I have been living a year and a half in a 4 level split with a hot air
furnace with the addition of A/C. There are return ducts on each floor
including one in the basement at the floor near the furnace. This is
the only return grille that can be open or closed. The rest are fixed
Someone had marked the grille "open for cooling, closed for heating" .
But I think this is wrong. I believe if you open the grille for
heating, it will pull down the warm air to floor level in the basement
making it more comfortable. My supplys in the basement are at ceiling
level, and since I opened the return grille a few days ago it seems
that it does get a bit warmer down in the basement.
The same might be true for summer. My supplys in the house are at floor
level, so the A/C might not cool as well as if the supplys were in the
ceiling. But if I close the return grille in the basement rather than
keep it open, I think that would help the return grille on the top
floor draw more cool air upward, rather than get sucked down into the
I was just wondering what everyone else did if you had a similiar HVAC
My guess is it is to be kept closed for heating to prevent a venting
problem due to a drop in pressure around the furnace and pull CO into the
I don't think I would like the idea of having a return of any kind near
a furnace, but I really have never looking into the question of weather is
is proper or not. I don't believe it would be safe if it were possible to
close off the area where the return and the furnace were located.
The other issue might be that someone wanted to draw in the cool air
from the basement where it would normally settle and send it through the
home upstairs to help cool it during the cooling season. They did not want
to bring in the cool air during the winter, and would rather leave it in the
With a closed pvc intake- exuast system, chimney draw is never an issue
with a return on the furnace. But even with return closed I dought that
issue would be true as it only pulls more from upstairs.
My cool basement air unless dehumidified for me is more uncomfortable
and harder on my AC since my AC is oversized , leaving me with high
humidity issues all summer. So I keep a dehumidifier on in the basement
at a cost of 3-4$ a month in summer.
This is a fair point. You can run simple the fan without the A/C on in
the summer. opening the basement intake would make that work even
better. But as stated above, your humidity levels rise. It tends to be
"Then said I, Wisdom [is] better than strength: nevertheless the poor
My basement return and supply I usualy keep full open in winter only if
I want to heat it more for usage otherwise I leave returns and supplys
closed, my reason is even though heat rises it costs me more as I clock
the furnace run times and 24 hr run times as much longer with returns
and supply open. In summer I dont want my basement cooled as it is cool
and would be below 70 with supplys open, I have a dehumidifier in the
basement and leave it partialy open just to circulate air. Now and
usualy it is just slightly open for air circulation, since my basement
is tight and all apliances use Pvc fresh air intake and exaust
Hot is a relative term. It may be hotter than the basement but cooler that
the rest of the air on the floor, thus it may return. There may be some odd
reason in a split level to achieve proper balance. I'd experiment to see
Yes I am well aware that hot air rises. The upstairs is the warmest
place in my house even with the vents closed off. The basement is the
coldest. By opening the return grille at the furnace would pull down
the warm air to the basement.
Also, I do not know how leaving the grille open would risk getting CO
sucked in since the blower is at the bottom of the unit next to this
grille and the burners are above the blower. It seems it does not
matter whether the grill is open or not. The burners are aft of the
grille and blower.
Let's give more details and make SQ happy. It will suck in whatever
happens to be near the return vent, and that will probably be, or on
average be, the coldest air in the basement. Then it will suck in the
cold air next to it. As it suck that cold air in, the air above it
will fall down**, get close to the vent, and get sucked in next.
**Hot air sinks when there is nothing beneath it.
Remove NOPSAM to email me. Please let
me know if you have posted also.
I think it is more an issue of air flow than drawing the warm air from the
ceiling down to the lower level of the return. That is, in order for air to
come OUT of the supply vents, it must replace the existing air in the room.
When the basement return is closed, the returns on the other levels of the
house are 'pulling' in the air, and that is in turn being replaced by the
air from the supply vents on those levels.
So, if the basement return is closed it is probably unlikely that the
supplies in the basement are going to be as effective, since the return air
would have to be 'forced' to the upper levels to be 'returned'. Open the
return and you have created a shorter 'path', and hence better flow in the
Be forwarned however that this could also result in less heat to the other
levels, depending on the size of the furnace. Normally they are sized for
the normal living areas of a home which may not include the basement.
I would not have an open return duct in the basement for heating or
cooling. You do not want to create low pressure area in the basment,
this will encourage the entry of radon and slightly increase the risk
of pulling CO out of the furnace...
I leave my output ducts open in the basement but not the returns.
and to the other poster,,,, a dehumidifer will comsume more than 4cents
of power in a month... probably more like 4 cents per hour.
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