HVAC heat distribution and increasing efficiency

RatLabGuy said:
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- yes he keeps it closed alot (but I told you that so no points!). We keep opening it, but he's 6 and determined to keep it closed... not an easy fight... and at night obviously it must stay closed.
Click to expand...

I'd remove your sons door until he understands the concept of leaving the door open a little better...
 
Now that you have the duct reasonably well sealed, i would go armed with a thermometer next. I think you will find you're not losing all that much heat, sounds more like a problem with airflow to me. Take the register temp in his room and a few others and see what youve got. If it is within a couple degrees then insulating may not help your problem(even though it is a good idea to do).
 
Look up digital LED thermometers on ebay, $2.00 and they're 12volt, hundreds of uses.
 
cold room

I like the suggestion of another duct for son's room or you can replace duct from main supply to floor register with a larger duct. More air will mean more return . Leave return open , cut off bottom of door for at least 1" clearence.
 
Sounds familiar, where did I see that?
 
One observation, you want to even the temp in your sons room and you open the door to help and he closes the door for privacy, Then who cares about the temp other than your son that sleeps in that room.

Otherwise, if you want get the room evened out, and opening the door does help, what you are doing effectively is creating more return for his room. Really sounds like an air flow problem to me. Couple things I may have missed:


Ok I went back and re-read your posts so I'm editing my questions again!
--Is the room cold in winter and hot in summer, or ok and even temp in summer?
--14 6" supplies should be a 3.5 ton ac and approximately 70-100k btu. Is this corrrect?
--You said the trunk reduces, what is the total size 24x? and 20x? and 16x? Also how many supplies come off each section?
--What size return is in you son's room?


Standard rule of thumb: for supply

5"=50cfm
6"=100cfm
7"=150cfm
8"=200cfm

5" good for walk in closets and baths
6" small bedrooms
7" rooms over 13x13

If your son's supply is close to the furnace then there may not be enough air in the system to fill his duct (like a hole at the top of a bucket full of water versus at the bottom of the bucket) You can put in a "scoop" in the duct at the collar in the trunk to catch air for his duct?

It really could be many things. Give me some updates and Ill try to help

Jon
owner:Star Heating
 
Ah, glad you brought this back up.

I got the anemometer and measured all the registers while it was running. Of course its difficult to know if its in the exact same relative position every time, but was close at least.

Most of them read pretty close to the same, around 1.3 m/s held right against the grate. The lowest one was actually in the living room, I'm not surprised b/c that's the only supply duct I couldn't get to from underneath to tape/seal up yet, have to move some junk first.

Just as a review, it's a long ranch-style house w/ gas heat. The furnace is about 1/4-1/3 of the way along the length, in the middle, with kitchen aon the short side, living room is above furnace, then all rooms are on the other side, Jonas's room (~10x12) is at the far end as is ours. Ours is bigger (12x14) but has 2 supplies.

All the main rectangular trunks run the center of the house, with 6" round runs coming off the top, between the joists, with the registers on perimeter walls.
The long side of the main supply trunk starts out @ 20", after ~10' decreases to 16", then after maybe 20' drops to 12" for the last 10' or so.

Closing off 1 of the vents in our room (chose the very last one in the line) did help out a little - but we also keep our door open all the time, even night so we can hear the kids.

Unfortunately the thermometer on the anemometer I got is junk and clearly unreliable.
However what I did notice is that there is a substantial difference in the "time to warm" after the blower starts blowing.
That is, in the living room (which is above the furnace), when the blower first starts, it takes about 15 seconds for the air coming out to feel "noticibly warm"... then after about 15-20 more secs is is at max heat about as hot as it will get.
Meanwhile in Jonas's room (far end), its over a minute of blowing before hitting that "noticeably warm" mark, and then probably 30 secs before hitting heat plateau. And it only blows for a few minutes before cutting off.
Meanwhile, I can hear the metal ducts clanking from expanding/contracting from the temp change - but only on that far side.

Also, since I finished sealing all the joints, the basement noticeably cooler than the house, and the living room is now warmer than everywhere else; it feels like the differential between his room and the others (e.g. hallway, babies room, our room) has decreased a bit.
Since the air flow is fairly close (all within .2 - .3m/s rate), i'm still leaning towards my theory of needing insulation - all the cool air collecting in the ducts is just getting blown into the house, much less so on one end than the other, and maybe the sealing has actually made this effect worse. Maybe?
May try partially closing the registers in the living room to push that air elsewhere and balance it a little.
 
Seal everything up! This may take time and you may change your temperatures in every room in the house. From your comments, it apperas that you may have done this a little already.

Once everything is sealed, insulate and it looks like you have or are planning on it.

Then, you may have to start playing with the dampers/registers some to help balance the system to get everything balanced.

Something that we have in our house and it works very well (but may be too costly for your application) is dampers at various points in our system. These dampers are controlled by a thermostat in a couple of rooms. The thermostat opens/closes the damper more or less depending on the temperature in that room. The thermostats are all wired together to a central point that then controls the on/off of our unit. That way each room can really be individually controlled. One room can even be set for AC and the others set for heat...

retrofitting that system may be out of the question but it would be worth looking into especially for key areas of the house.
 
Yeah I already sealed everything, went through a whole bucket of the duct sealant (that stuff is like bull snot) and about 100 yards of 3" foil tape.
I couldn't believe the gaps in the system, especially the return side; all the return "lines" are just joist and stud spaces that they framed in w/ flashing, but did a miserable job at the edges of.

After doing all that I can tell a difference in teh temp downstairs, and the air flow is notably louder, especially in the living room (which is closest to the furnace)

I may look into those baffles, easier to do now that before everything is wrapped up in insulation. I'll probably get manual ones those, that elecronically controlled business soudns cool - and expensive.
 
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