# Thread: Do you call 90 degree bends in panel?

1. ## Do you call 90 degree bends in panel?

Just curious. I'd prefer less angle and stress on branch wiring.

2. ## Re: Do you call 90 degree bends in panel?

If that was all I had to grip about in a panel that neat, I would jump up and down like a kid in a candy store.

3. ## Re: Do you call 90 degree bends in panel?

I'd be much more concerned about all those conductors going into those conduits.

Left bundle is *at least* 4 conductors - meaning derating to 80%.

Second bundle from left is *at least* 4 conductors (probably 6 conductors) - meaning derating to 80% (whether 4 or 6).

Third bundle from left is *at least* 4 conductors (probably 6 conductors) - meaning derating to 80% (whether 4 or 6).

Second bundle from the right is *at least* 4 conductors - meaning derating to 80%.

Right bundle is *at least* 4 conductors - meaning derating to 80%.

Looks like all circuits should be derated to 80%.

4. ## Re: Do you call 90 degree bends in panel?

I ran into bundled cables once. In fact, it was every 110 volt cable leaving the panel all clamped together. Except, once they left the panel they spread back out. I talked to a couple electricians and the city inspector about it and they said it was okay because it was less than a certain length (18" ?, I think).

From the picture you don't know what happens in the wall above the panel. I'm sure JP will correct me or clarify the rule. Is there a certain length that the conductors must be bundled for the de-rating to be necessary?

5. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Matt Fellman
From the picture you don't know what happens in the wall above the panel.
Actually, we do know what those conductors do ... they are in conduit.

I'm sure JP will correct me or clarify the rule. Is there a certain length that the conductors must be bundled for the de-rating to be necessary?
Longer than 24".

6. ## Re: Do you call 90 degree bends in panel?

JP,

Do you have the code on that? I'll rec. review by lic. and qual electrician.

7. ## Re: Do you call 90 degree bends in panel?

It's 310.15(B)(2)(a) exception 3

8. ## Re: Do you call 90 degree bends in panel?

"Prefer?" That panel is installed in a perfect textbook illustration of exactly what the appropriate NECA standard defines as "good workmanship."

9. ## Re: Do you call 90 degree bends in panel?

Overall, looks like a pretty neat installation, I would check wire size and amps for derating, also is this a main or sub? does the neutral need to be bonded? I dont see the bonding screw installed to the right of the main breaker.

10. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Inspector 3500
It's 310.15(B)(2)(a) exception 3
The above is what allows for the 24", not what does not allow for longer than 24"

Here is the code for it. (underlining is mine)

310.15 Ampacities for Conductors Rated 0–2000 Volts.
- (B) Tables. Ampacities for conductors rated 0 to 2000 volts shall be as specified in the Allowable Ampacity Table 310.16 through Table 310.19, and Ampacity Table 310.20 and Table 310.21 as modified by (B)(1) through (B)(6).
- - - (a) More Than Three Current-Carrying Conductors in a Raceway or Cable. Where the number of current-carrying conductors in a raceway or cable exceeds three, or where single conductors or multiconductor cables are installed without maintaining spacing for a continuous length longer than 600 mm (24 in.) and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(2)(a). Each current-carrying conductor of a paralleled set of conductors shall be counted as a current-carrying conductor.
- - - - FPN No. 1: See Annex B, Table B.310.11, for adjustment factors for more than three current-carrying conductors in a raceway or cable with load diversity.
- - - - FPN No. 2: See 366.23(A) for adjustment factors for conductors in sheet metal auxiliary gutters and 376.22(B) for adjustment factors for conductors in metal wireways.
- - - - Exception No. 1: Where conductors of different systems, as provided in 300.3, are installed in a common raceway or cable, the derating factors shown in Table 310.15(B)(2)(a) shall apply only to the number of power and lighting conductors (Articles 210, 215, 220, and 230).
- - - - Exception No. 2: For conductors installed in cable trays, the provisions of 392.11 shall apply.
- - - - Exception No. 3: Derating factors shall not apply to conductors in nipples having a length not exceeding 600 mm (24 in.).
- - - - Exception No. 4: Derating factors shall not apply to underground conductors entering or leaving an outdoor trench if those conductors have physical protection in the form of rigid metal conduit, intermediate metal conduit, or rigid nonmetallic conduit having a length not exceeding 3.05 m (10 ft) and if the number of conductors does not exceed four.
- - - - Exception No. 5: Adjustment factors shall not apply to Type AC cable or to Type MC cable without an overall outer jacket under the following conditions:
- - - - - (1) Each cable has not more than three current-carrying conductors.
- - - - - (2) The conductors are 12 AWG copper.
- - - - - (3) Not more than 20 current-carrying conductors are bundled, stacked, or supported on “bridle rings.”
- - - - - - A 60 percent adjustment factor shall be applied where the current-carrying conductors in these cables that are stacked or bundled longer than 600 mm (24 in.) without maintaining spacing exceeds 20.

Table 310.15(B)(2)(a) Adjustment Factors for More Than Three Current-Carrying Conductors in a Raceway or Cable states:

4-6 conductors / derate to 80%
7-9 conductors / derate to 70%
10-20 conductors / derate to 50%
21-30 conductors / derate to 45%
31-40 conductors / derate to 40%
41+ conductors / derate to 35%

11. ## Re: Do you call 90 degree bends in panel?

Originally Posted by John Steinke
"Prefer?" That panel is installed in a perfect textbook illustration of exactly what the appropriate NECA standard defines as "good workmanship."

John,

"panel is installed in a perfect textbook illustration of exactly what the appropriate"

Did you not see the bundling?

Or are you just ignoring it?

12. ## Re: Do you call 90 degree bends in panel?

Table 310.15(B)(2)(a) Adjustment Factors for More Than Three Current-Carrying Conductors in a Raceway or Cable states:

4-6 conductors / derate to 80%
7-9 conductors / derate to 70%
10-20 conductors / derate to 50%
21-30 conductors / derate to 45%
31-40 conductors / derate to 40%
41+ conductors / derate to 35%[/QUOTE]

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Jerry, the derating of the conductors refers to actual load applied to the circuits. Which is what the installing electrician needs to take into account when planning his circuit layout.

