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Brock
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| 06/23/2009 3:24 PM |
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Our master bedroom is warmer in summer and colder in winter, it is the farthest room from the furnace and exposed on three sides. Winter is fine, but I would like to even it out a bit in summer. I was thinking of adding an 8 inch duct booster to the supply for the 2 vents in the room. If I put the booster on the supply side should be closer to the furnace or closer to the room or somewhere in the middle?
I also was wondering if anyone ever puts the duct booster on the return side? With the doors shut I would think more air would flow from the supply ducts? |
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Green Bay, WI. - 4 ton horizontal, 16k gallon indoor pool, 1.8kw solar PV setup, 3400 sq ft |
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Bruce Frey
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| 06/24/2009 2:21 AM |
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I have seen duct boosters actually pull room air through upstream supply outlets rather than increasing the overall supply. It is hard to make something form nothing.
Look carefully at the return path and rebalancing the supply (to put a greater % of air donwstream) before you try the booster. A booster will not help if there is not a good return path.
Also check your duct for obstructions and/or leakage.
Bruce |
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Brock
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| 06/24/2009 9:15 AM |
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It's a new construction. There is a 8 inch line running to the far side and splitting to two 6 inch ducts under the windows, on that same 8 inch line there are two vents in the dining room as well (which I shut and that helped, but still warm. The return is also 8 inch on the closer side of the room. If I put a piece of paper in front of the return it will stay there if the doors are shut, but once I open the doors it falls off. There seems to be good flow, about the same as any other ducts it just a big room at the end of the house.
I was thinking the same thing, if I put the booster after the two taps for the dining room will it just try to pull the additional air backwards in from those vents. But if I put the fan before those splits will it just force more air to leak out those since they are about 1/2 the distance from the furnace? The real reason I ask is because we are about to sheet rock under the mater bedroom and then I won't be able to get at the ducts, at least not easily. I do plan on putting an access point below where ever I put the booster. I plan on connecting the booster up to only run when the AC is actually on. |
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Green Bay, WI. - 4 ton horizontal, 16k gallon indoor pool, 1.8kw solar PV setup, 3400 sq ft |
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Bruce Frey
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| 06/24/2009 11:54 AM |
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Does it heat/cool better with the doors open? If so, you should improve the return with a jump duct or similar. Based on what you descibe with the paper, it sounds like the return could be insufficient.
If it cools the same with the doors open, you need to improve the supply side (and probably the return, too).
My experience with booster fans is that when I see one in a commercial building, I know there is a problem...most likely the run is too long, too many bends, too much flex, pinched duct, etc. or a blocked return. The boosters rarely provide much benefit unless the duct has outlet(s) only at the end. Putting it on the return side may help the bed room at the expense of the dining room, but that may be OK for you.
Out of curiosity, how long is the 8" run? What type of duct construction? Internal or external insulation? Residential duct construction is historically poorly done, so anything you can do to seal it or improve it usually helps. If you have any flex, replacing it with hard duct will help.
Bruce
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Brock
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| 06/25/2009 1:00 PM |
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It's hard to say if it heats or coolers better with the doors open. The only times I notice a difference is when I wake up and walk out of the room and the rest of the home is 1-2 degrees cooler in summer or 1-2 degrees warmer in winter. During the day the doors are both open and I don't notice a temp difference walking in and out.
From the furnace there is a 15 foot 12 inch by 18 inch duct running south from the furnace, then at the end of that there is an 8 inch running west about 25 feet. In that 8 inch run at 2 feet there is the first 6 inch in the dining room, then at about 8 feet is the second 6 inch to the next dining room register, then about 15 feet down is the first 6 inch that runs an additional 12 feet to the first bedroom window and finally at about 24 feet the second 6 inch line that also run an additional 12 to the other bedroom window. These are by far the farthest you could physically get from the furnace and at least 15 feet further than any other registers in the house.
I was thinking of putting the booster either at the beginning of the 8 inch run just off the big box duct or just after the second 6 inch tap off for the dining room but before both bedroom taps. Again the dining room vents are shut off. The kitchen, dining, living and entry hall are really all one space. The entry and living room is almost directly above the furnace.
One thing I wonder about duct boosters is if the furnace fan is in high speed would the booster really add anything anyway? And if the furnace fan is in low speed and the booster is off, would it then reduce flow to the bedroom? |
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Green Bay, WI. - 4 ton horizontal, 16k gallon indoor pool, 1.8kw solar PV setup, 3400 sq ft |
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slenzen
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Posts:265
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| 06/25/2009 2:33 PM |
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| Does it help to shut off vents in lower levels while running AC in order to "push" more cool air to upper levels? (have a loft bedroom that is much warmer than lower levels) |
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Dana1
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| 06/25/2009 4:49 PM |
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Posted By slenzen on 06/25/2009 2:33 PM
Does it help to shut off vents in lower levels while running AC in order to "push" more cool air to upper levels? (have a loft bedroom that is much warmer than lower levels)
Help? Yeah, kinda, but significantly? Rarely.
