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Old 04-29-2013, 06:55 PM   #1
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Single Air Return


Hi Folks, new homeowner here. Just purchased our 1873 sq ft house, built in '05. Our Master bedroom and bathroom have windows that face due west with no shade whatsoever.. naturally they're warmer than the rest of the house... a good 3-4* F. Our master bed, master bath, and master closet all have 2 air registers each.. but they still don't cool the areas off at all. I'm going to look into planting some shade outside the windows, and maybe tint, etc, but my main question is about the air return. The only air return, 25"x25", is located in the hallway towards the front of the house, marked by the red square in this crude picture (exterior walls are to scale in this picture, interior are not.. but they're generally pretty close.) Should there be two air returns in this size of a house? I've seen some newer homes, single story, lately that have two large returns, and they're only slightly larger than my home. I would think having another air return (maybe in the location marked with a blue square?) could benefit my home.. but I'm not sure.

If that were the case, what sort of cost is involved in adding a return? Is that a pretty large undertaking for an HVAC tech or contractor?

[edit] I guess I should add my home is a single story, on slab. I'm unsure of the size/capacity of my HVAC unit.

Thanks in advanced!
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Last edited by NegativeTen; 04-30-2013 at 08:07 PM.
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Old 04-30-2013, 04:48 AM   #2
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Single Air Return


I would put the additional return inside the master bedroom.

Depends on the attic as far as how hard it is.

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Old 04-30-2013, 09:17 AM   #3
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Single Air Return


to directly answer your question,

cost varies depending on location and tech. It is a fair undertaking as you have to split the return duct and extend it to the new location. then you have to cut open the drywall etc.

if you are handy you can do it yourself.

if it were me, I would have the system checked for the following, prior to adding a new return.

1. find unit size (1,2,3,4,5 ton??)
2. have evaporator coil checked and cleaned if necessary (not the ducts, just the coil!!)
3. have the static pressure checked at the air handler.
4. check cfm from each register in the house, with and without registers installed.
5. review the installation of the ductwork. if flex duct was installed be sure it is installed correctly (google how to properly install flex duct)

once you have all of that done, your tech can begin to make a plan to correct your comfort issues.

My house had similar issues. we found the unit was too large for the ductwork. The static pressure was way too high. The small amount of flex duct (17 feet) was causing a huge static pressure problem. The return 25 x 30 was too small, causing a restriction. we also found massive house envelope air leaks.

to fix my house, I replaced the flex with steel, added a second return, replaced all the registers and sealed up the house and the ducts as best I could. we also replaced the standard fiberglass air filters with 4 inch media filters for better filtration. These changed got the static pressure down to within Manufaturer specs. All told, the house now has no hot or cold rooms, the dust in the house is way down (desert dweller here!!) and the electric bill dropped by 25 percent. Note that I am just a regular guy and I did all the work myself. considering the electric bill drop, I am guessing that the pay back was less then 1 year. It was hard work in the attic, but worth it.
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Old 04-30-2013, 12:44 PM   #4
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Single Air Return


I am in a similar situation to the OP where I want to add a new return. In my case I want to add a return to the ceiling of my 2nd story hallway, as there is only a return halfway up the stairs right now. I can find most of what I need at the big box stores, but I have not yet found the return air box I want to install in the ceiling. Is there a good mail order place other than Grainger that anyone can suggest? I am in Northwest Houston, TX, if anyone can suggest a local retailer that would work too. Thanks.
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Old 04-30-2013, 01:23 PM   #5
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I got all of my "parts" from a local sheet metal fabrication shop..

If you can, make sure that the return box is at least 7 inches deep... thats the minimum for depth if you want to use a 4 inch media filter... you dont have to use it,, but its a nice option to have available.
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Old 04-30-2013, 06:54 PM   #6
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Single Air Return


Well last night was pretty miserable for us, we like to keep the house around 72*F to stay comfortable in the warmer months, and the entire house was 71-72*, while our bedroom was 74*-76*. The air coming out of the vents was between 58-62*. We couldn't sleep so I went and dug out the ladder (12ft vaults in the mbr, 9ft in bath and closet) to check air flow rate, informally. The left most vent in the bedroom was barely blowing at all, while the right vent was blowing normally.. the bathroom and closet (both left, north of the 'normal' vent) were blowing inadequately as well. I'm convinced that this is one of my problems. The puzzling thing is that I checked the other two bedrooms, on the other side of the house, and they were blowing properly. The unit is in the attic above the laundry room (which shares a well with the garage and master bedroom). Theoretically, if the unit wasn't sized properly, I would think that I would have problems at the vents further away from the unit, not the ones closest to it.

I'm going to get in the attic this evening and poke around to look for any potential 'obvious' things, broken ducts/connections, specifically. I'll also make note of the brand/size/model of my unit while I'm up there. Are there any other things I should be looking for?

Also, as an aside, the previous owners planted Holly bushes around the outside condenser, would this impeded proper cooling? They're probably 6-8" from the grills on the unit. Should I remove them? My gut is telling me yes (or, at least move them further away.. but probably just get rid of them..)

Thanks for the replies!
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Old 04-30-2013, 07:38 PM   #7
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Single Air Return


Post pics, so we can see if they are blocking off air flow to the condenser.
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Old 04-30-2013, 07:52 PM   #8
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Here's a couple quick pictures.. I wasn't up there for long, had to run a couple errands.
Lines 3 and 4 are the MBR lines, 3 being the one that isn't blowing at all, and 4 blowing quite well. You think it's because of the near 90* turn?

