Heating, Ventilation, and Air Conditioning
Before we get into this, I want to share our thoughts and dreams of how to best heat and cool our project. Way back when this entire garage-apartment thing was still on the drawing board in my mind, I was certain that we were going to go with geothermal for the HVAC system. With the current federal government rebates and the long term cost savings, geothermal made perfect sense. We even located the structure on the building site is such a manner as to allow enough room to bury the thermal exchange lines. Then, as the commitment got closer, the subject was researched in further depth to prepare for the installation. This is when ROI kicked in (or maybe I should say it kicked back). Quite simply, return on investment of a geothermal system comes from use. If you are not using it, you are not enjoying the savings that would be balanced against the same amount of use of a traditional gas or LP system. Since the garage apartment will be a part-time kinda place for us (mostly weekends) , we figured that the geothermal costs would likely take as much as 12 - 15 years before we would break even. At that point, the actual heat pump and other related equipment would also be getting pretty old. Add to this that the upfront costs to take on geothermal is almost 3 times that of a traditional HVAC system, and our budget takes a front row in the decision. In the end, I kick the dirt, grit my teeth, and admit that the prudent choice for what we are doing is going to be a gas fired HVAC system. The compromise, to help me justify this decision, is that we will use a 95% efficient furnace. The jury is still out on the efficiency of the central A/C unit...we haven't yet made that purchase....yet....but it's comin'....soon.
We had never been exposed to calculating, engineering, and installing an HVAC system. My point?....what the hell, why should that stop us from doing it? Like every other facet of our garage-apartment construction, we accept the challenge of making it happen on our own. Before I hurt my arm by patting myself on the back, though, I must come clean and admit that I did have some vital assistance and ongoing support through the entire process from Bill the HVAC guy. Bill is a friend and associate that I know through work. Moreover, Bill is an HVAC wizard and an invaluable ally as we prepare for and execute the HVAC work on our garage-apartment. As we saunter through this entire process, whenever I tell you that "we did this" or "I did that", please know that much of the subject "doing" was overseen and advised by Bill. We are lucky to have his participation.
A true, professional HVAC engineer will do alot of calculations and preparations for sizing and selecting the equipment to best fit the structure. We follow this "best practice" path...or, at least, we follow it in a sort of HVAC
Cliff Notes kinda way. I spent a good amount of time discussing the particulars of the structure with Bill and he gives me a good direction to follow regarding the sizing of the ductwork, how many registers, and other related details of proper ductwork installation. I then googled around online and found a decent free, down-and-dirty, online program for calculating heat loss for the type of structure we are building. The program requires input like the interior cubic footage, the square footage and R values of the walls, the square footage of glass and their corresponding R values, exterior door square footage and R values, outside temps (highest and lowest under normal averages for the region), blah, blah, blah. In the end, the program will spit out a bunch of technical heat loss numbers that can be translated into properly sized HVAC equipment. I share these results with Bill and the decision is made to use a furnace at about 40,000 btu and a central A/C unit at 2.5 tons.
The decision to use LPG gas was a no-brainer; we did not have an option for natural gas available in our area. So....we will need a propane tank, popularly known in rural zones as an iron pig. I really like the idea of being able to purchase my LPG from anybody I want, so owning the tank is a must. Rented tanks will lock the renter into the singular source that provided the tank; no room for negotiation or shopping. I also don't wanna purchase a new tank when a used tank will do just fine. Saving $500 or so is another driving factor in the used tank decision. We found a 500 gallon iron pig on Craigslist and negotiated it down to $350. We hooked up the trailer and took a ride into corn country to a farm to inspect and claim our iron prize. It passed my cursory inspection (as it hung from chains at the end of Farmer Jones' front end loader) and got lashed down to the utility trailer for the ride to LNP.
Many, if not most, installations of LPG tanks is a very high tech method of laying it onto a bed of gravel. We take it an extra step and pour 2 small, but thick and well reinforced, concrete pads.
I put the coarse wire wheel cup onto the die grinder and hit as many of the rusty spots as I can, brought it down to bare metal, wiped it with thinner to clean and dry, and put the Rust Oleum spray primer and zinc gray spray paint to it. Visually, it looks like it's got iron pig measles. Practically, it is ready for installation. We will give it a good cleaning and final coat of tank paint at some time in the near future. In the meantime, though, it will be just fine and ready for action.
