I have an 80% efficiant forced air furance in good woorking condition and wood like to change from b vent exhaust to a pvc forced air exhaust

Not sure you can do that on an 80% unit. 90%+ works OK but your flue vent temp may be too high. Why the desire to change?

I agree, no can do. Exhaust temps are too high for an 80% furnace, it would melt the PVC

2 great minds working as 1!

i have an 80% efficiant forced air furance in good woorking condition and wood like to change from b vent exhaust to a pvc forced air exhaustIndeed... why? Flue gas temperatures from a non-condensing furnace are too high to be safely vented with PVC. What is the problem with your existing B-vent?