We have found a few cases where the heating equipment does not operate due to a pressure switch opening, when the vent length appears to be within guidelines.

Goodman has a note on several venting tables to "add" a distance of pipe.

This word "ADD" has been the subject of question, as 50% read this as "ADD" the total distance allowed. others CORRECTLY read to "ADD" the extra measurement to the actual distance of vent, plus the added equivalent distance for fittings.

 

The "UP FLOW" position means: The venting is positioned vertical, UP and out of the installation location. (Out the roof)

The additional restriction of the vertical rise, and the condensate clinging to all sides of the piping (vs mainly on the bottom of a pitched, horizontally vented installation) requires adding distance to the actual equivalent vent length.

 

*MSS920402BN - add 20' of 2" pipe for upflow position

*MSS920803BN - add 10' of 2" pipe for upflow position, add 66' of 3" pipe for upflow position

*MSS920804CN - add 25' of 2" pipe for upflow position, add 58' of 3" pipe for upflow position

*MSS920805CN - add 15' of 2" pipe for upflow position, add 58' of 3" pipe for upflow position

 

1. Maximum allowable limits listed on individual lengths for inlet and flue and NOT a combination.

2. Minimum requirement for each vent pipe if five (5) feet in length and one elbow/tee.

3. Tee used in the vent/flue termination must be included when determining the number of elbows in the piping system.

4. 2 ½” or 3” diameter pipe can be used in place of 2” diameter pipe.

5. Increased Clearance Configuration using (2) 45 deg. elbow.

6. One 90° elbow should be secured to the combustion air intake connection.