09:35AM | 01/03/06
Member Since: 11/28/05
12 lifetime posts
I need some help. Just bought a new house. 1980 sq. ft. on main level, 10 ft. ceilings, 9 ft. in basement that is walkout and unfinished. The builder installed a WeatherKing 92% AFUE upflow gas furnace.

We have four cold air returns. One in each of three bedrooms, and one in the living room. All of them are located on the wall near the ceiling. The house seems cold to me even with the thermostat set at 72. Windows and doors are ok. I sealed all electrical boxes and holes for ext pipes, wiring myself. 2X6 construction with enough insulation to qualify for energy efficiency rebates. So, I'm down to the furnace and duct design.

Are my cold air returns improperly placed. Would that have anything to do with the problems. There is a large cold air return vent in the basement that I decided to "choke off" half way. I don't want to completely block it without checking with someone here who knows. Duct runs are straight (i.e. not a lot of bends or s-curves).

On a side note, the furnace seems noisy to me. Is this because it's a high efficiecy furnace? Or, does the brand suck? I talked with a local HVAC tech who said the fact that the blower compartment is not insulated would only be cause for noise surrounding the unit and would not affect noise coming through the ducts. Is this true? Sorry for the slew of questions and I appreciate any responses that I get. Thanks folks.



02:41PM | 01/03/06
Member Since: 11/28/05
12 lifetime posts
Thanks for the info. Sorry about not including the unit info. It's a 90RJ 105k btuh. It's a small looking unit, but makes some noise.

Any suggestions on the cold air return locations? I've read on other boards that you should have some cold air returns located near the floor. Thanks for the advice.

Also, the dealer is giving me the option of swapping out the unit if I'm not happy with it. Any suggestions given how I described the house. Any A/C suggestions? They were supposed to put in a 13 SEER and put in a 12, so they are already going to have to take that one out.



10:25AM | 01/04/06
Member Since: 11/28/05
12 lifetime posts
Thanks so much for your prompt and detailed replies. I called a couple of local heating and cooling places, and they both, independently, told me something else. They both said that they think the ducting might be slightly undersized. The one said that the builder met the requirements, but just barely. They said the smaller duct work would cause more air flow to be pushed through a smaller space and more noise. Now I'm not sure what to believe. I've always thought the noise from the motor was the culprit as I can hear it through the duct. You seem very knowledgable, so I'll give you the duct dimensions I gave them. Please let me know if you think it's an issue (keep in mind, someday I'll finish the basement and will have to probably add six more runs)

The main trunk directly above the furnace unit measures 20" x 20.5"

From that main trunk I have two trunks that run toward each long end of the house. They measure 8" x 14". One actually is 8" x 16" for about four feet, then reduces.

I have 7 supply runs on one side of the furnace and 6 on the other. They are varying lengths--a few real short (depending on where register is upstairs, and most longer)

These guys are telling me they would have put in 8" x 18" trunks off of the main and this would have reduced the noise. The one is a Lennox dealer and he said he wouldn't even try to sell me a unit without looking at the ducts first. They mentioned something about CFM which means nothing to me. He also said the 105k is sized right.

Am I screwed if I want to add more runs in the future? Do you still think the unit itself is the culprit. I trust your advice--you have nothing to gain from helping me other than the fact that there is a guy out there--me--who appreciates your time and help. Thanks in advance.



09:59AM | 01/05/06
Member Since: 11/28/05
12 lifetime posts
You are awesome. Also, I tried the program that you have linked to and I highly suggest it to anyone. Even someone like me with very little knowledge about this stuff can use it. Your credentials are I trust your opinion.

I input my info based on my recollections of what I've got. Couple quick questions that I couldn't figure from the help menu.

I've got a ranch-style home with a walk-out basement. I called everything on the main floor zone a and everything in the basement zone b. Is that the correct way to look at it? I figure I have to include the basement even though it's not finished right now. I'll finish it someday.

On the cooling estimate. When it asks for the people in each room, is that the number of people that would normally occupy the room, or the number that would be there permanently. In other words, if there are three of us in the house, should I put two in the master bedroom and one in another and leave the other rooms empty?

I calculated zone b as the basement as one giant room. I'm concerned that the zoning means something different than the way I have it calculated.

The program show than I need a furnace of 71,868 and cooling of 41,307. However I may have the people figured wrong and it looks like they add a lot of heat. Also, it shows that I need trunk snap duct size of 2 8X19. Does this seem reasonable for a 2000sq. ft. house in Iowa with a walk-out basement that basically has almost three sides exposed?

I found a site that will sell snap ducting sufficient to cover my needs for about $250. Of course, I'll have to put it in. Is there a trick to doing it, or do I just remove the old and put the larger in its place, hook up my supply runs and tie it into the main? What gauge of steel should I use?

Also what does trunk ducts at .1 per 100 ft. mean?

I realize I just bombarded you with questions again. I'm sorry. I really find your information useful. The program is awesome and I'll recommend it to anyone I know who is building a house to make sure they get the right system for their needs.

Thanks so much for your help



06:20AM | 01/06/06
Member Since: 11/28/05
12 lifetime posts
Sorry to bug again, but I'm really finding this stuff interesting. Too bad I didn't do that before we built the house.