Our local, friendly excavator was in the area one weekend with his mini and I hooked up with him (ok, I paid him) to help move the tank from the trailer to the new pads. I also had him cut a trench between the house and the tank so a 2" PVC conduit could be laid in. I plan on using a 1/2" corrugated stainless steel tubing (CSST) to carry the gas from the tank to the house; we will pull it thru the 2" conduit a little later in the story.
We are using 2 separate pressure regulators. This is normal practice, particularly in colder temps. The first regulator is right at the tank, under the lid on top. It will allow 10 PSI of gas. Although 10 PSI doesn't sound like much it is fairly high. LPG will slow down in very cold temps, so the 10 PSI will provide enough pressure to move the LPG along thru the 1/2" line that runs from the first stage regulator (10 PSI) to the second stage regulator at the house. The second regulator knocks the pressure down to about 2 PSI. At this point, the LPG enters the house, so it has some protection from cold extremes...2 PSI will be fine and is the correct pressure to fuel any gas appliances, including the furnace. The line to carry this lower pressure must be increased to allow enough volume, so we will use 1" as the main line inside the structure.
I picked up both regulators off of Ebay. Since we did not even have a furnace yet, nor any gas in the propane tank, we shifted our focus on the area that we currently working in; the garage interior. CSST (corrugated stainless steel tubing) is our choice as the main LPG conduit.....the yellow flexible tubing.
The CSST, like so many products, has it's pro's and con's. On the plus side, it is flexible and pretty easy to install. On the down side, it is a bit expensive and the fittings to terminate the ends are proprietary to the manufacturer, so they ain't cheap either. Having the beauty of flexibility to simplify installation also has a down side. The tubing can be readily punctured if struck by a nail or screw. They sell a very expensive shielding to cover the tubing as a protector, but we take a more econmical route. The exposed interior side of the wall is a no-brainer. We use nail guards as protection. The only other concern, then, would be the possibility of something piercing the CSST from the outside of the wall. My first reaction was to just blow that possibility off as "never gonna happen". The entire exterior is completed and sided, so there is no chance that a nail or screw or something similar might be driven from the outside. Then, better judgement kicked in and I figgered that now is the time to do something about it, cuz someday, somewhere, someone is gonna prove me wrong and find some crazy reason to drive a nail in right where I swore it could never happen.
I didn't wanna pay for that expensive shielding product. I decided that if conduit can protect electrical wiring from this same threat, it should be suitable to protect a flexible gas line. We purchased a length of 1-1/2" conduit, cut it to length, then split the shorter lengths in half, lengthwise. They tapped in nice and snug between the 2 x 6 stud hole and the CSST passing thru the hole. I feel much better about our decision.
We also added a couple of smaller 1/2" auxilliary lines to 2 areas where one might some day want to install a small wall furnace. One area is the living space upstairs:
....and one is in the garage
All lines come together near the ceiling inside the mechanical room, right behind the where the furnace will reside.
The LPG line coming into the structure is piped with 1" black pipe. I have to use pipe because the pipe itself is part of the structural support of the second stage regulator hanging off of it just outside. We measure, cut, strap down, and caulk this pipe transition. Also, another electrical conduit is added through the exterior wall to allow running another grounding circuit to another ground rod driven into the subsoil next to this new LPG line. This new grounding circuit is also connected to the structure's electrical grounding circuit (which has it's own grounding rod) by an 8 ga wire. This 8 ga wire connects both grounding circuits to eliminate the possibility that one circuit could send a charge into the ground, follow the soil, and come back up and into the structure through the other grounding circuit.
While we have all this grounding stuff going on, we decide to pull a conduit down from the satellite dish (which just happens to be installed directly above at the roof) and tie it's grounding element into this same rod.
The final link in this whole LPG feed line program is at our old pal, the iron pig. We've been watching the price of propane, and true to form, the summer ushers in some fairly low prices. The tank is 500 gallons, so the maximum load is 400 gallons. We perform due diligence researching prices and commit to a propane supplier. It turned out very well. They knew that my tank is used, empty, and new to my system. This means that they are going to take responsibility to make certain that the system we have just created is done correctly and leak-free. In fact, they actually replaced most all the old fittings and valves on the tank...at no charge. Their motivation is to woo us back to buy more propane when that time comes. I'm all in.
Start pushin' tin...
