Solar Hot Water Mounting Strategies 6.28.2010

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Date: 06/28/2010

Okay, well, I’d like to welcome you all to another of our SunMaxx Solar webinar series. Today we’re gonna be talking about mounting strategies. Gotta short half hour PowerPoint planned, and I’d like to go over several techniques of how mounting various collectors– thermal connectors to different types of roofs. For the rest of you who have been with us before, you can type a question in the little chat box and I’ll try to respond to it right away. For those questions that are beyond me, we also have Kirsten Thorp, our solar hot water coordinator, she might be able to help you as well. So please feel free to type in any questions, and I’ll either answer them directly and immediately or we can follow up after the webinar, okay.

So what I’d like to first talk about are just a couple of options of connecting the collectors to the roof. How we fasten those to the rafters, or to the decking itself. But additionally, I’m gonna go over some different mounting techniques in terms of placement on the roof and how to make full advantage of the roof in terms of orientation and everything. Fastening to the roof has been pretty well established with these five most common and proven methods. The spanner with threaded rod, log bolt, toggle bolt, J-bolt and then the picture here shows a pitch fan. A pitch fan is one of the older methods. Basically you need to find a rafter and drop a lag bolt in. Lag bolts need to be at least 2 inches into a rafter regardless of the size of the rafter. We gotta go at least 2 inches and the lag bolt itself should be bigger than a 1/4 inch. So 3/8 is the most commonly used lag bolt, or for this particular method. So again, we gotta sink it in at least 2 inches, and the lag bolt outa be quarter inch, or 3/8 inch is even better.

The spanner with a threaded rod, in method number one, we have to find the rafter. This only works if you have access to the rafter. And you put a spanner between the rafters. You can either cut the spanner to be the exact dimension from inside to inside and fasten those in between the rafters. Or the spanner could be placed outside the rafter, and basically spans several rafters. Using the spanner method, you can find any location on the roof where you wanna put your feet or your– or your channel, and that location is determined by aesthetics or functionality, and that determined by location of the rafter. So the one benefit of using the spanner is it allows you to locate your points of fastening, regardless of location or the rafter. Okay, a lot of times, especially on small roofs you have some aesthetic appeal that you have to consider, and by mounting them to the rafters, it may be asymmetrical or. . .

A lag bolt with flashing is probably one of the simplest methods and I’ll show you a couple of pictures of that, again, but number two, you’ve gotta find the rafter. So if you have trouble finding the rafter then it can be relatively tricky because if your lag bolt is– or if you’re missing part of the rafter, then you can jeopardize the integrity of the rafter itself, so you really–if you use method number two, you’ve gotta be sure that you found the rafter, and that you know where the center of the rafter is.

Toggle bolt is another one that has been used quite often. The only drawback to a toggle bolt is that you have to drill a sizable hole. And by drilling a larger hole, it usually means you’ve gotta some roof boots, or flashing, larger flashing to cover up that hole. However, like method number one, method number three allows you versatility. You can move anywhere you want on the roof. So you can really accommodate the aesthetic appeal with number three, because your not tied down to the location of the rafters.

Another one, the J- bolt is pretty commonly used. In this case you’ve got to be able to find the rafter and access it from below. Okay, the J-bolt, just as the name would suggest, hooks around the bottom of the rafter. And so, the machine thread part sticks out of the roof, and allows you to mount right to the top of the J-bolt. And you’re basically connecting it right to the roof structure without puncturing the rafter itself. So a lot of guys like that because it doesn’t reduce the integrity of the roof — of the rafter, but it does secure it to the rafter.

And, obviously number five, the pitch fan, it’s a lag bolt, but the pitch fan is a way to prevent any leaking through the pitch fan. And you fill that up with pitch and then you don’t get any leaking through there, and that sort of serves the same purpose as other methods that use the neoprene washer.

