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Hvac duct work question?

DaBank

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I bought a rental and it has a flat roof. Attached is pictures inside the attic showing what is coming from the unit on the roof. What is the correct way to attach the ducting to the collars, I doubt this is correct?
 

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DaBank

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I just pulled out both ducting and this is what the look like, obviously someone did something and just stuck them through the metal ducts.
 

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TrollerDave

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Yeah the duct is supposed to slip over the outside of the round sheet metal transition. He probably had the wrong sizes and “just made it work”. There are sheet metal reducers you can add to make it work.
The inner lining of the duct goes over the metal and is sealed with duct tape or a huge zip tie.
 

DaBank

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This is how it looks on the roof.
 

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Dalton

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What’s the issue? Is your unit freezing up? Return and supply look same size...not sure if it’s undersized but normally the return will be larger


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rrrr

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Troller Dave is correct. You can purchase sheet metal concentric reducers. Slip the reducer over the existing duct, then attach it with #8 X ¾" long sharp tipped screws, called "zip" screws. Use enough screws to eliminate large gaps between the two joined pieces.

Buy duct sealer, which is sort of a paste, and apply it to the round duct and reducer surfaces before joining.

The flex should be joined by applying the sealer to the reducer, fitting the wire wound inner flex duct over the reducer, then securing the inner flex duct (not including the insulation) with a large tie wrap.

The insulation should be secured with a tie wrap and 4" wide aluminum adhesive tape as close to the plenum as possible, and finished by applying fiberglass mesh tape (the adhesive type used for drywall joints is similar), then applying duct sealer over the tape liberally, making it a complete vapor barrier. This will prevent condensation moisture from forming on the duct when it is supplying summertime conditioned cold air.
 

Dalton

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I think I see the thermostat wire going through the duct


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DaBank

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What’s the issue? Is your unit freezing up? Return and supply look same size...not sure if it’s undersized but normally the return will be larger


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The return and supply are the same size. The condo is 900sqft, 2 bedroom. Thee unit was installed in 2013 and all the ducting is from 1986.
The problem is that the heater will turn off in the middle of the night and the fan blow cold air all night. I tested all the limit switches since the flashing code said it was a limit switch and they tested fine on the multi meter. I then checked the attic and the air duct was ballooning up a little and I saw the ducting inside of the metal. I removed the ducting and have the hot air just blowing in the attic and the heater has stayed on for a half hour now instead of 10 minutes. I believe there was not enough airflow and the system got hot. I what to make sure I correct the ducts properly now.
I also see that air is also coming out of the side of the ducting on the roof that I will have to seal also.
 

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Dalton

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Get ready...you may have undersized ductwork AND a oversized unit


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DaBank

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The new unit was installed in 2013 and has been working good.
This week was the 1st time running the heater this season. The Hoa had a contractor a few months ago in all the attics redoing gas lines and roof drains. I have a feeling the ducts where moved them and then shoved into the metal ducts.
The last 3 months the electric has been almost double what it has been in the last 8 years.
 
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Justfishing

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I just pulled out both ducting and this is what the look like, obviously someone did something and just stuck them through the metal ducts.
In your 2nd pic in post #2. Those metal tabs are meant to be folded in to a metal trunk line. That is how the collar is secured to the trunk.

The inner liner of the flex is pulled over the collar. It is best to attach the liner with a large zip tie pulled tight with a zip tie gun. The insulation sleeve is pulled up and sealed with metal foil tape. Duct mastic, gray goop, can be used to seal air leaks.

Screws are not a goodway to attached flex to the collar although it is done. Of course i have seen many that pull away too
 

SoCalDave

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This has been installed since 2013, has worked perfect.
This week has been the 1st time turning the heater on this season and now having these issues. The Hoa contractor a few months ago was in all the attics redoing gas lines and roof drains, I have a feeling the ducts where taped on and they moved them and then shoved them in to the metal ducts. The last 3 months the electric was almost double what it has every been in 8 years. The AC most have been really working hard and now the heater would just shut down.
And there you have it.
Like others have said connect the ducting the correct way and it should be fine for a rental property.

