?? (From the battery component)

IMHO, these ballasts are a PITA, but you have to live with it. You could find the wiring schematic at 'Dual-lite' BUT you need the model # from the ballast.

John, no I took voltage before it ever got to the ballast and even with the ballast not hooked up. I went to another fixture that didn't have the emergency ballast in it, and got 90 volts. I pulled up the wiring diagram on dual-lite, and it don't show 2 hot feeds feeding the ballast, but it says there may be other diagrams. On the cover of the fixture, it says "Caution, this fixture is fed from 2 power sources". So now I'm a little confused. I put in 2 calls to Dual-lite, but haven't got a response yet. On the 90 volts problem, I even checked my meter again to make sure it wasn't messed up. I took a reading on an outlet nearby and found 120 volts, so I know my meters ok. Thanks for the reply anyway. Hopefully Dual-lite will call me today. Steve...

sparkync:
You may have to dig deeper. Can you locate the source of the 90 volts? There may be an 'emergency power source' located in the facility.

Is there any info on the 'e' ballast?

Look around by the panel(s).

sparkync;

The link below will take you to Dual-Lite's "Somewhat Common" Fluorescent Battery Backup Ballast Wiring Schematic (PDF File):

UFO-3AW

Schematics on the last page (page 4).

There are Two Ungrounded Leads for the Battery Backup Ballast: "Switched Power" and "Unswitched Power".

I have a few questions to ask...

1: The Voltage Measurements you posted, were these taken L-G (Line to Ground), or L-N (Line to Neutral)?

2: Is there a readable Voltage between the Two Ungrounded Conductors feeding the Ballast (at the Fixture)?

3: Which Circuit is feeding the Em. Battery Backup Ballast's "Unswitched Lead";
the "115 Volts" Circuit, or the "90 Volts" Circuit?

4: If you turn off the Switch(es) controlling the Lights on the effected Circuit, does the Voltage on the "Unswitched" Circuit at the Em. Ballast change?

5: What is the length of the Switched Circuit? (from Panelboard to Fixture you are Shooting Trouble at),

6: What is the FLA (Full Load Amperes) of the effected Circuit - measured at the Branch Circuit OCPD?

7: What is the Voltage between N-G (Neutral to Ground) at the Fixture with the Switched Fixtures:
a: ON,
b: OFF

The issue appears to be poor makeup in One or more Fixtures.
Could be Open Common Neutral, Fried Wirenut(s), incorrect connections at Fixture(s), Open Neutral to Panelboard - Grounded at One (or more) Fixtures...
Or maybe a Voltage Drop issue from too many Fixtures on same Circuit.

Will wait for your reply.

-- Scott

Scott, I can answer a few of your questions now. I don't have the answers to the other ones yet. Will probably know in the morning; that's when I'm going to trouble shoot it some more. #1. I took voltage reading from Line to ground and line to neutral. Got 90 volts on both ways.
#2. I took voltage reading between the two and got around 34 volts I think. # 3. I'm thinking the 115 volts is feeding the "unswitched lead" and the 90 volts is feeding the switched lead. I'll have to verify that tomorrow.
The other questions I'll find out tomorrow. If it IS the switched lead that is 90 volts, then I'll start my trouble shooting at the switch. Could be a switch going bad. I have thought about two many lights on the circuit. I took a quick look at the electrical prints the other day and noticed a bunch of light that seemed to be on the circuit, but didn't have time to verify it. Thanks a lot for your questions. It will give me some idea of where to start tomorrow. Steve..

If the circuit is dropping 30 volts at a switch, it should be easy to find. For example, a 10 amp load and a 30 volt drop across a device equals 300 watts. That's a lot of heat.

Maybe start with voltage readings at the panel. It sounds like a bigger problem than one circuit, perhaps a bad neutral coming into the building.

twh, I've already checked the voltage at the panel and everything seems alright. 120 volts leaving all the single pole breakers (no double poles are there. Thanks anyway.

I wish I could be there with a cup of coffee to watch. My last guess is that there is a UPS supplying power to one hot. Good luck!

Steve,

Good luck with the Troubleshooting!
Hope you find the problem(s) easily, and without too much searching.

