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Author Topic: What's the worst thing that can happen?  (Read 7304 times)

John Roberts {JR}

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Re: What's the worst thing that can happen?
« Reply #20 on: May 15, 2016, 12:16:18 pm »

Just a point of conversation.  I have had the fan on the out side compressor unit go bad.  The compressor would start out drawing normal current and then clime to just over 50A before the 30A breaker would cut out.  This over draw could take a very long time to build up and trip.  I strapped an industrial box fan to the top of the condenser unit till the 1/4 hp motor could be replaced.
I am keeping my fingers crossed that the compressor is OK (it's not very old)... the anecdotal evidence suggests the wiring under the house may have been accidentally sabotaged.

In hindsight they are lucky their house didn't burn down. I hope their luck holds.

JR 
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Rob Spence

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Re: What's the worst thing that can happen?
« Reply #21 on: May 16, 2016, 01:27:51 pm »

I have been enlisted by my (86YO) neighbor to take a look at his house wiring. Last winter he had a minor fire (smoke?) incident, and I don't know all the details, but some wire(s) supposedly over heated because they had too much garbage stacked up on top of them??  I do not know that I buy the explanation, but their short term remedy was to cut the wires... ::) Probably stopped using the central heat, and reverted to the old in wall room heaters.

Now that warm weather is arrived, the wiring needs to be restored for the central air conditioning to work... So I promised to go over tomorrow and take a look. I'll know more tomorrow after I get some eyeballs on it. I'll beg off if it looks too dicey, but i'd like to save my neighbor a few bux if i can.

Anything obvious to look for? I think they said it was Romex, so not original (very old) house wiring, but could be a few decades old. There's a sub panel (or two) for the central air maybe 100 feet from the power meter and main panel.

The house was expanded upon, once or twice, which is probably why there are multiple electrical panels.

I ASSume romex is still legal for house wiring?

What could possibly go wrong, burn down a friends house?

JR

PS: BTW his house is better wired than mine with actual grounded outlets in the kitchen.   8)

I am a bit behind here but...

Actually, Romex (RX) isn't legal for new work these days. What most people mean when they say Romex is NM or non metallic wiring meaning not armored.
So, if it is plastic coated it should be NM. If it is fabric/jute covered that might be RX.

Strange that the wire melted without tripping a breaker.
Also, note that many compressors are actually 240v and a 20a #12 is common.



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John Roberts {JR}

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Re: What's the worst thing that can happen?
« Reply #22 on: May 16, 2016, 02:13:40 pm »

I am a bit behind here but...

Actually, Romex (RX) isn't legal for new work these days. What most people mean when they say Romex is NM or non metallic wiring meaning not armored.
So, if it is plastic coated it should be NM. If it is fabric/jute covered that might be RX.
Looking on the WWW there are still people selling wire called "romex", but they also call it "non-metallic" wire, which sounds a little odd to me (wire universally uses metal conductors). They probably call it romex in addition to non-metallic, because people want to buy romex, and the customer is always right. 
Quote
Strange that the wire melted without tripping a breaker.
Also, note that many compressors are actually 240v and a 20a #12 is common.
yup... The sub-panel right there has breakers (not fuses like my house) and they were all in the off position by the time I got to look inside the closet. My sense is that the breakers did not trip from the fault that melted the wire, but i was not there when it happened, and I get different stories from 3 different people who were there. I think there is another breaker(s) at the main panel feeding the sub panel... my NCVT detected power on two lines coming into the top of the sub panel.

The melted romex was not very heavy gauge wire (definitely not #12). Start up current for a big compressor may be well up there.

The electrician may need to test/replace the breaker(s) too.  In light of recent drama AFCI breakers might be useful, while it feels like closing the barn door after the horse is gone.
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I've already begged off the re-wiring gig, since I'm not going to crawl under his house (among other good reasons for me not doing it). I will try to look over the shoulder of the electrician they finally get to do the work, and ask appropriate questions, if i can without being too intrusive. 

JR
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Scott Holtzman

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Re: What's the worst thing that can happen?
« Reply #23 on: May 16, 2016, 02:32:13 pm »

I am a bit behind here but...

Actually, Romex (RX) isn't legal for new work these days. What most people mean when they say Romex is NM or non metallic wiring meaning not armored.
So, if it is plastic coated it should be NM. If it is fabric/jute covered that might be RX.

Strange that the wire melted without tripping a breaker.
Also, note that many compressors are actually 240v and a 20a #12 is common.



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Romex is not used in new residential construction in MA anymore?  Still is in Ohio

Personally I always use BX, it's not that much more.



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John Roberts {JR}

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Re: What's the worst thing that can happen?
« Reply #24 on: May 16, 2016, 02:50:37 pm »

Romex is not used in new residential construction in MA anymore?  Still is in Ohio

Personally I always use BX, it's not that much more.
I remember working with BX when I was a kid, and it is definitely more labor, but I guess a professional has tools nowadays to cut the armor instead of using a hacksaw like we did.

JR
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Jonathan Johnson

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Re: What's the worst thing that can happen?
« Reply #25 on: May 16, 2016, 03:06:01 pm »

Actually, Romex (RX) isn't legal for new work these days. What most people mean when they say Romex is NM or non metallic wiring meaning not armored.
So, if it is plastic coated it should be NM. If it is fabric/jute covered that might be RX.