My point being that as a HI, you are not doing clamp-on amp meter load testing, how would you know if proper derating was applied ? (even if you could determine actual full load conditions). In other words, a 14 ga copper wire can run 15 amps max however, it can only be loaded to 80% (up here in Canada anyway) if the load is continuous (powered at rated load for 2 or more consecutive hours at a time). So if I am understanding your comment, in this condition a continuous load on a 14 ga conductor is good for 12 amps them derated further to 80% due to pipe fill would equal 9.6 amps max permitted load on a 15 amp breaker ?? How would you ever determine if it is loaded correctly or not & why would you even write that up on a home inspection ?

I think writing that up would create mass confusion and an unnecessary over-reaction to an unproven hypothetical situation. no ?

13. ## Re: Do you call 90 degree bends in panel?

I vaguely remember something about ( 2.5 X Wire diameter ) as mimimum radius on bends.
May be imagination, but, I think those bends were made over the jaws of a pair of strippers or kleins.
If the 90's get called, then, twice for the 180's?

14. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Joe Klampfer
Jerry, the derating of the conductors refers to actual load applied to the circuits.

No, the derating is applied to the rating of the conductor, regardless of what load is placed on the circuit.

First, you start out with the higher rating for the conductor based on the insulation (look the rating for that insulation up in the table), then derate for ambient temperature (anything going into an attic, crawlspace, exterior wall, etc, gets counted regardless 'how much of it is there' - but that mainly applies to attics, then, after derating for ambient temperature, you apply the derating for the bundling.

Basically, the conductor insulation used today (such as used in NM-B) allows for ambient derating to get back down to what was the rating for NM before people started realizing 'Hey, I'm supposed to be derating for ambient temperature'. which, of course, derated the conductors down below their circuit protection rating.

That is the reason NM-B came out - to solve that problem with ambient temperature derating.

Then, as now, there is still the derating for the bundling (based on rating, not on load, not on load other than it now limits the load, the percentage is based on conductor ampacity rating, not load rating - maybe I should state it that way, which is more clearly stated), and that bundling derating is what I posted.

Also, of great note: "bundling" is not only applicable to "bundling" but to "lack of maintaining spacing" for multiconductor cables (i.e., 12-2 NM is a multi-conductor cable), lack of maintaining spacing between two or more multi-conductor cables requires derating based on the table by number of conductors in the "lack of maintaining spacing" "bundle" or "non-bundle".

15. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Steve Lowery
I vaguely remember something about ( 2.5 X Wire diameter ) as mimimum radius on bends.
4 times the diameter is the minimum radius of the bend.

If the conductor (and insulation) is approximately (#12 THHN, THWN, THWN-2) 0.111 inches, then 4 X 0.111 = 0.444, or approximately a radius of 7/16 inches.

Yes, those are bent too sharply, however, as I stated: "I'd be much more concerned about all those conductors going into those conduits."

May be imagination, but, I think those bends were made over the jaws of a pair of strippers or kleins.
Probably over the side of long nose pliers (done that myself). Should have been bent over my thumb, that would provide a bend more closely resembling the proper minimum diameter bend.

16. ## Re: Do you call 90 degree bends in panel?

[QUOTE=Jerry Peck;37739]No, the derating is applied to the rating of the conductor, regardless of what load is placed on the circuit.

I think we are talking about the same thing. My reference to load amps was intended to illustrate the max load the conductor would be able to carry once you are done with all the applicable derating, assuming that the 14 ga conductor is initially rated for 15 amps.

The point I was trying to make is, as a HI why would you even enter into that discussion with a home buyer (who would normally be confused trying to understand the operation of a 3-way switch). Derating of conductors is and can be a very confusing topic as detailed conductor ratings and load calculations are needed to verify a problem does not exist.

17. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Joe Klampfer
The point I was trying to make is, as a HI why would you even enter into that discussion with a home buyer

Yes, I did all the time.

My buyers easily understood 'greater than 24" ' and 'spacing not maintained' and 'causes heat build-up' and 'causes less voltage at the receptacles'.

I never had a problem explaining it where my clients understood why 'it was not a good thing'.

Last edited by Jerry Peck; 03-28-2008 at 05:33 PM.

18. ## Re: Do you call 90 degree bends in panel?

Since you use the 90 degree amp rating for de-rating purposes which is 30 amps for #12 romex, you can derate to 70% and still use a 20 amp breaker. This would allow up to 9 wires in the bundle it seems.

19. ## Re: Do you call 90 degree bends in panel?

I agree it is a really neat panel. The 90's are a bit tight for my taste though. I can say that some of the municipal inspectors around here won't comply a new panel if it doesn't look pretty much like that.
As far as derating for bundling, I think you guys are nit picking in this case. I have four eyes and I can't tell whether the wires are going into 1/2" or 3/4" pipe.
I am very detailed in my inspections but let's get a grip here.

20. ## Re: Do you call 90 degree bends in panel?

Originally Posted by James Duffin
Since you use the 90 degree amp rating for de-rating purposes which is 30 amps for #12 romex, you can derate to 70% and still use a 20 amp breaker. This would allow up to 9 wires in the bundle it seems.

First, a lot of wiring used is THHW, THWN, THW which is 75 degree C rated insulation.

Yes, THHN, THHW, THWN-2 are 90 degree C rated insulation.

The first step in derating is to derate for ambient temperature.

THHW, THWN, THW which is 75 degree C rated insulation derates to 67% for only 123-131 degrees F ambient, many attics are 132-140 degrees F in the summer, which derates to 58%. In hotter climates (South Florida, Texas, and other states) attic temperatures can get to 141-158 degrees F, which derates to 33%.

So, first, lets say Chicago as that is where the original poster is located, and (for lack of not knowing) lets presume the attic temperatures only get to 131 degrees F in the summer for a derating to 67% (any hotter and you jump down to 58% or even less).