Will be looking for your update.

-- Scott

Great stuff, Scott.
Yet I ask the question.
When you are down 30V in a 120V system, that is a fair chunk of your supply voltage, I question what this was tested with.
Was this with a high-impedance meter that gave "ghost voltages"?
One other thing about fluorescent fittings, is the fact that they need to be loaded before they will output proper voltage and current.

Steve, don't get me wrong at all, I'm not looking to make you look bad, I just want to help out with some sort of a solution to the problem

Went to check my job today. I think at this point it is obvious what the problem is. (32) (2x4) 2 tube (2x4) lay in fixures on 1 circuit, not counting 13 exit lights on same circuit, all pulling constant load. Another 7 outside emergency lights that only come on with the exit light battery when power is off. Total amps on circuit is 19 amps, on a 20 amp breaker. All lights are controlled from 8 locations. The light furthest away from the electrical panel is operating on 95.3 volts. The light I actually started working on, (on the original trip) was working at 90 volts(actually looks closer to electrical panel, but who knows how the conduit is run). From one end of the hallway to the other is 184 ft. (by the scale on prints), not counting the hallways that branch off to the front and back of building at the different entrances.
Total sq. ft. of building is 13,254 sq. ft.
As far I can tell now, all the lights are left on 365 days of the year. There are no emergency lights that stay on when the hall switches are turned off. The emergency lamps only come on when the power to the circuit goes off. Out of 13 emergency lights (2x4 layins) shown on the prints, only 8 are working. Probably the reason they leave the lights on all the time, is for security reasons. Looks like the archetect would have designed for some lights to stay on constantly. I looked at the wiring diagram for the emergency ballast, thinking that the brown leads may need to be connected for this purpose, but not so according to the Notes they include.
Voltage on the unswitched feed is 120 volts.
Voltage on the switched feed, (which controlls all the lights)ranges from 90 volts to 95 volts.
Conclusion #1: Looks like I get to schedule another Saturday trip to replace 5 emergency ballast.
Conclusion #2: Looks like "Voltage drop" is causing the low voltage through all the switches. (No feasible way to remedy except to do "major, major" dividing of the circuits and switches).
Conclusion #3: The effects of low voltage on the lights and ballast will give me more service work:)
This building is only about 2 years old.
If you have any ideas on my "conclusions" please let me know. It took me about 4 hrs including drive time
(this clinic is about 25 to 30 miles from my office).
In my opinion, the archetech made some errors and the inspection dept. that reviewed the plans missed them.
Thanks again for replies... Steve
P.S. One more question: Wondering why the emergency ballast I originally checked was causing the regular ballast not to work in the fixture, yet the other lights in the hallway that have bad emergency ballast, are still working?? Thanks again..

Trumpy, I checked the voltages with a "fluke meter". I double checked my meter on a receptacle outlet that had 120 volts. No problem on me looking bad. If I'm making a mistake, I'll be the first to want to correct it.
Thanks for the reply. Steve...

Instead of "major major" dividing of the switches and circuits, can a lighting contactor be inserted such that the switches control the contactor coil and the contactor powers the fixtures? This would remove the fixture current from the switches and would require minimal rewiring.

Just unsolicited advice from a non electrician engineer.

Larry C

I would never have believed that someone could devise a lighting circuit with a 25% voltage drop. You did a good job recognizing the problem.

19 Amps on a 20 Amp breaker...

The circuit needs to be rewired.

Steve,

Just read your recent message, regarding the Lighting issues.
I will quote parts of the message with my comments.



As Tesla said above, the Circuit should be Rectified, as the Load is > 15.999 Amps, and running _Continuously_ for more than 179 Minutes, 59 Seconds.
Unless the Conductors are all #10's, this is an issue.
Poor Design and Installation is the culprit.

The 2x4 2 Lamp Fixtures would draw 64 VA each (0.534 Amps @120V). Thirty-Two Fixtures equals 2,048 VA - or 17.067 Amps @ 120V.
The Exit Signs (if they are LEDs), would draw 5 VA each, for a total of 65 VA for all 13 Exit Signs.
65 VA @ 120V = 0.54 Amps.
Base total for the single Lighting Circuit so far: 2,113 VA, or 17.61 Amps @ 120V.

