Where is my air?

[WAYNE3298]

The measured static pressures are highly suspect because of the location. How was the filter sized? What is the calculated design velocity thru the filter? Do you know the actual (measured) airflow? Do you know the airflow needed in each space?
Without the actual design and measured info you can only guess.

[joemach]

"All flex duct is 6" ?

Joemach, can You Physically see this Flex? Starting at the Furnace, & working towards the end of the S.A. Trunkine, & then the sam efor for the R.A. Trunkline, what are the sizes?

On the First floor,... Where are the Supply Registers located, as well as the Returns?

The only area with access to ductwork is in the mechanical area. The rest is a hard lid. I did cut a hole in the ductwork at the furnace and look down the supply trunk. What I saw looked OK. I did not look down the return, but noticed that the the installer downsized the return as it ran (not good). I did not actually measure the size of the duct runs. This little project had me running late for other calls. He live 5 minutes away and told him I would do some research on possible causes and solutions, thus I am here.

The supplies are in the floor and the returns are low on the walls. But the main floor satisfies the thermostat.

I know this issue requires more investigation. His big problem is heating the basement in the winter. Since the issue is the basement, he is OK for the summer since it is about 50% below grade. And the sun is beginning to shine here. So I have some breathing room to get this resolved. But it would be nice to get rid of some of the humidity in the basement for the summer.

What is odd to me is that the main floor satisfies the thermostat but there are certain rooms and the basement that are not comfortable. He needs a space heater for the guest room in the winter.

I recommended closing off the basement supplies and put in a ductless system for the basement. No Go on that one. He does not like the ductless look.

[joemach]

Trunkline duct leakage caused by too much 6 inch flex.

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I am thinking the same thing.

[icy78]

Are there too many diffusers, in the way that there is not enough can, to provide a decent exit velocity at the diffusers so you are actually moving the correct cfm, but not stirring the pot so to speak.

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[BNME8EZ]

Correct me if I am wrong but you need to take the supply static between the furnace and coil and the return between the blower and filter and filter. You may find that your static is way over what you think. If you have the blower curve after you get the static in the new locations you can see what the blower is listed to move at that static which will be less than what you think you have. Another thing would be to take off a register and look down the flex with a mirror and flashlight to see if it is stretched or not which will affect overall performance.

[udarrell]

Have a customer with a 4 ton LP & A/C. Complaint was not enough air flow in basement. Furnace in basement blower set to high. 3300 square feet equal between firs fllor and basement built in 2005. One story and basement. Filter is new (4" Merv 8) and cleaned blower wheel which was not too bad but getting desperate on what is going on. Even pulled the filter and left cover off with almost no change. He had the ducts cleaned hoping that would solve the problem. I am the third contractor to look at this. No one else had a solution.

The 4-Ton evaporator could have a .43" PD, if the filter rack area is undersized causing a 600 to 700-fpm velocity through it, the PD could be .36" or more; that's a 0.79" PD. The static readings are being thrown way off due to various factors occurring in those long flex ducts.

There is no excuse for not having 'a very low cost' model EA3010U La Cross anemometer to check the fpm velocity of the supply registers & the E-Coil & filters. You need to multiply 88 x the mph readings to get 'fpm' velocities.

In his situation, it is probably critical that velocities be between 500 & 600-fpm to get proper room air mix & CFM delivery to all the rooms.

If velocities re real low it will probably need more filter-rack area sizing to drop the velocities to below 300-fpm which is where PD numbers are figured; nobody sizes racks to get anywhere near 300-fpm, therefore pressure-drops are always way higher than those misleading published figures.

You have to start testing the evaporator & filter PDs; otherwise you're actually in the dark guessing & possibly making erroneous assumptions...

[heatingman]

A foot above the coil and 3 feet down the mail trunk.

You need to measure the return side between the filter and the blower, or the blower cabinet itself, and the supply side above the furnace, but below the evap(or remove the high limit and test there)

Then add the 2 readings as if the return side is positive

-.25 return plus .25 supply is .5 (not 0)

Thats your total static.

If you have a means to measure actual flow, I would.

You say its a heating issue mainly?

Where are the returns in the basement? Low?