Now, #12 AWG, THHW, THWN, THW which is 75 degree C rated insulation, is rated for 25 amps. This 25 amps derates to 67%, which is only 16.75 amps ... WITH NOT DERATING YET for lack of maintaining spacing.

Okay, we now have conductors rated for (derated to) 16.75 amps, these are then bundled in a raceway as shown in the photo, 4-6 conductors, derated to 80%. 16.75 x 80% = 13.5 amps.

Not even sufficient for a 15 amp breaker, however, because this is over 10 amps, this is allowed to be protected by the next size up breaker - 15 amps. You are allowed to continuously draw 80% through the conductor, and THAT IS ALL these conductors are now rated for (don't forget, we are talking about #12 AWG, *NOT* #14 AWG conductors).

Repeat using THHN, THHW, THWN-2 are 90 degree C rated insulation.

Ambient derating goes from 30 amps X 67% = 20.1 amps X 80% = 16.08 amps, only suitable for a 15 amp breaker.

And that is ONLY FOR attic temperatures which are not over 131 degrees F.

Let's take the higher rated conductors (to satisfy Jim, and maybe John when he chimes in) of THHN, THHW, THWN-2 which are 90 degree C rated insulation and derate for attics which are one step hotter (132-140), still only 4-6 conductors in a raceway:

30 amps X 58% = 17.4 amps derated rating for ambient X 80% for 4-6 conductors in a raceway = 13.92 amps.

Don't try to say there is no need to derate, that everything will be hunky-dory, use a #12 AWG THHN in a raceway with 4-6 conductors and which runs up into an attic of 135 degrees F and you now only have a conductor rated for 13.92 amps!

Jim, you need to learn how to read the tables and derate, and do the math, before saying 'that's okay'.

21. ## Re: Do you call 90 degree bends in panel?

You didn't mention 334.80 in that tirade....2005 code

Last edited by James Duffin; 03-28-2008 at 06:17 PM. Reason: Added code year

22. ## Re: Do you call 90 degree bends in panel?

Originally Posted by James Duffin
You didn't mention 334.80 in that tirade....2005 code

First, it was not a tirade, second, no need to - I was referencing conductors in a raceway, not NM cable, but that only backs up what I stated.

334.80 Ampacity. 3rd sentence:
The 90 degree C (194 degree F) rating shall be permitted to be used for ampacity derating purposes, provided that the final derated ampacity DOES NOT EXCEED that for a 60 degree C (140 degree F) rated conductor.

The derating DOES NOT EXCEED that rating, it IS LESS THAN that rating.

Did you read the last paragraph, newly changed in 2005? Does not even need to be 24" before requiring derating.

23. ## Re: Do you call 90 degree bends in panel?

Table 310.16 shows 60 degree #12 rated at 25 amps. 80&#37; of 30 amps is 24 amps. 70% of 30 amps is 21 amps. Both are under the 25 amps shown in the 60 degree column of Table 310.16. Both of these deratred values can be put on a 20 amp breaker. This means that you can put nine #12 romex cables in a properly sized conduit any length you want and fuse them at 20 amps each. IMHO.

Correction to my post above:
If there are nine #12-120 volt romex circuits in a properly sized conduit the breaker size would have to be a max of 15 amp.....not 20 amp as I stated above. This is because I applied the wrong derating factor. Sorry for the error!

Last edited by James Duffin; 03-30-2008 at 02:24 PM. Reason: Correction on breaker size due to incorrect derating factor applied

24. ## Re: Do you call 90 degree bends in panel?

Originally Posted by James Duffin
Table 310.16 shows 60 degree #12 rated at 25 amps. 80% of 30 amps is 24 amps. 70% of 30 amps is 21 amps. Both are under the 25 amps shown in the 60 degree column of Table 310.16. Both of these deratred values can be put on a 20 amp breaker. This means that you can put nine #12 romex cables in a propely sized conduit any lenght you want and fuse them at 20 amps each. IMHO.
Dead wrong, or, should I say 'fire-in-the-hole-house-burning-down' wrong.

25. ## Re: Do you call 90 degree bends in panel?

[QUOTE=Jerry Peck;37774]Yes, I did all the time.

.... and 'causes less voltage at the receptacles'. ???

huh ?? are we now talking about voltage drop or ampacity ratings or derating of multiple wires ?

Two totally different discussions.

26. ## Re: Do you call 90 degree bends in panel?

I woiuld advise folks to read 334.80, Table 310.16, 310.15, and 312.d(c) and make their own decision. These code sections are from the 2005 code.

27. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Joe Klampfer
huh ?? are we now talking about voltage drop or ampacity ratings or derating of multiple wires ?

Two totally different discussions.
Joe,

Q: What is one cause of conductors heating up more than they should?
A: Ambient temperature higher than rated, requires derating, results in conductors heating up when not derated and used for the higher ampacity.

Q: What is another cause of conductors heating up more than they should?
A: Bundling more than 3 conductors together, requires derating, results in conductors heating up when not derated and used for the higher ampacity.

Q: What happens when conductors heat up?
A: Their resistance goes up.

Q: What happens when resistance goes up?
A: Voltage drop goes up.

"Two totally different discussions"

Really?

They are 'two different discussions', yes, but not two "totally different" discussions. They do have a common link.

28. ## Re: Do you call 90 degree bends in panel?

Originally Posted by James Duffin
I woiuld advise folks to read 334.80, Table 310.16, 310.15, and 312.d(c) and make their own decision. These code sections are from the 2005 code.
Let's do that.

Here they are, read the 2002, 2005 and 2008 and see the strengthening of the applicable derating which has gone on in just these last 3 code editions:

From the 2002 NEC.
334.80 Ampacity.
- The ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15. The ampacity shall be in accordance with the 60°C (140°F) conductor temperature rating. The 90°C (194°F) rating shall be permitted to be used for ampacity derating purposes, provided the final derated ampacity does not exceed that for a 60°C (140°F) rated conductor. The ampacity of Types NM, NMC, and NMS cable installed in cable tray shall be determined in accordance with 392.11.