Linking, rather than attaching, I didn't resize them:
http://justinrowan.com/ac/20130430_190605.jpg
http://justinrowan.com/ac/20130430_190611.jpg
http://justinrowan.com/ac/20130430_190620.jpg (this is line 3 where it terminates)
http://justinrowan.com/ac/20130430_191302.jpg (the unit itself, didn't get any model specific information.. I assume I'll need to pull the cover for that, and the unit was on so I didn't want to take it off)
http://justinrowan.com/ac/20130430_191307.jpg (runs to the front [east] side of the house.. they all blow quite well, because there are no bends maybe?)

While I was up there and the unit was running, I didn't see any signs of a leak in the ductwork (no insulation blowing around, etc).. but obviously I don't know precisely what I'm looking for.


I'll go outside and grab some quick pics of the condenser, and edit this post.

[edit]
Here's a couple pics of the condenser outside with the plants (I think it's Holly?).
http://justinrowan.com/ac/20130430_195514.jpg
http://justinrowan.com/ac/20130430_195533.jpg
http://justinrowan.com/ac/20130430_195610.jpg

And here's the back of the house that gets all that western sun. Just by stepping from the grass onto the patio I can feel a temperature increase on my arms and skin.. just from the cement and brick radiating heat.
http://justinrowan.com/ac/20130430_195827.jpg

Last edited by NegativeTen; 04-30-2013 at 08:06 PM.
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Old 04-30-2013, 07:53 PM   #9
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Air is very stubborn about changing flow directions. Even with the doors all open to the problem area, return air is going to have difficulty getting back. Look at the drawing and count the number of 90 turns it must make from that area of the house to the blower. I'd also be interested in where the register is located in the mbr.

As beenthere mentioned, a return in the mbr is a must. And If possible I would take it one more step and increase the duct size to that area. Why duct size is often reduced as distance from the blower increases is a mystery to me and it's usually a mistake.
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Old 04-30-2013, 08:10 PM   #10
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For what it's worth, with the MBR door shut, I can feel air being pulled from under the door (albeit, not much.. the carpet is pretty high and the door probably needs to be shaved down a little bit more). So would it be more practical to add a single return to the MBR, or to add a larger return outside the MBR for that side of the house. Even so, do you think that would really solve my problem here? And are we talking a couple hundred bucks, or a couple thousand? I'm pretty handy, but I'd much rather leave a closed system that needs a perfect set of checks-and-balances to the pros.
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Old 05-01-2013, 09:54 AM   #11
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great pictures!!! they (to me) really tell the story.

in the first picture, it is very apparent that your flex duct is not pulled tight as per the manufacture instructions. The bends are good, the runs are nice and flat, , but there is no way in the world that the rest of the run, past the bend, is pulled tight. Without being tight, the air flow is very turbulent and thus no air to your vents and as a bonus, high static pressure in the system.

also in the same picture, I dont like the take off boots that were used. I believe, from my reading, that you really should have angled take off boots at the transision from the steel duct to the flex duct. Additionally, its my understanding that take offs must be at least 6 inches from each other. Yours are grouped together (which made it easy for the installer!!! as they only had to cut one hole!!).


take a look at this website http://askweldin.com/Flex.html and this website too http://www.alabamahabitat.org/sustai...lers_Notes.pdf


I also see a very large flex duct running directly above the steel main duct. Is this your return??? if so, I would either replace it with steel or make sure it is pulled very tight. Note that I am talking about pulling the inside wire wound part tight, not just the outside. And how tight is tight??? very very tight.. so tight that the interior ridges and valleys between the wires are almost no existant.


Picture 4 (the unit) shows that the return has a bend in it and it looks like a fairly sharp bend and again, its not pulled tight...

you are correct that the others are flowing air because they have no bends, but they also to have the minimum of 6 inches between take offs.

your next task is to draw out the way the ducts run for us... draw up a top down view and we can get a better feel for what is needed to fix this up!!!

Oh and get the plants away from the outside unit (condenser).

The good news is that this does not look like a very hard fix!!!!
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Old 05-01-2013, 10:15 AM   #12
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I forgot to add that you can try a couple of things in the mean time to get more cool air into the master bedroom...

1. keep the master bedroom door open
2. remove the registers in the master bedroom as they maybe restrictive. This is a temp fix only. it should allow more air to enter the room.
3. change your air filter
4. close the curtains in the master bedroom to block any sun coming in. Alternative might be to hang a blanket (temporary) over the window to help insulate and seal out any heat gain. again, just temporary.
5. I dont like this idea, but I have seen it used here in phoenix... again a temp fix.... after the sun goes down, water down the back wall and patio. the evaparation makes the wall cooler... again, I dont like this idea for the long term, but it might help for the short term.

Last edited by bobinphx; 05-01-2013 at 10:18 AM.
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Old 05-01-2013, 10:56 AM   #13
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Thanks for the informative response. When I get home this evening, I'll reread your post and evaluate your suggestions, and also try to get a better idea of how the ductwork is laid out and get a sketch up.

We do sleep with the master bedroom door open, and the air filter is brand new. We don't have curtains on the windows in the MBR, only blinds. Beyond that, we have arches above the windows that have no coverings whatsoever. You can't really tell from the picture, but we have a pillow stuffed in the arched opening in each window to block light and heat. We'll get some proper window coverings soon, though! I have read about 'watering' the wall and patio, I might give that a shot, as I've got a spigot right there. I'm also going to look in to planting a bit more shade outside the window there.

Thanks for all the informative responses, keep 'em coming!

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