Furnace 80% exhaust question

[street131]

I just bought a replacement single stage 80% 60,000 furnace to replace my old unit. The last furnace had a couple screws in the furnace flue to hold on the exhaust pipe, but this new furnace just has a small lip that the metal exhaust pipe fits over. Am i expected just to have silicone hold on the exhaust pipe? If I dont silicone the exhaust pipe coming out of the furnace, how likely is it to leak gases into the house? Also, where my crimped end of the pipe fits into the next pipe, if I put zip screws into it and can only get it to fit only 3/4 the way in, is that okay or does it Have to fit in fully?

 

[Jim greengo]

3 screw in each fitting is code around here in single wall or b vent.

 

[nadogail]

IMHO, That's why TEK Screws are sold.

 

[Jackfre]

It has to be fixed to the unit as Jim describes. If you are not comfortable with what they have you could buy some small angle clips and secure it with those. Oh, and having a venting question on a gas appliance, make sure you CO detectors are good and put one in the mechanical room.