From the 2005 NEC. (underlining of the new part from the 2002 is mine)
334.80 Ampacity.
- The ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15. The ampacity shall be in accordance with the 60°C (140°F) conductor temperature rating. The 90°C (194°F) rating shall be permitted to be used for ampacity derating purposes, provided the final derated ampacity does not exceed that for a 60°C (140°F) rated conductor. The ampacity of Types NM, NMC, and NMS cable installed in cable tray shall be determined in accordance with 392.11.
- Where more than two NM cables containing two or more current-carrying conductors are bundled together and pass through wood framing that is to be fire- or draft-stopped using thermal or sealing foam, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a).

From the 2008 NEC. (much was re-worded in 2008)
34.80 Ampacity.
- The ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15. The ampacity shall be in accordance with the 60°C (140°F) conductor temperature rating. The 90°C (194°F) rating shall be permitted to be used for ampacity derating purposes, provided the final derated ampacity does not exceed that for a 60°C (140°F) rated conductor. The ampacity of Types NM, NMC, and NMS cable installed in cable tray shall be determined in accordance with 392.11.
- Where more than two NM cables containing two or more current-carrying conductors are installed, without maintaining spacing between the cables, through the same opening in wood framing that is to be fire- or draft-stopped using thermal insulation, caulk, or sealing foam, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a) and the provisions of 310.15(A)(2), Exception, shall not apply.
- Where more than two NM cables containing two or more current-carrying conductors are installed in contact with thermal insulation without maintaining spacing between cables, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a).

For Table 310.16, make sure to read and understand this part:
"CORRECTION FACTORS"
"For ambient temperatures other than 30 degrees C (86 degrees F), multiply the allowable ampacities shown above by the appropriate factor shown below."
That part gets applied before any other correction factors (derating).

For 310.15, "310.15 Ampacities for Conductors Rated 0-2000 volts", make sure to read and understand "(B) Tables" "(2) Adjustment Factors".

312.d(c)??? Huh????

29. ## Re: Do you call 90 degree bends in panel?

Talk about making a mountain out of a mole hill. Which one of you can puff your chest out more. You aren't even talking about single conductors anymore, you've moved onto romex. Which by the way isn't allowed in Chicago.
It's a 100 amp res panel. Could there be a problem at some point in the future? Sure, anything is possible. I don't agree that taping the wires at the top of the panel constitutes bundling. Many electricians tape inside the panel for neatness. I don't know a single electrician that tapes the entire run ... therefore the 4-6 wires are freely spaced within the pipe.
I've become very adept at explaining things to clients in simple terms but this would make their eyes glaze over.
I would consider bringing this up on a comm insp but on a res insp if/when everything else looks good, it's nonsense.
Bash me if you want but I think you guys have gone overboard on this one.
Have fun, Markus

30. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Jerry Peck
Joe,
Q: What happens when resistance goes up?
A: Voltage drop goes up.

"Two totally different discussions"

Really?

