Opinion: 'Over-sized' furnace vent

Inquiry: 00-04

Subject: "Over-sized" furnace vent

Code: UMC Appendix C, Chapter 9

Submitted by: MN B.O. Uniformity Committee

Approved by: Thomas R. Joachim, State Building Official

Issue Date: January 12, 2000

Question: In the case of BTU/h input on a common vent being reduced, may a water heater, or similar appliance, remain on the common vent by itself?

Answer:
Yes. The Uniform Mechanical Code Venting Tables in Appendix C, Chapter 9 address maximum Btu//h input ratings, not minimums.

Comments:

GAMA and other agencies have developed their own venting tables. Some of these tables show minimum and maximum input values. If an appliance manufacturer refers to a specific venting table as part of the appliance listings and testing, then that table should apply to that appliance. Thus, if that specific table lists minimum Btu/h inputs and any remaining appliances do no meet the minimum threshold, the inspector should order corrections/remedy.