Welcome! Here are the website rules, as well as some tips for using this forum.
If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Category I Venting Questions
I have a couple of questions on Chapter 13 of NFPA54.
According to 13.1.2, Vent downsizing is permitted if we follow the following rules:
1:total height at least 10'
2:flue collar 12" or smaller not reduced by more than one table size
3:flue collar larger than 12" not reduced by more than 2 table sizes
4:maximum capacity for fan assisted is reduced by 10%
5:draft hood outlet is greater than 4"
Also according to 13.1.7:
we should use the tables 13.1a and 13.1b (b-vent tables) for corrugated stainless steel liner systems, but maximum capacity is reduced by 20%
If I am downsizing and using a corrugated stainless liner, do I have to first reduce my Fan Max by 10% for the downsizing, then also reduce by 20% for the liner?
If I have a boiler such as an older HB Smith that had a 7" breach but may have only had a 90,000 firing rate, can I only reduce this down to a 6" liner according to 13.1.2 #2. even though a 5" liner would work better at increasing velocity to carry away condensate?
Thanks for taking the time to read.