How to Disconnect These Hot Water Solar Panels?

[mike s.]

They are coming off my roof but need to separate them first. The pipes between them are like in the pic below. I can turn the hex ends easily enough but nothing's coming loose. I'd hate to damage anything.

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[peakbagger]

Those frames sure look like they need a lot of rehab. It looks like a pretty standard set up where the two male ends of a half coupling were sweated to a short pipe. In theory you loosen the hex nuts all the way back and then the male half coupling just pulls out the collector. Obviously in order to pull it out, you need to separate the two collectors. I have run into unions that have been together for many years where the union faces have stuck together and require a good smack with a sledge to break them apart. The other thing I have run into with sweated copper fittings is that the plumber allowed solder to run into the joint faces and soldered the union faces together. I would just take sawzall and cut the short length of pipe to get the collectors off the roof and then deal with it on the ground. If you are reinstalling, you can sweat coupling over the cut.

IMHO, those panel frames look real rough. I would expect that you need to take the collectors apart and see if the frames are still structurally sound. If they are, sandblasting is the best way or otherwise scrape and sand then and then hit it with a rust converter and then a top coat of moisture cure polyurethane. I use a POR 15 system but there are a couple of systems out there. Its likely that you will also need to replace the rear insulation, if its fiberglass, you can upgrade to isoboard.

There really is no market to speak of for old solar panels except for scrap value if the absorbers are copper, most folks have switched to Heat Pump Hot Water Heaters with a couple of extra PV panels to make up for the extra annual power use.

[J.P.M.]

Those frames sure look like they need a lot of rehab. It looks like a pretty standard set up where the two male ends of a half coupling were sweated to a short pipe. In theory you loosen the hex nuts all the way back and then the male half coupling just pulls out the collector. Obviously in order to pull it out, you need to separate the two collectors. I have run into unions that have been together for many years where the union faces have stuck together and require a good smack with a sledge to break them apart. The other thing I have run into with sweated copper fittings is that the plumber allowed solder to run into the joint faces and soldered the union faces together. I would just take sawzall and cut the short length of pipe to get the collectors off the roof and then deal with it on the ground. If you are reinstalling, you can sweat coupling over the cut.

IMHO, those panel frames look real rough. I would expect that you need to take the collectors apart and see if the frames are still structurally sound. If they are, sandblasting is the best way or otherwise scrape and sand then and then hit it with a rust converter and then a top coat of moisture cure polyurethane. I use a POR 15 system but there are a couple of systems out there. Its likely that you will also need to replace the rear insulation, if its fiberglass, you can upgrade to isoboard.

There really is no market to speak of for old solar panels except for scrap value if the absorbers are copper, most folks have switched to Heat Pump Hot Water Heaters with a couple of extra PV panels to make up for the extra annual power use.

Mostly agreed on cutting the tubing and dealing with the issue once off what's probably the roof. I'd be careful in the cutting however, to produce as little torque as possible in the header cutting/sawing process so as to minimize the chances of weakening or opening up/cracking a joint or several header to riser joints, either by overstress or, if a hand cut, by inducing cyclic and alternating stresses in the header.

On the frames: They do indeed look rough, but looks are not always related to performance.

If there is no condensation under the glazing, it's likely that the frames are at least leak tight which is their main function.

Aesthetics aside, I'd be very careful sandblasting or abrasive treatment on the frames. Most thermal collector frames have been made of aluminum for quite a while now. That your frames are steel would probably mean they are long in the tooth. That's not a negative at all, and if they are still functional, a tribute to the collector quality.

Here's the point on abrasive treatments: Looks like some repairs or resealing the glazing joints has been done. Sandblasting will probably raise hell with the glazing joints, both caulking and gasketing material, as may some chemicals used as rust removers. all that may increase leak potential and therefore be counterproductive. .

I'd also think that the gasket material (looks like buna type material) may be dried out. If there is condessation under the glazing, I might consider caulking around and over that gasketing. Buna does not last forever when exposed to UV. A long time maybe, but steel framed collectors are pretty old as well.

If it was me, I'd (carefully) cut the joints and, clean up the frames, keeping in mind that if the collector frames are not leaking, I might want to find beauty in the aesthetics of old age over chances of opening a leak by fixing something that ain't broke now but might be by fooling with it too much.

I'd also flush the collectors with vinegar just for poops and giggles while the piping was open.

[mike s.]

Thanks guys, looks like I'll have to cut the pipes, then. A reinstall with new male ends and new pipe would be easy enough. The boxes are from the early 80s and are very well built. I'm giving them away (lots of people seem to want them even in this condition) so I'll just give whoever gets them this info and let them do the cutting.

[J.P.M.]

Thanks guys, looks like I'll have to cut the pipes, then. A reinstall with new male ends and new pipe would be easy enough. The boxes are from the early 80s and are very well built. I'm giving them away (lots of people seem to want them even in this condition) so I'll just give whoever gets them this info and let them do the cutting.