They are 'two different discussions', yes, but not two "totally different" discussions. They do have a common link.
``````````````````````````````````````````````

oh pleaaaase ! yeah ok Jerry... you can report it that way and unecessairly scare the crap out of every one from the buyer to the owner and if an electrician were to be called out to service the problem, I'm sure he'd fall over in laughter and someone would be out the cost of a service call.

The voltage drop you refer to in your example would be so very small that it would have no effect whatsoever on electrical appliances connected, in fact, it is not uncommon to see voltage fluctuations during peak-usage times anyway - all well within tolerance.

The installation pictured above is found everywhere and is quite acceptable to the AHJ's. The situations you are describing are so far over the top of any SOP, I still don't understand why anyone would even get into that discussion during a home inspection - unless the wires were running hot (to the touch).

btw... can someone tell me how you get the little boxes to appear when you respond with previous quotes... doesn't seem to work for me.

31. ## Re: Do you call 90 degree bends in panel?

well lookie there... now the quote box appeared ! still don't get it. ha

32. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Markus Keller
You aren't even talking about single conductors anymore, you've moved onto romex.
That's why I started out talking about raceways.

I don't agree that taping the wires at the top of the panel constitutes bundling. Many electricians tape inside the panel for neatness. I don't know a single electrician that tapes the entire run ... therefore the 4-6 wires are freely spaced within the pipe.
Markus,

"freely spaced within the pipe"

That is what derating is all about, it has nothing to do (with reference to raceways) with the tape.

The simple fact that there are 'more than 3 current carrying conductors in the raceway' is what causes heat to build up.

The tape for neatness did not even come into play with the need to derate.

It's all in those code sections. You will find that it states:
- - - (a) More Than Three Current-Carrying Conductors in a Raceway ... "

Nothing in there about 'taped together'.

33. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Joe Klampfer
I still don't understand ...
I know, that is why I was trying to explain it.

Alas, though, apparently to no avail.

Best thing I can tell you, then, is "read the code" and "pay no attention to that man behind the curtain" ... *READ* the code and think about what it is stating.

34. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Jerry Peck
...pay no attention to that man behind the curtain
haha.... very clever use of cut-n-past to pull the thread out of context

35. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Joe Klampfer
``

btw... can someone tell me how you get the little boxes to appear when you respond with previous quotes... doesn't seem to work for me.

Joe,

There are two areas that must remain intact to get the Quote Box to appear.

At the end of the quote all the symbols on either side of the word quote must remain (or be added back if deleted.)

At the start of the quote a symbol,an equal sign,Name, another symbol,a number, another symbol appears.

If you delete any of those things at the beginning or end of the quote no quote box appearers in your post.

You may also see what your post will look like by pressing the Preview Post button next to the Submit Reply button.

Last edited by Billy Stephens; 03-30-2008 at 06:59 AM.

36. ## Re: Do you call 90 degree bends in panel?

That's great Billy, thanks for the help.

37. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Jerry Peck
... pay no attention to that man behind the curtain
Originally Posted by Joe Klampfer
haha.... very clever use of cut-n-past to pull the thread out of context
My statement was referring to me ... pay no attention to me ... read the code ... it is all in there.

38. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Jerry Peck
4 times the diameter is the minimum radius of the bend.

If the conductor (and insulation) is approximately (#12 THHN, THWN, THWN-2) 0.111 inches, then 4 X 0.111 = 0.444, or approximately a radius of 7/16 inches.

Yes, those are bent too sharply, however, as I stated: "I'd be much more concerned about all those conductors going into those conduits."

Probably over the side of long nose pliers (done that myself). Should have been bent over my thumb, that would provide a bend more closely resembling the proper minimum diameter bend.
Jerry,

Can you show me that cite? According to Mr. Hansen and Mr. Katen, although sharp bends are discouraged from a workmanship viewpoint, specific bending radius minimums are supposed to apply only to cables and to wire less than #8 in diameter.

ONE TEAM - ONE FIGHT!!!

Mike

39. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Jerry Peck
First, a lot of wiring used is THHW, THWN, THW which is 75 degree C rated insulation.

Yes, THHN, THHW, THWN-2 are 90 degree C rated insulation.

The first step in derating is to derate for ambient temperature.

THHW, THWN, THW which is 75 degree C rated insulation derates to 67% for only 123-131 degrees F ambient, many attics are 132-140 degrees F in the summer, which derates to 58%. In hotter climates (South Florida, Texas, and other states) attic temperatures can get to 141-158 degrees F, which derates to 33%.

So, first, lets say Chicago as that is where the original poster is located, and (for lack of not knowing) lets presume the attic temperatures only get to 131 degrees F in the summer for a derating to 67% (any hotter and you jump down to 58% or even less).

Now, #12 AWG, THHW, THWN, THW which is 75 degree C rated insulation, is rated for 25 amps. This 25 amps derates to 67%, which is only 16.75 amps ... WITH NOT DERATING YET for lack of maintaining spacing.

Okay, we now have conductors rated for (derated to) 16.75 amps, these are then bundled in a raceway as shown in the photo, 4-6 conductors, derated to 80%. 16.75 x 80% = 13.5 amps.

Not even sufficient for a 15 amp breaker, however, because this is over 10 amps, this is allowed to be protected by the next size up breaker - 15 amps. You are allowed to continuously draw 80% through the conductor, and THAT IS ALL these conductors are now rated for (don't forget, we are talking about #12 AWG, *NOT* #14 AWG conductors).

Repeat using THHN, THHW, THWN-2 are 90 degree C rated insulation.

Ambient derating goes from 30 amps X 67% = 20.1 amps X 80% = 16.08 amps, only suitable for a 15 amp breaker.

And that is ONLY FOR attic temperatures which are not over 131 degrees F.

Let's take the higher rated conductors (to satisfy Jim, and maybe John when he chimes in) of THHN, THHW, THWN-2 which are 90 degree C rated insulation and derate for attics which are one step hotter (132-140), still only 4-6 conductors in a raceway:

30 amps X 58% = 17.4 amps derated rating for ambient X 80% for 4-6 conductors in a raceway = 13.92 amps.

Don't try to say there is no need to derate, that everything will be hunky-dory, use a #12 AWG THHN in a raceway with 4-6 conductors and which runs up into an attic of 135 degrees F and you now only have a conductor rated for 13.92 amps!

Jim, you need to learn how to read the tables and derate, and do the math, before saying 'that's okay'.
OK,

Why is the 90° rating even being brought into this? I'm remembering Hansen and Katen on this as anything under 100 amps requires one to use the 60° column anyway.

ONE TEAM - ONE FIGHT!!!

Mike

40. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Michael P. O'Handley
OK,

Why is the 90° rating even being brought into this? I'm remembering Hansen and Katen on this as anything under 100 amps requires one to use the 60° column anyway.

ONE TEAM - ONE FIGHT!!!

Mike

Because derating starts from the rating of the insulation (which is typically higher, rarely is 60° C insulation used any more), with the final rating being "not to exceed" the rating in the 60° C column.

