- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
The difference among 3.0x10^-5 and 3.3 or 2.8x10^-5 seems too small to get excited about.
Tapatalk!
PVC Conduit
- Thread starter Little Bill
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The difference among 3.0x10^-5 and 3.3 or 2.8x10^-5 seems too small to get excited about.
Tapatalk!
FionaZuppa
Senior Member
- Location
- AZ
- Occupation
- Part Time Electrician (semi retired, old) - EE retired.
perhaps so. i was just looking for a definitive coefficient that is common across various code books. apparently not.
Agree.
As to accuracy, I will go with the one published in the Code. Not because we have to, like Bob iwire posted, but because it is probably specific to the PVC composition of conduit. There are many variations of PVC compounds, each likely having a slightly different CoTE.
kwired
Electron manager
- Location
- NE Nebraska
What does inside look like? Will fish tape or for blowing systems will a conduit piston hang up in it? I don't care so much about water tightness as anything outdoors will fill with condensation anyway in most of the US. And after working in a dairy foods processing plant where everything is washed constantly, there is no keeping water out in a place like that either. You always need a place for water to drain in such locations.
PetrosA
Senior Member
- Location
- Lancaster, Pennsylvania
It's an interesting idea, but this seems way too thick. I don't think the rubber should be much thicker than the bell end of the PVC it's being used on or strapping the PVC to a flat surface becomes an issue.
kingpb
Senior Member
- Location
- SE USA as far as you can go
- Occupation
- Engineer, Registered
Carlon lists coefficient as 3.38E-5 in/in/deg F
The NEC chart looks like the Carlon chart. I have a feeling Carlon was nice enough to provide it for NEC.
Interesting to remember, but often overlooked is that this is expansion and contraction.
Add 30deg F to temp change if conduit is installed in direct sunlight. ASHRAE is a good place to get Extreme low and high temps.
Good question though - do you use, 5 yr, 10yr, 20 yr or 50yr for max/min/temps? I would assume 20 yr would be about right for a permanent installation.
So, for Miami, FL the 20 yr extreme temp variation is just about 100 deg, if you assume conduit installed on roof in sunlight it goes up to 130DegF delta. therefore - anything over 4.7 ft (straight run) requires expansion/contraction fitting.
The NEC chart looks like the Carlon chart. I have a feeling Carlon was nice enough to provide it for NEC.
Interesting to remember, but often overlooked is that this is expansion and contraction.
Add 30deg F to temp change if conduit is installed in direct sunlight. ASHRAE is a good place to get Extreme low and high temps.
Good question though - do you use, 5 yr, 10yr, 20 yr or 50yr for max/min/temps? I would assume 20 yr would be about right for a permanent installation.
So, for Miami, FL the 20 yr extreme temp variation is just about 100 deg, if you assume conduit installed on roof in sunlight it goes up to 130DegF delta. therefore - anything over 4.7 ft (straight run) requires expansion/contraction fitting.
mgookin
Senior Member
- Location
- Fort Myers, FL
In building codes we assume a 50 year lifespan for a building and that ownership will change which is why you can't cut people slack on how they set up or operate a particular occupancy. Assembly is assembly and you can't take the guy on his word that fewer than 500 people will ever be in there; you need that 4th exit.
- Location
- Massachusetts
kwired
Electron manager
- Location
- NE Nebraska
Yes but do they get to say we will never have 500 people in here if they have enough area for 500? Or if they do they likely get some kind of certificate of occupancy that says the designed occupancy even if space would otherwise allow for more.
- Location
- Massachusetts
Huh?:?
Just because a space can hold 500 people does not automatically make it a assembly occupancy.
kwired
Electron manager
- Location
- NE Nebraska
I was not trying to qualify it being an assembly occupancy. The post that started this was about needing an additional exit - based on occupancy. Owner likely does get to choose what a space is used for, but can not necessarily change that later on without approval of an AHJ. So if there is space for 500 people according to codes and owner wants to say they will never have more then 300 people in there that will either limit them to 300 people on their COA or AHJ will say no, you have space for 500 - any codes that change because of that higher number will apply, and they will get a COA for 500.
ADD: I would guess most cases the owner can get his wish of 300, but better not get caught having more then 300 if things are only designed to accommodate 300 and the COA says 300.
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fmtjfw
Senior Member
- Location
- Fairmont, WV, USA
The between 2.8 and 3.3 the ratio is 84%, it is quite a difference, especially since you multiply by the value.
- Location
- Massachusetts
I think we have a failure to communicate. 
I am done unless mgookin adds more info.
I am done unless mgookin adds more info.
- Location
- Massachusetts
mgookin
Senior Member
- Location
- Fort Myers, FL
Maybe I should have written a paragraph instead of a sentence.
IF you have Assembly occupancy, and IF you have an occupant load of 500 or more people, you need a 4th exit. You can't take a particular church's word, or the word of a nighclub owner, etc. that they will limit it to 499 people, or limit it to 299 people to avoid having fire sprinkers. The occupant load is the occupant load. That guy will be gone in 5 years and someone else will come along.
The issue came up because someone asked how long we assume the life of our installations. In the building code we assume 50 years. We know roofing, water heaters, etc will need replacement but the overall building is deemed to still exist 50 years after you build it.
IF you have Assembly occupancy, and IF you have an occupant load of 500 or more people, you need a 4th exit. You can't take a particular church's word, or the word of a nighclub owner, etc. that they will limit it to 499 people, or limit it to 299 people to avoid having fire sprinkers. The occupant load is the occupant load. That guy will be gone in 5 years and someone else will come along.
The issue came up because someone asked how long we assume the life of our installations. In the building code we assume 50 years. We know roofing, water heaters, etc will need replacement but the overall building is deemed to still exist 50 years after you build it.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
mgookin
Senior Member
- Location
- Fort Myers, FL
Unless of course it has been carried away by the 100 year flood....
Very good friend of mine is civil engineer and gets on a rampage every time someone brings up "the 500 year flood" and his logic is "you have 100 years of data on a 4 billion year old rock and you want us to design to protect against everything since Christopher Columbus got here; yeah, just give me Chris' records and we'll get right on that!"
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
How true!
The other side of the problem is that some areas are now getting a "100 year flood" several times per decade.
kwired
Electron manager
- Location
- NE Nebraska
There might be some records around 400 years old out east, but not here in the midwest. Lucky to find anything much more then 150 years for records here, and even that depends exactly where you are in the region.
mgookin
Senior Member
- Location
- Fort Myers, FL
50 year event occurs with a probability of 1:50 = .02 or 2% probability.
It does not mean it occurs on 50 year intervals.
100 year event = 1:100 = .01 = 1% chance in any given year, and so on.
500 year event = 1:500 = .002 = 0.2%
And with respect to hurricanes and floods, we build to a minimal category 3 hurricane. Any time we have tropical storms or a Cat 1 or 2 hurricane coming, I ignore the drama queen weather forecasters who want you to believe the world is ending.
It does not mean it occurs on 50 year intervals.
100 year event = 1:100 = .01 = 1% chance in any given year, and so on.
500 year event = 1:500 = .002 = 0.2%
And with respect to hurricanes and floods, we build to a minimal category 3 hurricane. Any time we have tropical storms or a Cat 1 or 2 hurricane coming, I ignore the drama queen weather forecasters who want you to believe the world is ending.
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