On Fri, 12 Sep 2008 12:01:17 GMT, JohnR66 wrote:

I heard that adjusting the gas valve on my standard natural gas furnace will
make it more efficient.
By partially closing the gas valve reduces the flame. Although the furnace
would run longer, the flue temp is reduced meaning lower heat loss and
improvement in efficiency.

An analogy is like driving a car the same distance once fast and once slow.
When driving slower, it obviously will take longer, the engine is on longer,
yet fuel usage is less.

I have no way to verify if this is BS or not.


BS. To make a gas furnace more efficient you must either get more BTU's
out of a fixed amount of gas or improve the heat transfer from the flame to
the house. More efficient furnaces have lower flue temps not because of
lower flame temps, but because more heat is transferred to the house. To
measure efficiency compare the flue temp to the duct temp.

Simply lowering the flue temp will also lower the duct temp.