adding air return
I recently enclosed a back porch and made it a regular room. I need to get an air return installed since the room doesn't maintain temperature although it has double pane windows, insulated walls and insulated floor. I have an air return close to where I want to install a return for the room. It is 12 inch flexduct and is about 10 feet from the main return where it is connected. Can I "T" into that flexduct with the new return and still accomplish my goal of more air return for the new room?
You need to have a pro assess the ductwork otherwise it could create expensive problems.
Who installed the supply grill for the room? Is the unit sized for the additional load on your a/c? How does it return the air now and were you told that a return could or would be required? Get a professional now instead of later!!!!!
A lot of relevant data would need to be collected before making more changes.
Originally Posted by ace064
- If it were my home I'd start with a Home Energy Efficiency Audit & do retrofitting to reduce the equipment loads.
- I would then do a manual J room-by-room heat-gain/heat-loss load calc
- Then a manual D duct system air handler analysis
That might indicate whether the existing equipment, plus air handler & new duct system design will deliver adequately, both heating & air conditioning to every room.
You need experts in those areas to get everything right.
…and then there are those here who continually say “you cannot have too much return air”. It seems with that motto you could T-off anyplace along the return ducting and put a return just about anywhere allowed without detrimental effects, right?
Personally, I do not believe a return can go anywhere allowable without bad effects, but plenty here do. I cannot see why anyone here would object to your proposed return re-duct.
Well Brian, the reason I outlined that procedure is because we don't know enough about the situation he is dealing with. (Just trying to justify my prior post.)
He might install a return & T it to the other Return duct & still have heating & cooling problems in that room.
You are right in that no one is going to have too much Return, & that is especially true of RA filter areas.
House has 2 year old HVAC system. Ran one register into new room 10/20 feet. Only air return is thru door opening into main house. Get decent air flow thru one register, but believe adding another register and an air return would improve situation. House size before adding new room was approximately 1450 sq ft. Could go thru all of the tests but wanna bet that the end result will be to get air out of the room via air return to solve problem. Trying to keep this as simple as possible. By the way, the new system is a 3.5 ton with high efficiency furnace. Furnace natural gas fired. A/C is electric.
Additional info-- House has three air returns. Main return in hallway above HVAC unit. 20/25 size. Second is about 27' from main return 10/10 size. Third is small 4x6 size in den approximately halfway between other returns. All windows in house are double pane, Argon gas, etc. Attic has 12 inches of insulation with new roof. No basement.
3.5 ton unit on a 1450 sf house...
I wouldn't T-into return duct.
maybe a jump duct in the ceilings
or a transfer grill over door.
hard to tell without seeing.
lots of info needed...
where are you located?
what size room?
what size ducts did you add?
where are the ducts located? attic?
is there room on the plenum to add ducts?
and that's just to start.
did you call a hvac company to do this
you do know this isn't a diy site??
best of luck.
The cure of the part should not be attempted without the cure of the whole. ~Plato
Very true about the supply side possibly not being adequate, but re-ducting the return as he described couldn't cause any problems, could it?
Originally Posted by udarrell
Originally Posted by energy_rater_La
Very few pros here seem to use returns to control and regulate airflow patterns? Rather they use them to reduce pressure and as an “air path back to the handler”. That means to most pros here a return could go just about anywhere allowed.
3.5 tons. 1450 sf.
Hoboy, here we go AGAIN! What's the furnace, 100,000 btu?
Love to see pictures of the unit.
Doesn't 3.5 tons generally require side/side or bottom/side return to have enough airflow/filter area?
Which makes more sense to you?
- turning your thermostat back and being uncomfortable. Maybe saving 5-10%
- leaving your thermostat where everyone is comfortable. Saving 30-70%
DO THE NUMBERS! Step on a HOMESCALE.
What is comfort? Well, it AIN'T just TEMPERATURE!
Energy Obese? An audit is the next step - go to BPI.org
, or RESNET
, and find an auditor near you.
Doesn't 3.5 tons generally require side/side or bottom/side return to have enough airflow/filter area? - tedkidd
Since furnaces now-days don't have filter racks, that leaves a lot of things to consider:
- Is there only one, or even two Returns with a filters close to a 90-ell with no turning vanes, resulting in much higher velocity through portions of the filter.
- Is the Return on the blower motor side; increases static & lowers CFM some.
- Did they reduce the ducting prior to the 90-ell resulting in a smaller filter area?
- Are all of the Return Air grilles large enough?
Willing to bet the equipment is way oversized.
By the way, to keep the electric bills down, we need to go to the most efficient blower motors possible on the smaller sized longer running furnaces.
A smaller condenser furnace requires more airflow to keep the temp-rise within 60-F, some require even lower temp-rises.
I have seen some situations where they had belt-drive blowers on oil furnaces where the new smaller condenser furnace set-ups will use nearly twice the wattage with considerably longer run-times. This is heating only even without an A/C cooling coil. The customer should always be shown the full-disclosure options so they can make an informed decision.
Hopefully those super efficient motors will get less pricey, both initially & when needing repairs.
Last edited by udarrell; 09-16-2011 at 08:43 AM.
Reason: Yes... Heating only setups...