wrote:

On Fri, 06 Feb 2009 22:51:46 -0500, wrote:

On Mon, 02 Feb 2009 14:53:10 -0800, Kate wrote:

I have a Trane furnace.

One of the heat registers in my livingroom is underneath my sofa.
There are two registers in that room.

Is it safe to completely close off the register, or would it be better
to leave it open a tad?

I am not sure if this could damage my unit, and thought I would get some
expert advice here.

Many thanks.

Kate

Why don't you just deflect it with an extent ion like this:

http://www.improvementscatalog.com/h...deflector.html

There are two registers in my bedroom BECAUSE the dresser is over one.
You guys saying it being blocked is going to damage my furnace?

All closing one or two registers is going to do is make the rooms with
the closed registers cold and make the other registers in the house
provide a little more air. By blocking one 4" pipe out of ten you are
NOT reducing the flow by ten percent. Not likely even by two percent.
The pressure in the plenum will possibly go up .1 of an inch of water
The blowers are generally rated at 1200-1700cfm at .3 inches water
column pressure.
Doubling the static pressure reduced the efficiency of the blower by
half. - not the delivery, but the efficiency in CFM/watt. The average
furnace fan is 10-15% efficient, and produces something like 2
cfm/watt. Actual airflow dropped by one third when plenum pressure
was doubled from .6" to 1.3"
In a study of furnace installations, plenum pressures were in the
range of .25 to 1.9".
That same test shows that a brushless PM blower motor is SIX times as
efficient as an AC split cap motor at low speeds (used in constant
flow systems extensively here in Canada). This amounts to a 74%
savings in electricity used by the furnace - and as much as 25% of
whole house use. The loss of heat output from the inefficient fan
motor increases the gas consumption by 14%.
(I guess that's why I didn't see ANY gas savings when I put in the new
Medium efficiency (80+%) furnace but saw a huge difference in
electrical consumption!!!

If you doubt what I'm reporting you can read the report yourself at
http://repositories.cdlib.org/cgi/vi...7&context=lbnl

The test was done under the auspices of the Ernest Orlando Lawrence
Berkeley National Laboratory at the University of California by Ian
Walker and Jim Lutz. for the California Energy Commission and the US
Department of energy.

VERY interesting reading if you are into that type of thing.

Apparently YOU did NOT READ this research draft.

I suggest you DO READ page 13 wherein the TEST SETUP is described.
Here's an excerpt pertinent to the issue of whether a furnace can be
damaged by blocking heat registers:

"The burners did not operate during the test and no gas was hooked up.
No cooling coils or filters were installed. In real field installations
the cooling coils and filters will act as additional flow resistance
leading to increased pressures across the blowers."

In other words, ONLY the air-handling characteristics of the furnace
BLOWERS were being examined in the test reported in this study, NOT the
heat characteristics of the furnace and their effects.

Blocking supply registers can result in damage to a furnace by
decreasing the heat dissipation from the heat exchanger and its
environs.