That being said, if the terminals of the equipment are rated at 75° (and some are being rated at that) then that 75° C rating may be used for the conductor. However, being as many terminals are still only rated for 60° C, that is the maximum rating allowed to be use (the lowest of all ratings is the maximum rating allowed).

41. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Michael P. O'Handley
Jerry,

Can you show me that cite? According to Mr. Hansen and Mr. Katen, although sharp bends are discouraged from a workmanship viewpoint, specific bending radius minimums are supposed to apply only to cables and to wire less than #8 in diameter.

ONE TEAM - ONE FIGHT!!!

Mike
I got the requirements from the wire manufacturers by calling them and talking to their engineers.

As you can see in the attached, the minimum bending radius is 4 times the diameter of the conductor and its insulation, with larger conductors requiring a minimum bending radius of 5 times the diameter of the conductor and its insulation - see Table H-1.

42. ## Re: Do you call 90 degree bends in panel?

Hi,

OK, I understand that. But I only see reference to "cables" that are less than 1" in diameter with specified thicknesses of insulation on those cables. Cables contain conductors (wires).

There are specific rules for bending radius of cables and conduit, and that only makes sense, because once you start bending those too tight you bunch the wiring inside of them together, but it was my understanding that, where individual conductors (wires) are concerned, there is no concern for bending radii in a panel with anything less than a #8 conductor.

ONE TEAM - ONE FIGHT!!!

Mike

43. ## Re: Do you call 90 degree bends in panel?

[quote=Michael P. O'Handley;38000]OK, I understand that. But I only see reference to "cables" that are less than 1" in diameter with specified thicknesses of insulation on those cables. Cables contain conductors (wires).[/quote

The conversation went through conductors and cables, and the responses were that the same applied to the bending radius of cables and conductors.

There are specific rules for bending radius of cables and conduit, and that only makes sense, because once you start bending those too tight you bunch the wiring inside of them together, but it was my understanding that, where individual conductors (wires) are concerned, there is no concern for bending radii in a panel with anything less than a #8 conductor.
The reason for the minimum bending radius is to not damage the insulation, even bending a #14 AWG too tightly will 'crimp up' the insulation, damaging it.

The NEC code reference to minimum bending radius applies to ALL conductors (regardless of size) in systems for "over 600 volts, nominal". Nothing to do with "size" it's the insulation, damage thereto, and, at 600 volts, that is much more critical.

From the 2008 NEC. (underlining and bold are mine)
- II. Requirements for over 600 Volts, Nominal
- - 300.34 Conductor Bending Radius.
- - - The conductor shall not be bent to a radius less than 8 times the overall diameter for nonshielded conductors or 12 times the overall diameter for shielded or lead-covered conductors during or after installation. For multiconductor or multiplexed single-conductor cables having individually shielded conductors, the minimum bending radius is 12 times the diameter of the individually shielded conductors or 7 times the overall diameter, whichever is greater.

"The conductor" ... singular.

There is an NEC "bending radius" for:

- Type AC cable - 320.24. (five times the diameter of the Type AC cable)
- Integrated Gas Spacer Cable - 326.24 (see Table 326.24 Minimum Radii of Bends)
- Type MC cable - 330.24 (varies - 10, 12, 15 times the external diameter)
- Type MI cable - 332.24 (varies - 5, 10 times the external diameter)
- Type NM cable - 334.24 (5 times the diameter)
(there are other I've left out)
- Type SE and USE - 338.24 (5 times the diameter)
- Type UF - 340.24 (5 times the diameter)

You will notice that none of the above is consistent with the information sent to me by the wire manufacturers. The above is specified in the NEC.

The manufacturer's requirements (which I posted) are covered in the NEC in 110.3(B), superseded by those requirements stated in the code (see above). (I know, "superseded" is not the right word to use there. I should have said "Where not specified elsewhere in the NEC, those apply.")

Last edited by Jerry Peck; 03-30-2008 at 03:24 PM.

44. ## Re: Do you call 90 degree bends in panel?

Sorry Jerry,

While I agree that damaging the insulation isn't good, I don't see where it's going to matter in the panel. I think your pedantic nature is showing through again. I think I'll stick with Katen & Hansen on this one.

ONE TEAM - ONE FIGHT!!!

Mike

45. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Michael P. O'Handley
I think I'll stick with Katen & Hansen on this one.

No problem, but if you read through Code Check very carefully you will find errors there too.

Stick with whatever you like, it's your life, your business, and all decisions are not always correct.

46. ## Re: Do you call 90 degree bends in panel?

Hi,

Well, it all boils down to how one interprets the code. The problem I have with your interpretations, Jerry, is that it's often the case that where Katen, Hansen, and countless AHJ's and inspectors interpret those codes one way, you interpret them another way and no amount of debate can change your mind, so I know better than to try.

Like I said in the other post, to each his own.

ONE TEAM - ONE FIGHT!!!

Mike

47. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Michael P. O'Handley
and countless AHJ's and inspectors interpret those codes one way,
Which is where I get most of my interpretations - AHJ, inspectors, manufacturers, UL, NFPA, etc., real "authorities" whom I ask.

Likewise, I've stopped trying to reason with you, too stubborn to listen to others - you must always be right, it's "Mike's way" or no way.

48. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Jerry Peck
... too stubborn to listen to others - you must always be right,

Jerry, now that's funny, coming from you.

49. ## Re: Do you call 90 degree bends in panel?

Yeah,

That is cute coming from Jerry. He's just miffed because I won't stay and play. Playing to Jerry is continuing to maintain an endless argument wherein he resolves to eventually wear you down and get you to yell Uncle.

I'm proven that I'm wrong all the time and freely acknowldge that I am when I'm shown that I am. Electricity is an area that I'm extremely weak in, so I have to rely on others to provide me the answers that I want to hang my hat on. This question has been debated here, on my forum, and on the ASHI forum many, many times by various people and Jerry has taken part in those debates. In this case, I choose to hang my hat on Hansen's and Katen's interpretation of things instead of Jerry's.

I'm comfortable doing that and I don't bear Jerry any ill will; I just don't have the time or energy to hang around here feeding his ego. So, that's it, I'm out of this thread. It's all your's, Jerry.

FWIW, I agree with you about the derating.

ONE TEAM - ONE FIGHT!!!

Mike

50. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Dom D'Agostino
Jerry, now that's funny, coming from you.
Dom,

You and everyone here knows that when I am shown I am wrong, I say it and 'take my 40 lashes with a wet noodle and go back to my corner'.

I've said that many times, and, no doubt, will say it many more times.

With Mike, though, Mike 'has to have it his way', to disagree with Mike is 'not acceptable' to him. Mike and I have disagreed many more times than we have agreed - Mike does not like that.

Too bad is all I can say. When he is wrong, I am there (here) to call him on it. When he is not wrong, I don't call him on it - no need to.

51. ## Re: Do you call 90 degree bends in panel?

Jerry,

Relax, it's just an observation.