The link that I'm looking at for duct supplies is:

Per the heatpro program, it is suggesting that I have 8 x 19 trunk duct sizes as opposed to my current 8 x 14. As you can see from the link they sell either 8x18 or 8x20.

What size would be the best? Better to go a little high than low?

What gauge should I buy? Seems to vary from 26 to 30?

Also, I am assuming that I will need to resize the cold air return trunk as well. It is also 8 x 14. Am I correct? It would seem return size should equal supply size, but I'm less than a novice when it comes to this stuff.

You have been an amazing source of info. I appreciate it. I realize you have better things to do than reply to ciltep all day long. Thanks again.



10:13AM | 01/06/06
Member Since: 11/28/05
12 lifetime posts
In an effort to sound completely naive, what is the return box? Do you mean each cold air return grill that is located upstairs? Or the part that feeds into the side of the furnace at the bottom. My returns upstairs (one in each bedroom and one in the living room + one in the basement at the ceiling height)all run down through the studs on the interior 2 x 4 walls. Each bedroom has a return grill that is the width of the distance between the studs (16" - I think). The one in the living room spans is twice that size (i.e. there is a stud right in the middle that you can see when looking up at the grill. I don't have any other returns than that. Thanks.



06:13AM | 01/09/06
Member Since: 11/28/05
12 lifetime posts
Any thoughts on that last question? Sorry to see that some people tried to "slam" you in some other posts. You're just trying to help. I appreciate it, even if some of them don't.

On a side note, I think I found an oops on my cold air return. I was looking at some of the runs that are boxed in the floor joists that run over to the cold air return trunk line. Basically, the returns run through the studs from upstairs and into a cut out through the floor. The return then becomes the floor joist which has some carboard with a silver coating on it stapled to the bottom of the joist. Those returns then run over to the cold air return main trunk (am I describing that correctly?). Each of the runs is "capped" off at the end with the same cardboard stuff and is taped with foil tape. All of them are like that. However, I noted that on one of the runs near the furnace, there is no cap on the end. I stood on a ladder and wiggled my head between some plumbing so that I could take a look. Sure enough, there is a large 16x16 hole cut into the cold air return right near where it then runs down vertically and over into the furnace.

Can this be correct? Shouldn't that end also be capped off like all the others. I can't imagine that I'm getting a lot of suction from the other returns, especially the one in that run, with an exposed 16x16 hole cut right in the top of the return trunk. To me, and again I'm a novice, if that end were also capped off, I would get a lot more pull from the other return areas. What to you think? I realize that my description probably sucks. I'd love to email you some pictures of my system if you'd be interested in looking at them. Let me know. Thanks and have a great day.


take it easy on HKestenholz....he knows his stuff.



08:04AM | 02/02/06
Member Since: 11/28/05
12 lifetime posts

Quick question. You mentioned in an earlier post that there is no trick to duct installation. You also mentioned that my existing duct work would not be able to handle over 4 tons of cooling. I had a Lennox guy tell me that my duct trunks would be too small to add additional runs.

I don't get it. I've done some searching on duct design, and I can't seem to find much. I've looked at other newer homes as well. What I've found is that a lot of them will have larger runs than I do, say 18 x 8 for a certain length only to reduce down to 12 or 14 x 8 for the last 10 feet of the run.

Is that so the installer can save money, or does it make a difference depending on how many air runs come off of one trunk and within a given length. When I talked to the Lennox guy, he was interested in knowing how many runs came off each trunk on each side of the furnace.

What am I missing here? I plan on adding five more runs in the basement sometime soon. It seems to me that adding more runs will reduce the air pressure within the trunks (more holes to push air down to). I don't understand why then my existing ducts wouldn't be ok. I also want to make sure that if I'm running additional runs, I'm not screwing up air flow to other parts of the house( mainly upstairs)

Am I making this more complex than it needs to be? Or, should I just tap into the existing caps (builder put in for me) and run my runs?

Thanks for any advice you or others might have.



06:06AM | 09/25/06
Member Since: 09/24/06
2 lifetime posts
I also have a Weather King 90 top discharge in a house I recently purchased that was installed 2003. The furnace is located in an unfinished crawlspace. The main return air plenum is located on one side of the furnace and connects to the cold air return ducts throughout the house. The opposite side of the furnace has a plenum connected as well that draws cold air from the crawlspace. I have talked to the previous owners and they don't know why there is a cold air return from the crawlspace. Its an old house and there is considerable infiltration from the exterior into the crawlspace. Why would the contractor have installed this connection? Why not pull all of the return air from the occupied floors?



12:19PM | 10/11/06
Member Since: 10/10/06
1 lifetime posts
I am wondering what the correct size of air return vent I need for my home. We have one in the floor of the living room that is approximately 6x10. The second one was in the dining room/kitchen floor (simply panned in between two floor joists)and measured 12x30, however we've remodeled those two room and have replaced the subfloor.

Now it's time to cut the subfloor for the return but am not sure what size of hole I should cut. I would prefer to use a cast iron grill cover and the company I want does not make one in the size of the previous return hole. Also, the location of the panned joists is not the most convienent so I would love to be able to downsize if possible.

The house is a 2-story and is approximately 1600 square feet (excluding the basement). Any input or ideas would be most helpful! Thanks!
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