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Should old braided NM be replaced? Can I use gap next to the chimney as chase?

Should old braided NM be replaced? Can I use gap next to the chimney as chase?

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  #1  
Old 12-10-14, 03:25 AM
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Should old braided NM be replaced? Can I use gap next to the chimney as chase?

I need to dive in and help an old friend out. He's freezing his arse off in this 1920s block home and spending a fortune on oil. After deciding to properly insulate the attic floor he rips up the old sub floor and finds a boat load of knob-n-tube. Obviously he can't leave that there and now he's up a creek with it all ripped open and winter setting in.

I haven't fully traced it all out yet. But it's actually wired pretty well. Lots of outlets in relatively new boxes (no ground screw though) and all of that appears to be fed with early braided cable in OK condition and that tied back to the knob-n-tube.

Given that everything is going to be totally exposed and given that all the braided cable seems to be very loose in the block wall. My suggestion is that we replace all of it with 14/2 UF and run that 14/2UF down along the chimney to the basement - as opposed to a small sub panel in the attic. There's plenty of space on the panel yet.

The question is, is that overkill? Should I just run a couple new feeds and properly junction into the old braided cable?

Once this is done it's all going to be buried under 2' of blown insulation. My house, no question, replace it all. But they aren't in this for the long term. If I just do a couple circuit feeds we can probably be in and out for $100 in materials. My time will be probably be bartered.

Thoughts?
 
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  #2  
Old 12-10-14, 04:54 AM
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Has that panel and incoming power line been up upgraded to breakers with a ground to earth?
You can not splice into or add onto an ungrounded circuit.
Why UF? That's for direct burial outside, and is far harder to work with.
What's in that attic? Just lights and outlets?
Why 2' of insulation? All you need is R-50 which is 12".
 
  #3  
Old 12-10-14, 04:55 AM
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Doesn't really seem necessary,if the K&Tis in good condition,and no overload problems and if they are not there for the long term.
At any rate use NM-B and not UF.
Just a thought
Geo
 
  #4  
Old 12-10-14, 05:00 AM
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But.....don't cover the K&T with insulation!
 
  #5  
Old 12-10-14, 05:36 AM
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The K & T isn't in great shape and will be completely covered after the insulation is blown in.......................

Yes UF sucks to work with, but from the attic down to all the outlets is old braided Romex through the masonry wall. It's been ten years since I took my electrical classes at the local trade school, but I'm pretty sure in that scenario you need UF or metal clad & metal clad isn't happening. There is also a possibility of retro fitting a phenolic foam into that block wall. At which point you will never get new wire in there again. UF should be a 100 year solution.

The panel is a fairly new SquareD and much of the basement/1st floor wiring looked to be modern NM-B.

2' was an exaggeration. But what is planned is still overkill. The block walls are all hollow, air leakage everywhere and so on. 1' is probably plenty. But that's a discussion for another thread.

By this afternoon he hopes to have the rest of the attic floor out and everything cleaned out for easy access. I hope to spend a couple hours tracing everything out and coming up with a final plan. Maybe even start pulling some wire if I'm lucky.

Edit - you guys got me searching. It looks pretty clear that you can use regular NM inside the hollow block portion as long as it's dry. That will be much easier than UF, assuming we go that far.
 

Last edited by speedy72; 12-10-14 at 06:09 AM.
  #6  
Old 12-10-14, 06:28 AM
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K&T cannot be covered with any type of insulation. That is a huge fire and electrocution hazard -- imagine crawling around in the cellulose and getting your hand under an uninsulated wire! Additionally K&T is usually very overloaded #14 wire, the insulation traps heat in and causes the overload problem to get worse. Every bit of the K&T has to be gone from the attic before you blow in cellulose.

I would use NM instead of UF, but there's no prohibition on UF if you choose to do it.
 
  #7  
Old 12-10-14, 06:45 AM
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Even though they are not in it for the long run it should be a feature during the sale. I would vote for replacement.
 
