Emergency lighting - is there a better way to do this?

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steve66

steve66

Senior Member
Location
Illinois
Occupation
Engineer
I am doing the electrical for a remodel in a hospital. Their emergency lights are on a generator. However, I haven't found a way I like for switching some of the lights.

Take a toilet room for example with two light fixtures as an example. Only one light needs to be on emergency power, so I put the other one on normal power. Now it would be nice to switch these both on and off from the same switch. However, I can't use a double pole switch because I would have normal power and emergency power in the same box, and there is no exception for switches. Same problem with a relay.

If I use two separate switches, someone may just turn on the normal power light. Then if the power goes off, they are in the dark.

Other options would be to make the emergency light a night light that is always on. That becomes less desirable in a large room that may have 10 emergency lights.

Any ideas what is the best way to handle switching lights on a generator?

Steve

PS. I do know that in the nursing corridors, the emergency lights have to be unswitched 24 hour night lights.
 
Re: Emergency lighting - is there a better way to do this?

How about a remote emergency powered light in the bathrooms. It would only be on if the power failed. It would only have to be enough light to see your way out, say 60 watts, or less. Electrically speaking, hookup a relay on regular power. Run the emergency light feeds through NC contacts on the relay. When the regular power fails, the relays drop out, closing the contacts, the generator starts, and the remote lights go on. When the regular power returns, the relays pull in, and shut off the remote lights.
 
Re: Emergency lighting - is there a better way to do this?

Thanks, but both solutions sound a lot more complicated and expensive than installing two switches.

I guess I think the best solution would be a double pole- double throw switch. The only problem, is that the code won't allow normal and critical power in the same switch box. A single pole switch controlling a relay would have the same problem - both normal and critical in the relay enclosure.

It would be great if someone made a double pole-double throw switch that also had a divider to separate a 4x4 box into two halves. A conduit for normal power would enter the box on one side and terminate on that side of the switch. A conduit for critical power would enter the other side of the box and terminate on that side.

It would be even better if the NEC just let normal and critical power enter the same switch box, but I don't think I can call a switch "transfer equipment".

Steve
 
Re: Emergency lighting - is there a better way to do this?

Steve, why would you want to put switches in a public rest room? Most hospitals I work in have 24/7 normal and critical lighting in the public (multiple occupant) rest rooms.

Roger
 
Re: Emergency lighting - is there a better way to do this?

Steve if these bathroom lights are truly emergency lights covered by article 700 you can not shut them off without means to have them automatically come on when needed.

700.17 Circuits for Emergency Lighting.
Branch circuits that supply emergency lighting shall be installed to provide service from a source complying with 700.12 when the normal supply for lighting is interrupted. Such installations shall provide either one of the following:

(1)An emergency lighting supply, independent of the general lighting supply, with provisions for automatically transferring the emergency lights upon the event of failure of the general lighting system supply

(2)Two or more separate and complete systems with independent power supply, each system providing sufficient current for emergency lighting purposes

Unless both systems are used for regular lighting purposes and are both kept lighted, means shall be provided for automatically energizing either system upon failure of the other. Either or both systems shall be permitted to be a part of the general lighting system of the protected occupancy if circuits supplying lights for emergency illumination are installed in accordance with other sections of this article.
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The most common way I see this done is the use of a normally closed relay in parallel with the wall switch controlling the emergency light(s)

The coil to this relay is powered by "normal power" so when normal power goes out the relay closes and lights the emergency fixtures regardless of the wall switch position.

This is simple if you can live with separate wall switches for normal and emergency.

If you want one switch to control both systems it takes more relays.

As far as the two sources in the relay enclosure it can not be avoided.

Can you leave the lights on? ;)
 
Re: Emergency lighting - is there a better way to do this?

You are da man, iwire. That gives me a lot to think about.

I'm not sure if these are truely emergency circuits. I think as far as toilet room go, our local code requires emergency lighting in a one hole outhouse. One of the rooms I'm thinking of is basically a glorified one-hole job (one toilet, one urnal, no dividers, and a lock on the door).

Another larger room I'm thinking of is for physical therapy. I don't know for certain that emergency lighting is required. (The definition's of exit way, exit access, and so on in BOCCA and IBC don't seem to give much guidance.) However, I'm sure the hospital expects some emergency lighting even just for conveinence.

Iwire, you said
As far as the two sources in the relay enclosure it can not be avoided.
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I don't personally have a problem placing both sources in a relay enclosure, but I don't think the code allows that. See 517.30(C)(1). It seems like the relay would have to be in the fixture.

STeve
 
Re: Emergency lighting - is there a better way to do this?