This is what appears to be restricting the system.
692264-4e18945f0599ef0f60c0cb61dd5e6947.jpg
 
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DaBank

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I am going to go to Ferguson tomorrow and get the supplies I need. Thanks everyone for the suggestions.
 

jet496

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What's the model number of the unit and main duct sizes going through the wall?

They could have upsized the unit when they replaced it thinking they were doing good & ductwork could be undersized.
 

DaBank

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What's the model number of the unit and main duct sizes going through the wall?

They could have upsized the unit when they replaced it thinking they were doing good & ductwork could be undersized.
The unit is a Kenmore /ICP PGD33006K001C1.
I tried to draw up the layout of the ducting, this is the best I could do.
The living room has a vaulted ceiling and no attic and the register is on the wall, the rest of the register's and the return air are on the ceiling.
The condo is 1k sqft and the ducting is from 1986. I am thinking maybe it is time to just replace it, the longest run is maybe 20ft.
 

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jet496

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The unit is a Kenmore /ICP PGD33006K001C1.
I tried to draw up the layout of the ducting, this is the best I could do.
The living room has a vaulted ceiling and no attic and the register is on the wall, the rest of the register's and the return air are on the ceiling.
The condo is 1k sqft and the ducting is from 1986. I am thinking maybe it is time to just replace it, the longest run is maybe 20ft.
That is a 2.5 ton unit (1000 cfm) and 12" ducts are small but most likely that's what it was designed for. I would use minimum 14' mains. Check to make sure all your dampers are open. That would cause airflow problems.

Maybe the fan speed needs increased. They typically come from the factory set on low for the heat mode, which would be fine if you had larger ductwork, and if so you could increase it to Med or Med-High. I would check the fan speed first.
 
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DaBank

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That is a 2.5 ton unit (1000 cfm) and 12" ducts are small but most likely that's what it was designed for. I would use minimum 14' mains. Check to make sure all your dampers are open. That would cause airflow problems.

Maybe the fan speed needs increased. They typically come from the factory set on low for the heat mode, which would be fine if you had larger ductwork, and if so you could increase it to Med or Med-High. I would check the fan speed first.
If I replace the duct work and start with 12" like the cut outs from the roof are now does the rest of the original layout dropping to 6" look fine?
Where is the fan speed located on the unit?
I installed new high flow dampers and the air return when I painted the condo and they are all opened.
 

jet496

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The speed change could be at the motor or on the circuit board. The schematic will tell you, but if you're not electrical savvy, I don't recommend you doing it. I'm betting this will work. The rest of the ductwork should is fine.

The 12" mains are small though. I am curious what the other units are for your square footage.
 
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Flying_Lavey

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The return and supply are the same size. The condo is 900sqft, 2 bedroom. Thee unit was installed in 2013 and all the ducting is from 1986.
The problem is that the heater will turn off in the middle of the night and the fan blow cold air all night. I tested all the limit switches since the flashing code said it was a limit switch and they tested fine on the multi meter. I then checked the attic and the air duct was ballooning up a little and I saw the ducting inside of the metal. I removed the ducting and have the hot air just blowing in the attic and the heater has stayed on for a half hour now instead of 10 minutes. I believe there was not enough airflow and the system got hot. I what to make sure I correct the ducts properly now.
I also see that air is also coming out of the side of the ducting on the roof that I will have to seal also.
I am going to go to Ferguson tomorrow and get the supplies I need. Thanks everyone for the suggestions.
That entire install is fucked up. The square to round "transitions" they have one the unit appear to be from the original unit and don't line up correctly to the current one (you can see the side of the unit cabinet inside the ducts in the pics you took). I would HIGHLY recommend having the system completely reducted. The gas and electric savings would be very substantial based on how horribly everything is done in those pictures. I have to imagine your static pressure is up around 2" of W.C. for the entire system (only rated for .5" of W.C.). Also, I'm gonna go out on a limb here and say you have some warm and/or cool spots in the house as well. Also symptoms of incredibly poor duct work.

