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Old 01-30-2009, 03:37 PM   #46
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HVAC - Airflow Issue


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Makes a real BIG difference in the return.

I usualy use a$$ checks in the supply if I have to dead head like that.

Its basically a simple v.

You have to position it, for the air flow you need in each duct.

So you need to knw which side needs more air.
I believe you, I am just trying to grasp why it makes such a big difference in the return. I understand the dead head of coming out of the AH...although it is WAY quieter than it used to be. I could just make a V and insert in there too, right?

To increase airflow through the filter rack, should I do a 4" deep filter instead of a V design?

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Old 01-30-2009, 03:39 PM   #47
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In summary:

Total Heat Gain: 37,917 BTUH
Total Heat Loss: 61,166 BTUH
Sensible Gain: 34.694.
Referencing back to the load J I did.

Is my problem that my house is losing 61,000 BTU/HR? and at 17 degrees the heat pump can only generate 36,000?
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Old 01-30-2009, 05:22 PM   #48
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HVAC - Airflow Issue


That does require your strip heaters to make up the difference.
And the strip heaters cost a lot more to run, then the heat pump.

The U turn, the air makes at the base, is very restrictive. You don't want an air filter right there. The air is too turbulant.

With your current set up. Air is not moving at the outer areas of the duct.

So your not using the full area of the duct.
Vanes will help the air to be able to use the full area of the duct.


Be carefull, not to make the V too deep, or it can restrict air flow.
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Old 01-30-2009, 06:44 PM   #49
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HVAC - Airflow Issue


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With your current set up. Air is not moving at the outer areas of the duct.

So your not using the full area of the duct.
Vanes will help the air to be able to use the full area of the duct.

Be carefull, not to make the V too deep, or it can restrict air flow.
I understand now. As for the location of the air filter, did I pick a good spot to put it in? Near the middle of the return trunk?


I thought about taking a 2"x2" 90 degree piece of sheet metal and putting in the supply duct right about the AH....would that be an ok size?

I figure I can notch a V in the side of the supply trunk and slide it in rather easily.
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Old 01-30-2009, 09:11 PM   #50
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HVAC - Airflow Issue


The V can be 2 to 4" deep depending on how far it must be moved toward one side or the other, for air flow.
And the wide for eaxh sde should be 1.5 times its depth.

You want to put a radius on it, similar to this drawing.
Attached Files
File Type: pdf Radiused V For Supply Duct.pdf (3.8 KB, 83 views)
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Old 01-30-2009, 09:12 PM   #51
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HVAC - Airflow Issue


The air filter in the horizontal duct is a good location.
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Old 01-30-2009, 10:11 PM   #52
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HVAC - Airflow Issue


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The air filter in the horizontal duct is a good location.
I am still puzzled why a 4" thick filter is better than a 1 filter in a V design....wouldnt a v design offer my sq in for filtration?
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Old 01-31-2009, 05:57 AM   #53
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Because of the way the air is forced through the filter.
At the sides.

A 4" media air filter will have several times the surface area of the V coniguration. Much less restrictive.
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Old 01-31-2009, 05:39 PM   #54
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Quote:
Originally Posted by beenthere View Post
Makes a real BIG difference in the return.

I usualy use a$$ checks in the supply if I have to dead head like that.

Its basically a simple v.

You have to position it, for the air flow you need in each duct.

So you need to knw which side needs more air.


hi guys sorry to jump on your project here but i have a very similar problem with air flow. on two registers in my house i have a 20 degree differnce in air temp from any other register in the house. both of these ducts are 6inch rounds into the same side of the vertical plenum. they also have the same air flow problem from the rest of the registers in the house. do you think if i installed the 'V' at the top of the plenum it would help the air movement and heat differential to both of the affected registers??? thanks so much for your knowledge.
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Old 01-31-2009, 06:13 PM   #55
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Not enough info to say for sure.

Is it a heat pump.
Do those supplies run through an unconditioned area.
Are those runs a lot longer then the ther runs.
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Old 01-31-2009, 07:04 PM   #56
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Thanks for your reply.All runs are through a "comfoftable Basement" 50 degrees or so.
I have taken temps on each run.Each sample was taken 12" from the plenum and at the registers.
The run in question is 25 degrees cooler than the other runs(12"from the plenum and at the registers on the first floor). This is a gas forced hot air furnace.
Thanks in advance.

Last edited by derryank; 01-31-2009 at 07:20 PM. Reason: revise
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Old 01-31-2009, 08:38 PM   #57
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HVAC - Airflow Issue


Changing their take offs to scooped take offs, may help.

Pull your air filter, and then see if they blow out more air. It could be a lack of return air problem.

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