Loads for the Charging functions on the Exits and the Em. Ballasts:

a: Exit Signs: 2 VA each - total of 26 VA (0.22 Amps @ 120V),
b: Emergency Ballasts: 12 VA each; total of 156 VA (1.3 Amps @ 120V).
Total of 183 VA (1.52 Amps @ 120V).

Add the Charging Loads to the Lighting Loads:
2,113 VA Lighting + 183 VA Charging = 2296 VA (19.134 Amps @ 120V)

If the Lighting was connected to a 277V 20 Amp Branch Circuit, Thirty-Two Fixtures on the same Circuit would not be a problem (I wonder if that was the original idea...)

---------------------------------------------



Is the Building's Service Voltage only 208Y/120V 3 Phase 4 Wire? Seems the Footprint Area of +13K Sq. Feet would have 480Y/277V 3 Phase 4 Wire Service Voltage.

---------------------------------------------



It appears the Lighting Circuit runs through (2) 3-Way Switch "End Points", and (6) 4-Way Switch "Mid Points", then to the First Fixture near that last 3-Way Switch location.
If the end of the Switch Loop is at the end of the Hallway (184 Feet), the Voltage Drop at that point would be 11.51%; which would yield 106V (figuring #12 Conductors).
This is just the Switch Loop, not including the Home Run Length.
Figuring an additional 100 Feet for the Home Run (total Circuit Length from Panelboard to last 3-Way Switch = 284 Feet), the Voltage Drop becomes 17.76%.
17.76% loss from 120V = 98.69V.

The Fixture which readout at 95.3V is probably closer to the Panelboard - per total Circuit Length, than the Fixture showing 90V.
At these lengths, the Circuitry should have been at least #10's, with (2) Circuits coming in to the "Middle" of the Hallway.
Occupancy Sensors would have been a better choice for this Corridor's Lighting Controls.

---------------------------------------



I agree - there should be a few Unswitched Fixtures in this Corridor for Egress purposes (Emergency Egress without complete Outage, and Non-Emergency Egress).

The Non-Functioning Emergency Fixtures may have failed due to Heat + Voltage Drop.

--------------------------------------




Is this information from the Dual-Lite UFO-3AW Schematic?
I only see (1) Brown Lead, which connects to the "Charging Indicator" Lamp (Lamp Loop = Brown + Violet).
If you have a different Schematic / Ballast type, please let me know.

-------------------------------------------



It appears the Unswitched Lead is from the beginning of the Switch Loop (at the Home Run location), and since there is less than 240 VA (2 Amps @ 120V) Load on this segment, the Volt Loss is dramatically less.

This slightly changes my Voltage Drop Calculation, as the Load at the end of the Switch Loop is 1.52 Amps less.

--------------------------------------



Good question!

The Ballast you worked on may have been setup to drive the Lamps only when there is an Outage, or the Voltage on the Switched Circuit was below the Threshold for Ballast Operation.

If the Failed Ballasts were connected, so as to drive the Lamps only during an Outage, the Failure of the Ballasts would probably exclude them from the Circuit... I am not too sure, though.

Chances are these Fixtures will have several "Variations" in how they were Connected (i.e. Whom ever got the exciting task of installing the Em. Ballasts, made up some Fixtures as Switchable, and others as Normally Unlit... possibly due to a "Liquid Lunch" experience).

-- Scott

"Chances are these Fixtures will have several "Variations" in how they were Connected (i.e. Whom ever got the exciting task of installing the Em. Ballasts, made up some Fixtures as Switchable, and others as Normally Unlit... possibly due to a "Liquid Lunch" experience)."

Sounds like the root cause of the complete lighting situation as described herein.

Scott...

I'd bet on multiple teams wiring up this beastie...

That certainly was the malpractice that I've witnessed in the trade.

I also agree that the EE expected a 277V circuit.

I've seen more than one installation wherein the lights are on 277 across the board -- until the EM lighting circuit! It went down to 120 VAC. In that instance it had its own EMT run -- even though the EM fixtures were in-line with 277V strips.

