Thread: De-rate this?

Much has been written about de-rating wires. I wrote it up with a few other HO wiring ie: water heater with 14/2.

So I think sparky is coming to visit the site anyways. Is this a significant issue.

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Originally Posted by Stephen G

Much has been written about de-rating wires. I wrote it up with a few other HO wiring ie: water heater with 14/2.

So I think sparky is coming to visit the site anyways. Is this a significant issue.

Well to start with, I believe bored holes/slots in joists need to be two inches from the edge of the material (why you don't bore holes in 2 X 4 trusses)

Yeah Jerry, if you're on heart meds top them off!

De-rating is definitely an issue here. The number of cables and the way the cables lay puts most of them in the "without maintaining spacing" category. I'm counting between 18 and 22 cables in the slot, kinda hard to tell.

5, 6 or 7 holes would have been easier to drill and probably pull - some of the cables look tight enough to play a few cords on. Most folks I know limit pulls to 3 in a hole due to pulling issues

Originally Posted by Bill Kriegh

De-rating is definitely an issue here.

See? We agree more often than not.

I'm assuming that the cables are bundled for more than 24" that's why you wrote it up, you can't really tell from the photo.

I do my level best not make assumptions. A little binary in that regard
I couldnt see where the wires go after it enters the return, joist spacing being what it is, I couldnt see much after this pic.
It is one of many HO wiring, in Canada HO are allowed to wire their own homes, and it appears he did much of it over the years.
Ref the nice notch, yes its wrong, although, just to the right of is where the I beam is, it was commented upon.

Originally Posted by Robert Meier

I'm assuming that the cables are bundled for more than 24" that's why you wrote it up, you can't really tell from the photo.

In addition...



The electrical code (CEC) requires a minimum air space of 25 mm (1") between the cable and heating ducts or piping.


As an alternative, the electrical code permits a thermal barrier conforming to the Ontario Building Code to be installed between the cable and the heating duct so as to maintain an ambient temperature at the conductor of not more than 30° C. Fibreglass thermal insulation is one example of a thermal barrier that conforms to the Ontario Building Code.
Rule 12-506.
Ontario Electrical Safety Code 24th Edition/2009.

Hey Raymond

That heat duct had some sort of heat sheild jammed in there, the realtor removed it and it crumbled. I am starting think it was an old ceiling tile

Originally Posted by Stephen G

Hey Raymond

That heat duct had some sort of heat sheild jammed in there, the realtor removed it and it crumbled. I am starting think it was an old ceiling tile

Hmm.....heat shield, crumbling, sounds like asbestos.

Originally Posted by Robert Meier

I'm assuming that the cables are bundled for more than 24" that's why you wrote it up, you can't really tell from the photo.

"bundled" is not the requirement.

"lack of maintaining spacing" is the requirement.

Originally Posted by Jerry Peck

"bundled" is not the requirement.

"lack of maintaining spacing" is the requirement.

If you're referring to 334.80 the words without maintaining spacing, that applies to holes that are fire or draft stopped or in contact with thermal insulation. I don't see either in the photo.

Absent of those conditions then bundling would be the only issue.

Originally Posted by Jerry Peck

"bundled" is not the requirement.

"lack of maintaining spacing" is the requirement.

Originally Posted by Robert Meier

If you're referring to 334.80 the words without maintaining spacing, that applies to holes that are fire or draft stopped or in contact with thermal insulation. I don't see either in the photo.

Absent of those conditions then bundling would be the only issue.

Nope, I'm referring to the fact that bundling is being replaced with "lack of maintaining spacing" in the code. Bundled has not been replaced entirely throughout the code yet, but the change toward "lack of maintaining spacing" began several cycles back.

Stephen

From a Ontario electrical contractor.

For 2012, the table for ampacities are now, (@75*C) #14 = 20, #12 = 25 and #8 = 50. The 90*C table is even a bit more, #14 = 25, #12 = 30 and #8 = 55. So these new numbers work better in the conduit fill / bundling scenarios, however rule 14-104(2) still applies for breakers, max breaker size #14 = 15, #12 = 20 and #10 = 30.

Where the issue also comes into play is the temp rating, most equipment is rated at 75*C so that will be the table used now for ampacities unless the device (breaker, switch, etc) is stamped at a higher level. So what that means is that regardless of the rating of the wire, since it is being terminated on a 75*C device, the 75*C rating of the wire will be used for calculating ampacity derating.

Thanks Ray,

Is the 75c a change. I remember 90c or am thinking something else

Does the CEC have an allowance that would accept NM being used above a 60 degree rating? Under the NEC NM-B can use the 90 degree rating to use as the starting point for derating, but cannot be used above its 60 degree rating.

Originally Posted by Jim Port

but cannot be used above its 60 degree rating.

... for overcurrent protection sizing.