Technically, we started our sheet metal work for the HVAC system way back when we started framing for the second floor. As much as I try to anticipate and think of everything that may present a problem, I have come up short plenty of times. The key to making a mistake is to learn from it. Even more important is the chance to exercise whatcha learned. Preparation for the HVAC sheet metal during framing of the second floor is a perfect example of live and learn....and here are the simple facts. Inserting long, rigid lengths of any type of mechanical equipment (like pipe or conduit....or ductwork) can only be done when there is a clear and straight path into which to slide the subject equipment. 10 foot lengths of anything that won't bend or fold are like that. Let's take a look at a pic that explains what I mean.
We had to slide all that stuff into the holes in the I-joists before we erected the 16" tall wall @ gable end and before installation of the double lam beams . If, for some dopey reason, we forgot to do this when we did, we would have had to likely cut holes in the other end of the house later on to give us the shotgun lineup of holes. I know this cuz it's what I had to do when we built our gambrel garage at our principal home (ironically, the inspiration structure for this garage-apartment project). I forgot to anticipate the need for black gas pipe for our garage heater and I had to pop off the vinyl siding and cut a 2" hole thru the siding that lined up with all the other holes I cut into the joists at the interior....followed by sliding the pipes in from the exterior, gluing back the 2" hole corks, patching the house wrap, and replacing the siding. Anyway, that was my learning curve for this current situation and I remembered....yes, the key is actually remembering in the first place. We did, we prepared, and we reaped the benefits of good forethought some months later when we hooked up each pre-staged part to it's respective system. Win-win.
So....back to the ductwork.
To start, and I want to point out one fundamental fact right away: all the ductwork is woven into the 16" tall depth of the I-joists that support the second floor. Since the second floor subfloor restricts access from the top side, this means ALL the work has to be done from below....yeah, ladder work. This is further complicated by the fact that the work area is 10 feet from the concrete slab of the first floor. Yeah...sucks.
The garage apartment is a pretty darned simple layout; one 28' x 44' rectangle with 2 levels....one directly above the other. I like simple. I'm all about simple. The ductwork layout should follow this theme. To this end, we ran an 18" x 8" rectangular main duct directly down the center of the structure. Continuing simple, each register comes off of this 18 x 8 main and is fed by a 6" round or a 6" oval duct. Whenever possible, we used 6" round; it's simpler to work with, a little cheaper, and provides a bit less flow restriction than the equivalent 6" oval duct. The only reason we used 6" oval duct was because of intersection crashes.....places where the real estate was very poplulated with other mechanical stuff and the 6" round duct was just too big to sneak by. This, then, brings up the next passel of forethoughts: how to squeeze all that mechanical crap into those restricted areas. There are some really tight and congested intersections, and they probably would have been less congested if only I had thought of a different plan way back when, but I didn't and I ain't gonna try to re-route something that I already busted my ass on installing. We take advantage of the myriad of different fittings for the different mechanical systems and make it work....period!
We are trying our best to make everything leak-free in the garage apartment, whether it's exterior air infiltration, water permeation, or tight ductwork to send the conditioned air to the living space....not the floor framing cavity. We are using aluminum tape wherever it makes best sense, latex duct sealer, and good old fashioned silicone caulk. Huh? Silicone caulk? Yeah, that was my reaction when HVAC Bill told me that one. Before I could argue with him, he quickly pointed out: it's cheap, it's easy to apply (caulk tube), it seals extremely well (particularly unusual cracks and crevices) and it holds up to something like 450 degrees. What's not to like. He also pointed out that some big city inspectors may frown on it because of strict codes, but he says he uses it a lot and has never had an issue with more rural codes and performance is proven. Personally, I'm not real crazy about silicone for galvanized metal contact because the bond is not super duper, but it is plenty tough for this project. I watch the sales at the home centers and Menards comes up with some real good silicon deals....I load up.
OK, ENOUGH PREP.....SHOW ME THE GALVY !
The first ductwork is in the shop area. This is the first area we completed to the point of drywall installation to provide our upgraded living quarters to allow escaping life in the 10' x 12' love nest. This area is also a good place to cut my teeth on sheet metal work because there will not be much of any conflicts with other mechanical stuff. It is directly below the larger living/family room and there are no water lines and no drain lines. Yeah, there is a bunch of electrical circuit wiring, but that stuff is virtually invisible since it is so skinny.