( Grocers )

Another question concerning this lighting problem. Is it "Code" to have some unswitched lighting for egress in a facility like this? I looked in the Code (old code book)but couldn't find it. Wondering if the inspector may have missed this if there is. Still trying to get my solutions together before I present them to the customer.
Thanks.. Steve

Such matters are decided by the Fire Marshall in most jurisdictions.

It's not to be found in the NEC.

Other building codes may address it.

Building inspectors here determine egress illumination, both day/nite, occupied/unoccupied, and emergency. Determinations are based on the 'Use Group' & occupancy of the structure. Also, if the path is used by other occupants of the structure in multi-tenant occupancies.

It is also a 'design' issue; to provide illumination for security reasons.

Thanks, that's kinda of what I thought. In the rest of my explanations, I'll just make a recommendation that if they want to save on ballast etc.. they install some unswitched lighting. I'll try to come up with the simplest way to remedy their problem. Of course the simplest short term way is just to replace the bad emergency ballast, but the chance of overheating the #12 wires, ballast and the bulbs may become a problem later. I still haven't presented it all to them yet:)

I know the effects of voltage drop will shorten the life of the ballast etc., but what is your opinion of the damage to the wires and possibility of fire hazard in this situation. This will be a very involved job to change any of the wiring. I need my facts together before I present them to the customer. They will be taking my word for this, since there is no one knowledgable at these offices.
Thanks again. Steve

Steve:

IF the circuitry is #12 and has a 19 amp load, eventually (real world) there could be heat damage to the insulation, leading to a L/L, L/N, or L.G short. Understand, 'long term'.

You may want to stress the fail rates of the e-ballasts units ($$$) and the possibility of fines ($$$$) from the local fire officials as a reason to correct the issues. Our Fire Official has a violation book with a lot of $$$$ fines.

Scott35 probably has facts on the heating issues that are more in depth than my 'street' version.

I saw reference to this earlier, but can't see the reasoning why since #12's are rated for 25 amps, they should be fine loaded to 20 amps indefinitely.

The devices connected to it may not be, but the wire will be fine with the full load heat.

Vin:
Yes, by the chart, but it is max 20 amp OCP! Now, this being a continuous load, comm lighting; that's down to 16 amps max load.

As mentioned within this thread by others; the design intent may have been 277 volt, and there was oversight by the installer & others it seems.

Yes, as I implied #12 will survive, perhaps for a long time, but...it is not compliant.

Ahh, but #12's are compliant.

OCP has no bearing here on the #12's, their allowed ampacity is still 25 amps regardless of OCP and 80% of 25 is 20, so compliant they are, as long as the circuit ampacity doesn't exceed 20 amps (connected).

The OCP IS overloaded though whether by accident or design (unless it is fully rated, doubtful).

Vin...

We're not allowed to use the 25 Amp rating for this calculation. It must start at 20 Amperes.

The 25 Amp rating can only be used for derating calculations such as multiple conductors and WRT certain motor load calculations.

One aspect of this that is normally overlooked is that these branch conductors are typically installed where shedding heat is not favorable. ( It's a lot warmer up high and when sandwiched within walls. That's why the Code kicks in an extra derating.)

Another aspect is economics. Taking the conductor up to its limit is VERY poor economics for the building's owner.

In all of the commercial contracts that I've dealt with it has been mandatory for the EC to bump up all homeruns to #10 ... and to #8 for site lighting runs when specified.

Tesla:

Thank you!

This is simply not true, I have worked for and with EE's for 25 years and this has NEVER been the case. Only OCP must be limited to 20 amps for #12's. The derating comment would be true if the 25 amp allowable ampacity was in the 75d or 90d column, but it's in the 60d column.



I am not saying it's good engineering practice to do otherwise, what I'm saying is that it is allowed (by code).



We do nothing but commercial work, most in the 7-8 digit range and it is not normal to make homeruns #10 by default. The length of the circuit determines the size and inside the building, anything larger than #12 for a 20 amp circuit is the exception. For site lighting Vd calcs are a necessity based on circuit length and load and many times even #8's or #6's are inadequate.

