Improve flow from ceiling registers

Pauline Sallee · 12-01-2011, 12:10 PM

I had a new furnace installed last year. Apparently the people giving me references were getting kickbacks from the HVAC contractor. Let's just say that the Attorney General is investigating him and I can not go back to him for questions. I reviewed a lot of material regarding the installation of the flex ducts and had him rework quite a bit. However, I still have a problem with most rooms not getting the warmth down to the floors (registers are in the ceiling, duct work in an accessible attic). I have looked at how the flex ducts attach to the metal parts and how they are run so that there do not appear to be kinks, rises and drops, or any of the other things I read that would constrict the flow. The size and position of the registers are the same as what the other company suggested. I received two quotes, both were very similar. I have one room, actually the farthest from the furnace, which has great flow. I can feel the heat flowing down and the floors are warm. The other rooms are not that great. Getting on a ladder to get in the top of my closet, I just noticed how warm it is up by the ceiling. But, not so at the bottom of the ladder. I know that there can be an inherent "heat rises" situation with registers in the ceiling. But the fact that my office has great flow makes me think that I have missed something with the duct work on the other rooms. As mentioned, I can not go back to the contractor. This is a 100k 95% efficient furnace. I have had another HVAC company review everything. But it makes no sense to me that the room farthest from the furnace is heated perfectly and the other rooms are not. I have thought about unhooking the flex duct from the boots to see if I am missing something. I have downloaded and reviewed a number of documents on the proper installation. But I don't see anything wrong. My bedroom is the closest room to the furnace and is the same size as my office with the same type of wall and ceiling material but does not have the warmth like the office. Any suggestions?

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**Joseph Hagarty** · 12-01-2011, 01:14 PM

Where are the Return vents located in relation to the Supply Vents?
In every room or centrally located?

Pauline Sallee · 12-01-2011, 03:37 PM

There are two cold air returns. One in the front hallway which is located between the office and the bedroom. The other return is at the back of the house in a 20x40 Great room. These vents are high on the wall. I did think about the fact that it would make more sense for them to be at the bottom of a wall. But I am guessing that neither company recommended changing them because the depth of walls wouldn't accommodate the ducts which look like they are 12" diameter. It did not seem to me that this could cause the disparity between the office and the bedroom. If they were not adequate, I would think it would affect all of the rooms. The company that I hired to check everything was rated highly on Angie's list, BBB, etc. But, other than looking at the inside of the furnace wiring, everything else was a visual inspection from the outside of the system. In checking the exhaust and intake they only stood on the ground and looked up at the roof.

**Alton Darty** · 12-01-2011, 05:03 PM

Got any photos of the ducts? This is a very visual bunch here, we love pics.
Shots of the plenum where the flex ducts tree off could possibly help. Pics of any splices/connections in the duct may be helpful, and wide shots of the duct runs, connections at boots, condition of insulation, kinks and bends...

**Jack Feldmann** · 12-01-2011, 05:10 PM

It might be a simple balancing problem. I had a ceiling register that had very little air flow (1 of 2 in a room). The HVAC guy installed a baffle in one of the trunk lines and fixed the problem.

Pauline Sallee · 12-01-2011, 05:18 PM

I will take some pictures tomorrow. It is easier to move around up there in the daylight. I appreciate every one's help. Regarding the balancing, wouldn't that situation usually send most of the air to the register that is closer to the plenum rather than farthest from it? The run that is the farthest away is getting greater flow.

**Joseph Hagarty** · 12-01-2011, 06:32 PM

The farthest room (one with most air flow), how close is that to the return?

**Jerry Peck** · 12-01-2011, 06:48 PM

You really need a knowledgeable HVAC company review the installation and let THEM make the recommendations. It sounds to me like you are trying to re-design the system, the previous contractor did what you wanted, then your re-design and corrections did not solve the problem, now you are faulting them. That is what I get from your posts about all that you have researched and done.

There is no way that we can tell you what is wrong or what needs to be done based on information you give us.

Get a true professional company, one with a mechanical engineer who can proper assess the system, and let them tell you what needs to be done, then let them do it - if it does not work, then it is there fault, not yours.

The problem 'could be' something as simple as the distribution boxes and ducts not allowing the proper static pressure to build up in the duct work. Without the proper static pressure, the distribution of the air will not be consistent.

You say the supply which is farthest from the furnace provides good air flow and heat, in which case it may have been tapped off incorrectly, not allowing the static pressure to build up, which allows the air to basically flow through the duct system and out the 'open' far end, with no pressure build up to all the air to also equally flow out the other supplies.

Again, though, that is just a guess, and probably wrong we just do not know enough of your specific installation to be able to design it for you - let the professional HVAC designers do that work.

Bob Spermo · 12-02-2011, 08:38 AM

Pauline,

Jerry is correct! You need a reputable and knowledgeable HVAC contractor that makes a business of diagnosing HVAC problems. Your issue could be incorrect diffusers to incorrect unit size to inadequate airflow. All of these items can be tested.

**Wayne Carlisle** · 12-02-2011, 09:32 AM

And there is no way you are going to get the floors the same temperature as head height.

Pauline Sallee · 12-08-2011, 12:36 PM

I had to wait until a sunny day so that I could see in the attic. But, I now have the answer. After the initial installation I could see in the new unfinished room addition that there were sags in the flex duct. I got up on the ladder to look into the attic over the original part of the house and I could see bends and kinks that should not be in the runs. So, I made the guy come back and supposedly this was fixed. What I could see in the open areas and from the ladder appeared to be in pretty straight runs. Yesterday I climbed all the way up into the attic and walked all over. Although they fixed the runs towards the back of the house, they did not fix all of the runs to the front of the house. The office room has a nice straight run. That explains the great air flow to that room. For some reason the other runs were brought up over the truss bottom chord instead of having them nice and straight and under the chord. There is one run going up then down then up again...for no good reason. Yes, I looked for evidence of liquor bottles or some other mind altering drug. The runs of flex duct were that bad. I will have to wait for a day when the furnace can be shut off and then it should be easy enough to unhook the ducts at the plenum and run them in a straighter fashion without all the bends.

Regarding hiring a reputable HVAC company to analyze the situation, I hired one from Angie's list that installs this same type of system. Apparently no one wants to climb around in an attic. He probably did the same thing I originally did, stand on the ladder and look in.

Thanks for all the suggestions.