On Sun, 08 Feb 2009 08:56:27 -0500, Bubba
wrote:

On Sun, 8 Feb 2009 05:28:55 -0800 (PST), wrote:

On Feb 8, 1:35Â*am, Erma1ina wrote:
wrote:

On Sat, 07 Feb 2009 21:49:28 GMT, Erma1ina
wrote:

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...2923067-heat-r...

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 Â*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. Â*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...le=3527&contex...

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.

Â*I did read it, and I did understand it. And what's more I can test
the static pressure in my system if I want to. I know how and caould
make the required test equipment very quick;y and cheaply.

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."

Fully understood.

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.

And the airflow change (which can be tetermined by the pressure
change) is all we need to know Â*to know if there will be a problem.
Accorsing to the information shown in the graphs included, it is
obvious it is not going to cause a problem unless there are fewer than
something like 5 outlets and you block one.
In my house there are mo less than 12. For most of the time I have
owned the house (26 years - 20 with the original (at that time 8 yr
old) furnace) at least 2 of those registers were completely closed,
one has been under/behind a couch, and 2 are shut off about half the
time when 2 bedrooms are not needed (daughters not home).

Add to that the FACT that many homes have balancing Â*dampers installed
in the branch runners - my house has at least 3 (exposed in the
finished basement) Two of them are set to about 2/3 flow (on the six
inch pipes heading to the upstairs of the 2 story) to restrict the
flow to the upstairs so enough heat gets into the main floor.

This was all checked when the new furnace was installed about 7 years
ago, and the plenum pressure/airflow was all well within the specified
parameters. Both the pressure difference across the exchanger, the
heat rize across the exchanger, as well as the pressure in the plenum
was checked, and all were well within limits.
I don't have the pressure numbers but IIRC both pressure readings were
well under an inch of water.with the fan speed adjusted for the
desired heat rize. The installer did say the ducting was "generous".

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

For Pete's sake, just admit you didn't understand the study YOU cited.
Stop trying to kick up a bunch of dust in a lame attempt to obscure that
fact.- Hide quoted text -

- Show quoted text -


It sounds to me like he understood what he cited perfectly well.
BTW, if it's so damn bad to close a couple of registers, why do the
vast majority of homes have them? New construction here has
virtually every output register with a closeable flap and user
operated lever.

and do you actually know trader, that if all duct systems were
properly sized and installed, you would not need a closeable flap on
them. Unfortunately, most systems are installed by the lowest bidder.
Its all driven by the builder. He builds the home, hires the lowest
bidding subs and profits at the highest sale price. This process
happens in some of the least expensive and most expensive homes
around.
Bubba


Which is why on a proerly designed and set up forced air heating
system you will generally find the main plenum/duct gets smaller the
farther it gets from the furnace, and not all heating duncts coming
off that main duct are the same size, AND there are balancing dampers
in at least several of those "take-off" ducts heading to various parts
of the house to balance the air flow.

In cheap contract housing you seldom see these features.

That said, if you don't want your bedroom, for instance, as warm as
the nursery or the livingroom, you partially (or fully) close off the
heat flow to that room. (whether the system was properly designed or
not)