As far as 19 amps continuously on #12's, it isn't wise, but it IS allowed by code when fully rated OCP is provided. If you disagree, please prove me wrong (provide relevant code sections).

No one makes a fully rated C/B... they are ALL 80%...

The cram down to 20 Amp is right in the NEC...

And has been there for years and years.

See Uglys...

Safeway, Albertsons an Walmart are as cost oriented as you can get.

They all spec #10s on home runs.

ALL major manufacturer's do and HAVE for a LONG time.



B.S., provide a code section



NOT a code



AND clueless as to what they're paying for as well, but they are big box stores and as such usually have long homeruns. Regardless, a blanket spec of all homeruns being #10's is wasteful.

"Because so and so said so is NOT an answer", if it's not prohibited by the code it is allowed.

As I understand it, the NEC only allows a complete listed assembly to be operated at 100% of its rating. This would mean not just the circuit breaker, but all of the attached components, devices and conductors would have to be tested together and listed as an assembly. This is probably not something that you can design and put together on your own without a field visit from UL.
Take a look at the wording in the first sentence of [NEC 2011] 210.19[A],1, Exception regarding branch circuit conductor ratings and then 210.20[A], Exception regarding overcurrent protection device ratings. They are exactly the same with regard to listed assemblies rated for operation at 100% of their rating.
It looks that according to 210.20[A], a circuit breaker would normally be sized for 100% of the non-continuous load, plus 125% of the continuous load, just like branch circuit conductors.
So, if in this case you have a 19A calculated continuous load, then it appears that both the circuit breaker and branch circuit conductors would need to be sized for 19A X 125%= 23.75A.
Since #12 conductors for all temperature ratings in Table 310.15[B],16 are limited to a 20A maximum OCP by 240.4[D],5 it seems you basically have two choices. Reduce the continuous load on the circuit or increase the size of the circuit breaker to 25A and the conductors to #10.

IMO, in this situation the 25A rating for #12 in table 310.15[B], 16 would not help because the circuit breaker also has to be considered, but also IMO, when you get into #12 being used as a neutral conductor where OCP is not involved, then that is when the 25A rating can sometimes come into play.

I probably should have said listed assemblies for continuous operation at 100% and that a circuit breaker can be sized for use at 100% for non-continuous loads.

I found this article which does a pretty good job explaining things. It’s from 1996, so the NEC articles probably have changed since then.
Sizing Circuit Breakers

It is done all the time, I have seen jobs where 100% of the distribution gear was 100% rated.



Again, if the breaker and assembly is fully rated (100%) it can carry the 19 amp load and the wire is not an issue because it's allowable ampacity is 25 amps.



See previous comment.

This to me is a simple, apparently widespread misunderstanding of what the code allows. In my world this has been commonplace for decades (fully rated panels and breakers, etc.), so when someone says you have to upsize #12's to 10's because the load exceeds 16 amps and others are taking that for granted I see a need to speak out.

"Just because" or "because I've always done it that way" doesn't fly with me, ever.

The 20 amp limitation for #12's is for OCP only and always has been.

It isn't wise, but it is OK (by code).

Okay, but I think it would be a misunderstanding to consider that only the panel, breakers and conductors constitute an assembly that is listed for continuous use at 100% its rating, regardless of what someone is used to doing.
IMO, an assembly listed for this type of use would also include all the equipment and devices attached to the circuit in addition to a circuit breaker and conductors. As I understand it, this would require all components, conductors and connected equipment, etc., to be designed with terminals and connections rated at 90-Degree C.
Even though the circuit breakers are listed for use at 100% of their rating for non-continuous loads, aren’t most CB terminals only rated at 40-degree C ?

All circuit breaker terminals are rated at 60d C minimum. Many are also rated at 100% continuous load ratings at 40d C ambient, which should not be confused with the 60d C insulation rating.