Ductless a no go? How bout some baseboard heat, or european panel rads, like Myson or buderus make.

Or he can gut the basement and do it right.

There’s only so much you can do w/o pulling down ceilings.


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[heatingman]

The 4-Ton evaporator could have a .43" PD, if the filter rack area is undersized causing a 600 to 700-fpm velocity through it, the PD could be .36" or more; that's a 0.79" PD. The static readings are being thrown way off due to various factors occurring in those long flex ducts.

There is no excuse for not having 'a very low cost' model EA3010U La Cross anemometer to check the fpm velocity of the supply registers & the E-Coil & filters. You need to multiply 88 x the mph readings to get 'fpm' velocities.

In his situation, it is probably critical that velocities be between 500 & 600-fpm to get proper room air mix & CFM delivery to all the rooms.

If velocities re real low it will probably need more filter-rack area sizing to drop the velocities to below 300-fpm which is where PD numbers are figured; nobody sizes racks to get anywhere near 300-fpm, therefore pressure-drops are always way higher than those misleading published figures.

You have to start testing the evaporator & filter PDs; otherwise you're actually in the dark guessing & possibly making erroneous assumptions...

Why not just buy something that reads in FPM?

A Dwyer 460 can be had for under 50 bones. And can easily be used to traverse a resi duct for an accurate measure of airflow.


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[joemach]

The measured static pressures are highly suspect because of the location. How was the filter sized? What is the calculated design velocity thru the filter? Do you know the actual (measured) airflow? Do you know the airflow needed in each space?
Without the actual design and measured info you can only guess.

Wayne,
I am quite curious about the static pressures as well, just way off from what I am used to seeing. How would a partially clogged heat exchanger affect the static? Any thoughts?

Yes, I am guessing. I am by no means an air flow expert, but wanting to learn and get better. I know that I do need to get some tools to test velocity and volume.

udarrell,
Not sure what PD is. But at least you have shamed me in ordering an anemometer

heaterman,
I will do a proper static test when I go back on Friday. I do know how to add static pressure, thanks though.

Still wondering if secondary heat exchanger could be causing this issue.

More info... The house was a foreclosure and empty for several years. The bank had some work done which the current owner has no idea what was done. I did see some drywall dust in the blower section, so some possible drywall work with system running and plugging secondary HE. The a/c coil is new with the condenser so that should be OK, but I will check it on Friday when I return.

I feel there is enough system to handle to needs of this house. I am down to the secondary HE or some other restriction stopping air flow. Just trying to think with all this info; it seems that there is not enough airflow coming out of the system. I do not think that I have ever seen .1 supply static. It seems to me that limited air flow could cause that or a disconnected flex duct.


Thank you guys for all the help and suggestions. I come from a refrigeration background so air flow issues (other than a solid coil of ice) is a little foreign to me. But still learning.

[rundawg]

Thank you guys for all the help and suggestions. I come from a refrigeration background so air flow issues (other than a solid coil of ice) is a little foreign to me. But still learning.

I emailed you a pdf on TESP testing - check your inbox.

[DavidDeBord]

Joemach, ... Correct me if I'm wrong, but, "if" there was a restriction in the furnace, then how would it be possible that the"problem" is only in the basement?

And, unless I missed it, ... Did You post anything about how this System worked in the past?

[heatingman]

Wayne,
I am quite curious about the static pressures as well, just way off from what I am used to seeing. How would a partially clogged heat exchanger affect the static? Any thoughts?

Yes, I am guessing. I am by no means an air flow expert, but wanting to learn and get better. I know that I do need to get some tools to test velocity and volume.

udarrell,
Not sure what PD is. But at least you have shamed me in ordering an anemometer

heaterman,
I will do a proper static test when I go back on Friday. I do know how to add static pressure, thanks though.

Still wondering if secondary heat exchanger could be causing this issue.

More info... The house was a foreclosure and empty for several years. The bank had some work done which the current owner has no idea what was done. I did see some drywall dust in the blower section, so some possible drywall work with system running and plugging secondary HE. The a/c coil is new with the condenser so that should be OK, but I will check it on Friday when I return.

