HVAC - Oversized furnace vent

Opinion

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.