Mod/Con equivalant vent length

aemeeich

When figuring out the equivalent vent length of a venting system, do you add up both the intake and exhaust pipes, or do you just add up 1 way?



For example, say the exhaust pipe has a total of 20ft of straight pipe, and (4) 90° elbows. 

The intake pipe also has a total of 20ft of straight pipe and (4) 90° elbows.



When looking at the manufacturer's max vent length - in particular the Lochinvar Knight WBN-081 which says for 2" vent a max equivalent of 40ft - would the above example count as 40ft, or 80ft?



Thanks for your help,



Michael

Ironman

It Applies...

To one pipe, not both added together. The "vent" pipe is the exhaust, not the intake. Since both pipes should terminate in the same pressure zone for direct venting, it is only necessary to calculate the "vent" pipe.

Jack

The way

We do it with the Rinnai's when the two pipe option is used is to figure each pipe individually for fitting equiv, pipe length and then X .5. Doing each X.5 accounts for any discrepancies in the pipe/fittings used

aemeeich

Thanks

Thanks for your guidance.  Sorry about the delay in responding - I wasn't able to log in the past couple of days. 

Steve_210

split venting

some manufactures do allow split venting (not in the same pressure zone)

bob eck

length of vent pipe

Take a look at using Triangle Tube Prestige Solo or Prestige Excellence 95% AFUE condensing gas boilers. With 4" PVC you can go to 100' (must add 90 ells and 45 ells to determine total lengths of the exhaust pipe only.) With there PS250 it only goes 60' These boilers do NOT have to have the vent pipe and fresh air inlet in the same pressure zone. Great boilers.