  #8  
Old 12-10-14, 07:09 AM
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The K&T will go, any inference from my posts that it might stay was pure sarcasm. The question is whether to leave the braided or not and if not, what to replace it with. After thinking about it a bit more, I'd go with metal clad. But I'm going to suggest we pull standard yellow NM. That presents a box fill challenge with the existing boxes. But I'd rather have a box fill issue and have the 12/2 in the walls.

I've got a call in to my very knowledgeable foam guy to see what we'd be looking at to fill those blocks and what that might do to wiring requirements, de-rating and so on.
 
  #9  
Old 12-10-14, 07:17 AM
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Ok good -- you never know sometimes. I would probably replace the old braided romex as well. Code says you should, the local inspector probably would say you should (this is bigger than a "repair" which allows you grandfather existing stuff). If you can pass this work off as a repair, you could probably keep the braided if you really have to. Generally that stuff is okay if you just leave it alone, but once you start messing with it the insulation cracks and the copper fatigues.

The only reason to go with metal clad would be if you have a known rodent problem and they would chew up the NM.

Derating on new NM won't be an issue as long as you keep some separation between the cables. If you have a bundle of them under insulation, that's a derating issue.
 
  #10  
Old 12-10-14, 07:36 AM
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Agreed that de-rating is of minimal concern. But the labor is basically the same. I'm guessing I can pretty much do the whole project with a 250' roll. So we are talking about $50 more in cost? I'd rather have the extra headroom.

There's four bedrooms and a bath on the second floor. If there's room in the panel I'll make the outlets in each bedroom one circuit, bath on it's own circuit of course, lights on one circuit and drop an extra 20amp outlet in the attic for good measure. I have a hunch I'm going to find the bath is all new already and home run to the panel.

Edit - has anyone EVER been called out on box fill? I know I calculated every box when I pulled out all the K & T in my own home. My daily job is low voltage but in all the years I've been on jobs and encountered ECs and inspectors I have never once heard of anyone getting called out for box fill. I seem to remember those standard angled back metal boxes don't have enough box fill for more than one 14/2 (no daisy chains) and one device. I just don't want to daisy chain 12/2 though those boxes and then have him get called out by the home inspector at time of sale. Then you are trying to put in larger boxes in a plaster and block wall. That would suck.
 

Last edited by speedy72; 12-10-14 at 07:51 AM.
  #11  
Old 12-10-14, 08:20 AM
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You could wire the old way from a central junction box and run one cable down the the boxes to avoid box fill issues.
 
  #12  
Old 12-10-14, 08:32 AM
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Trying to avoid that. But again, I think from a box fill perspective those boxes are barely legal for a single 14/2 and a device. Another area of code that seems slightly insane to me. I'm not a code hater at all, I'm sure there's a reason they went as conservative as they did, but it's not making life easy!
 
  #13  
Old 12-10-14, 08:44 AM
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Why would you want to go with 12/2 in bedrooms and at light fixtures?also don't forget about the AFCI and GFCI requirements.
Geo
 
  #14  
Old 12-10-14, 08:53 AM
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For lighting I run 14/2, but I like to run 12/2 for outlets. Yes I had forgotten about arc faults. More circuits means more expensive arc fault breakers.

This is why you hire a pro and just pay the man.

Edit - from what I saw it's basically one 15A circuit for lighting and outlets for the entire 2nd floor, about 1000sq ft. No way am I leaving it like that. Even if they haven't been having overload problems right now.
 
  #15  
Old 12-10-14, 10:47 AM
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Pretty typical for a K&T replacement job. I'd probably do one 15A circuit for all the lighting and the smoke detectors, one 20A circuit for all the bedroom/hallway receptacles, and one 20A circuit for the bathroom unless the homeowner really wanted more. That's two AFCI breakers at about $40 each.

You can figure a minimum need of about 3W general purpose load per square foot, or 3000W for the upstairs area. A 15A + a 20A circuit will give you 4200W supply, a bit over minimum requirements.

If you know they'll be using window A/C units or space heaters, provide a 20A circuit for the receptacles in each room.
 
