The fans suggested have more static capability (able to overcome more resistance to air flow),then a propellar type blade.You seldom ever see a propellar type fan blade conected to a duct.
You saw little improvement when closing off the upstairs grilles,but we are not sure your existings system is clean,and moving all the air it should be capable of,could be dirty coil,blower wheel,etc..
blower fans in hvac ducts
Thanks. The machine is brand new, so it is unlikely to be a weak motor or dirty coils and we cleaned the ducts out when we were working on the house. At the time I knew little about ducts and simply assumed a system that had been there 30 years must work okay.
Now I can see partly why it does not work. One of the trunk lines starts after the first bend from a 12 x 6 and then goes to a 10 x 8 rather than the other way around. Then it has to do 3 90 degree bends and go another 25 feet before exiting in one of the 2nd floor bedrooms. I am thinking of dismantling this part of the trunk and keeping it 12 x 6 the whole way. Does this seem like a good idea? It would be costly, because I would have to tear out new drywall, but somehow I have to solve this.
I bought a $30 Equalizer from HD and put it in the 12x6 register in the worst bedroom. The cfm went from about 23 to 55 which is still not enough to heat a 12x14x8 room, but still it was an improvement.
12X6 is the same resistance to air flow as a 10X7 ,so 10X8 is less resistance.
I'd look at installing turning vanes in those turns(90° elbows,I assume),they would reduce resistance to air flow.
You could try running flex duct from the larger portion of the trunk,to a point as far as you can go in the 10X8.That's called a helper duct.
Posting the diagram of the duct would help a lot.
I did not know one could post on this website anything but messages. I shall post the diagram (as soon as I figure out how) but need to add the location and direction of the joists and main supporting beams, because they are probably the cause of the duct design in the first place.
I also have digital photos of the system that could be added. Would these help?
post the pics!
Originally Posted by rkthomas13
photos of duct system
These photos are not of my house, but a neighbor's, which has exactly the same system. Mine are unfortunately covered in drywall.
1. photo shows the central support beam and joists which are 16" on center. In the background you see the rear trunk line that turns up to split and feed the kitchen and, above that, the back rear bedroom.
2. photo shows the furnace, plenum and one trunk line before it makes a right angle turn to go down the length of the house (30x36').
3. photo taken under trunks just outside plenum shows beams plus the large return ducts.
4. shows a branch of the trunk plus one 6" that service the living room and the masberbedroom on second floor. These lines have plenty of force.
5. Shows rear trunk line coming over the return just behind it and coming out to go to kitchen duct.
This is the maximum 5 files I can send on this post. I shall try to send others on the next post. If I can find a way to digitize my diagram, I shall post it also. That would probably do the most good.
Need a professional HVAC person to physically check this out
Everything you are doing is just a guessing game. You need to have a balance person check this thing out and determine if you do or do not have the numbers necessary for supplying the building.
I agree, but have been unable to find anyone who clearly knows what he is doing and is willing to do it. The guy who installed the new furnace turned out incompetent on duct work. He installed a new furnace and never even warned me that the ducts did not produce adequate airflow. Maybe I am too hard on him, but would not a pro be required to measure the airflow and say if it is adequate when installing a new furnace?
I recently worked with a hvac design school, but they looked at the system and just gave a promise to work on it once they install a heat pump in the attic to cover the top floor. No assurance that they would be able to get adequate air flow to the other side, although with this much duplication and expense it seems likely they could. But why not try to get the existing system to work first at relatively low cost. If it tryly can not, then spend the money for a whole new system.
I have met very few pros who actually measure air flow. Probably about 1 in 20 do it, whether with a flow hood, annemometer or by static pressure in conjunction with manufacturers charts. Most just feel the register flow with their hands or do nothing at all. It is a sad state of affairs.
Originally Posted by rkthomas13
Remember, Air Conditioning begins with AIR.
So what city and state are you in? Some one on this site should be able to do this work.
If you ask your friends, neighbors, co-workers, etc... I'll guess that over 75% will note at least one room not having adequate airflow.
Of the major home system areas (electrical, plumbing, framing, HVAC), I'll wager the HVAC sub-system is the LEAST professional and WORST implemented.
Why? Most home owners know right away whether plumbing leaks, hot water is inadequate or fuses pop. However, it may take a homeowner years to "discover" poor HVAC performance - weather changes and demand of the HVAC system is hugely dependent on changing weather conditions.
ductwork gives inadequate air flow
Good idea. I now have two houses with the same problem, one in Arlington, Virginia and the other in south Alexandria, Virginia, just outside Mt. Vernon. (This is northern virginia, just outside WashDC). If anyone is looking for a challenge, please contact me at email@example.com. This is not a problem of money, although I do not to avoid buying two new heatpumps. . I expect to pay and realize nobody guarantees results from old ductwork. It is probably a matter of trial and error, but why not try the cheaper way first?
A local pro design school says I should put in a heat pump in the attic in both cases with ducts for the second floor, cap the ducts on the first floor and use the existing gas furnace and ducts on the basement and first floor. The only drawback is the expense and the duplication, although this may be right. In Arlington I have to build a new roof to enclose the ducts on half the house,(this house is a '50s small colonial with a '60s large addition).
But I still think examining the old ducts and seeing if helper ducts or some modifications, maybe booster fans, etc., might do the job. Two new heat pumps is a lot of money. But they do not want to do trial and error first. The design school guys say they must first put in the heat pump and cap the existing ducts before they can know whether the existing system can handle both sides of the house. Does this make sense? Wouldn't it be better to plug the registers of the second floor so no air exits and then see if this forces air to heat or cool the far side of the house. They say simply plugging the register still leaves air coming into the ducts of the second floor and does not augment the airflow going to the other side of the house. This seems wrong to me, but what do you guys think?
how find an hvac designer for duct work?
I would appreciate anyone's comments on my overall plan. I have a 1950s three level house with an addition from 1964. Heating came from a gas forced air furnace in the basement. The ductwork was added-on to the addition and never worked properly. Now I have yet another addition. I want to take down the existing ducts and install a bigger unit in the attic and put up ducts that go down to the main floor rather than up. Is it easier to force air down that up? Is it best that the same person design the system as installs the ductwork or can that be divided up? Can one hire a special hvac inspector to be sure it is done right before closein?
The basement I am making into a semi-separate, 3 room unit with its own heating. It does not need cooling. What would you suggest for heating this 400 sq. ft. space and a 200 sq. ft. space on the side that was formerly the underground garage? I have gas and electric there. I am thinking of putting in a ventless fireplace in addition to regular heat both upstairs and in the basement, because they give off a lot of heat in case the system is overwhelmed on very cold nights.