We find a local HVAC supply house that will entertain cash sales. These kinda places are hard to find since most of them are dedicated to servicing only contractors. Bill gives me a couple of names that he is pretty sure will take my cash business and the more convenient option is a player. Actually, my first act with this vendor was back when we purchased the 18" x 8" duct main that we pre-staged back when framing the second floor. Here now, it is some 2 years later and we are back for more....and our business is still welcome. The staggered flow of sheet metal purchases begins and we start piecing it together.
I spend one of my Sheet Metal-101 classes discussing proper methods of cutting with Bill. He is all about a good pair of snips and a sharpened screw driver to punch the start-holes where necessary. I respect his craft, and respect his advice, but I am all about spending a little more time and maybe a little more money to purchase the gadgets to make some of this stuff easier. Bill isn't crazy about the drill powered circle cutter and almost talks me out of it...but...I perservere and buy it for about $30. The first time I used it, I was ALL smiles. That thing is the nuts and gets used for all my 6" diameter take-off holes at the main trunk....highly recommended by this DIY'er.
The register holes are cut into the subfloor upstairs. The register boots are loosely staged, at the correct height and position, with a couple of screws run horizontally thru the sheet metal and into the edge of the 3/4" thick subfloor.
...toe kick registers, too
Although we are only really working below the living/family room for ductwork, we go ahead and cut in all the register ducts at the bathrooms, bedrooms, and hallway.
Given these location commitments, we move back downstairs to set the 4 ceiling registers that will send HVAC to the shop area just below. Time to get serious about connecting some ductwork. Thankfully, nearly all the runs are straight.
First, cut the holes into the main trunk.
(NOTE; the round pipes in the background are pre-staged stock for cold air returns and will be shifted over to the other end of the building....not needed at this end)
After the holes are cut, the start collars (shown installed above) are boogered up heavily with silicone, slid into the hole, and the fold-over tabs are bent into the inside of the main truck to secure the start collar. The excess globs of silicone are smoothed over (with my favorite tool....my finger) at the connection point around the outside and around the inside at the fold-over tabs. This is done the week before we actually start connecting everything to give the silicone a chance to set up. When we come back the next week, the connection is firm, secure, and air tight...very nice, very strong. There is no worry of dislodging this connection. This is the point where I become a believer in Bill's silicone lesson. I'm sold.
I had to use Bill's favorite method of cutting holes with a pair of snips when I got to the oval ductwork. It sucked, nothing like the ease of the hole cutter.
After the start collars are set and the silicone is allowed to thoroughly dry and set, it's time to start connecting the main trunk to the register boots.
and the 2 registers underneath the bank of picture windows are a little trickier, but not that big of a deal.
We are using dampers wherever possible to provide every advantage possible of fine tuning the air flow when all is said and done and it's time to fire up the HVAC system. Since all this ductwork is going to be completely buried between the sandwich of the subfloor above and the drywall that will soon be applied below, it will be impossible to just reach up and adjust a damper. We exercise the only other practical option and put the dampers at the very end of the register runs so a skinny arm can be slid down into the duct (starting at the register boot from within the living space) and reach down to adjust the damper. It's not the best option, but more like the only option if we want dampers. I am concerned, though, for the nuts that hold those cheapie dampers stable inside the duct. If it is too tight, it will be difficult to move the damper. If it loosens, the damper won't stay where we want it and may even rattle a bit. I cure this fear by improvising a bit.
We take the standard 6" round damper and remove the adjustment lever. It will be useless since it would be inaccessible. We add 2 stainless washers and one locknut.
Standard installation into the 6" round duct is utilized; one 3/8" hole is drilled. The damper is inserted into the duct with one washer on the inside and one washer on the outside. The nut is snugged down and the damper is manually moved back and forth a few times to work it in. The lock nut is adjusted a bit, the damper moved a bit more, and the final nut pressure is set.
When we are satisfied that the damper can be moved reasonably easy and still remain solid and snug, we install the length of ductwork permanently....DONE.