Okay, so just to show you, this picture of this J-bolt, you can see down here the J-bolt will wrap around the rafter and then you connect your threads and your standoff to the top of the roof. This one, like I mentioned before, minimum of 2 inch depth of the lag bolt into the rafter. Okay, so typically rafters are larger than 2×6 but a 2×6 means that we are gonna be sinking our lag bolt down half way through the rafter at least, okay. And again, the thickness of lag bolts should be 1/4 inch or bigger, 3/8 is better. The quarter inch lag bolt is a little bit on the small side but its okay if you don’t have much wind load as with the evacuated tube installations.

Okay, I wanted to point out in this particular install, the installer used quick mount PV, this is a flashing, with a lag bolt off of a standoff block. Now this particular installer required the location of the rafter so there’s Bosch. Bosch makes really nice rafter finder. I’ve used it several occasions, and really can’t come up with a better solution to finding the rafters. There’s all sorts of techniques of using your hammer and listening for vibrations and even stud finders looking for nails, but nothing better– nothing short of a rafter finder would make me confident that I’ve actually not only located a rafter, but finding the center of the rafter. So Bosch, I’m not sure of the price, its a couple hundred dollars, but probably money well spent, just in the confidence that you found the center of the rafter. When you use these quick mount type of roof penetrations, you can tie in the SunMaxx rail which is an extruded aluminum allows you to mount the feet right to that lag bolt and then the collectors can slide to the left or to the right anywhere they want, so your– although the rail is mounted directly to the rafter and your fixed to the rafter point, the collectors themselves can slide horizontally and then if you have some ends, you can cut these ends off to allow them to look better, I suppose. Another important point that I should make is that these standoffs really shouldn’t be more than 48 inches apart, using most manufactures rails systems. Rails are really designed to have at least a 48 inch pressure point and not to exceed that. So that becomes pretty easy. You can–the rafters are generally spaced out, 16 inches on center, so you shouldn’t have too much trouble finding 48 inches where you can mount these standoffs.

All right, now, to point out a couple of different flush mount flat plate installs, this particular one up in Syracuse is one of our most recent that this installer used the TitanPower plus, and a couple of things I wanna point out with this, is there’s very little space between the roof and the collector itself. Actually an inch and a half of space, so it doesn’t allow for much debris build up. Certainly some of the other collectors will allow for debris and even a home and a habitat for pigeons and whatnot, so there’s very little space between the roof and the bottom of the collector, and in this case you really don’t see the mounting hardware at all. And I’ll show you that with the picture, what this hardware system looks like, and the space in between, these collectors are actually mounted to one another sitting on the same rail system, and the fittings allow them to have just about an inch and a half space between one collector and the next one in the same series.

So these systems are mounted using our lag bolt which you see here, which is sunk into the rafter, and in this case we went in 4 inches. So we pre-drilled a quarter inch hole, and on the top of our lag bolts is a hex nut which allows us to tie right into our drill, and we can sink that in, it’s got a neoprene washer, so you see a little neoprene washer there, and in this case we cut out a small piece of flashing and we slipped it up underneath the previous, this row of shingles, 4 inches. So we go up 4 inches and sunk our hangar bolt in place with the clips. Now these clips are gonna tie directly into this upside down or inverted T rail, okay. The T rail is gonna be the rail that the flat plates sit on, your gonna see here in the next picture. Okay, so here’s our large hangar bolt. The hangar bolt can drop down, the distance here is 4 inches, so we try to get in and take in as much as this 4 inches as possible, and if we can go in even further with this remaining space, then we do. And then the clip is double nutted, so we can change the height of our collectors very easily with this double nut on the clip. We decided we wanted to bring it down as close as possible, so that’s what we did. And then once we sink it down with our hex nut, we can basically cut it off, okay. Now these slots. You see the slots on this rail. They’re gonna accept this bolt that’s being pulled out of this collector right now. The collector itself is the frame. So it’s very easy to mount our rails to the collector, there’s no additional hardware. So basically your hangar bolts, the T-profile and the collector. Okay, the collector comes with these bolts already embedded into a dry well. So there’s a dry threaded socket in the bottom and top of the collectors.

