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Old 01-21-2012, 08:19 PM   #1
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Major pressurization issue


Just moved into our newly constructed house and we are having a number of HVAC issues. One of them is a pressurization problem. When the basement HVAC kicks on, it blows a tremendous amount of air from the basement up to the first floor. You can hear it whistling through the bottom and sides of the basement door. When you you slightly open up the basement door, you can feel the door being "buffered" by how string the airflow is.

Just the opposite happens when the first floor HVAC kicks on. You get a tremendous rush of air going from the 1st floor down into the basement.

I uploaded a couple of videos to youtube so you can see just how much air I am talking about. If you stand next to the basement door, it will literally blow your hair back.

The HVAC sub-contractor and the home builders site manager were here the other day, and they said they didn't know why it was happening and don't have any solutions at the moment. I don't think they plan on doing anything to fix it, and will just keep giving me the run-around.

Any thoughts as to why this would happen and what can be done to fix it?

Thanks!

Here are the videos I posted to youtube:

In the first video, when you see the door fly open, that is me simply letting go of the door and the wind blows it open. These are not hollow-core doors either. They are relatively heavy doors.



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Last edited by stickner; 01-21-2012 at 08:21 PM.
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Old 01-21-2012, 08:27 PM   #2
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Major pressurization issue


Are they (2) individual units or one zoned unit?

Alright I will venture a guess, its (1) zoned unit with a common return air, when your lower level calls for heat your fan is still running at high or med speed putting too much air to that level, the excess is looking for a way back to the system, via the door openning.

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Old 01-21-2012, 08:50 PM   #3
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Major pressurization issue


these guys are still building down from you,and don't know whats going on with HVAC techs on site that is BS.all that air movement when the unit starts up is the funaces "return air" pulling from anyplace it can.so you have 2 systems 1st flr and baemant?or one for the entire house??? and where are your return grills?are the units standing in a closet with a ducted return or louvered doors? these are gas fired furnaces with AC.what is happening sounds like there are no return grills...
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Old 01-21-2012, 09:19 PM   #4
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these guys are still building down from you,and don't know whats going on with HVAC techs on site that is BS.all that air movement when the unit starts up is the funaces "return air" pulling from anyplace it can.so you have 2 systems 1st flr and baemant?or one for the entire house??? and where are your return grills?are the units standing in a closet with a ducted return or louvered doors? these are gas fired furnaces with AC.what is happening sounds like there are no return grills...
We have a total of 2 units in our house. The "primary" unit is in the basement and it is dual zone. This unit takes care of the basement as well as the first floor.

The basement has one cold air return that is I believe 14"x25". The first floor also has one cold air return that is the same size. The basement is currently unfinished and wide open. The cold air return in the dining room is also wide open.

I validated that both cold air returns are working by placing a tissue over them when the system kicks on. The tissue is immediately sucked up against the grill.

This is a gas furnace with central AC. The furnace has ducted returns.
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Old 01-21-2012, 09:55 PM   #5
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Major pressurization issue


the basement is wide open raw no walls or registers if so where is that return?or is there a ceiling with supply registers.that door in the video is that a basement doorway with the unit behind you in the shoot.like i said all that air moving is return air ....supply air can't pressurize a room that much.do you have a stat in the basement and one up on the 1st floor for that primary unit

Last edited by biggles; 01-21-2012 at 10:15 PM.
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Old 01-21-2012, 10:00 PM   #6
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Major pressurization issue


It sounds like your unit is staying in high speed when only one of the zones is calling for heat (or I assume cooling) and the single return area in that zone cannot bring in sufficient air to compensate for the units output. The solution is probably to rewire the unit so it comes on in a lower speed when only 1 zone is calling for heat. The return air ducts may also have to be upsized.
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Old 01-21-2012, 10:19 PM   #7
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It sounds like your unit is staying in high speed when only one of the zones is calling for heat (or I assume cooling) and the single return area in that zone cannot bring in sufficient air to compensate for the units output. The solution is probably to rewire the unit so it comes on in a lower speed when only 1 zone is calling for heat. The return air ducts may also have to be upsized.
Interestingly, when either the basement or first floor zone is running, they pull cold air from the basement AND the first floor.

When the basement is running, should it only be pulling cold air return from the basement area?

Same thing for the first floor, when it is running, should it only be pulling cold air from the first floor area?
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Old 01-21-2012, 10:41 PM   #8
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Originally Posted by stickner View Post
Interestingly, when either the basement or first floor zone is running, they pull cold air from the basement AND the first floor.

When the basement is running, should it only be pulling cold air return from the basement area?

Same thing for the first floor, when it is running, should it only be pulling cold air from the first floor area?
Normally the colder returns do not have dampers that open and close. They're just oversized sufficiently to prevent problems.
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Old 01-22-2012, 12:25 AM   #9
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Major pressurization issue


It sounds like your next call should be to your lawyer and let him call a qualified contractor.
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Old 01-22-2012, 10:25 AM   #10
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It sounds like your next call should be to your lawyer and let him call a qualified contractor.
I am afraid that is where this is headed.
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Old 01-22-2012, 10:29 AM   #11
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Major pressurization issue


I think you need a professional balance performed on your system......
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Old 01-22-2012, 11:16 AM   #12
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Major pressurization issue


I would also bet that the installing contractor did not use a zoning panel, had he the furnace fan would run at, at least (2) speeds, low for a single zone and high for both zones.

Its a simple fix, I am surprised the installing contractor is not responding to the problem.

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Old 01-22-2012, 12:01 PM   #13
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Major pressurization issue


yep, you need a skilled contractor to look over the system. on a zoned system there should be a barometric bypass damper/pipe to relieve or reroute the excess pressure when 1 zone closes and to run it at a lower speed. be prepared for a fight and pizzing match as the primary contractor will discredit the 2nd one and say he is lying etc etc so it ends up with a lawyer and a LOT of hassle.
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Old 01-22-2012, 12:07 PM   #14
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Major pressurization issue


Post pics of the furnace, and the duct work at it.

Looks like the basement has more supply ability then it does return.

Shut off the furnace at the thermostats. Cover the first floor return with cardboard, tape it fast so its air tight. Then turn on the heat for the basement. And see if it still blows out the basement door.

If not, then you need the supplies balanced. if it does, then check to see if you have a fresh air intake connected to the return duct.

Does your system have a bypass damper?
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Old 01-22-2012, 02:20 PM   #15
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Originally Posted by beenthere View Post
Post pics of the furnace, and the duct work at it.

Looks like the basement has more supply ability then it does return.

Shut off the furnace at the thermostats. Cover the first floor return with cardboard, tape it fast so its air tight. Then turn on the heat for the basement. And see if it still blows out the basement door.

If not, then you need the supplies balanced. if it does, then check to see if you have a fresh air intake connected to the return duct.

Does your system have a bypass damper?
I did the following:
  • Taped off the first floor cold air return
  • Turned on the heat for the basement
The result:
  • The amount of air blowing from the basement to the first floor was DRASTICALLY REDUCED. There was still a little bit there, but not even close to what it was. Not even close.
A few pics of the furnace.
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Major pressurization issue-f1.jpg   Major pressurization issue-f2.jpg  

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