We are getting into an area about the difference between safe and legal. 240.4(D) was put there for safety and it is really there because the NFPA people know 14/12/10 is used on circuits where the loads are likely to be cord and plug connected.
The assumption is that the installer will not know what the user will actually plug in. People will keep plugging in things until the breaker trips and then unplug the clock. They build the 80% into the maximum breaker size. That still does not change the requirement that hard wired continuous loads are still limited to 80% of the breaker size, as KJay points out.
Whether the NFPA should put the same kind of exemptions for lighting loads into the code that they have for motors is conjecture but you still have a few weeks to write a proposal and see what they say.

The 40C has to do with the trip curve, not the terminal rating.

Here are some typical breakers and the terminal rating.

Sorry, I meant 75-degree C.

Agreed, but the use of 100% rated OCP is mostly limited to industrial and institutional settings where competent personnel are generally involved in the design, construction and maintenance of said facilities.



What requirement is that? If the fixture, receptacle, piece of equipment, etc is rated for 20 amps (or whatever the 100% rated OCP is) then you are good. The code does not address derating end-use devices as far as I know.

I suppose I could write 1000 words but here is a picture from the handbook.

Greg,

You failed to include the 100% assembly exception that immediately follows that example.....

100% assemblies don't exist.

If you mean panels and breakers, yes they do, but they have to be specified that way and there is a cost impact (sometimes significant).

specified and used at the proper location and time though and it will save money otherwise spent on oversized branch and distribution gear feeders and breakers.

I am having a hard time finding a breaker that says it is rated for 100% continuous load.

Finding 100% rated breakers hasn't been the problem, but finding a 20 amp 100% rated breaker is proving difficult, which is annoying since I've seen them spec'd and installed on several waste water treatment plants over the last 5-6 years.

Guys:

We are talking about what seems to be either a design issue that fell through the cracks in a commercial setting, not industrial, etc.

Vin: I see all your points, but they are out of the league (IMHO) on the OPs points.

I sent a request in to the SQ.D company to see if they could tell me what the 20 amp QO breaker was actually rated at. Haven't got a response yet, but obviously whatever it is rated at, on the job in question, it has been holding for 2 years at 19 amps. Of course the 5 emergency ballast that are bad in the facility right now might bump it up a little more, when they are replaced ,( of course I realize the amperage, if any, will very minimal). I've sent my information in, to my customer, and am waiting on their reponse as to what they want me to do.
I've also sent "South Wire" (one of the manufacturers) an email to see if they could actually tell me what #12 thhn is good for, before the insulation actually breaks down in real life, in their test labortories. Still looking for their response also. Thanks again for all the response.

If it's a standard 80% breaker that is amazing, but you have to wonder if all of the lights are on all the time too.

I am so familiar with 100% breakers because I spec them so often, most recently on a bunch of PV jobs. The switch gear for a large portion of these cookie-cutter jobs we've been doing has several 100% rated 500 amp breakers with parallel 250's to large inverters, the inverters have a maximum output of 440 amps at 480 so the breakers are fine. If we used 80% breakers we'd have to use parallel 350's and upsize the conduit and that would quickly cost more than the additional $500 or so for the 100% breaker since the distances between the inverters and switchgear are usually 200-400'.

We had a vendor supply us with an 80% breaker by accident this summer and when the array went online everything was fine until August when it tripped a dozen or so times. Every time the meter recording showed it tripping between 402 and 405 amps, right at the 80% rating.

So, having an 80% 20 amp breaker hold 19 amps for 2 years is exceptional IMO.

That circuit should really be split into 2 circuits IMO, but I don't think the circuit length and load is the issue on the 90 volt readings unless the total circuit length is around 500+ feet which it doesn't sound like it is.

Is it a counterfeit? Or made by FPE?

LOL

Me too I bet they are wondering what is going on.

I did look at the online documents I could find on QO breakers and they keep talking about the NEC 80% rule.
The trip curve does make it look like they will hold at the rated capacity forever at or below 40c.

Subj: RE: Product Technical Inquiry [T20111104011NS010Z4733638]
Date: 11/4/2011 3:57:57 PM Eastern Daylight Time
From: ContactUs_Web@us.schneider-electric.com
To: gfretwell@aol.com
Sent from the Internet (Details)



The QO is standard rated (80%) for continuous loads of 3 hours or more. 100% rated for loads less than 3 hours.