Okay, another picture, a close up of the finished product; you see the bolt that’s connected directly to the connector itself, in that slot. And our clip is fastened and this T profile has 2 edges, one edge has small serrations that correspond to serrations on the clip. So as we tighten down this hangar bolt, this clip will compress and the friction won’t allow it to move horizontally, side by side, and the serrations along with the compression, don’t allow it to move vertically, okay. Using a simple little quick connect adapter on this flexible stainless steel line set, the fittings are already built into the collector and all we have to do is screw it in nice and tight with a double nut, and we are ready to go.

The TitanPower also has this little drip edge, this chrome drip edge that comes off the bottom, so as you look–let’s go back to this slide here– these little, this what is silver drip edge along the bottom allows the water to move down off the collector and then extend the drip down onto the roof without being inverted, because just under this drip edge is a little air release port. And it allows for the removal of condensation and humidity in the air, any high pressure steam that might build up from the latent moisture will be forced out of that port. This drip edge allows that to happen. In fact, I can speak to it personally; I just had a flat plate that we installed for training on Friday. It was tipped upside down all weekend getting moisture, and then once we installed it, with the drip edge down, over the course of the day, the moisture just–you could feel a light stream of air forcing its way out through that port.

Okay, now, a couple things I just wanna– a couple things I’d like to point out, different strategies, one is the ability to increase the reflectivity. When you use evacuated tubes, you really try to consider ways to increase performance, and one of the best ways is be increasing the reflectivity. And this installation up near Boston, the installer included a white roofing material behind the collectors, and this did increase his performance by 11%. So we know for a fact that this system is over performing our original calculations and that the factor is this reflectivity.

And this particular, over here on the left hand side, you see four collectors there, two of which have the tubes in already, and the front row does not have the tubes. But being installed on this highly reflective tin roof, this particular install is gonna see upwards of 20% increase in performance, based on some preliminary data done by Pete Schinara at SunDog, they put some reflective surface and nothing real reflective, it doesn’t take a highly reflective and moderately reflective. One other thing I wanna point out about reflectivity is the more reflective it is at the beginning, the less reflective it is at the end. In other words, the reflectivity curve is very sharp for surfaces that have a lot of reflectivity. They tend to lose that dramatically. So even something like a tin roof will maintain the same reflectivity for 5, 10 15 years without decreasing too much. So increasing reflectivity is one . . .

Another, in this picture, is just a couple different miscellaneous mounts. The installer here used flexible line set. And, he wanted to change his inclination angle. The inclination angle is the angle of the incline of the collectors, okay. So he put his collectors on a swivel, so that twice a year he comes out with a little hand crank, and I know you can’t see it, but he’ll crank hand crank down, and it will tilt these collectors back to maximize summertime production and tilt these forward to maximize winter production. Although this isn’t going to be suitable for the normal installs, it will definitely increase his performance, however, it is questionable whether it will increase the performance relative to the value and cost of this type of installation. One benefit to the evacuated tubes is they have a high degree of variation in their incline and orientation that allows it to maintain 90-95% of what they normally would expect. All right so he’s just going to be able change his inclination angle. With this one he won’t be changing his orientation angle. On this ridge mount, the hardware that came with this set of collectors was added to by a couple of struts off of the roof. It keeps them level all the way across, so the hardware was adaptable for use like this, and it might be recommended that you put something on your roof. It’s not as aesthetically appealing as one might like. In the middle of town, you might not want to go this way, knowing that– even flat plates have a high degree of variation if we were to mount these on a western slope, then we probably would decrease efficiency only by 15% that can be compensated by adding 15% more collectors and get the same results, or the same is true if we were to mount these collectors on the east. Nevertheless, it is relatively easy to do something like this, but it may not be overall aesthetically appealing for most people.

I just want to remind you that if anybody has any questions, please do feel free to type away. I like to be responsive to anybodies– I have a certain slide show that I’d like to show you, but if you have any questions, now is a really good time to do that.

