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Old 05-06-2010, 08:58 PM   #1
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Adding new register via tee off existing register


First, I have ample capacity in my HVAC system due to previous owner splitting the house into two separate systems. I did the capacity calculations and determined I can run HVAC to my newly added 3-season room (converted covered porch) now with glass front. I'd like to make the job simple, so I eyed a register in adjacent room (about 12' off from main duct right at furnace) that I thought I could Tee and connect existing duct to one side and a new 15' duct off other side going to a new register in the new room. Any problems doing this? Within codes (generally)? I'd use same size duct as existing. Only problem I have with this is I can't find a specifically designed tee for this application. Are tees made to do this? Or could I cut I accomplish same thing some other way, like cutting hole in a 25' one for first register and then connect new register to end. Any help would be appreciated. I realize running new duct to main trunk can and probably would be the proper solution, but, this room will probably have heat shut off or throttled to it during the winter (expecting it to be several degrees cooler in winter).Thanks.

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Old 05-29-2010, 12:13 AM   #2
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Adding new register via tee off existing register


Didn't know my question was that difficult. Maybe stupid, but not difficult. Let me ask another:

SHOULD I steal air flow from an existing register (or two of them) by T-ing in order to get air flow to a new register (or two) in my Sun Room, OR

SHOULD I just tie into main trunk for the Sun Room (210 sq. ft.) register?

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Old 05-29-2010, 06:12 AM   #3
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Adding new register via tee off existing register


Not all questions get seen.

So some post go unanswered.

The answer to your question is. No, run a new duct for that new room. Do not tap off an existing run.
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Old 05-29-2010, 10:28 AM   #4
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Adding new register via tee off existing register


Thanks beenthere. Will reserch how to do that.
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Old 06-28-2010, 06:03 PM   #5
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Adding new register via tee off existing register


Since my last post I have done considerable research and my sun room is finished except for HVAC. Have a few questions re different options availoable to me. First, the sun room is a glass attachment: 14 L x 8 H facing south, 4 L x 8 H facing west, 14L x 4 W glass roof. The run is 200 sq ft. (was a covered patio -- brick walls, ceiling now insulated to R-30 minimum except for the glass roof section). I have 2 HVAC systems for my house, each separate zone. The only one I think I can tap into is the one that services 1200 sq ft at the moment. This system is a 4T Heat Pump (A/C and Heat) + a 48,000 btu furnace (Heat). My options I I see them are:
1. Add supply duct(s) to main trunk supply to register(s) in ceiling along southern side and manually open/close register(s) as desired. No retun required.
2. Same as above, but convert the system into 2 zones. One exclusively for the 200 sq ft. sun room, the other for the existing areas. Air would be controlled by automatic dampers instead of manually. A return would be requireed.
3. Install a small minisplit system (heat pump) and forget about using it when temperatures drop below 40F. Is a return required? Part of system?

My Questions/concerns:
a) I vision the minisplit system (#3 above) as a doable implementation since I probably can live inside for the 2-3 weeks of real cold time (live in northern Texas). Questions related to this implementation are: recommendation of system, ball-park estimate of system + installation, pros and cons. I understand these to be ductless, but require power and collant tubing. Ceiling vent installation is only possibilty and running power (110 or 220) is no big thing (one wall is the garage with power box). If cost estimate not feasible given the info provided, can I at least get an indication of less or more than option 1 and 2.
b) #2 option with zoning I figured wouLd be simply dropping in dampers, controller, 24v power, etc. Until I started to read about static pressure, slugging, damage to compressor, etc. Servicing a 200 sq. ft. run on separate zone fits into the scenario of "watch out" for slugging. I read about bypass and other options to try to keep static pressure and CFM in a controlable range that wouldn't harm the existing heat pump and furnace. I figured I'm way over my head on this now. Maybe I can reduce my options with a simple question: Given one zone for 200 sq. ft. and a second zone for 1200 sq. ft. am I looking at the impossible? If not, what are the main considerations I should seek answers for to ensure a successful modification of my existing system? Also, can you give me a minimum cost I would be looking at?
c) #1 option is practical I assume. I ran a load model (heat gain/loss) at acdirect.com where I used the least insulation for the sun room. It kicked out a 3T requirement. I understand that this may not be a detailed model since it was free and that my existing system is mostly felxible ducts. But, I have tested the system to heat/cool the areas covered by my other system (i.e., that system turned off and all doors opened) and it responded better than I expected given no supply ducts into the rooms. So, ASSUMING a 4T system is satisfactory, I am at a loss in determining the size and number of ducts to run to the 200 sq. ft. sun room. Is there a safe recommendation as to size and number of supply ducts?No return would be installed in this case since the room would be open to other areas.