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DaBank

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That entire install is fucked up. The square to round "transitions" they have one the unit appear to be from the original unit and don't line up correctly to the current one (you can see the side of the unit cabinet inside the ducts in the pics you took). I would HIGHLY recommend having the system completely reducted. The gas and electric savings would be very substantial based on how horribly everything is done in those pictures. I have to imagine your static pressure is up around 2" of W.C. for the entire system (only rated for .5" of W.C.). Also, I'm gonna go out on a limb here and say you have some warm and/or cool spots in the house as well. Also symptoms of incredibly poor duct work.

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I believe you are talking about the unit being off set from the metal ducting going through the wall? If so the Hoa would not allow those to be moved and the new unit had to sit on the original footprint and the made everything not line up. The ducting in the attic is original from 1986. I bought 14" to 12" reducers that I will be installing tomorrow to fix what the Hoa contractors did a few months ago, it looks like they pulled the ducting out to make room to run new gas lines and then realized that the collars attached to the outside and they had not access unless they removed the square/round duct work on the attic and reseal it, so they just shoved it in and blocked alot of air flow.
I electric bill has never been over $100 in the summer and that is keeping it at 72 but the last 3 months it was over $200 every since the hoa contractor was in the attic and now I know why.
I taped the ducts on 2 days ago and the heater has worked since, so once the reducers are on the correct way I should be ok until I get someone to inspect the ducting and see what it will cost to install new ducting in the attic.
 

Flying_Lavey

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I believe you are talking about the unit being off set from the metal ducting going through the wall? If so the Hoa would not allow those to be moved and the new unit had to sit on the original footprint and the made everything not line up. The ducting in the attic is original from 1986. I bought 14" to 12" reducers that I will be installing tomorrow to fix what the Hoa contractors did a few months ago, it looks like they pulled the ducting out to make room to run new gas lines and then realized that the collars attached to the outside and they had not access unless they removed the square/round duct work on the attic and reseal it, so they just shoved it in and blocked alot of air flow.
I electric bill has never been over $100 in the summer and that is keeping it at 72 but the last 3 months it was over $200 every since the hoa contractor was in the attic and now I know why.
I taped the ducts on 2 days ago and the heater has worked since, so once the reducers are on the correct way I should be ok until I get someone to inspect the ducting and see what it will cost to install new ducting in the attic.
The new and correct reducer will solve your immediate issues for sure.

But yes, new ductwork coming off the unit is totally necessary to keep it running properly for a long time. Cause even if your electric bills are low, you're still DRASTICALLY shortening the life span of the unit. What state is this in?

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DaBank

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The new and correct reducer will solve your immediate issues for sure.

But yes, new ductwork coming off the unit is totally necessary to keep it running properly for a long time. Cause even if your electric bills are low, you're still DRASTICALLY shortening the life span of the unit. What state is this in?

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I understand that the lifespan will be affected. I went back and forth with the Hoa and they would not allow the unit to be moved.
This condo is in Apple Valley Ca.
 

Flying_Lavey

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I understand that the lifespan will be affected. I went back and forth with the Hoa and they would not allow the unit to be moved.
This condo is in Apple Valley Ca.
The unit is probably fine where it is. The existing ductwork needs to change. If the HOA has a problem with that, you can always just refer them to the title 24 code. They can't Trump State building codes.

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CLdrinker

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I’m in Apple Valley as well. I have 10yrs experience in HVAC. I gave up on the trade years ago but I can still help you out if you need it. My dad also did HVAC for 30yrs up here so we know what guys you can trust and who will screw you.

Mike
760 912-3547
 
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