For my part, you're most welcome.

One reason people seem to want them: Depending on what the absorber material is, the collectors may just have a boatload of copper in them. Something called "rollbond" absorbers, often made with aluminum, but sometimes from copper, with the copper ones weighing about 2 or so lbm/ft.^2, and not uncommonly used in quality products. Even .007" thick strip copper soldered to copper risers with 4" O.C. spacing risers will have about 30 lbm or so of copper per 4 X 8 panel.

Scrap copper is about $2.10 - $2.50/lbm at this time. Might be worth a peek behind the glazing.

Just sayin'.

[littleharbor]

Just a common sense suggestion but, if you use a sawzall to cut the panels apart. be sure to keep the body of the saw above the cutting area to prevent any residual water from spraying into the motor.

[J.P.M.]

Just a common sense suggestion but, if you use a sawzall to cut the panels apart. be sure to keep the body of the saw above the cutting area to prevent any residual water from spraying into the motor.

Drain the system first. Common and best design practice is to use proper sloping to ensure full drainage for a well designed system, at least partly as backup freeze protection, but for other reasons as well. Besides, for what looks like probably 3 or 4 cuts on 1" tubing, and the 5 or so minutes total it will probably take for all of them, I'd use a hand saw anyway.

[mike s.]

Thanks, everybody. Inside the boxes are "radiators" similar in appearance to a car radiator, only much larger. I suppose those are usually made of aluminum. In any case, I'll appreciate someone getting some use out of them one way or another. I already cut off the inlet and outlet copper pipes and all is dry. But I was intending to separate the boxes by handsaw or even pipe cutter, anyway. Three boxes; 6 cuts.
Thanks again to all!

[J.P.M.]

Thanks, everybody. Inside the boxes are "radiators" similar in appearance to a car radiator, only much larger. I suppose those are usually made of aluminum. In any case, I'll appreciate someone getting some use out of them one way or another. I already cut off the inlet and outlet copper pipes and all is dry. But I was intending to separate the boxes by handsaw or even pipe cutter, anyway. Three boxes; 6 cuts.
Thanks again to all!

Copper tubing can and is sometimes/often wrapped in aluminum fins. FWIW, that material arrangementarrWorks best with the tubeside fluid warmer than the fins so that the tube to fin connection, which is usually a simple press fit gets a bit tighter as the tube heats up, giving the tube to fin joint at least and hopefully a lesser tendency to separate. It's a crappy bond any way you look at it, but there's so much fin area that the bond conductance across that joint takes on less relative importance.

If you are going to break into the collector frames, easiest way is to simply lay the collectors horizontal, glazing up, put a tarp over them and break the glazing which is tempered glass and which will fall into the collector box. Depending on the fin pitch. maybe a bit of a PITA getting the bits of glass out, but at least it's in one container. Cutting the metal will probably result in breaking the glazing anyway.

Best Wishes for a Happy New Year.

[peakbagger]

By the way, I was not advocating sandblasting the frames with the glazing in. When I see older collectors, they inevitably are fogged up permanently and never were a sealed unit. Generally the people I know who have rehabbed collectors have attempted to remove the glass with mixed success. If the glass comes out in one piece it usually can be cleaned. The backing insulation is usually deteriorated and worth replacing. The ones I am familiar with were not welded frames, they were assembled on site out of lengths of extrusions screwed together at the corners.I have also see the frame made up out of bent sheet metal sections. With this design its not that difficult to unscrew the hardware at the corners and end up with straight lengths of metal that can be inspected and then re-coated. A light brush blast with appropriate media is the best prep for a catalyzed polyurethane coating to coat the frame. Rarely have I seen the bent sheet metal frames be worth salvaging as inevitably the metal has lost enough thickness that its not worth fixing.

At that point its a crap shot on what the absorber is made up of, some do have a lot of copper, mine are solid copper risers roll extruded over copper absorber fins. Many others are mix of aluminum fins and copper risers and some were all aluminum. They all do have scrap value, but the copper ones usually are the best score.

I rarely if even see old collectors get reinstalled, Most folks who grab them are either dreamers or scrappers. The dreamers don't realize that they are getting a half a system. Even if they can salvage the rest of the system its rarely operational. I know of one system like this, the panels have been leaned up against a pole outdoors for several years, the stone lined storage tank's liner is shot, the controls are non standard and the heat exchanger bundle has freeze damage.

Scrappers have a couple of approaches, the smart ones call every listing on craigslist or other local sales site and spin a story that they really want a set of solar hot water panels but cant afford the asking price, that gets their foot in the door to physically show up to take a look at them. They usually can figure out what they are made of and then can offer to take them to a good home for reuse. The typical homeowner just wants them off their lot and frequently they just give them away rather then hassle with them. More then a few scrappers I have met are folks on unemployment or disability and scrap under the table so they dont really mind spending their time playing the percentages so if they get one score out of several ads , its free money to them.