So far, I have been unsuccessful getting a HVAC contractor to work with me -- must be a busy season with much higher cost systems installing. Any direction on how to proceed would be appreciated. For example, narrow down my options, then explore any additional details needed to firm up a solution. Thank you.
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Old 06-28-2010, 06:10 PM   #6
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Adding new register via tee off existing register


A mini split is probably your best option.
You can get heat pump mini splits.

Zoning, can present problems. Since the return path could end up being through the rest of your house. Unless you have room to also run a return to the sun room.

You would probably need a 10" supply min to cool that room.
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Old 06-28-2010, 06:21 PM   #7
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Adding new register via tee off existing register


Through the wall AC with heat elements might be another option. Those are DIY install and basic plug in and you're running. A heat pump one with elements is under $1000.
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Old 06-28-2010, 09:52 PM   #8
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Adding new register via tee off existing register


Beenthere,
Quote:
Zoning, can present problems. Since the return path could end up being through the rest of your house. Unless you have room to also run a return to the sun room.
Is the return you are referring to here for the mini-split? Or the new zone off existing system? I assume the necessary mimisplit tubing would go up my outside wall through the roof eave next to the sun room and then to the inside parts installed in the ceiling of the sun room about 3' from the entry. Whereas, the return for #2 option would go from sun room across the attic about 18' to the furnace return.

Quote:
You would probably need a 10" supply min to cool that room.
. How about two 6" off a main truck 10"? Would 2 registers in the room provide any benefit beyound a single 10"? Thanks.

Definitely will look more at minisplits. Do you have a preference for a 200 sq. ft. SUN room. Would you say about 6000 BTUs minimum? Or even less, even if it is a SUN room?
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Old 06-28-2010, 09:59 PM   #9
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Adding new register via tee off existing register


Marty,
A through-the-wall won't work for me -- no wall to outside any more except the glass attachment of the sun room. The heat pump with elements of course. Were you also thinking of a minisplit that has elements? Consider my only access to the room would be through the roof eave just outside and across the sun room ceiling. I'll dig around to see if I can find what you are referring to. More details or specific type/brand as an example would be appreciated. Thanks.
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Old 06-28-2010, 10:59 PM   #10
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Adding new register via tee off existing register


2-6" won't do much in that room.

I was referring to return for the system being zoned.
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Old 06-28-2010, 11:50 PM   #11
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Adding new register via tee off existing register


Beenthere...thanks for clarification on return. The return I was planning would be directly to furnace return, plus a filter in register.

Do you have a QUIET mini-split recommendation? I would prefer a ceiling recessed. The smallest unit I have seen is a 9000 BTU which should be more than needed. I believe it was a Sanyo. I have had no luck finding HVAC people so far. Can this be installed without an expert? I've never done refridgerant lines before, but am handy at both electrical and plumbing. Does it require special equipment to charge/pressurize the lines? I see most are 220v also.

Any comments about portable heat pump/AC mini-split units? I discovered that Home Depot has some. Also saw that Sears assists in sales of outside/inside unit mini-splits, so I have request into them to see what they can offer.

Any specific brand recommendation would be appreciated.

Thanks so much.
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Old 06-29-2010, 12:13 AM   #12
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Adding new register via tee off existing register


I use Sanyo mostly when I do mini splits.

Most mini splits are quiet. Atleast the higher end ones are. Lots of windows, will mean you will probably need 12,000 or more BTUs.
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Old 06-30-2010, 01:04 PM   #13
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Adding new register via tee off existing register


Beenthere,
Thanks again. Saw the 12000 Sanyo. Finally had a HVAC contractor respond. Most installing Mitsibusi Mr. Slim in this area...say their support is great. Looking at the 9000, 21 or 26 SEER model. The 12000 is also in the picture as an option.

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