The next sheet metal issue was installing the ducts that will connect the furnace to the 18 x 8 main trunk line. Remember; I'm kinda making this thing up as I go, so there are plenty of moments when I hit a brick wall and survival insticts kick in. This duct run between the furnace and the trunk line was one of those moments. The amount of room to do this is very limited. I did take many precautions and laid quite a few plans to help this transistion to occur, but when it came time to actually procure the proper fittings and do the actual installation, I had to take a time out. I shared the particulars of the issue with Bill. I told him that I have just about enough room to run two separate 12 x 8 ducts. This limitation is entirely based on the availability of exactly 2 ceiling bays that were left for just this purpose. Bill runs a bunch of numbers and tells me that this should be enough to keep the whole system operative and balanced. Now, it's up to me to come up with the parts and make the installation.
I studied the logistics for many minutes, quite a few times. Since my only access is from below, this area is VERY cramped for space. I did not want to have to cut open the floor above. After I wrestled with cutting open the main trunk line to install the take-off collars and finished their installation, I was running out of patience and starting to realize that I am nuts for thinking that I am going to be able to complete this installation from the bottom side only. Here is a look at the 2 ceiling bays (over the furnace area from within the mechanical room). At the far end, the metallic looking stuff is the 2 take-off collars that are installed into the side of the 18 x 8 main trunk line.
We have to come off of those two 12 x 8 openings, run them about 3 or 4 feet through the ceiling bays (toward the camera) and then turn 90 degrees to drop down and into the mechanical room (that we are standing in, on a ladder, taking this picture). Complicate that by the fact that the 3-1/2" wide flanges on the bottoms of the I-joists barely leaves 12-1/2 inches of opening. Further complicate this by knowing that the bay on the left is even narrower because of the way i framed in the walls of the mechanical room. In this area, there is barely 9". My point?....there is no way we can flip that horizontal run coming in to drop down between the I-joists.....not enough room. I know what size and shape fittings I want, but I don't know where to find them. They surely aren't a stock item. I reach out to my cash payment supply house and they hook me up with a custom sheet metal fabricator that does exactly that kinda stuff. I am quoted $50 each for the 2 necessary duct fittings. OUCH!....but I gotta have 'em. In the end, it's a small price to pay if they fit.
The fittings are finished, and I add the necessary short 12 x 8 rectangular ducts and 90 degree elbows. After pushing and pulling the assemblies, trying desparately to slide, shove, or swear them into position, it becomes glaringly obivous that it's time to cut open the subfloor above. Dammit....gimme the circular saw and set it for a 3/4" deep cut. Oddly, after removing the 2 flooring blanks to reveal the previously inaccessible work zones, a wave of relief swept over me as the project went from impossible to totally do'able. The special fittings are pre-assembled with the other stock parts and attached to the 12 x 8 take-offs already attached to the main trunk line. They actually look pretty cool and worked out very well.
and a quick look up from inside the mechanical room...
At this point, we have completed the ductwork contained in the area over the shop. We stop HVAC progress to continue on with finishing the entire shop area. This plan comes together well and we are rewarded with about 350 sq ft of new living space that allows us to abandon life in the 120 sq ft shed that we have been habitating for the last 2 years. The plans and progress continue to ebb and flow. Once we are settled into the new digs, we shift back to the myriad of other projects that still face us. One of these projects is the balance of the ductwork that will be buried in the same maze of ceiling bays, but located over the garage. So, in the spirit of jumping around while telling a long story, some months later we rejoin the sheet metal work on the other side of the workshop wall. Here we go....
Welcome to the other side of the wall. Yeah, I know...whatever. Actually, from the DIY perspective, this area within the garage is way more complicated for packing mechanical stuff into the ceiling. Not only is the balance of the HVAC sheet metal work over on this side (most of it), but I also have to sneak in the cold air returns (CAR's) too. Let's not forget that I already stole alot of the strategic real estate over here when the plumbing drains were installed some months ago. When those drain lines were set, there were not a lot of options for routing simply because they must move in a constant and consistent downward slope. They pretty much go where they want, so long as they all inter-connect and meet together at the single 4" main soil pipe exiting the structure. For this reason, along with the need to have a functional toilet (this was, and continues to be, a very important detail...oh yeah, Donna laid down that law a long time ago), the drain lines were the first system items to get stuffed into the garage ceiling cavity. I will admit, though, that there was a little bit of location adjustment for some of the drain lines, but it was minor tweaking to try and yield a little bit here or there in anticipation of HVAC stuff that will eventually have to co-exist in some of these same ceiling bays. There is quite a bit of criss-crossing of all these different mechanical systems, but it worked out in the end. Before I conclude this prelude to mechanical traffic control, I should note that the water lines are also up there. We used Pex, though, and the simplicity of installation really made them a non-issue for real estate demands within these zones. Those details can be reviewed in the Plumbing Water Lines section (when I finally get around to creating that section; soon come...I hope).
