On Thu, 09 Dec 2010 14:27:24 -0500, wrote:

On Thu, 9 Dec 2010 05:42:21 -0800 (PST), wrote:



But if you turn the blower OFF when the furnace is off like most real
people do, then it is less relevant.

MOST people turn the blower off???
Not up here. Running the blower on low speed keeps temperatures even,
and makes the air filter a lot more effective.

I would bet 90%+ of the HVAC installed in the USA runs the blower only
when
the furnace is heating or the AC is cooling, not 24/7. In a typical
house with an
unfinished basement or crawl space, I would think running it
constantly would be
a significant waste of energy from two standpoints. One is that it
obviously uses
a lot more electricity. Second is that while circulating all that
air around you are
running it through the basement or crawlspace, attice, etc that is
unheated and
you are losing heat through the duct work on each pass.

With a properly designed system, I don't see the need for constant
circulation.



You don't see the need for it, but the VAST majority of new furnace
installations in ontario are set to run the blower on low, constantly.
All 3 contractors we contacted for quotes for my daughter's furnace
(multi-story condo) strongly recommended it.


Strange that Canadians do that.
Maybe makes sense for that multi-story condo building.
Wouldn't make sense for my house.
Small 3-bedoom, no "zoned" heating.
Though you can "zone" by closing vents and doors to some extent.
In some situations a blower always running during heating cycle would
work that works - to distribute fireplace heat is one.
In my house the thermostat is located in the hallway adjacent to where
we spend most of our time - bedrooms, bathroom and kitchen.
The dining room and living room are cooler. Maybe a degree or 2.
And they are as big as the other rooms combined.
This suits us fine.

When we have company and are in the living room/dining room body heat
and sometimes cooking heat spilling from the kitchen keeps those rooms
comfortable.
When it's hot though I have to lower the thermostat to keep those
rooms cool.
I could reverse all that by moving the thermostat if I wanted to, but
it works how it is.

What would happen if my blower was constantly running during heating
and cooling times is this.
In winter heat would be lost through living/dining room walls and
windows, and when the A/C is running heat would be gained through the
same.
All of this come down to personal tolerance for uneven heat in
different rooms, and how much you want to pay.

There's absolutely no question that in my house a constantly running
blower would cost me both in electricity and natural gas.
Because it would move heat or cool air to places it's not needed.
I used to argue with my wife all the time about heating and cooling.
She can't take it cool in the winter, or warm in the summer.
I gave up the argument. You got to know when to fold 'em.
But I never even started an argument with the laws of thermo dynamics,
and don't intend to.

BTW, this reminds me how car A/C compressors kick in on defrost mode.
I used to pull the A/C plug when winter rolled around because I never
had a problem defrosting with just undried hot air and didn't wait to
waste a couple/few HP all winter just to blow dried air on the
windshield.
I stopped that when I heard the compressor seals could suffer from
disuse, but mostly because I lost my "need for speed."

--Vic