Use of existing flue to exhaust an infinity condensing gas furnace

[ron3637]

Installer planning to run exhaust up an existing flue which which is not in use. Can a condensing furnace's, infinity 58mvb-100,, exhaust be exited in this manner or must it be exhausted through a wall to work properly . Will it cause a decline in effiency or any other problems thanks ron

[second opinion]

Installer planning to run exhaust up an existing flue which which is not in use. Can a condensing furnace's, infinity 58mvb-100,, exhaust be exited in this manner or must it be exhausted through a wall to work properly . Will it cause a decline in effiency or any other problems thanks ron

Answered in your previous post. Yes

[ron3637]

I am a little confused. can you clarify what you mean by yes--It's ok to run the exhaust in the flu's chase or there may be problems thanks ron

[kwilcox]

yes, its ok but your roof might look a little funny with a PVC candy-cane coming out of the chimney...

[ron3637]

How much will the PVC stick out above the chimmney ? thanks

[ZZZRSC]

If they're only running the vent, I thought no elbows were necessary. The inlet would require 180 degrees. Pipe has to be sized properly and possibly insulated depending on length and outdoor temps. Roof venting is recommended by Carrier. Is it going to be a non direct vent 1 pipe? I would be more concerned that they are not getting combustion air from inside the house. See fig. 43 & 44, 24" max height, 12" min. height required above roof,maybe only a few inches above chimney? http://www.docs.hvacpartners.com/idc.../58mvb-1si.pdf

Don't quote me, I'm not that familar with these.

[ron3637]

Is it beter to draw combustion air from inside the house?

[ZZZRSC]

I'm sorry I wasn't very clear on that. No, it is better to use outside air. Air in the house has contaminants that might cause problems with these furnaces.