___________________________________________________________________________

Marshall Barker | Schneider Electric | North America | Senior Product Support Specialist - Circuit Protection

Toll Free: +1-888-778-2733 | Fax: +1-319-369-6600

Email: cedarrapids.psg@schneider-electric.com | Site: www.schneider-electric.com

Address: 3700 6th Street SW, Cedar Rapids, IA 52404


On November 4, 2011 at 12:01 PM, gfretwell@aol.com wrote:

>
>
>

Greg, you must have special connections with Sq.D
I haven't got my response yet. I have got a response back from "South Wire". They only point me back to the NEC. I was hoping they could tell me actual data from their laboratories:)
BTW, Wa2ise, it is Sq.D not FPE thank goodness:)

As far as I can tell from looking at their catalog, the regular SQD QOB style breakers are only available with the standard 80% rating. The SQD PowerPact molded case cb’s are available in either the 80% or 100% rating, but these apparently won’t fit the standard QO or NQO panelboards.

THHN is usually multirated MTW with a 105c rating so I bet that stuff could get so hot you could cook a chicken on it without any serious insulation damage but that does not relieve us from 240.4(D) or in special cases 310.16.

Greg:

Back on page 3, I threw in the heat deterioration comment, with the word "eventually".

Occasionally, from field experience as an electrician & contractor, I stray from the hair splitting ways of reading the NEC, as do the majority of people I deal with as AHJ.

Trade practices, exceeding code minimum and maximum standards are hard to forget sometimes.

All that said, and not to 'fan any fires'.....how long did ya cook the chicken??? LOL

These days THHN is usually rated THWN-2 AND MTW...

THWN-2 is very important since it permits reasonable wire size for underslab conductors.

Trick anything might be possible.

In the commercial trades 80% is a hard limit.

Everything about this circuit smells like the EE thought that 277 VAC would cut it.

Yet the EM ballast world is not oriented towards 277 VAC; namely the battery inverter scheme.

I've seen this addressed time and again only at the last minute as a change order -- in the field.

Are you sure it is actually dual fed I did a Barnes & Noble awwile back with the same readings 90 volts on the "red" ballast come to find out it as a voltage drop on the lighting circuit thru the emergency ballast.

Bummer for the commercial EM ballast world since 80-90% of them ARE 277 VAC.......

Mike, I got my voltage readings directly off the switched wire with ballast disconnected. Steve...

That sure is an interesting discussion... I always thought the 80% rule merely applied to good design (as in not overloading a circuit right from the beginning) rather than to actual breaker tripping. Interestingly enough, breakers commonly used in the 230V part of the world (B or C trip curve DIN rail components) are designed to hold 100% inifinitely and overload tripping is specified as within less than 1 hour at 145%. The EU low voltage directive (on which to some extent most European electrical codes are based on) also only specify 100% circuits in the form of Ib<=In<=Iz (the load current must not exceed the CB rating which in turn must not exceed the current carrying capacity of the circuit conductors). As it says <= you can perfectly well load a 20 amp circuit to 20 amps, but not 20.01 amps.

From this point of view, a breaker that trips at 80% seems to be very limiting, if not pointless - after all, it could then be called a (current rating*0.8) amps 100% breaker all the same.

When you read the actual technical literature it never really says the breaker won't hold 100%, in fact the trip curve seems to imply it will hold 100% up to an ambient of 40c. They simply reference the NEC rule. This may be lawyers trumping engineers.

Greg, I think I may have found a solution for one of my problems, the egress lighting we discussed on page 2. I should be able to tie the emergency ballast straight into the hot wire (120 volts)so that the fixture stays on all the time. I would just wirenut off the switch leg to the fixture, and have a hot wire going to the test switch and also straight into the emergency ballast which feeds the regular ballast. That way they can turn the rest of the hall lights off at nights and on the weekends, plus it seems I have the right voltage on the hot wire, so that should take care of those fixtures at least. Got to give my wife a little credit here. We was going over the whole scheme again, and she mentioned something to that effect, and the light bulb went off in my head:) I looked at the ballast diagram again, and it should work. Probably the way it was ment to be to start with:)