  #16  
Old 12-10-14, 03:15 PM
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I just spent a few hours tracing things. It's a mess and is going to beat the hell out of me for several days. The only thing done with any sort of craftsmen approach is the panel itself. Everything else is bleah, even the new stuff is all over the place and spliced everywhere. I found four places in the basement with hot feeds going to K & T risers, three of which had a matching neutral right there as well. I disconnected all the hots and still had power to a third of the second floor and still appeared to have live K & T in the attic. But I lost lights in two rooms on the first floor. So I may not be able to completely eliminate the K & T. The braided cloth is in pretty rough shape in most places. It's going for sure now.

Insulation plan may change. He has someone willing to hit the whole floor with 7" of open cell for a reasonable price. So for sure the electric has to change.

We settled on just pulling 14/2 for simplicity with the boxes. The house has central AC and there are AC outlets below the windows run via wiremold, all straight to the basement. I will pull home runs for the rooms though, so if they start having overload problems we could break it out.

Moral support needed
 
  #17  
Old 12-10-14, 04:35 PM
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Just curious are there any energy rebates in your area for insulation? Might be worth him checking with the local POCO.
Just a thought.
Geo
 
  #18  
Old 12-10-14, 06:45 PM
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there are AC outlets below the windows run via wiremold
If those are 120 volt outlets, the bedroom ones will also need AFCI protection. You never mentioned what version of the NEC your community is on. If it is any version up to 2008 only the bedrooms outlets need to be on AFCI breakers. If you are on the 2011 NEC, you'll need a lot more AFCI breakers.
 
  #19  
Old 12-11-14, 07:28 AM
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I believe it's 2008 but honestly I'm not thinking about the breakers right now. I'm just going to get the feeds into the basement, leave them long and sort that out after. I just need to get out of the attic as soon as I can so he can insulate up there. It may not be quite that simple though because if he goes foam he'll also spray a thin layer on the basement ceiling to air seal all that up good. So I may end up with a day or two cleaning up the basement as well.
 
  #20  
Old 12-14-14, 03:28 PM
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We got a good day in on it today. Looks like all the lighting is K & T and all the outlets were retrofitted later with braided. Found a nice chase in the block from the basement to the attic for all our feeds. I'm not sure we'll get as many feeds up through that chase as I'd like, to keep everything logically separated, but we'll certainly have it better than it was before.

The hardest part so far was probably the exterior outlets as they were concrete patched in place. Nothing a hammer and cold chisel couldn't fix quick enough.

Please refresh my memory on the bathroom circuit. Do bathrooms need to be a dedicated 20amp circuit? I know GFI but I can't remember if they have to be a dedicated 20a. At this point I'd rather just pulled a dedicated 15a and be done with it.

Haven't touched the K&T and lighting yet and not looking forward to it either. There's an awful lot of it running around for just powering a few lights.
 
  #21  
Old 12-14-14, 03:59 PM
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You can feed all youor bathroom GFCI receptacles with one 20 amp circuit, no lights or fans on this thouigh. If you want to add lights and fans to this circuit, you'll need one 20 amp circuit per bathroom.
 
  #22  
Old 12-14-14, 04:19 PM
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Thanks Joe,

There is only one bathroom on the 2nd floor. I had hoped to keep it simple and stay with 14/2 pulls. But if it' needs to be 12/2 then that's what it needs to be. It will probably just be the two outlets on that run though, maybe add the fan exhaust fan to it to keep it off the light circuit. The other concern is how much room we have in that chase, but only one way to find that out!

But that code specification does explain why my in-laws big $$ house has all the bathroom GFCI outlets strung together. Four bathrooms on two floors in a 5500 sq ft house. Every holiday season we pop that circuit.

My buddy was really going back and forth on whether it was even worth replacing the braided. The inside jacket was in good shape and it's in a masonry wall for the most part. But I'm glad we are doing it. As soon as you touch the braided jacket it's just falling off the wire. It's got no life left at all.
 
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