booster fan or mini-split

[Bushum]

I had a new furnace and a/c installed and at the same time additional ductwork to a new addition. The new ductwork is 2 6" supplies and 1 8" return. The airflow is almost non existent so I need to do something. I looked into Fantech fans which look like high quality but even so the consensus here seems to be they don't work. Fixing the duct work with bigger runs is NOT an option as space is extremely limited. The system was sized with this addition in mind (about 20% of total house) so there should be plenty of airflow available. Do these fans really not work or is it just another Goodman scenario where some people just don't like them?

My other choice is a mini split which sounds like it will work well but obviously a lot more money in addition to the thousands I just spent on the new equipment. If I do go this route will the return and low flowing supplies effect the performance of the mini split? Do I need to close them off to keep the room sealed and separate?

[beenthere]

Properly applied, they can work.
You got a new system sized for the addition?
Or you got new equipment, and they reused your old ductwork, and just tapped the 2-6" supplies off of it.
I wouldn't close off those supplies if they increased equipment size.

[Bushum]

Or you got new equipment, and they reused your old ductwork, and just tapped the 2-6" supplies off of it.

Yes this one. They used two previously unused 6" taps off of the original plenum. What I meant by sizing for the addition is the a/c went up 1/2 ton for the additional sq. feet.

I wouldn't close off those supplies if they increased equipment size.

Even if I go with a mini split?

[lost_art]

Yes this one. They used two previously unused 6" taps off of the original plenum. What I meant by sizing for the addition is the a/c went up 1/2 ton for the additional sq. feet.



Even if I go with a mini split?

i wouldnt close off the supplies even with a mini split. ive seen this happen so much a customer adds an addition and the contractor gives the impression that it will work but just hooking new ductwork to an existing setup usually causes more problems. im sure if you had any rooms that had a slight temp difference from the main part of your house they are probably even warmer now. even if the duct work was "big enough" to handle the increased air flow it probably wasnt sized and ran properly from the beginning.

do feel bad this is a very common problem especially with the new home construction. when a duct system is sized and ran properly you will get the same amount of airflow out of every register regardless how far away from the system it is. its just like your blood pressure its at your heart and the same at your little toe.

either way you look at it your not traveling down a cheap route. you need to redo all of your duct... lol... or put in a mini split to properly condition your new area.

[beenthere]

You increased the size of the new A/C. It needs X amount of air flow weather or not your addition is cooling right. If you shut thos 2 supplies down. You may not have enough air flow, and could shorten the life span for your new A/C.

[dash]

Larger system,same ducts,tapped off for new supplies instaed of bringing them off the new,likely larger plenum,bad idea,poor air flow to addition.


Get a real Pro to evaluate the ducts.

[Bushum]

According to this site http://www.engineeringtoolbox.com/eq...ter-d_443.html my 2 six inch supplies should flow 600 cfm. I don't know how accurate that is but I'd say they are flowing less than 100 cfm each just by comparing to my computer fans. (I know this isn't a great comparison but just know the airflow is almost non-existent) The Fantech fans say they can boost at least 300 cfm each. If the system was sized correctly and these fans actually work I think this should be enough airflow. Assuming the contractor installed something that had a chance of working. Now I know I can't ask prices but would you guys even take on a job as small as installing duct fans or is this a strictly DIY fix?

[Bushum]

Larger system,same ducts,tapped off for new supplies instaed of bringing them off the new,likely larger plenum,bad idea,poor air flow to addition.


Get a real Pro to evaluate the ducts.

The ducts work ok for the rest of the house. All rooms are within 1 degree except the new addition which has virtually no airflow. It's hard to explain but the furnace and new addition are right where two roof lines of the old house come together and structurally it is a nightmare. The very low crawl is also restrictive to the plenum because there are footers everywhere and there is no room to do it over without major work to much more than just the HVAC. My only realistic options are get the new flex duct to flow more or get a mini split. My house is only worth $130,000. I'm not going to throw 5-10% of it's worth into something that will get no return.

[Bushum]

You increased the size of the new A/C. It needs X amount of air flow weather or not your addition is cooling right. If you shut thos 2 supplies down. You may not have enough air flow, and could shorten the life span for your new A/C.

Ok that makes sense. So whatever I decide those will stay. Thanks!

[beenthere]

Your 2-6" don't flow 600 CFM, if they did, you wouldn't hear anything but the air coming out of them.