[J.P.M.]

By the way, I was not advocating sandblasting the frames with the glazing in. When I see older collectors, they inevitably are fogged up permanently and never were a sealed unit. Generally the people I know who have rehabbed collectors have attempted to remove the glass with mixed success. If the glass comes out in one piece it usually can be cleaned. The backing insulation is usually deteriorated and worth replacing. The ones I am familiar with were not welded frames, they were assembled on site out of lengths of extrusions screwed together at the corners.I have also see the frame made up out of bent sheet metal sections. With this design its not that difficult to unscrew the hardware at the corners and end up with straight lengths of metal that can be inspected and then re-coated. A light brush blast with appropriate media is the best prep for a catalyzed polyurethane coating to coat the frame. Rarely have I seen the bent sheet metal frames be worth salvaging as inevitably the metal has lost enough thickness that its not worth fixing.

At that point its a crap shot on what the absorber is made up of, some do have a lot of copper, mine are solid copper risers roll extruded over copper absorber fins. Many others are mix of aluminum fins and copper risers and some were all aluminum. They all do have scrap value, but the copper ones usually are the best score.

I rarely if even see old collectors get reinstalled, Most folks who grab them are either dreamers or scrappers. The dreamers don't realize that they are getting a half a system. Even if they can salvage the rest of the system its rarely operational. I know of one system like this, the panels have been leaned up against a pole outdoors for several years, the stone lined storage tank's liner is shot, the controls are non standard and the heat exchanger bundle has freeze damage.

Scrappers have a couple of approaches, the smart ones call every listing on craigslist or other local sales site and spin a story that they really want a set of solar hot water panels but cant afford the asking price, that gets their foot in the door to physically show up to take a look at them. They usually can figure out what they are made of and then can offer to take them to a good home for reuse. The typical homeowner just wants them off their lot and frequently they just give them away rather then hassle with them. More then a few scrappers I have met are folks on unemployment or disability and scrap under the table so they dont really mind spending their time playing the percentages so if they get one score out of several ads , its free money to them.

Most early and current collectors if they were of a good design, were and are, not intended to be a sealed unit. Good designs recognize the folly of expecting a collector to be so tight it will float, and recognize the need for intentional venting. That's what the small ,1" or so vents with bug screens on the backside of collectors are for, usually at or near opposing (katy corner) locations.

Even with those considerations, early and even later collectors often fogged and continued to fog for mainly two reasons. For single glazed collectors, the worse of the two reasons was in the early days before everyone caught on to the idea that when standard insulation like batt fiberglass and also most rigid foam as used in the building trades was used for side/backing insulation, it would usually outgas at the higher temps. in collector service with the effluent stuff coating everything but mostly showing up on the hot (interior) side of glazing. The other and more usual fogging was the result of a combination of some small leaks that allowed ingress of liquid, along with inadequate/no intentional venting of collectors. One way or the other, moisture and water vapor will inevitably get into a thermal collector and it (the collector) must be adequately vented, otherwise the H2O will build up, wreck the insulation, and most everything else, and things will only get worse, including performance.

Double glazed collectors, which aren't around much any more, had the additional and likely problem similar to double glazed windows that have inadequate sealing between the lites. Since, and in spite of assurances to the contrary by glazing mfgs., all such seals will eventually leak, it being only a matter of when, not if, and the harsh service conditions in solar collector applications of daily and large temp. differences one side of a double pane assembly to the other, moisture will get between the lites. Sometimes, if not too severe, the inter lite moisture will vaporize when the collector heats up and condense/recoat the collector side of the outer lite. It might also freeze and likely wreck the seals when it does.

This isn't a knock, but I don't know if you've ever attempted to reglaze a collector. In my ignorance, I tried it once and quickly disabused myself of the idea that it could be done without proper equipment. Besides, I'd probably never get the glazing detail and sealing details anywhere near correct with as much as a glimmer of hope for a good and adequate seal, and I think I know what that part of the job requires. In that case, I'd need to rely on a lot of intentional and excess venting to save my butt.

As for dis/reassembly, most collectors I've seen are sometimes bolted at the corners, but more often riveted, with the side rails most often having the back sheet riveted to them, making disassembly more difficult.

So, if you're saying that rehabbing a thermal collector may not be the cake walk it might first appear, I agree.

For all the work it entails, and for those still reading this and interested, it might be just as easy to pull the absorber out of the old frame, while saving the glazing if possible, and build a new frame around the bones of the old collector. Just get the right insulation (see Johns Manville, they once sold insulation specifically for solar thermal collector applications), allow for adequate venting and remember that when it comes to caulking and glazing, the devil is truly in the details and that cleanliness IS godliness.