On Fri, 12 Sep 2008 12:01:17 +0000, 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.

Gee, unless the source of this information is an Engineer, and a H & C
mechanical engineer at that, I would treat that wild donkey guess with a
grain of salt.

Reducing Flue temp will not make your furnace more efficient. Improved
design of the heat exchanger will. Aside: your furnace's gas burners are
inside a 'firebox' which keeps the carbon gas in the flue and not in the
house. The firebox has the house air blown around the outside which
picks up the heat. The better the design of the heat transfer from the
firebox to the air, the more efficient the furnace will be in heating
your home. Heat transfer also has to do with the velocity of the air,
the metal used (better transfer metal will not last as long), and of
course the temperature inside the firebox. ( I may have forgotten
something!)

Replacing the pilot light with an electric gas flame starter (like
propane outdoor grills have) will also save money.