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Maximum Allowable Pipe Length For Carrier WeatherMaker 9200 (Model 58MXA100)

Maximum Allowable Pipe Length For Carrier WeatherMaker 9200 (Model 58MXA100)

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  #1  
Old 04-24-14, 07:32 PM
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Maximum Allowable Pipe Length For Carrier WeatherMaker 9200 (Model 58MXA100)

I am trying to understand the maximum allowable pipe length for my Carrier furance. See the attached diagram for my furnace and I highlighted the three 3inch pipe as I think that is applicable to my setup. I have 2" vent and inlet coming out of the furnace, that has the following elbows:

- 2" 90 degree elbow
- 2" 45 degree elbow
- transitions into a 3" pipe
- 3" 45 degree elbow
- 3" 90 degree elbow
- 3" transitions into a concentric pipe (I would add another 45 deg elbow to represent this).

See the attached image that shows most of the above but the transition of pipe into the concentric pipe. The total length of the existing system looks to be around 26'. Based upon the chart that I attached, it appears that if you are using 3" pipe, there is not reduction in maximum allowable pipe as there is when you are using 2 or 2 1/2 pipe. My first question, is this really correct in that even with 6 elbows, the maximum pipe lenght stays at 70 feet?

For my furance, I want to remove the concentric pipe and cut off the the PVC about two feet inside the house, add a 90 degree 3" elbow and go out the other side of the house. The way I would count the number of elbows is that I already have four near the furance and I woudl be adding one more to the end of the pipe before I exist the house. I will not be using a concentric pipe again to exist the house but using the set up as shown in the top image within the Termination attachment. My undestanding is that the elbows on the outside do not count when it comes to determining total maximum allowable pipe lenght.

Can someone clarify if I am reading the table correct in that when using 3" you still maintain 70 feet of allowable pipe lenght even with 5 or 6 elbows?

Even if the pipe coming out of the furnance is 2" and transitions into 3" about 2 feet away from the furnace, is it correct to assume that I can use the maximum allowable pipe length as if I have a 3" all the way so I can use 70"?

It really seems strange that a 2 1/2 pipe with 5 elbows only gets 10 Feet of maximum pipe length but a 3" gets 70 feet even with 6 elbows.
 
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  #2  
Old 04-27-14, 04:39 PM
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I hope that picture is upside down. I've never seen a properly installed vent system which goes downhill from the furnace. When going from the furnace 2" connections to 3" pipe, the increase is normally done before any elbows.
 
  #3  
Old 04-27-14, 05:02 PM
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The picture with the furnance and PVC pipe should be rotated 90 degrees to the right, the pipes are going out and up from the furnace. Sorry for the confusion.
 
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Old 04-27-14, 07:40 PM
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Had me worried. With the pic rotated, it makes a lot more sense. The chart is pretty clear. You can use up to 6-90* ells & run up to 70' when using 3" pipe.
 
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Old 04-27-14, 08:31 PM
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Interesting gas line situation there. I'm used to seeing all the gas lines fastened.
It looks like the copper lines can come in contact with duct work. :NO NO NO:

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  #6  
Old 04-28-14, 02:31 PM
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Those gas lines would never fly around here. They would have to be supported, not touching the ducts or each other & not cross over each other. The regulator as close as it is to the furnace probably wouldn't work either unless there is a vent limiter on it.
 
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