A lot of people go with the ground mounts. And one purpose is they find it much easier to maintain. These collectors can be washed off very easy, sprayed down. They can be even given a sponge bath if they wanted to keep them nice and shiny, although most collectors are pretty effective at self-cleaning in some good rains, but if you live in areas that don’t receive a lot of raining, or rainy days then you might need to service them once a year, and wash them down. Well if it’s on the roof, it makes it a little bit more difficult. The one on the left here shows the back leg of the SunMaxx 30 that was basically rotated 90 degrees. This back leg used to be mounted here, as it is with this top one, and the triangle bracket that fits in this extruded aluminum, was basically slid down to the bottom of the rail and turned backwards so now the back leg is used to help support this cantilever off of this frame.

In this particular case, the client used our existing extruded aluminum, but built a concrete embedded pipe, basically a piping design, used black pipe and painted it silver. Here’s another picture of looks like a ground mount, but in fact it’s on top of a commercial roof with a rubber membrane underneath some gravel. Now I do want to point out that this install did not require the roofing company to re-warranty the roof, there were no bonding issues, in fact this was inspected and certified by the code enforcer simply due to the lack of wind load on these evacuated tubes. So if you have a situation where you’ve looked at the performance and they’re similar, you’ve looked at the aesthetics and their similar, you’ve looked at the cost, but now you have a wind load issue, there is an advantage in evacuated tubes in that this install is basically mounted right on these blocks. The blocks are setting on the stone and then the feet of the collectors are fastened to the blocks themselves. So we have 10 SunMaxx 30’s here in series totaling, just themselves totaling 2500 pounds connected directly to one another through the piping, so there really wouldn’t be substantial– yeah, I actually just got a question from Anthony, this is non-penetrating. That’s right, it’s sitting on top of the roof, and the pipes actually run down the side of the building six stories into the basement. So this was a very simple install. You can do this with flat plates as well, but the curbs or the concrete blocks that would be required are more significant in weight.

This particular install is a carport, so collectors can often be used to provide shading. This in on top of a parking garage, the top story of a parking garage with a carport that was already in place to provide shading and then these– the additional collectors provide even more shading to the carport. Some clients like to use the ridge, and get to the top of the ridge as much as possible and support the back legs on the opposite side of the ridge. Now this can be either flat plates or evacuated tubes, it doesn’t matter, but it makes very good use of the available roof space. Because if you look at the amount of roof that this particular install required, in terms of gross area, it’s much less than it would if we were to move these collectors down, and take the back legs down a bit. By straddling the roof, you consume less roof real estate, which is fairly important especially when it comes to larger systems or in Combo systems. A combo system where you have PV and thermal and as many of you probably know the PV collectors would take up more roof real estate relative to their solar gain and energy saved than thermal. So by doing it this way, that ration becomes even more apparent. That the thermal collectors are taking up much less roof space relative to the solar input.

Here’s some flat roof installs. One thing that I’d like to point out about this is the shading. All right, so this installer took some– this was up in Massachusetts. This particular one on the right, this installer used some large pre-manufactured floor joists. And he set those up so they are 18 inches off the roof and the spacing is such that during the Winter solstice, the angle of the sun will not cast a shadow on the second row. Okay, so for latitudes that are between 40 and 43, that spacing is 12 and a half feet from front to front. Latitudes of 38 to– 37 to 40 that space is about 11 and half feet and latitudes of 35 to 38, the distance is just about 10 and 1/3 (10,3 feet) that is the distance from the front of one collector to the front of the next collector to prevent shading. Now this installer on the left used the same rule of thumb in terms of shading, but he took his second row and mounted it up at a higher elevation than the first row, which allowed him to take up less roof real estate.
Okay, another way to consider installations is how you can increase the performance from the back. I showed you a couple of the reflective surfaces, but additionally, this white is gonna shine. Any of these light, the non-shadow portion of this roof, that’s gonna cast light back up to the back side of the collector. It’s real apparent on this photo. You see this beam of light that’s being reflected down onto these collectors? That’s what you’d normally see from the front of a collector. Yet, we are looking at it from the back of the collector. So it becomes very clear that a roof that has a highly reflective or even mildly reflective white membrane is going to be able to increase the performance of the collectors, estimates are from 11 to 20%, okay.