It's usually more about duct-impedance than insufficient pressure delivered by the air handler. Closing down ducts will increase the pressure (and thus the delivery) slightly, but it also adds to the load on the blower and further unbalances the system. That also increases the amount of outdoor air infiltration inherent in any ducted air system. Keeping the door open to use the common space to lower the return impedance is a good idea, but closing off lower-floor source won't show a whole lot of improvement.
Lowering the solar gain (upgraded insulation R-values, low-E window film, exterior shades/shutters, etc) will be more effective than blocking AC vents on lower floors. Tiny window AC units work too...
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Bruce Frey
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Posts:272
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| 06/26/2009 9:52 AM |
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Posted By Brock on 06/25/2009 1:00 PM
It's hard to say if it heats or coolers better with the doors open. The only times I notice a difference is when I wake up and walk out of the room and the rest of the home is 1-2 degrees cooler in summer or 1-2 degrees warmer in winter. During the day the doors are both open and I don't notice a temp difference walking in and out.
Based on that observation and the paper-on-return-grill that falls when the door is open, my guess is that your return air is bigger problem than the supply. If you put in a booster fan on the supply side without increasing the return capacity, nothing will likley happen.
Look at the possibility to add a jump duct or use the space between two studs to increase the return. If you have a ducted return, the idea of putting a booster fan on the return side may have merit depending on how the return system is set up.
Bruce |
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Brock
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| 06/27/2009 11:20 AM |
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The system is 2 zone with the finished basement being one zone and the main floor being the other. The basement zone is usually off in summer.
My original idea, since I actually want to have our bedroom cooler than the rest of the house was a window A/C or a mini split, but that isn't flying with my wife... So I am back to at least trying to even it out with the rest of the house. What I am trying right now is leaving the circulation fan on in second speed, which runs about 100w, maybe the extra air moving will just even it out more, I had been running the fan in low, about 65w, but maybe that just not enough air movement.
I should add that we insulated (4 inch bat) in all the interior wall for sound reasons since the bedrooms all border the living / dining room or each other, but I think that might be part of why the rooms vary more. The only way they could heat up is from body heat at night since the outside temp is in the mid 60's (but 90+ humidity), so I can't just open a window. The exterior is 2-inch foam with 4-inch bat on top of that. |
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Green Bay, WI. - 4 ton horizontal, 16k gallon indoor pool, 1.8kw solar PV setup, 3400 sq ft |
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Summers
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Posts:43
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| 06/29/2009 2:56 PM |
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OK, Can we try this on for size. I've got a similar scenario -- Fourth level has a interior insulated room about 250 sq.ft. No ductwork currently installed, but fairly easy to add. Only one return @ the HVAC unit on second floor, and adding another return two floors up isn't an option. Since a booster appears to have been ruled out, How About This?
Have seen advertisements on TV for a wall mounted, ductless 110 V unit to cool and heat small spaces. Is this marketing hype or is this or something like it worth a look. Anyone
have experience with a unit such as this? Brand on TV is Mitsubishi ? Thanx Glenn |
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The Cost Effective Answer to Concrete Corrosion |
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Bruce Frey
Registered Users
Basic Member
Posts:272
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| 07/02/2009 3:54 PM |
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Posted By Summers on 06/29/2009 2:56 PM
OK, Can we try this on for size. I've got a similar scenario -- Fourth level has a interior insulated room about 250 sq.ft. No ductwork currently installed, but fairly easy to add. Only one return @ the HVAC unit on second floor, and adding another return two floors up isn't an option. Since a booster appears to have been ruled out, How About This?
Have seen advertisements on TV for a wall mounted, ductless 110 V unit to cool and heat small spaces. Is this marketing hype or is this or something like it worth a look. Anyone
have experience with a unit such as this? Brand on TV is Mitsubishi ? Thanx Glenn
Where does the heat go?
In Europe they have mini-air conditioners that resemble a suitcase on wheels. One type has a hose like a dryer vent to expel heat and the other has a back pack sized condensor with about 2m of flex gas pipe that you hang out a window. Both have condensate pans that must be emptied. We had one of each type in bedrooms when we lived in Spain. They worked great for us!
Bruce
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