Ducting question

An AC company came and added heat strips to my heat pump unit. They also added two ducts. When I checked them, there is very little air coming out of them. When checking the ducts that were in place, there's a good flow of air from them. The new ducts are about 20' long on each leg. Could there be too much resistance to push the air that far? I would think a little bit, but there's hardly any air coming out.
I have called the company, but they can't send anyone out until Monday. I went up in the attic, and can't find any place where the flexible ducting is loose or not held together well with those bands.
Any ideas?
Steve
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SteveB wrote:

...
What about returns? If there's no return where these new legs go, they're pushing against a dam...
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I'm not so sure the new ones aren't returns

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dpb wrote:

The above response is apt to be part of problem, there could also be many other factors that need correcting. There is a proper way to install ductwork. The entire ductwork system should be evaluated for proper design & function in accordance with the "Manual D." Learn some of the fundamentals so you will know if the contractor is doing it right: http://www.udarrell.com/proper_cfm_btuh_duct_sizing_air_conditioning_systems.html
- udarrell . com
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ditch the sig. it kills your credibility. and don't post html to a newsgroup. that shows you have no credibility.
new here, huh?
dpb wrote: SteveB wrote:
An AC company came and added heat strips to my heat pump unit. They also added two ducts. When I checked them, there is very little air coming out of them. When checking the ducts that were in place, there's a good flow of air from them. The new ducts are about 20' long on each leg. Could there be too much resistance to push the air that far? I would think a little bit, but there's hardly any air coming out.
What about returns? If there's no return where these new legs go, they're pushing against a dam...
The above response is apt to be part of problem, there could also be many other factors that need correcting. There is a proper way to install ductwork. The entire ductwork system should be evaluated for proper design & function in accordance with the "Manual D." Learn some of the fundamentals so you will know if the contractor is doing it right: http://www.udarrell.com/proper_cfm_btuh_duct_sizing_air_conditioning_systems.html - udarrell . com
--
WISDOM PRINCIPLED EMPOWERMENT COMMUNICATIONS -
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SteveB wrote:

You have a right to your opinion. A sig is ok in any NG & when a link within the post is helpful & on topic I welcome them. I don't have to defend my credibility, all I want to do is help people live a better life. This is an NG that is supposed to be helpful to its readers. I will continue to communicate what is hopefully helpful irrespective of opposing opinions. Live & let live. :-) - udarrell . com
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Along with other replies...did they tap into the trunk or did they put Y splitters off an existing line? The latter is bad. If they put Y's on an existing one, the original one should have reduced airflow. It's just rerouting some of the air...rob Peter to pay Paul.
If they came off the trunk did they then Y the two new ones? I've seen this done effectively by tapping at the end of it with large flex duct then splitting that into the normal register duct run diameter.
I never actually saw one but an experienced AC guy told me baffles can be put in the duct where it comes off the trunk. Is it possible baffles were put in and set too par closed I wonder? Just guessing here.
Of course you know, done right or not, that new air has to come from someplace because the handler can only put out so much. Basically steals a portion from each of the other ducts.
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Actually, when they went in there, they took the duct off of a home made register box that split it to two registers. So, they killed those registers and put it to two more farther away in the same room. Flow should have been the same. There's a gate closed or a problem somewhere else, as it should not have changed much. Anyway, the guy is coming out to look at it, and I'm going to get up there with him and see what he tells me. A couple of young bucks came and did the work, and it looks right. It just doesn't get much air.
Steve
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They should have done a Manual D. That is a calculation that helps determine the proper size and design of the air distribution system. Without that anyone is just guessing. It is difficult to guess right. An experienced professional will use the calculation and use their experience to maybe tweak it. Then there is the installation and that can be done well or poorly. We just don't know enough about your specific situation to say.

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