Romex« is a registered trademark. It was originally owned by the Rome Wire Corporation, a predecessor to General Cable. The brand is currently owned by Southwire. http://www.southwire.com/romex.htm

What many think of as "Romex," properly called nonmetallic sheathed cable, was the stuff sheathed with asphalt-impregnated fabric. Originally, the conductors were rubber-covered with a fabric outer covering; the conductors were bundled in an outer fabric jacket.

As technology progressed, the individual conductors became covered with thermoplastic rather than rubber and fabric, but the outer jacket was still fabric. Sometime in the last 25 years the cable became color-coded, with white designating 14 AWG, yellow 12 AWG, and orange 10 AWG. Prior to that, most was either white or black. (Personal anecdote: a few years after the color coding, I purchased a dusty coil of 12 AWG wire with a white jacket, labeled and priced as 14 AWG. Someone wasn't paying attention.)

Side note: when an equipment grounding conductor was first included in nonmetallic cable, it was sized smaller than the current-carrying conductors. So while the current-carrying conductors may have been 12 AWG, the ground wire was 14 AWG. That is no longer permissible in the smaller gauges; code allows for the larger gauges -- I think 8 AWG and larger, but I could be wrong -- to use an EGC one size smaller.

With further advancements in materials technology, the outer jacket also became thermoplastic.

But it was all still Romex« when made by Rome, General, or Southwire*. And it was all type NM (though the modern thermoplastic version is, technically, NM-B).

Type NM-B -- thermoplastic insulation on the conductors, thermoplastic jacket, kraft paper filler -- is still allowed by the NEC for residential construction.

Many jurisdictions, however, have stricter requirements with a minimum of armored or metallic-clad (type AC and MC) cable or conduit. "BX" is not an official designation (at one time it was a brand), and generically refers to either AC or MC, or colloquially as really old armored cable that may have rubber/fabric covered conductors.

* Just like it's only Kleenex when made by Kimberly-Clark.

P.S. -- the stuff with a fabric jacket isn't legal for new installation partly because the insulation doesn't meet the temperature rating. I believe it is no greater than 60░C. Thermoplastic NM-B is typically rated for 90░C.
« Last Edit: May 16, 2016, 03:15:28 pm by Jonathan Johnson »
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Tim McCulloch

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Re: What's the worst thing that can happen?
« Reply #26 on: May 16, 2016, 03:31:12 pm »

I remember working with BX when I was a kid, and it is definitely more labor, but I guess a professional has tools nowadays to cut the armor instead of using a hacksaw like we did.

JR

Yup.  The selection of tools to cut, trim, and otherwise prep BX and MC are much better than days of yore.  I hope I never have to use them. ;)
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Stephen Swaffer

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Re: What's the worst thing that can happen?
« Reply #27 on: May 16, 2016, 10:59:48 pm »

The EGC size is determined by the breaker protecting the circuit it is part of-in larger sizes it can often be more than one size smaller-sizes commonly used by those on this forum would be the same up through #10, #10 is acceptable up to a 60 amp breaker.

NM has a temp rating of 90 deg C-but is still limited to the 60 deg ampacity column.

Technically, the code doesn't limit NM to resi only-it is restricted by the type of construction-but a wood frame commercial building in an area that is only limited by the NEC proper can use NM.  But then code is minimum-local jurisdictions and insurance companies might demand more.  My experience is that government entities spending your money are more than happy to include specs way above and beyond NEC minimums.

But none of that helps JR's neighbor!
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Erik Jerde

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Re: What's the worst thing that can happen?
« Reply #28 on: May 17, 2016, 12:27:35 am »

A lot of what people call BX these days is actually FMC (Flexible Metal Conduit).  MC and AC are for practical purposes nearly the same.  I just looked at my NEC 2014 and after reading the sections on MC and AC I can't really tell you what they practical differences are.  FMC is the stuff that you can pull new wires into.  I've got it all over my 80yo house and it's fantastic because I can replace all the rotten old wire with new THHN2.  Just make sure you're using stranded when pulling it into old FMC!
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John Roberts {JR}

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Re: What's the worst thing that can happen?
« Reply #29 on: May 17, 2016, 12:39:14 am »

The EGC size is determined by the breaker protecting the circuit it is part of-in larger sizes it can often be more than one size smaller-sizes commonly used by those on this forum would be the same up through #10, #10 is acceptable up to a 60 amp breaker.

NM has a temp rating of 90 deg C-but is still limited to the 60 deg ampacity column.

Technically, the code doesn't limit NM to resi only-it is restricted by the type of construction-but a wood frame commercial building in an area that is only limited by the NEC proper can use NM.  But then code is minimum-local jurisdictions and insurance companies might demand more.  My experience is that government entities spending your money are more than happy to include specs way above and beyond NEC minimums.

But none of that helps JR's neighbor!
I am pleased that we are all vertical to debate this dispassionately.

It could be much worse.

JR
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Re: What's the worst thing that can happen?
┬ź Reply #29 on: May 17, 2016, 12:39:14 am ┬╗


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