We start by connecting all the loose pieces of the 18" x 8" main duct running down the center of the ceiling. This run of main duct is simply the other 2/3 of the same main duct that runs thru the shop ceiling (detailed in the section above). All the corners are carefully taped with aluminum tape and every Ess and Drive cleat junction (S&D) is boogered up with silicone to seal it up.
...and the end of the run is capped off and sealed with more silicone.
And, just like in the shop, most all the duct runs that take off to the various registers are 6" round. Each round take-off hole is cut and the start collar is tabbed in and sealed with a liberal dose of strategically smeared silicone. NOTE; There is still a lot of various loose 8" duct laying up there waiting to be used for the Cold Air Returns (CAR's). You can see some of it in the background of the pic, below. We laid those in there when the area was framed, some 2 - 3 years ago. Some will get used, but most winds up getting cut up and scrapped as unnecessary. Oh well, it was an insurance policy for DIY'ers that could not properly plan for their HVAC plan.
And, of course, the runs to the registers are installed. 2 very short runs pop up to feed the main hallway running down the center of the 2nd floor.
There are 2 runs that terminate at toe kick registers. Each toe kick register is underneath the vanity in each of the bathrooms. These toe kick registers are constructed with 6" oval fittings. After manually cutting the oval hole at the main duct run for the kitchen toe kick register (occurred during installation over the shop area), I swore I would never wrestle with manually cutting another oval hole.....particularly since I had fallen in love with the way-cool drill powered circle cutter. So, a 6" round take off collar is mounted at the main duct run, and a transition is made during the duct run to covert over to the 6" oval duct I need to properly terminate at the toe kick registers.
And then.....a collison occurs !!
I knew this kinda thing would happen. Looking back, I don't know that I could'a changed much to avoid something like this, but it really isn't a huge deal. This is exactly why there is a myriad of sheet metal fittings and shapes and sizes. Plumbing and electrical meet HVAC at a very busy intersection and guess who ain't budging. Yeah....plumbing drains and a big bundle of power can be pretty damned stubborn. No worries; I have experience with squishing the 6" round duct into an oval and squeaking by (ok...it comes pre-squished...I just like to take credit for a succesful recovery whenever possible).
Ironically, in order to be able to install a damper right up next to the register boot, we had to convert the 6" oval back to 6" round and tie it into the register boot.
There are 3 main cold air return points. Each CAR will provide the inhale that the furnace seeks in order for it to expel and exhale the heated or air conditioned air. There is one larger main CAR in the largest living space, and one smaller CAR in each of the bedrooms. Also, since there are ceiling registers in the shop area, a medium sized CAR will be installed to service that same shop zone in the future (easier project that we will deal with later). For now, though, the 3 main CAR's for the living spaces must be installed because they run within this same second floor framing cavity.
The CAR's at the 2 bedrooms with utilize the wall cavity created by the studs and the drywall as the duct run. Typically, this is done quickly and easily by just cutting out the base plate of the wall section and cutting a hole through the subfloor. This would be too easy, though, for the King of Overkill. Instead, I want to maintain the continuity of the wall base plate. Doing so will also provide a thin wood area that will accept a drywall screw and even a brad for the baseboard trim. A hole is meticulously cut into the base plate and continues down through the subfloor.
Furthermore, as if to add insult to injury, one of these 2 CAR's winds up directly below a wall stud. It did not leave much option, and I did not want to remove the stud. Since it was at one end of where the slot would come thru, I cut off the stud at the bottom and sistered a piece of 4 x 4 at the other edge to kick out the stud and finish the connection to the base plate. Yeah... I know...crazy. Gee, thanks.
Beneath the subfloor, a register boot is slightly modified by folding back the edges to create a flange. The flanges are drilled for screws and coated with polyurethane caulk and screwed to the bottom side of the subfloor....directly below the CAR slots cut into the wall framing. Why not silicone caulk? Because the Advantech subfloor will not bond well with silicone, but grabs polyurethane caulk like gangbusters.
