HVAC DIY

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I will soon have my addition construction drawing from an architect. The architect does not do HVAC drawings, he mentioned I need to find (he has some he can recommend) HVAC contractors who can do HVAC drawings based on his plan. These HVAC drawing and then “fed’ into his construction drawings which then become integral completed blueprints.
Once I have HVAC drawings I need to decide how to install all HVAC stuff (forced air furnace, A/C, condenser, ducts). I expect it will be quite expensive. I am trying to stretch my small budget and see if any of HVAC work I can do myself and if it makes sense and can save me money at the end. Does anyone have any suggestion regarding what I can reasonably do to cut the addition HVAC work? I am handy, have extensive remodeling experience but no HVAC experience. I probably won’t be able to install furnace and A/C but can I install ducts? Will I be able to save money this way? Any advise would be appreciated.
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wrote:

Ask some friends if you can poke around in their houses to see what their HVAC system looks like. Then you will know if it looks like something you could do.
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If you look at a portrait of the Mona Lisa, will you know if you can paint?
I'm not sure looking at finished ducts tells if you can install duct.
--
Christopher A. Young
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On Wed, 16 Dec 2009 18:17:54 -0500, "Stormin Mormon"

Well, I know it wouldn't help you. But, that's okay, because I'm not talking to you. The guy my advice was directed towards is smart. He probably has a rough idea of what his skill level is, and seeing what the stuff looks like may be a big help.
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wrote:

When Stormin looks at the Mona Lisa, he's proly wonderin how it would look pasted on his shower curtain, next to the Elvis print.
--
EA

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On Wed, 16 Dec 2009 08:15:04 -0800, ls02 wrote:

Yeah, easy to do. It's the system design that seems the hard part (something I'm looking into myself right now and it's not as simple as just slapping a few bits of metal together)
By 'addition' is this construction onto an existing property that already has ductwork, furnace etc.? Or is it a separate building which will have its own heating?
If it's got its own heating (so you're going to have to invest in some sort of heat source anyway) I'd go with water-filled radiators (as Existential Angst says), gas-fired combi boiler, and heat your hot water using the same boiler. Pipes take up a lot less space than ducts do, and you'll have a lot more control over where you want the heat.
cheers
Jules
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On Dec 16, 12:36 pm, Jules

I am not saying it is easy or hard. Just to me installing ducts and registers appears to be more feasible for me to do then any other part of installing forced air equipment. It is possible though that even ducts are out of my reach or it won't save much $$$ at the end so it is best to hire pro to do all work. That's why I wonder what if any I can resonable do myself to save on HVAC work.
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wrote:

A lot depends on what kind of ducts you run. When I lived up north I installed metal myself but I did have a fishing buddy that hooked me up with the fabricator so it was just putting them in. All of the drops were run with round pipe and that just snaps together. The ducts themselves needed the lips bent over and the S Slips and drive flanges driven in. It was really pretty easy. A wrap of silver tape sealed everything up. The trick is getting a decent price from a fabricator. They are a pretty closed community. A lot won't even talk to you if you are not in the trade. Ever been to alt.HVAC? ;-) If you use duct board and flex duct, you need the tool to cut the angles in the duct board without breaking the foil. use silver tape, (not "duct tape") and get a plastic wiper doodad to seal the tape down. The HVAC supplier usually gives them away. Keep your flex straight and pulled pretty tight so it doesn't have a lot of ridges to slow the air flow. Some say it is best to run it on 1x running boards where it crosses truss chords to give yourself a flat surface. Seal all the joints with mastic when you are done.
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On Dec 16, 3:14 pm, snipped-for-privacy@aol.com wrote:

I am not going to use flex ducts, only straight metal ducts. I believe all ducts components (round ducts, elbows, registers, etc.) are available from big home centers. I have experience snapping them together and I nkow how to seal joints with aluminum tape and furnice cement.
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That were me with the Amcoraire. When I bought it, I roughly figured 3 years to amorize it. Now, it's gonna pay for itself in less than 2 years. I have a 12K microprocessor controlled version with a seer of 18. Central unit (old (for around here)) has a seer of 8 or 9. I plugged the Amcoraire into my Kill-a-watt for a couple of days (summer time). In 55 hours it used 6.8KWH!!!!! My honey and I like it cold in the bedroom. I have the "setback thermostat" set the house to 79 at 2300. I set the bedroom a/c (gotta love those zones) to 69 degrees. If I build another house, it will have several of these mini-splits (they are heats pumps also). Also one outside unit can run two inside units. The only wart I have found so far is this: the fan does't run all the time during the heat phase.
wrote:

I am not going to use flex ducts, only straight metal ducts. I believe all ducts components (round ducts, elbows, registers, etc.) are available from big home centers. I have experience snapping them together and I nkow how to seal joints with aluminum tape and furnice cement.
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Hey, good you popped up! Yeah, I often cite your older post in the useless alt.hvac.
6.8 kWhrs for 55 running hours? Or cycling on and off for 55 hours?
Is your unit 120 or 220V?
You cited 500 W at full load. Another poster here cited 10-12 amps at 120 V. If yours is running at 220-240 V, both would be in the same ballpark. If yours is running at 120, then there is a big big diff!
What does your killawatt read when you first turn it on, and how does it ramp down, current wise?
--
EA



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Insulated metal ducts are not available at any big box store I've been to. Just ends. Just about all installations these days use flexduct. It is far faster to install, lighter, and because you do not have as many junctions you have less risk of leaks.
You ask an installer to use all rectagular metal duct instead of flex and your quote will be thousands higher.
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Do flex duct have more resitance to air flow? I remember they are not recommended even for bath exhaust fan.
Also if metal ducts are not insulated, can I insulate them myself? Do I wrap ducts with special duct insulation wrap?
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I think you will be hard pressed to find a bath exhaust fan in a typical house built in the last 20 years that does not have a piece of 4" flex connecting it unless it is already at the exterior wall.
You need to size the flex appropriately. For short to medium runs use 6", for long runs use 8". If you have a lot of long runs in one direction then you use 12" or larger to a square hub and then run your multiple 6s from it. If you are doing it yourself you can fabricate boxes from ductboard. They make flex takeoffs for ductboard.
Metal duct work is insulated on the inside, not the outside. I believe there are condensation issues with insulating it on the outside. Metal duct work is galvanized but long term exposure to water will eventualy cause damage.
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wrote:

I think you will be hard pressed to find a bath exhaust fan in a typical house built in the last 20 years that does not have a piece of 4" flex connecting it unless it is already at the exterior wall.
You need to size the flex appropriately. For short to medium runs use 6", for long runs use 8". If you have a lot of long runs in one direction then you use 12" or larger to a square hub and then run your multiple 6s from it. If you are doing it yourself you can fabricate boxes from ductboard. They make flex takeoffs for ductboard.
Metal duct work is insulated on the inside, not the outside. I believe there are condensation issues with insulating it on the outside. Metal duct work is galvanized but long term exposure to water will eventualy cause damage.
============================================= Heh, makes sweating copper pipe for a hot water system seem more and more attractive, eh?
--
EA



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wrote:

Thank you for the info. All my walls including external ones are 2 X 4. So I cannot run 6" or 8" ducts inside them. I don't know if using rectangular or oval ducts is better than using 4" round ones. My 50 yo house has all 4" round ducts from plenums.
I also didn't know ducts are insulated from inside. Do all ducts need to be insulated even those running inside heated space? again. all my walls are 4" (actually 3 1/2 ") thich. This does not leave much space for insulated ducts.
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wrote:

You only need to insulate ducts that run outside environmentally controlled space.
Round and oval duct is more efficient per square inch of cross section than squares and rectangles because of the surface area. You see rectangles because that allows more square inches in a wall cavity. They swap size for efficiency. Flex can virtually match the efficiency of metal if it is installed straight and tight.
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If you are running forced air from below a ground floor to a 2nd story typically a large run is made somewhere inside like the back corner of a closet to a distribution hub in the attic. Then branched out from that with flex to ceiling registers. Personally on a 2 story house I prefer two smaller independent systems. Also handy when one fails at an inopportune time, you still have heat/cool in part of the house.
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As I said I want to new heating cooling system independent of existing one for new addition. The addition is master suite on second floor over the family room and office and the workshop on ground floor with new slab on grade foundation adjacent to existing house garage. I also want this new system to be two zone heating/cooling bedroom and workshop independently.
I don't know yet where new furnace and A/C will be, may be in the basement though I don't have space there. Possibly in garage, I don't know if it is good idea since garage is not heated. I will discuss this with HVAC guy who will be doing HVAC drawings and with the architect. If it is in garage I will have to run ducts from basement to second floor. The same probably for returns. Where is the best to position registers height wise? Is it better to position them close to floor (all my registers are 14" from floor level) or higher close to ceiling?
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wrote:

You are touching on the biggest problem with heating and A/C using the same ducts. The objective is exactly opposite depending on which you are using at the time. Cold air drops and hot air rises
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