Too much "suckage"

[DevoBuzz]

When my blower fan comes on (either during heating or A/C) there is so much negative pressure in the basement (where the HVAC system is) that my basement door shuts. Is this cause for concern? All my return registers are open and unobstructed. I'm wondering if this will cause a poor efficiency of the heating or cooling of the house? If so, how should I correct this?

Thanks,
Ralph

[t527ed]

return ducts need to be repaired. the big danger is you are probably sucking a backdraft on your chimney.

[RyanHughes]

return ducts need to be repaired. the big danger is you are probably sucking a backdraft on your chimney.

That's not good. I experience the same issue. If my basement door is slightly cracked, the return that was added to the basement (I assume when it was finished) can pull the door closed. If the door is open enough, it won't happen. It looks like they just cut a hole into the return trunk, so the force isn't surprising. My basement door is right off the room that has the chimney.

I also wonder if this is the reason why I don't get as much return airflow into the upstairs return--because of the return cut into the trunk right by the a/h.

[t527ed]

That's not good. I experience the same issue. If my basement door is slightly cracked, the return that was added to the basement (I assume when it was finished) can pull the door closed. If the door is open enough, it won't happen. It looks like they just cut a hole into the return trunk, so the force isn't surprising. My basement door is right off the room that has the chimney.

I also wonder if this is the reason why I don't get as much return airflow into the upstairs return--because of the return cut into the trunk right by the a/h.

sucking the basement door shut is always a bad thing, where will it suck from when the door is shut??

[RyanHughes]

sucking the basement door shut is always a bad thing, where will it suck from when the door is shut??

I would think the basement itself? I do have 4 supplies in the basement and a return that I believe is 14x14. I do try to make sure the basement door is left open. The basement hallway essentially acts as one big return plenum. I do have one return on each floor.

[bmathews]

You just need a passthrough. That will take care of your problems.

[t527ed]

I would think the basement itself? I do have 4 supplies in the basement and a return that I believe is 14x14. I do try to make sure the basement door is left open. The basement hallway essentially acts as one big return plenum. I do have one return on each floor.

if it is sucking the door shut there is not enough supply in the basement for the size of the return, you are putting basement into negative pressure.

if you have a gas water heater in the basement fell around the bonnet opening when the basement door is shut and a/c is running.........

[RyanHughes]

Luckily the home is all electric. What you're saying makes sense. Not enough supply in the basement so air comes from upstairs. There really doesn't seem to be a lot of supply air compared to the return in the basement. I do have one supply shut (yet air still pours out) because it seems like it too was just placed on the trunk line. I don't know why they would do that so close to the air handler since the velocity will be so high. Maybe I can partially block off that return... Thanks for your insight to this.

[canesfanforlife]

When my blower fan comes on (either during heating or A/C) there is so much negative pressure in the basement (where the HVAC system is) that my basement door shuts. Is this cause for concern? All my return registers are open and unobstructed. I'm wondering if this will cause a poor efficiency of the heating or cooling of the house? If so, how should I correct this?

Thanks,
Ralph

You should have your duckwork checked by a qualified contractor. Lack of ductwork cause the system to draw air from from anywhere it can. If the door is closed it will suck it from the cracks around the windows, doors, any draft vents of any gas appliances, even from gaps around light switches and outlets. Not only is it very inefficient but it will also bring in outside air pollutants.

[t527ed]

Luckily the home is all electric. What you're saying makes sense. Not enough supply in the basement so air comes from upstairs. There really doesn't seem to be a lot of supply air compared to the return in the basement. I do have one supply shut (yet air still pours out) because it seems like it too was just placed on the trunk line. I don't know why they would do that so close to the air handler since the velocity will be so high. Maybe I can partially block off that return... Thanks for your insight to this.

with an all electric houseyou don't have the danger of a backdrafting chimney to worry about.

rather than causing trouble by blocking the basement return you may be able to undercut basement door or put a jumper duct from basement into another room on the first floor.

[beenthere]

Not enough supply in the basement so air comes from upstairs. There really doesn't seem to be a lot of supply air compared to the return in the basement.

More like not enough return on the other floors.

[beenthere]

Devo.

You don't have enoguh return.
You need to have a contractor to check your system to see what can be done to fix the problem.

[RyanHughes]

More like not enough return on the other floors.

I do have one large return on each floor, and then the smaller one in the basement. I'm thinking if I had a jumper vent installed or maybe block off some of the return in the basement, it would be more balanced. Do you mean lack of return velocity for the two floors above the basement, or not enough return surface area? It could be a combination of what what you and t527ed are saying--not enough supply in the basement and not enough return in the rest of the house. The door will only shut if it's cracked slightly. If it's open, the velocity isn't enough to pull it shut. The door is very easy to move in the first place.