If you are experiencing difficulty venting a 90+ furnace in a non-direct application, the below instructions will help you.

Problem:
Venting a 90+ furnace in a Non-Direct (exhaust only) application.

When venting a 90+ furnace with a single pipe(Non-Direct) the combustion air ,which is cold air and needs to be heated, is pulled into the home around doors and windows, additionally the National Fuel Code states that a minimum of 4' clearance from bottom and sides, 1' from top of windows and doors is needed if terminating in a Non-Direct application to prevent pulling flue product back into the home.

Solution:
Use a Direct Vent (2 pipe) application. When doing so the combustion air is pulled from outside via PVC pipe directly to the furnace and not into the home. This reduces clearances by doors and windows to 6-12" based on BTU output.

Conclusion:
By using a Direct Vent application, the chance of pulling flue product into the home is drastically reduced making for a safer installation for the end user.