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CPVC Expansion

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jjmoore73

Mechanical
Apr 13, 2011
30
We are installing a CPVC 13R system it has some straight runs almost 200 feet. Daytime temperatures when we are installing this week range from a high of 65 degrees today to a daytime high of 35 degrees next week. The pipe will eventually be in a controlled environment of 75 degrees. The expansion calculations are based on change in temperature and length of pipe and attached is an easy chart to show the expansion. It shows there will be .04" of expansion for 5' of pipe. Obviously 1/32" of expansion is nothing to be concerned with. What I want to know is, when expansion reaches "X" inches.... then expansion protection is required. Please define "X".

Possibly 1" or 2" is acceptable. Maybe anything more than 3" or 4" of movement needs to be addressed. I understand how to calculate the expansion, and know how to size the loop. What I don't understand is when it is necessary. I have asked the manufacture, they can only say how to calculate the expansion and how to size the loop. No one can tell me at what threshold it is necessary. I could not find anything in NFPA. Any suggestions?
 
 http://files.engineering.com/getfile.aspx?folder=01ff3723-eb42-46c8-990d-6955dcd3e505&file=Table_C_Expansion.JPG
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One of my customers had a problem with this. The GC did not insulate per the plan. There was supposed to be a controlled environment, but it did not happen that way. Based on their experience, they figured that the system could generally handle an inch of expansion (when there were drops to ceilings - especially gyp ceilings). The jobs this customer does are typical multi-family with a main in a central corridor and then laterals going to dwelling units. They have requested that we make offsets about every 90'.

I don't think there is any hard and fast rule of when you have to put in the offsets. I think the manufacturers like to keep that from being published as it is less liability for them. But, go with what amount of expansion you think you can handle and place from there. From what I have seen, more than about an inch in hard ceilings can cause issues.



Travis Mack
MFP Design, LLC
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