Smoke detectors

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Re: Smoke detectors

I might be wrong about this like I said I was going off what I was told by other inspectors, but I don't remember seeing it any where that requires grounds from separate circuits to be tied together.
 
Re: Smoke detectors

Thought of that Jim,as a matter of fact I sent the service crew to the supply house to pick up Firex dectectors a completly differt brand and well 3 days later another call for the same thing
 
Re: Smoke detectors

Let's look at a metallic wiring method like EMT. I have circuits from different circuits and even separately derived systems coming into the same junction box, do I tie the grounds together? OK, there is no way to keep the grounding conductors apart. In light of this scenario, what is wrong with tying all the grounding conductors together in a junction box with a cable wiring method? In reality, all of the grounding conductors will go back to the same location and they are not current carrying conductors. :D
 
Re: Smoke detectors

Lets say you have a fault on both circuits at the same time, I know it is not likely, but you would be over your amperage rating.
 
Re: Smoke detectors

Allen give some thought to this idea.They might be smoking wacky weed and the smokes don't like it.Other than that is there a air block between smoke and the box,some require it.Are any other circuits tapped off of this smoke.Could another wire be running too close to your 14-3 for smokes and causing a magnetic field with the interconnect wire?
 
Re: Smoke detectors

Ken
Originally posted by kendog:
Lets say you have a fault on both circuits at the same time, I know it is not likely, but you would be over your amperage rating.
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think of it this way, as you are saying, a proper sized EGC will take care of the fault on it's own circuit, now we tie a second conductor to it from another circuit, this effectively increases the conductor to twice it's size and lowers the resistance proportionately.

These conductors in parallel can now handle twice the fault current, and even if a fault did occur on both circuits simultaneously, the paralleled conductors would be able to do the job.

If only one circuit faulted, the parallel paths would be welcomed by all the other conductors. ;)

Roger
 
Re: Smoke detectors

Jim you might be onto something there,something for sure is causing the smokes to signal and it wouldn`t take much to cause an EMF that would signal the LV signaling system that smokes use.I have seen hard starting compressors that caused a dip in line voltage that have set them off also vibrations at poor connections do it.With all other aspects being ruled out I will check this one out :D
 
Re: Smoke detectors

On equipment grounding conductors I don't know too many electricians that would run a seperate grounding conductor for each circuit that they would pull in a pvc conduit feeding through a slab to a work area with multiple 120 volt circuits in an industrial application. Just a thought.
 
Re: Smoke detectors

Stop me if Im wrong, but if you connect the grounds from 2 circuits together, wouldn't you have a parallel inductance?
 
Re: Smoke detectors

You only need a grounding conductor for the largest circuit that is in the raceway and you are working for a first contingency. It doesn't matter if all the grounding conductors are connected together and if they are different sizes. Under fault conditions, the current will divide on all of the paths but most of the current will travel back on the grounding conductor that is closest to the circuit conductors. The return path will not be the one of least resistance but the one of least impedance. :D
 
Re: Smoke detectors

Originally posted by kendog:
3, Grounds tied together from different circuits, Yikes.
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How would an ACFI know? It has no grounding conductors attached to it?

Neutrals (grounded) conductors tied to other circuits will trip an AFCI. Is this what was meant?
 
Re: Smoke detectors

You can`t tie the ground from an afci circuit to a non afci circuit,that will trip the afci when a load is introduced.The afci will see the ground/neutral fault!
 
Re: Smoke detectors

didn't mean to start an argument but there is a lot of good points being made. I am just trying to let you know of some problems that I have faced while troubleshooting.
 
Re: Smoke detectors

Allen I think your mixing up neutrals and grounding conductors. Grounding conductor do not enter the circuit for a AFCI except when there needed for a fault path. Connecting grounding conductors together will not cause any problems in any circuit! If it does then just explain to me how conduit does not cause any problems? It is connected to every run also. :p
 
Re: Smoke detectors

I ask my self the same question plenty of times. The last place that I worked we tested a little over 2000 sections of a house a year. After a while you quit asking how, fix and move on.
 
Re: Smoke detectors

Originally posted by allenwayne:
You can`t tie the ground from an afci circuit to a non afci circuit,that will trip the afci when a load is introduced.The afci will see the ground/neutral fault!
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If that were the case, I'd have had my fanny handed to me by now.

You sure you're not talking neutrals, here? :)
 
Re: Smoke detectors

grounding/grounded conductors....same as if you have a grounding conductor touching a grounded conductor at a afci receptacle,circuit will hold until load introduced.now take the non afci circuit introduced into this situation the grounding conductor back at the panel is grounding/grounded together the isolated grounded conductor of an afci will see it as a fault.Have seen it many times isolate the grounding conductor and problem clears.Remember the afci has to be isolated grounding from grounded. ;)
 
Re: Smoke detectors

same as if you have a grounding conductor touching a grounded conductor at a afci receptacle,circuit will hold until load introduced
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Could be a brand difference, but my Siemens AFCI's will not tolerate a neutral-ground fault under no load. When I trim out a panel, I will land the neutral, check to see if the breaker holds, with the ungrounded conductor dangling, to determine if I have a neutral-ground fault. It will trip, no possible load.

now take the non afci circuit introduced into this situation the grounding conductor back at the panel is grounding/grounded together the isolated grounded conductor of an afci will see it as a fault.Have seen it many times isolate the grounding conductor and problem clears.
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What I am hearing is "with a neutral-ground fault in a receptacle in a regular circuit, nothing happens, put it on an AFCI and it will trip." This isn't news. It doesn't address "tying grounding conductors from different circuits together will trip an AFCI." I'm not clear on what you're trying to say, I'm sorry. :)
 
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