since i can't find anything in the nec that requires the use of shunt-trip breakers, anyone here use any rules of thumb to decide when to use them? other than when the engineer specs them? i've seen them spec'ed on main services with elevators, escalators, kitchen fire suppression systems, ups's, and fuel systems, but nobody has told me why they have to be used..... they just say they are safer and protect property better, which doesn't tell me much.... 230.70(A)(3) refers to using remote control devices, which this is, but nothing says you have to use them, thanks
My experience with shunt trip breakers had to do with commercial kitchens. Like you mentioned you tie the shunt trip breaker in with the FA supression system. I have done a couple systems now. One system speced the entire panel for that area be shunted. Of course the lights and other emergency items were fed from another panel. Another system had me shunt certain items throughout the kitchen. They basically spec that anything under the hood being suppressed be shut down. Another instance of shunting is for elevator recall during a fire alarm. The distribution panel supplying the motors for the affected elevators are shunted. Of course the cab lights are fed from another source.
Elevators, kitchens, and gas pumps are the only things that I've ever used them on. I'll keep my eye out for any info, as to why they are used. I've wondered myself from time to time why another method is not employed. There may be reasons outside the NEC that govern their use.
I think that they are used because they are the cheapeast and easiest method of having a remote shutdown of the power to a system. This remote shut down in often required by building or fire codes, but not the NEC. In many cases, the codes that require the remote shut down do not permit a remote restart, so with a shunt trip breaker, you have to go to the breaker to close it and the second part of the rule is satisified. Don
We use shunt trips in many of our FDP panels at the site that I work for, We use them for computer rooms and other lab/machine shop applications.
Typically there are multiple EPO (Emergency Power Off)buttons around the room (usually at exit doors) that will open mains in ALL panels for that particular area. Done mostly for safety reasons and the ability to kill raised floor AC units in case of fire.
They can be a nuisance though, like when the janitor hears a door alarm going off and reaches up and slaps the nearest button he sees, thinking he is going to silence the alarm.
NFPA 72 (National Fire Alarm Code) 3.9.4 requires the shut down of an elevator that is recalled due to heat/smoke/sprinkler activation that recalls the elevator. The easiest way to do so is a shunt trip breaker, but it does not mandate the shunt trip, ANSI 17.1 may, but I doubt it. Don's pretty much correct when he said it's just the easiest cheapest way to insure deenergization.
Mr. Corron, How's the leg? You call out more regulations than anyone I've ever seen, and that's a good thing because the "wool" is not going to get pulled over your eyes. Do you have a book that gives you the ANSI rules, or do you get them off the web somewhere? I'm curious because my whole career has delt with NEC issues, and it seems that with this new job that I have, I'm dealing with other entities out there, and it would be nice to be able to find the rules. As you know, I'm always concerned about my medical practice. I never really felt a need to clean my trusty Case Knife between uses. You know, gut a deer on Saturday.....open heart surgery on Monday.
I shunt the sheriff, but I didn't shunt the deputy, Doc
NFPA is good, they have all the books I quote from them, such as NFPA 72, 13, fuel gas etc. ANSI is another organization, but geeeez are they expensive regs.
The most economic place I've found to buy them is "Construction Bookstore" but I'm sure Bill has some over at the ECN bookstore as well, and from what I've seen from the prices, he's just as good.
I will e-mail you the details from work in the AM, I've got all that stuff bookmarked on my 'puter there. Usually the company buys my books, and I don't get to dictate where their from, but I do purchase my fair share.
Shunt trips are specified for a couple of reasons. The Elevator Safety Code A17.1 requires shunt trip for elevators prior to application of water from a sprinkler. Article 645 requires power disconnect for electrical distribution on the equipment floor and HVAC serving that area. This is generally accomplished using shunt trip. When a generator is installed on a system that requires load shedding, it is often accomplished using shunt trip on the non-essential distribution breakers.
[This message has been edited by Ron (edited 07-02-2002).]
[This message has been edited by Ron (edited 07-03-2002).]