We are now starting to really feel the pressure of too much traffic. The more crap we jam up there, the more difficult it gets to find a way to squeeze by. The only savior is a little bit of luck, some really tight squeezes, and bunch of the flatter oval ductwork. Since the CAR's are critical to provide enough air movement back to the furnace, we use 8" fittings and duct runs.
The more we add, the more congested.....until we wind up with this convoluted mess....
What's really nuts is that the above pic is a bit misleading. There is a critical zig-zag happening above the main duct trunk line, as outlined below
There is a happy ending. Although I am certain that an HVAC pro would have come up with a more efficient and less confusing maze of ductwork, our plan will work. It's how I roll.
The main CAR at the great room upstairs presented it's own challenges. Actually, most of my challenges are self-inflicted....I just like to deflect as many of "Doh !!" moments as possible, so I blame it on bad luck. It surely can't be poor planning........can it?
Continuing on the theme of creating as much air flow as possible for the CAR system, the main CAR will require a very custom fitting. It must negotiate a very limited space for installation, accept the 8" feed from the other 2 bedroom CAR's, and bring them all down into the mechanical room and tie into the furnace. The only real pain is the limited space....again. I purchased a couple of sheets of galvanized sheet metal from the supply house, dragged out the pop rivet tool with 3/16" aluminum rivets, and carefully measure and plan. I have NEVER constructed a sheet metal duct fitting before, let alone one that has a variety of dimensions and angles. It is moments like this that have only 2 endings. One is success and one is total failure. There is no in-between.....no point where one can just modify the error and still bail out with a product that works. Fortunately....I emergedt victorious. Why?....hell, I don't know why....just lucky every now and then.
This 3 hour project gets jammed up into the ceiling cavity over the furnace end of the mechnical room. The oval take-off receives the feed from the 2 bedroom CAR's (both BR CAR's join up as one 8" oval feed). The top end of my dorky lookin' fancy-ass ductwork fitting receives the feed from the larger CAR from the great room living space directly above.
A CAR stack is framed upstairs. It winds up being located in a pretty good area. It's central location is ideal for controlling the return air. In order to make it disappear as part of the framing, it is framed about twice the width than it needs to be. The extra area will be used as a tiny pantry or closet....very tiny at about 12" wide. The other half of this framing is lined with sheet metal to create a 12" x 12" vertical duct that dumps directly down into my ho-made fitting...and...directly below that is the furnace CAR intake.
The left side of this little framing job is the storage. The right side is the CAR duct. A 12" x 12" opening is framed at the top and another is framed at the bottom. This will provide options of drawing in warm air near the ceiling during the summer and the colder air near the floor during the winter. We will control these flow options by closing off one opening with magnetic sheeting, moving it back and forth as the seasons change. If we find that the fan on the furnace is adjusted to a flow that will require more CAR air flow, both openings will remain open.
Gas line, Furnace, and A/C
We needed to terminate the corrugated stainless steel tubing that is going to carry the LPG to and from the mechanical room. We have one 1" main line coming in and two 1/2" lines leaving at the same spot near the ceiling.
The main will feed a manifold that continues on to the furnace, and that same manifold will feed out to the remaining two 1/2" lines. One 1/2" line runs out to a terminal built into the wall of the main living area in the upstairs living space. This will remain unused for now, but will allow the option of installing a small wall furnace in the future should it be required. We used 1" black pipe and fittings hung from a piece of uni-strut and 1/2" threaded rod. The pipe and manifold are routed to the side to allow room for the sheet metal duct connections that will be occurring within the same real estate. We are gonna really be packing inventory into this zone and every inch counts.
It's time to start messing around with the furnace and A/C stuff. As has been the case for the entire HVAC development and installation, my personal HVAC wizard, Bill, lines up the equipment I need and crams my brain with tips and installation instructions. Besides the fact that I have never done this before, this all gets further complicated by the small space that I have allocated to house all of it. I knew when I laid out the floor plan that the mechanical room would be on the small side, but now that it is actually time to begin filling it up with hardware, small shifts to tiny and cramped. There is no turning back, so every move is planned and orchestrated. Following is a pictorial summary of the progress.
With a little cussing and complaining, we got the furnace to kick on and operate. There will be important fan speed adjustments based on heat rise, but the system works. My other trusted HVAC pal, Tim, came down for a Saturday to donate his expertise in charging the A/C. It all came together nicely and we are once again pleased with the outcome of another project.