Nobody, including myself, likes to hear these things about themselves. But I think over the years, on this board at least, you have demonstrated a tendency to be, shall we say, confrontational, while insisting that your interpretation of a code is the correct one.

Yes, I have seen you admit when you're wrong and go back to your corner. But not everyone wants to go 10 rounds to get to that point.

So, "Don't shoot the messenger"... so to speak.

Dom.

52. ## Re: Do you call 90 degree bends in panel?

Most reputible electrical contractors install branch wiring in this same manner.

53. ## Re: Do you call 90 degree bends in panel?

Fifty one replies and here's what we have so far of substance that relates to the original question posted:

Originally Posted by Ross Neag
Do you call 90 degree bends in panel? Just curious. I'd prefer less angle and stress on branch wiring.
Originally Posted by Steve Lowery
I vaguely remember something about ( 2.5 X Wire diameter ) as minimum radius on bends.
Originally Posted by Jerry Peck
4 times the diameter is the minimum radius of the bend.

If the conductor (and insulation) is approximately (#12 THHN, THWN, THWN-2) 0.111 inches, then 4 X 0.111 = 0.444, or approximately a radius of 7/16 inches.

Yes, those are bent too sharply, however, as I stated: "I'd be much more concerned about all those conductors going into those conduits."
Originally Posted by Michael P. O'Handley
Jerry,

Can you show me that cite? According to Mr. Hansen and Mr. Katen, although sharp bends are discouraged from a workmanship viewpoint, specific bending radius minimums are supposed to apply only to cables and to wire less than #8 in diameter.
Originally Posted by Jerry Peck
I got the requirements from the wire manufacturers by calling them and talking to their engineers.

As you can see in the attached, the minimum bending radius is 4 times the diameter of the conductor and its insulation, with larger conductors requiring a minimum bending radius of 5 times the diameter of the conductor and its insulation - see Table H-1.
Originally Posted by Michael P. O'Handley
OK, I understand that. But I only see reference to "cables" that are less than 1" in diameter with specified thicknesses of insulation on those cables. Cables contain conductors (wires).
Originally Posted by Jerry Peck
The conversation went through conductors and cables, and the responses were that the same applied to the bending radius of cables and conductors.

The reason for the minimum bending radius is to not damage the insulation, even bending a #14 AWG too tightly will 'crimp up' the insulation, damaging it.

The NEC code reference to minimum bending radius applies to ALL conductors (regardless of size) in systems for "over 600 volts, nominal". Nothing to do with "size" it's the insulation, damage thereto, and, at 600 volts, that is much more critical.

From the 2008 NEC. (underlining and bold are mine)
- II. Requirements for over 600 Volts, Nominal
- - 300.34 Conductor Bending Radius.
- - - The conductor shall not be bent to a radius less than 8 times the overall diameter for nonshielded conductors or 12 times the overall diameter for shielded or lead-covered conductors during or after installation. For multiconductor or multiplexed single-conductor cables having individually shielded conductors, the minimum bending radius is 12 times the diameter of the individually shielded conductors or 7 times the overall diameter, whichever is greater.

"The conductor" ... singular.

There is an NEC "bending radius" for:

- Type AC cable - 320.24. (five times the diameter of the Type AC cable)
- Integrated Gas Spacer Cable - 326.24 (see Table 326.24 Minimum Radii of Bends)
- Type MC cable - 330.24 (varies - 10, 12, 15 times the external diameter)
- Type MI cable - 332.24 (varies - 5, 10 times the external diameter)
- Type NM cable - 334.24 (5 times the diameter)
(there are other I've left out)
- Type SE and USE - 338.24 (5 times the diameter)
- Type UF - 340.24 (5 times the diameter)

You will notice that none of the above is consistent with the information sent to me by the wire manufacturers. The above is specified in the NEC.

The manufacturer's requirements (which I posted) are covered in the NEC in 110.3(B), superseded by those requirements stated in the code (see above). (I know, "superseded" is not the right word to use there. I should have said "Where not specified elsewhere in the NEC, those apply.")
This discussion prompted me to do a little independent research of my own. The only specific reference to bends that is found in the electrical chapters of the 2006 IRC is as follows:
&#167;RE3702.5 Bends. Bends shall be made so as not to damage the wiring method or reduce the internal diameter of raceways. For types NM and SE cable, bends shall be so made, and other handling shall be such that the cable will not be damaged and the radius of the curve of the inner edge of any bend shall be not less than five times the diameter of the cable.
Note that the IRC is referring to wiring methods and cables, and not to individual conductors. This IRC section is cross-referenced to the 2005 NEC 320.24 and 334.24. NEC 320.24 applies only to type AC armored cable and specifies a minimum bend radius of not less than five times the diameter of the cable. NEC 334.24 applies only to type NM, NMC, NMS non-metallic sheathed cables and has that same "five times the diameter of the cable" restriction. Again, all references so far are to cables and not to individual conductors.

Bend radius for individual conductors is specified in the NEC, at section 300.24 as Jerry posted, but these requirements apply specifically to systems over 600 volts, and residential wiring is less than 600 volts.

I chose several wire and cable manufacturers at random, and tracked down their restrictions on bending. They are all very similar to the ones from the company that Jerry posted.

Calculating Minimum Electrical Cable Bending Radius - Okonite Wire and Cable
http://www.prioritywire.com/bending.pdf
Houston Wire & Cable Company - Bending Radii and Pulling Tensions

The term "bent for permanent training" means that the wire or cable is bent into position without it being under tension. Those are the types of bends that are found in the picture of the panel at the top of the post.

On all of the manufacturer tech sheets, including the one Jerry posted, single and multiple-conductor cables without metallic sheathing or armor, and with an overall diameter of 1.0 inches or less, have a minimum bend radius of four times the outside diameter, with the bend radius measured to the inner surface of the cable and not to its axis. Two of the three sources I posted mention this applies to cables rated up to 600 volts.

If you bend an insulated conductor too tight, you'll first damage the insulation. Bend it tighter, and you'll damage the conductor. I didn't go any farther and research where the 4x comes from. The sense that I got was that this was a manufacturing spec that the companies that make wire & cable need to meet and that the cable is not tested or listed for tighter bends.

So, in conclusion, I agree with Jerry. Its 4x for a single conductor inside a panel and this comes not from an explicit code requirement, but from the wire manufacturer and is covered in the NEC by 110.3(B).

Last edited by Brandon Chew; 03-31-2008 at 04:44 PM. Reason: format

54. ## Re: Do you call 90 degree bends in panel?

Seems like a slow week in the HI trade, I agree that the bends are a bit tight, but that might be spitting hairs, I would be more concerned about the derating than the bend radius but we don't really know from wire size, breaker size, location for ambient temps, and I don't think many many AHJ's from the Northern Chicago suburbs would have a problem with the installation in general. What might be more concerning would be grounding or bonding of this panel, Is it fed with emt or metallic conduit?, through a concentric knock-out? is the neutral bonded? does it need to be?, are there bonding bushings where required? Many N. Ill. municipalities would want to see some bonding wether or not this was the main service panel. An improperely grounded or bonded panel, I think would be at least as potentially dangerous as a wire with too tight a bend radius.

