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new furnace pcv air intake 2", but current pipes are 3": ok to use reducer?

new furnace pcv air intake 2", but current pipes are 3": ok to use reducer?


  #1  
Old 03-16-13, 11:14 AM
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new furnace pcv air intake 2", but current pipes are 3": ok to use reducer?

My old gas furnace required 3" intake/return pvc pipes. I want to replace it with a higher-effiiciency unit that has 2" pipe spaces.

Is it okay to attach a 3"-to-2" reducer coupler, rather than redo the whole pipe length? The current pipes are covered by finished ceiling -- don't want to break into that.
thanks, cap1816
 
  #2  
Old 03-16-13, 05:22 PM
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From the sound of your post, you are installing the furnace yourself.
If this is indeed the case, read the section on venting very carefully & pay strict attention to it. Rarely have I seen an oversized vent cause a problem but anything even close to the maximums in the install manual will almost certainly cause trouble.
 
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Old 03-17-13, 06:57 AM
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Most furnaces today have 2" openings but may still require to be upsized to 3" due to the length of the run. As suggested, read the manual section on venting for proper venting practices. Make sure you call for a permit from your locality to have the installation inspected.
 
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Old 03-19-13, 12:28 PM
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Thanks -- the installation manual said using a reducer coupler is ok -- of course in very small print.
 
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Old 03-20-13, 07:11 PM
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The best option is to get it professionally installed. I know a fair bit about this stuff but would never touch anything related to gas lines or venting -> I don't think anyone without a gas license should be installing. (keep in mind too that furnaces sold online may not have full warranty coverage)

If you go ahead with the install, call out a pro to check everything over and setup the furnace.

Among things that need to be done:

1. Gas input testing and adjustment (clocking the gas meter and adjusting the gas pressure if needed)
2. Checking the temp rise and adjusting the blower speed only if out of range
3. Setting the blower speed properly for the size of a/c if you have it

Good luck with whatever you choose.
 
 

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