Opened 5 years ago

Last modified 3 years ago

#694 new task

Furnace pilot light

Reported by: shorowit Owned by:
Priority: normal Component: Modeling - General
Version: Future Keywords:
Cc:

Change History (1)

comment:1 Changed 3 years ago by cchriste

Upon further investigation (Chapter 33, 2012 ASHRAE Systems and Equipment Handbook) – furnaces manufactured since January 1992 (23.5 years ago) have minimum 78% AFUE. Such furnaces typically have fan-induced combustion air and no pilot light. In these cases, there is little differences between AFUE and steady-state efficiency and little sensitivity to PLR. So, using a simple, constant AFUE value for furnace efficiency is probably OK.

One exception might be a situation where building envelope retrofits cause an older furnace (manufactured before 1992 with AFUE <78%) to become over-sized. Reduced furnace operating efficiency could offset some of the predicted envelope savings. This would be an unusual and increasingly rare case.

BTW, Chapter 28, 1996 ASHRAE Systems and Equipment Handbook has a lot of additional info, not in the 2012 handbook.

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