55. ## Re: Do you call 90 degree bends in panel?

The HI biz is rife with inspector folklore that gets passed around as fact. I continually try to track "rules of thumb" and things that appear to be guesses, no matter how certain the person making them is convinced they are right or absolute fact, back to a verifiable source. I consider it to be good education as well as a good business practice.

My quest was to answer the question: is there a minimum bend radius for a single conductor smaller than 1 inch in diameter and if so, what should it be? I know where 4x comes from and I feel comfortable that it is a good number to use until or unless I find something better to replace it.

Knowing what the bend radius should be, and whether or not I would call it out as a defect in that panel, and if I did call it out how big of a deal I would make of it, are three different things. I agree that there may be bigger fish to fry with that wiring than the bends in the conductors.

The biz is slow (halted) for me right now. Exactly one month ago today I had an accident that broke all four fingers in my left hand, and three of them were multiple fractures. For 31 straight days it feels like there is a truck parked on my hand -- all the time. Every now and then it feels like someone is running a lighter back and forth under my fingers. Each day gets a little better than the one previous and I'm looking forward to the day when it doesn't hurt all of the time. The pins come out on April 7 and the splint comes off a few weeks later. Then it's possible I'll need a second surgery to repair damaged tendons, and after that several months of physical & occupational therapy. I might be able to resume inspecting with a helper once the bones and surgery heal and I can start bearing some weight with my hand, but not until then.

56. ## Re: Do you call 90 degree bends in panel?

Originally Posted by Brandon Chew
Exactly one month ago today I had an accident that broke all four fingers in my left hand, and three of them were multiple fractures.
Brandon,

I did not know that, and simply stating 'I hope your fingers and hand get better soon.' seems useless given what you stated below.

For 31 straight days it feels like there is a truck parked on my hand -- all the time. Every now and then it feels like someone is running a lighter back and forth under my fingers. Each day gets a little better than the one previous and I'm looking forward to the day when it doesn't hurt all of the time. The pins come out on April 7 and the splint comes off a few weeks later. Then it's possible I'll need a second surgery to repair damaged tendons, and after that several months of physical & occupational therapy. I might be able to resume inspecting with a helper once the bones and surgery heal and I can start bearing some weight with my hand, but not until then.
For lack of being able to do anything else, though, 'I hope your fingers and hand get better soon.'

How on earth are you doing all of this typing, or was it your 'other' hand?

57. ## Re: Do you call 90 degree bends in panel?

I'm right handed and the left is injured. Mousing and typing with the right hand...

While I can't do inspections and bring money in right now, I'm still working on my business by sharpening my skills and reviewing & updating my business practices.

The message board is a good educational tool as well as good mental therapy and keeps my spirits up.

58. ## Re: Do you call 90 degree bends in panel?

No, Jerry, I did not miss the 'bundling.' Nor did I ignore it.

The NECA standard for workmanship says to do exactly that ... run the wires together, even zip tie them into a tight bundle, making a sharp, clean bend only when the wire arrives at the appropriate breaker. No extra wire. No slack. Just nice, neat, right angle bends.

We often reference "workmanlike" in our discussions; the NECA standard is the one that attempts to define it.

Yet, just because a standard says so, that doesn't make it mandatory. The NFPA has long held that the 'workmanlike' requirement of the NEC is unenforceable, and I am not aware of any NECA standard having the force of law. NECA standards are, however, often referred to in contract language.

Now, who is NECA? Despite the glorious name and long history, NECA represents primarily Union contractors. Considering the long history of training and workmanship the IBEW has, I find the sight of such a panel reassuring.

(Let anyone misunderstand, I have no formal connection with either NECA or the IBEW. Nor am I suggesting anything is inherently wrong with non-members).

59. ## Re: Do you call 90 degree bends in panel?

Originally Posted by John Steinke
No, Jerry, I did not miss the 'bundling.' Nor did I ignore it.

The NECA standard for workmanship says to do exactly that ... run the wires together, even zip tie them into a tight bundle,
John,

You did miss a few things, first, the bundling / lack of maintaining spacing / more than 3 current carrying conductors derating discussion is *NOT* about the conductors *in the panel* and to which you are referring. That derating discussion is regarding those same issues beginning from where those conductors enter the raceways.

making a sharp, clean bend
And that would not be a problem if done within the allowances specified by the manufacturers.

That said, though, you also must have missed it when I, and others, said in answer to Ross when he said "I'd prefer less angle and stress on branch wiring." ... to wit "I'd be much more concerned about all those conductors going into those conduits."

Again - "going into those conduits". Very clearly specifying that.

only when the wire arrives at the appropriate breaker. No extra wire. No slack. Just nice, neat, right angle bends.
Okay, now this part is where you got me confused on what you are saying is 'right' (see what you just said) and what you stated earlier (and again tonight):

From 03-28: "That panel is installed in a perfect textbook illustration of exactly what the appropriate NECA standard defines as "good workmanship." "

From tonight: "The NECA standard for workmanship says to do exactly that " and "I find the sight of such a panel reassuring."

Don't yet know what I am referring to and confused about?

You just stated, among other thing, "No slack" ...

Do you really look at that panel, or just glance at it?

There is about 2 feet of "slack" on each side. Follow the conductors down form the top raceways where they enter the enclosure, down, and down some more, all the way down to the sharp (too sharp) "U" bend at the bottom, then back up to the breakers.

BOTH SIDES.

We often reference "workmanlike" in our discussions; the NECA standard is the one that attempts to define it.
That's good, I also like good workmanship, which does not mean 'just pretty to look at', it also means "done correctly" ... conductors bent with proper radius, not bundled (up into the conduit - if there were 'no slack' in that panel then the bundling present in the panel would not be there).

I find the sight of such a panel reassuring.
Look at that panel again, it does not meet what you are saying it needs to meet.

I know, you will respond with something like 'those are just little things', but, in reality (*if those were "little things"* and they are not), it's the little things which make for good workmanlike work.

Aren't the little things important? Isn't that what separates 'good workmanlike work' from 'jeez, who did that crap'?

60. ## Re: Do you call 90 degree bends in panel?

It is a breath of fresh air when I see a panel wired neatly that way. One of the things I do is purposely step back for a moment and admire it. Then I move in closer and inspect it. Making a conscious effort to separate the two acts helps me keep from dropping my guard during the inspection.

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•