Question on return air grille in basement

[Mikepier]

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 open. 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 basement. I was just wondering what everyone else did if you had a similiar HVAC system.

[Joseph Meehan]

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 system.

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 basement.

[m Ransley]

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

[m Ransley]

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.

[SQLit]

You want to pull low pressure hot air DOWN? Let me know how this works.

Hot air rises, cool air settles Getting air to do other wise is note worthy.

[Edwin Pawlowski]

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 what happens.

[Mikepier]

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.

[mm]

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.

[dnoyeB]

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 cheaper though.

[mwlogs]

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 basement.

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.

[Mark]

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.

Mark

[m Ransley]

Malkober I said 3 - 4 dollars a month, not cents, I verified it with a Kill-A-Watt.