On 3/1/2014 12:22 AM, wrote:
Closing a cold air return in an unheated room won't impact the combustion
air intake.

No, but it MAY cause the furnace to "short cycle" because the plenum
temperature will rize too high due to restricted air flow. This causes
the high limit switch to shut off the burner untill the blower sucks
the heat out of the heat exchanger, when it will relight. This makes
the efficiency of the furnace drop SIGNIFICANTLY.

Heat can go into one of a couple places. Into the
house, into the cellar, up the chimney. When
efficiency drops SIGNIFIGANTLY, the heat is lost
some where.
Up the stack. When a furnace short cycles it is running in the
in-efficient zone for more of the time. The heat goes up the stack
instead of into the house.
SM: So, the air handler blower is running, the gas is off, and the heat
is going up the stack, you say? I'd think the heat is going into the
building.


So the burner shuts off, and the blower still runs.
How does this make the furnace less EFFICIENT? I
don't picture it. Shutting off the gas lowers
the efficiency? Really?

At church we have converted oil furnaces, which
now run NG. They have a high limit sensor in the
discharge air, when it gets to 110 or 120 it turns
off the flame. The three blowers keep running.

So, turning off the gas now and again makes the
efficiency of the furnace drop SIGNIFICANTLY?
How's that, again?
see:
http://www.ehow.com/info_12081271_sh...-problems.html

SM: Says decresed efficiency, but doesn't explain
the process, and where the heat goes.

http://www.ask.com/question/why-does...ing-on-and-off
http://books.google.ca/books?id=Vdxw...ciency&f=false

SM: This page is not available, or you have exceeded
your limit for the day (my limit seems to be zero).

SM: I still don't see it, sorry.

--
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Christopher A. Young
Learn about Jesus
www.lds.org
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