Steve
You mentioned that there is a generator system for the emergency lighting. Emergency lighting/wiring is required to be separated from other wiring, no matter how expensive it is to install it that way. Why can you not run a new circuit for these out of the emergency panel where the other emergency lights are fed from.

Bob
you mention that it cannot be avoided to keep the wires separated, not at all... just do not run them in the same enclosure. ;)

What about unit type emergency lighting, will that satisfy this type of installation?

Pierre
 
Re: Emergency lighting - is there a better way to do this?

Pierre the installation I described is done all the time here when emergency lighting is shut down with a switch.

The two systems (normal and emergency) and up occupying the same relay enclosure but not the same raceway.

700.9(B)(3)(3) Wiring from two sources in a common junction box, attached to exit or emergency luminaires (lighting fixtures)
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As Steve said attach the relay enclosure on the light fixture and you meet code. :)
 
Re: Emergency lighting - is there a better way to do this?

Why can't he simply use a 2pole single throw switch. Normal power on one side/ emergency power on the other. Its no different than bringing 2 different power sources to a contact block.
 
Re: Emergency lighting - is there a better way to do this?

Originally posted by bigjohn67:
Why can't he simply use a 2pole single throw switch. Normal power on one side/ emergency power on the other.
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Hi John. emergency power and emergency power must be kept separate except for a few specific places listed in 700.9(B)

700.9(B) Wiring. Wiring of two or more emergency circuits supplied from the same source shall be permitted in the same raceway, cable, box, or cabinet. Wiring from an emergency source or emergency source distribution overcurrent protection to emergency loads shall be kept entirely independent of all other wiring and equipment, unless otherwise permitted in (1) through (4):
(1) Wiring from the normal power source located in transfer equipment enclosures

(2) Wiring supplied from two sources in exit or emergency luminaires (lighting fixtures)

(3) Wiring from two sources in a common junction box, attached to exit or emergency luminaires (lighting fixtures)

(4) Wiring within a common junction box attached to unit equipment, containing only the branch circuit supplying the unit equipment and the emergency circuit supplied by the unit equipment
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Further a standard two pole switch will not automatically turn on the emergency lights on when the power goes out.

Say the emergency lighting is part of the overhead lights in a office and the occupant has left the overhead lights off because they are using a desk lamp to do their work.

Now a power failure happens they will be in the dark unless the switching for the overhead emergency lighting is arranged to automatically override the wall switch. :)
 
Re: Emergency lighting - is there a better way to do this?

Seems like it would simplify things by just adding one additional light on the regular branch and leave the emergency light on its own circuit in each of these bathrooms. Why do you need the emergency light on when there is no emergency?
 
Re: Emergency lighting - is there a better way to do this?

Steve,
take a look at Lighting Controls & Design GR2001 relay. It has a separation of normal and emergency power.
 
Re: Emergency lighting - is there a better way to do this?

Thanks IP, I haven't had time to look at those in detail, but it looks just like what I was thinking of.

It took me a few minutes to find the web site. Here it is for anyone else interested:

http:// emergency relay

Steve
 
Thanks Sceepe. How did you dig up this old thread anyway??

That looks like a variation of the controls by the other company.

I still wish I could just use a double pole switch. When everyone leaves the room at night, all the lights get turned off. And when they come in in the morning, one switch turns both normal and critical branch lights. A power outage on either branch still leaves the lights on.

I was thinking of a hospital when I asked this question. They often expect a space to remain useable during a power outage. A few unit lights won't give the illumination they want, and they only last 90 min.

With the double pole switch, I would wire just enough lights on emergency power to make the space useable and comfortable.

Maybe I should try designing a double pole switch with a metal divider on it that would divide a switch box into two separate enclosures. That's what some of those relays do. But my switch would be a lot cheaper and simpler. (Of course, it would have to be UL listed.)

Steve
 
Use a relay

Use a relay

A simple way we use to control normal light fixtures that are also EM lights is with an "Emergency Shunt Relay". This is a normaly closed relay, it falls shut during a power failure to turn on the emergency lights. We wire it to a single pole, double throw swith. Under normal operation the swith is turned UP to energise the normal lights and turn off the power to the relay which closes to energise the EM fixtures, so all fixtures are ON. When the switch is down the normal lights are deenergised and power to relay is on, the rely opens to deenergised the EM fixtures. When there is a power failure, the power to the relay is interuped independent of the switch position and EM fixtures come on.

The relay we use is UL listed to control EM circuits and comes with a box that has a divider to sererate normal & EM circuits as per code.

The relay we specify can be found at: http://www.lightingcontrols.com/productcatalog/overview.asp?p=emergencyshunt

There are other manufactures also.

We have found this to work great in classrooms and other places where additional fixures are objectional or cost prohibitive.
 
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