# understanding 352.44



## Murphy (Dec 10, 2009)

good questions i would like to know more about that as well


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## Dennis Alwon (May 9, 2009)

Where did you get 40 degree change from. 100-20= 80????? I don't think you use the temp it was installed at but I don't know.


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## Murphy (Dec 10, 2009)

ha yea true that is def 80 degrees man


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## McClary’s Electrical (Feb 21, 2009)

aksparky said:


> I was recently cited for not installing an expansion joint in a 15 foot run of PVC pipe along the side of a residence about 3 foot from the ground.
> Before I talk with the inspector I would like to be sure I'm clear on article 352.44.
> 
> 1)When I installed the conduit it was about 60F, the max temp in my area according to the local Temp Table is 100F and a minimum of about 20F so I figured a 40F temp change, is this correct method for figuring temp change?
> ...


 
I came up with the exact same answer. 0.0162 per ft for a 40 degree change. (per 352.44 (a),,,but I will say that a 40 degree change is a little on the light side. Around here, you would probably use 60 or higher.

0.0162X15 ft=.243,,,which is less than the1/4" max


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## aksparky (Dec 1, 2007)

Dennis Alwon said:


> Where did you get 40 degree change from. 100-20= 80????? I don't think you use the temp it was installed at but I don't know.


 
Thank you for the response, I showed in the 1st question how I got the 40 degree temp change, the question was is it the correct way to figure it.

To me anyway, it seems to make sense to figure it that way using the temp installed to get the temp change because your pipe is at that level of contraction/expansion when installed, and beings how it is at the middle of the min /max temp I would set the expansion joint to about the half way mark when installing it.

But then again, that is why I am posting I am not 100 percent sure.

Thanks again for the response.


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## goose134 (Nov 12, 2007)

I don't think the temperature is likely to swing from 100 to 20 in a day.


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## McClary’s Electrical (Feb 21, 2009)

I'd also like to add that he cannot apply 352.44(a) if the one end of the pipe goes underground. Only if it's mounted in between two rigid points. (like two boxes)


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## Dennis Alwon (May 9, 2009)

goose134 said:


> I don't think the temperature is likely to swing from 100 to 20 in a day.


 I don't think the temp. swing is in a day. I just read a nema article and it says "temperature cahnge can easily be 140 degrees with the temp. in the summer sun and the cold winter." This tells me the high and low for the year should be used.


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## Dennis Alwon (May 9, 2009)

mcclary's electrical said:


> I'd also like to add that he cannot apply 352.44(a) if the one end of the pipe goes underground. Only if it's mounted in between two rigid points. (like two boxes)


I agree. This is for straight runs of pipe. A 10 foot run with a temp change of 100 degrees is .4 inches. This means over 100 feet the movement will be 4 inches.


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## McClary’s Electrical (Feb 21, 2009)

Dennis Alwon said:


> I don't think the temp. swing is in a day. I just read a nema article and it says "temperature cahnge can easily be 140 degrees with the temp. in the summer sun and the cold winter." This tells me the high and low for the year should be used.


 


I agree, and that's why 40 degrees is a light number


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## Dennis Alwon (May 9, 2009)

Here is a nice article from Nema. You have to setup a user account and it takes awhile but you can save the document to adobe.


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## aksparky (Dec 1, 2007)

I could see where the temp swing could reach that if the pipe was installed at the max heat of summer or installed in the coldest of winter but when installed in the mid temp the temp change is not going to be that drastic.


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## aksparky (Dec 1, 2007)

mcclary's electrical said:


> I came up with the exact same answer. 0.0162 per ft for a 40 degree change. (per 352.44 (a),,,but I will say that a 40 degree change is a little on the light side. Around here, you would probably use 60 or higher.
> 
> 0.0162X15 ft=.243,,,which is less than the1/4" max


 
Could you please post the calc that you used to get the .0162 per ft for a 40 degree change that seems to be different than the way I am figuring it but is certainly the same result.

Thanks again for the replys


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## McClary’s Electrical (Feb 21, 2009)

aksparky said:


> Could you please post the calc that you used to get the .0162 per ft for a 40 degree change that seems to be different than the way I am figuring it but is certainly the same result.
> 
> Thanks again for the replys


 

I arrived at that conclusion by applying 352.44 (a) which states for 40 degree change(the number you provided) would be 1.62 per 100 feet.


So 1.62"expansion/100ft=0.0162*15ft=.243


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## RIVETER (Sep 26, 2009)

I guess I don't get out much but I have never had to worry about an expansion joint in a residence.


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## McClary’s Electrical (Feb 21, 2009)

RIVETER said:


> I guess I don't get out much but I have never had to worry about an expansion joint in a residence.


 

Me neither. I'm really surprised that he got called on a 15 ft run.


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## waco (Dec 10, 2007)

As a matter of habit, I use an expansion joint whenever (which is very seldom) I have to run PVC between two hard points. I have found it is just the best way to do it and it isn't any real trouble to do.

But, if I can, I'll make longer runs go underground and 15 feet is, to me, a longer run.


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## RIVETER (Sep 26, 2009)

waco said:


> As a matter of habit, I use an expansion joint whenever (which is very seldom) I have to run PVC between two hard points. I have found it is just the best way to do it and it isn't any real trouble to do.
> 
> But, if I can, I'll make longer runs go underground and 15 feet is, to me, a longer run.


That sounds waco to me. It's just a joke...Hope you understand.


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## aksparky (Dec 1, 2007)

I cant remember being called on this before , normally unless I was over 50 foot or so, or installing on a roof I wouldnt have worried about it, but I guess the inspectors in my area are starting to watch for this now.

After reading the article that Dennis posted a link to I would be inclined to agree that we are supposed to get the temp change by using the difference between the min and max temp.

Common sense tells me that I should be using the difference between the temp installed and the max temp, or the temp installed and the min temp to get the temp change and then set the expansion fitting accordingly, but common sense has got me into trouble before.

Thanks again to all who posted, while I dont post often I do log in and read post before and after work pretty much every day and am always learning things here.


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## Dennis Alwon (May 9, 2009)

I live in NC and I have never used an expansion joint. I guess nobody looks for it or they feel the temp. is not an issue. Who knows.


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## goose134 (Nov 12, 2007)

Don't feel bad Dennis, I've installed maybe 150' of PVC in my 10 years in the trade. I've used expansion fitting for EMT and Rigid, but here in Chi town PVC is limited to very few applications.

We had to use 2 of these expansion fittings for 4" EMT and they were somewhere around $600 a crack.


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## Innovative (Jan 26, 2010)

Damn.... I must use 2000 or more of them each year. They do get expensive when you are running 3 and 4" PVC. On long runs of 2" we usually install them every 100'.


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