emergency lighting controls scenario

[malachi constant]

Imagine if you will a corridor controlled by a relay panel. 2/3rds of the lights are controlled via normal relay, the remaining 1/3rd by a UL 924 emergency relay. Imagine that someone decides (perhaps as an energy savings strategy) to program the corridors such that they normally operate at only 2/3rds the light (i.e. the emergency relays get shut off). The system is wired such that loss of power at the building main is sensed at the emergency panel, and any switching of the emergency lights is overridden and they are forced on. BUT if the local 20A/1P lighting circuit is tripped or turned off the em switching would NOT be overridden, so the normal lighting circuit for the area would be deenergized and the entire corridor would be dark.

Sounds like a code violation, right? Show me where. I can't find it.

OK, what if the relays are controlled by a password-protected software such that only authorized persons have the ability to control the corridor lights. Does NEC 700.20 allow this? I think it might. (EDIT: Under this 'authorized persons only' scenario, there would be protocol in place such that the lights would not be shut off during occupied hours, but they would be allowed to be shut off after-hours. The end result would still be a local breaker trip would keep all lights off (and they already WERE all off, so no big deal right...?) But a building main trip would still turn emergency lights on.)

This is purely theoretical of course.

Oh, and if you don't like this design, please don't attack me as I am on your side. Just trying to find if there are any flat-out non-negotiable violations with it.

 

[iwire]

I do not understand, any emergency lighting circuit supplied from a breaker is not going to work if you shut off its branch breaker.

 

[GoldDigger]

It might arguably be a violation of the ?rule? that the em lighting be supplied from the same circuit that controls the main lighting in the area.

 

[malachi constant]

I do not understand, any emergency lighting circuit supplied from a breaker is not going to work if you shut off its branch breaker.

I'm referring to the breaker serving normal lighting of a given area. I was always taught if that trips then the associated emergency lights (if they were switched off) must then be forced on.

 

[malachi constant]

It might arguably be a violation of the ?rule? that the em lighting be supplied from the same circuit that controls the main lighting in the area.

Yeah, where is that rule? I feel if I can find that it could clarify what is allowed / disallowed.

 

[iwire]

I'm referring to the breaker serving normal lighting of a given area. I was always taught if that trips then the associated emergency lights (if they were switched off) must then be forced on.

I am puzzled how this is the case.

Any emergency override relays I have installed would see the loss of the normal circuit would let the relay close / override the emergency circuit.

 

[GoldDigger]

I am puzzled how this is the case.

Any emergency override relays I have installed would see the loss of the normal circuit would let the relay close / override the emergency circuit.

And the problem seems to be that there are two normal circuits, one of which has been programmed off while the other is switchable?
As a general practice, not necessarily code, the emergency lights are usually the same fixtures used for always-on "night lights".
I guess the programmer figured that a regular hour energy reduction to 2/3 of original light level was OK while reducing to 1/3 would not be tolerable.

 

[iwire]

And the problem seems to be that there are two normal circuits, one of which has been programmed off while the other is switchable?
As a general practice, not necessarily code, the emergency lights are usually the same fixtures used for always-on "night lights".
I guess the programmer figured that a regular hour energy reduction to 2/3 of original light level was OK while reducing to 1/3 would not be tolerable.

If the lights do not activate for any reason during a power failure in my opinion that would be a 700.18 violation.

700.18 Circuits for Emergency Power. For branch circuits
that supply equipment classed as emergency, there
shall be an emergency supply source to which the load will
be transferred automatically upon the failure of the normal
supply.

 

[malachi constant]

And the problem seems to be that there are two normal circuits, one of which has been programmed off while the other is switchable?

There is one normal circuit and one emergency circuit. No "switches" per se - both are only controlled by the relay panel, which contains both normal and emergency relays.

As a general practice, not necessarily code, the emergency lights are usually the same fixtures used for always-on "night lights".

I think the industry is moving away from that as a general practice. It's a waste of energy to have 1/4 to 1/3 of your egress lights on 24/7. UL 924 relays allow emergency lights to be legally switched off, as upon loss of normal power the relays override the switching and force the em fixture on. Where I'm confused is on this proposed scenario upon loss of normal power at a local (room only, not building-wide) level the emergency lights would not be forced on. This proposed scenario requires a building-wide loss of power for any em lights that are turned off to be forced on. Is that legal?

 

[malachi constant]

If the lights do not activate for any reason during a power failure in my opinion that would be a 700.18 violation.

There IS an emergency supply source - the generator. I think it depends on how you read "to which the load will be transferred automatically upon failure of the normal supply." 700.18 is about the CIRCUITS for emergency lighting, not the SWITCHING. I would argue that as the load will be transferred to the emergency supply source by an ATS, this appears to satisfy 700.18.

 

[malachi constant]

So no one has to look it up, 700.18 is under Part IV Emergency System Circuits for Lighting and Power, and reads in its entirety:

700.18 Circuits for Emergency Power. For branch circuits that supply equipment classified as emergency, there shall be an emergency supply source to which the load will be transferred automatically upon failure of the normal supply.

700.20 is under Part V Control - Emergency Lighting Circuits, and reads:

700.20 Switch Requirements. The switch or switches installed in emergency lighting circuits shall be arranged so that only authorized persons have control of emergency lighting.

Exception No. 1: Where two or more single-throw switches are connected in parallel to control a single circuit, at least one of these switches shall be accessible only to authorized persons.

Exception No. 2: Additional switches that act only to put emergency lights into operation but not disconnect them shall be permissible.

Switches connected in series or 3- and 4-way switches shall not be used.

 

[Smart $]

As far as the tripped breaker scenario, there is nothing you can do about that as long as all equipment and wiring are compliant. Even emergency circuits require OCP.

Seems like your problem is a non-authorized person can control the em' lighting relays. Can the lighting control software be set up so em' lighting relay control is secure and separate from normal lighting control?

 

[iwire]

There IS an emergency supply source - the generator. I think it depends on how you read "to which the load will be transferred automatically upon failure of the normal supply." 700.18 is about the CIRCUITS for emergency lighting, not the SWITCHING. I would argue that as the load will be transferred to the emergency supply source by an ATS, this appears to satisfy 700.18.

I think you are missing the part of 700.18 that requires the load to transfer to the emergency source not just that there be an emergency source .

 

[jcbabb]

The UL-924 relay's will have an input that should be powered from the normal un-switched hot that feeds the local lighting circuit. Now, if this normal local lighting circuit breaker gets turned off, the UL-924 relays will override the corridor switch to 'on'. The corridors will not be dark.

I think what you are describing is a relay panel with the UL-924 relay built into it. Now the UL-924 relay will 'sense' normal power from a single normal circuit (selected by engineer or contractor), but it may be controlling fixtures (via the relay panel) in different areas that are powered by several different circuits. Now if the normal breaker to one of those circuits is turned off, the 'sensing' lead into the UL-924 device will not be able to detect the loss of power. In this case, if the local switch is off, then the corridor will be dark. Is this what you are referring to?