Here is a couple of pole mount strategies. This installer in Las Vegas used a black pole which he mounted directly to the rafters itself as a supply and return so his supply and return piping went down through this black pole that he insulated and the pole is also supporting the collector, so that was a very interesting installation technique and I thought I’d share that one with you. Another one where, you saw the picture previously of mounting on the ridge, well this installer– this client did not want his collectors mounted to the roof, so the installer mounted some poles, upon which he secured these collectors.

I just had a question about reflective backing, and we actually have a couple of prototypes that we’ve worked on and they include parabolic reflectors, flat sheet reflectors, we also have just a reflective surface that can be taped on, or stuck on an existing material. But in terms of including it with our collectors, we do not include the reflective surface with our collectors primarily because the increase of wind load and the increase in cost. And if we look at the existing roof, there is many ways that we can use the roof as the reflective surface for much, much less cost. And a perfect example is Shewin-Williams. Sherwin Williams makes a real nice highly reflective roof paint, I believe it’s 35 dollars a gallon, and can be painted on asphalt shingles, increasing your solar performance by 11-20 % so additionally so for 35 dollar gallon of paint, we can get what amounts to performance of a whole another collector or 30 tubes.

Okay, just to show you again that another ground mount situation with concrete standoffs, this is the job at Wacol prison. This pre tube installation, and they took these concrete blocks, this entire pad was poured just for the collectors. These concrete pavers were glued together using concrete adhesive and then the feet of each of the collectors was mounted to these concrete standoffs. Okay, and this has been well, this was engineered by OGS engineers, and is expected to be stable for 20 plus years, all right. This is a close up of the picture I showed you that was actually on the roof, we just used these 6 inch, 6x6x12 concrete pavers with blue tapcons right into the concrete paver.

Here is an example of how we can reduce summertime performance using the mounting strategies. One is to mount them on the right here, vertically, and this eave is going to shade the collectors in the summertime. This installation is right outside the window here, I’m actually looking at it through the window right over there, and our tubes on a hot summer day right now are about 85-90 degrees, and in the middle of the winter, in January on a summer day they are upwards of 130. So even though we are getting more insolation now, we are able to decrease our performance. Why do you want to decrease performance? Well this is just for heating, so we really don’t want to produce excess BTUs and we are able to accomplish that by vertical mounting. Now remember, vertical mounts are only suitable for U-pipes, or flat plates; not suitable for evacuated tube heat pipes.
Another strategy was this fake roof that this installer built, where he’s got two collectors on top of the roof, and two collectors below the roof and as you can see in the winter time, both–all four collectors have full access to the solar radiation, and in the summertime as the sun goes higher, this bottom row production decreases dramatically. And he balances out his production with his consumption. Very smart method there.
Here is another way of overheating protection. One is to obviously cover your collectors on a ground mount situation, not real accessible for most, but I thought I’d point out that this client is having good luck obviously with reducing his production in the summer time for heating system by covering them up. And in this case we have stood these up at such a steep angle, the maximum angle these tubes can be place at is 75 degrees. And that’s pretty consistent even with the flat plates, they can go vertical although you wouldn’t want to mount a vertical flat plate on top of a roof like this just because the amount of mounting protection it would need from lift and up force, and the evacuated tubes you can increase the incline angle, and it decreases the summertime production because there is virtually no wind load there.

All right, I like to keep on schedule. I actually went two minutes over. This was just a 30 minute little webinar. I really do appreciate all of you joining us and I hope it helps with your understanding of solar thermal. Checkout our website for upcoming schedule. We are going to be doing this every Monday for as long as we can. I’ll stay online here for just a few minutes if anybody has any questions, otherwise I hope to see you next week and you can access any of the past webinars that have been recorded without any technical difficulty, or if I forgot to record them their not gonna be there. But so far I’m 2 for 2 in the last 2 of recording. Any questions? Okay, well I will say thanks again, and hope you guys have a great solar week, and keep getting the word out because it won’t be long – solar thermal is going to be right there at the top in terms of the industry and market potential. Take care.

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