I feel there is enough system to handle to needs of this house. I am down to the secondary HE or some other restriction stopping air flow. Just trying to think with all this info; it seems that there is not enough airflow coming out of the system. I do not think that I have ever seen .1 supply static. It seems to me that limited air flow could cause that or a disconnected flex duct.


Thank you guys for all the help and suggestions. I come from a refrigeration background so air flow issues (other than a solid coil of ice) is a little foreign to me. But still learning.

I was not trying to be condescending, if thats how it read. Just thorough. I dont know you, or what you know. I just know that so many people I know would add the numbers wrong.


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[udarrell]

PD is pressure-drop.
Pull the blower & check the secondary ht-exchanger, if partially plugged that could drop the pressures in all the ducts, & if the take-off to the basement was not done proper it may not deliver any air with other pressures being low. That is why I wanted you to check supply-air diffusers' airflow velocities; nearly everyone ought to be doing it.

[joemach]

I was not trying to be condescending, if thats how it read. Just thorough. I dont know you, or what you know. I just know that so many people I know would add the numbers wrong.


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Heaterman,

I did not take it that way. I appreciate your help.

I like to say, "You never know what someone else knows."

[Tommytools]

Please do not forget to tell us fix!!!

Also if the "fix" is another system show him the LG art frames tell him the wave of the future. LOL!

[joemach]

Joemach, ... Correct me if I'm wrong, but, "if" there was a restriction in the furnace, then how would it be possible that the"problem" is only in the basement?

And, unless I missed it, ... Did You post anything about how this System worked in the past?

Thanks David,

Now you are making me think. There is air flow into the basement and all other diffusers. There are 11 diffusers on the main floor and 6 diffusers in the basement. It is possible that there is just not enough air flow into the basement overall. Although the basement in the front of house is entirely below grade, it slopes down and there is a walk out basement in the back of the house.

No, I did not post anything about how the system worked, OOPS. The current owner has only been there a year & a half and it has not worked properly since he moved in.

Although this is somewhat frustrating and humbling, it is also what makes this trade so interesting. I am very interested in solving this problem.

[HVAC_Marc]

I would like to hear your spewage.

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Well, flex causes a LOT of turbulence, especially if it is installed wrong, which is often the case. Long runs make it worse. Long runs are contrary to most good install practices. In bad install practices, other corners are often cut.

My theory is that excessive turbulence causes a higher static in the long runs only resulting in little to no air out the far end and most of it leaks out of leakage holes elsewhere. Static is not a constant number across the entire duct system.

[DavidDeBord]

Like Reagan told Gorbachev (Sp?), ... "Tear down that Drywall!" Well, he said "Wall", but I hope you get my drift. But, somehow the Basement Supplies are restricted, ....LOL, They may even be Dampered down, & Covered up.

And again, ...."If" there was an Air Restriction in the furnace, then the First Floor would suffer as badly as the basement,.... So what stops air to the basement registers, but allows air to the First Floor?

[shellkamp]

Well, flex causes a LOT of turbulence, especially if it is installed wrong, which is often the case. Long runs make it worse. Long runs are contrary to most good install practices. In bad install practices, other corners are often cut.

My theory is that excessive turbulence causes a higher static in the long runs only resulting in little to no air out the far end and most of it leaks out of leakage holes elsewhere. Static is not a constant number across the entire duct system.

That's most certainly true - you thought your idea would be met with defiance, here?

I was expecting something really out there. :grin:

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[udarrell]

... "And again, ...."If" there was an Air Restriction in the furnace, then the First Floor would suffer as badly as the basement,.... So what stops air to the basement registers, but allows air to the First Floor?

The indication that the air is being restricted to the rest of the home 'is evident by the extremely low static pressures' in the duct system.

Enough airflow is getting through to the main floor to cool it, however, when the static pressures are that low the feet per minute velocity and the CFM will be low exiting the diffusers, resulting in a lower rate of cooling.

I have seen this happen where the static pressure in the ducts was very low due to a restrict at the evaporator resulted in one bedroom not getting any air at all because additionally the takeoff was ill-conceived and resulted in no air flow, yet the small 1.5-Ton A/C cooled the home but ran nearly all he time. .

Therefore I believe there is a partial restriction in the secondary heat-exchanger and that is part of the problem along with improper takeoffs to the basement diffusers.