General (63)

Solar 3: Connecting

[This is the third in a series of articles describing installation of a solar hot water system.]

With the panel now securely mounted on the roof, we can turn our attention to plumbing. With an electronics background, I have done plenty of soldering– but only wires, not copper pipe. YouTube has several videos demonstrating the procedure, so it is time to get some pipe and practice “sweating”…


Time to “tool up” for the job:

From the top and counter-clockwise: propane torch, teflon tape and pipe dope (more on that below), lead-free solder, 4-in-1 cleaning brush (for removing oxide from 1/2″ and 3/4″ copper tube and fittings), flux with brush, and pipe cutter. Not shown but also recommended are leather work gloves and a bench vise.

We want to avoid as much down-time for hot water availability as possible: teenagers getting ready for school in the morning are not particularly open minded about the advantages of solar energy when they are taking a cold shower. Without disconnecting the current system I could start on the roof and connect the solar panel with pipe near to where the pipe will pass through the roof to turn down towards the storage tank.

Our panel has four connecting ports, two on top and two on bottom. One top port is used for coolant output, and the other can be connected to another panel– not necessary in this installation.

We used the extra top port to connect a pressure relief valve and a coin vent used to purge air bubbles from the coolant loop, which should be installed at the highest point in the system.

Since the solar panel might someday have to be temporarily removed when our tar and gravel flat roof is redone, we installed unions at the top and bottom ports.

After roof work, I soldered several sub-assemblies of parts together, to make final assembly go faster. Several parts, such as boiler drain valves, pump, and gauges, had pipe threads and required solder-to-pipe adapter fittings.

I tested sub-assemblies when possible, using a collection of threaded end-caps and a Schrader valve adapter. I built the adapter using a Schrader valve stem (from an auto parts store), a brass 1/4″ female to 1/2″ male threaded adapter, and a small quantity of JB Weld metal epoxy. The brass adapter is not sized to thread with the valve stem, and relies on epoxy to seal and hold the parts together.

Here is the gadget in action, testing a sub-assembly.

Pressure testing showed no leaks on solder joints, but revealed several leaking threaded joints. Searching the web, we ended up using three layers of yellow (not the thinner white) teflon tape on a male pipe thread, and on top of that brushing on a modest coating of RectorSeal TPlus2 pipe joint compound. Problem solved.

The plan is to remove the old water heater and replace with the solar storage tank on Friday, after the dread teenagers have left for school. My goal is to get cold water back by the end of Friday, finish connecting the coolant loop by end of Saturday, and fill coolant Sunday morning to begin heating water. A professional could work much faster, but I wanted to be methodical, and expected to take breaks to ponder any problems.

Behold our old gas water heater.

In addition to the hot and cold water connections, you will observe the required pressure relief valve and pipe, as well as some other  devices particular to our installation: a pressure limit switch on the cold water line for our water pump, and a valve connecting to 1/4″ copper tubing supplying water to an evaporative cooler. Our new installation will try to “neaten up” this extra hardware.

After turning off the gas supply to the water heater, I turn off the water supply, drain any extra water in the lines, unscrew the hot and cold supply to the tank, cut the soldered pressure relief line, and remove the exhaust vent. The hole in the roof for the exhaust vent will make a handy pipe run (passageway) for the coolant loop going to and from the solar panel. After connecting a hose to the tank drain valve, I let the tank empty and moved it out of the way.

Before putting in the new tank, I attached a plywood mounting panel to studs in the wall with lag bolts. (With hind-sight, I would have mounted the pump-gauges-and-expansion-tank assembly to the panel beforehand, and would mount the panel lower for improved accessibiilty. More on woulda-shouldas in Part 4 of this series.)

I rolled in the new tank and made connections for hot, cold, pressure relief, and the extra bits mentioned above. All threaded connections used the tape and pipe dope combination mentioned previously. I added a anti-scald mixing valve sub-assembly to prevent scalding in case water in the storage tank got hotter than a normal water heater.

Notice I added thermometers at both the input and output to the mixing valve, which is overkill. The mixing valve requires an extra connection between hot and cold lines, making the connections look more complicated.

See the aluminum foil? I placed that on tank and sometimes walls to shield parts from solder drops and heat.

After turning on water, I was delighted to find no leaks! After a well-deserved break it is time to complete the coolant loop.

I fastened the expansion tank and coolant circulation pump to the mounting board with metal plumber strap, after cushioning between the board and parts with foam rubber to reduce vibration. Unions were used for the pipe runs up to the roof, to make it easier to disconnect for servicing. I thought about adding unions to make it easy to remove the pump– the most likely part to fail after decades of service.  Too many unions have aesthetic and reliability issues, so I plan to cut and solder for pump replacement.

With everything connected in the coolant loop, it is time to pressure test.

I used a bog-standard bicycle pump with integrated gauge, and pressured up to 10PSI. Sadly, the pressure did not hold, so soap solution was applied to solder joints and threaded joints until a leak was identified:

This was one of the last solder connections made, so perhaps I was in too much of a hurry or too complacent. After using wire brush and flux on the pipe and fitting, I did have to let this joint wait for several minutes before sweating. Perhaps this time delay was also a factor. Re-heating and applying more solder did fix the leak.

I pumped the pressure up to 20PSI and discovered another leak that did not leak at 10PSI. This leak would not close with more heat and solder, so I actually had to cut out the leaky fitting and try again with fresh clean parts. Rather than be discouraged, by this time I was getting quite comfortable with cutting pipe and soldering, and glad to be able to take time to do the job right.

After fixing the two leaks, the coolant loop held air at 20PSI for hours with no noticeable loss, so the system is ready to add coolant. I wanted to do that in the morning before the sun is up to begin heating the panel. More on that in Part 4 of this series.

Related Posts: Solar 1, Solar 2

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Related Post: Countdown

Voyager 510 Headset USB Charger

We often use a Plantronics Voyager 510 Bluetooth headset with our computer, so we can a) listen to streaming video/audio without inflicting our choices nearby innocents,  and b) remain untied by a corded headset when we jump up with sudden inspiration.

A previous post explored building a USB charger for our cell phone, and we decided to try the same thing to charge our headset. Over time, we are trying to reduce the number of wall-wart chargers used with our laptop, so we don’t have to carry chargers on business trips and to eliminate wasted electricity when the charger is plugged into a wall socket and not charging a gadget. The USB charger for our cell phone used zero standby current, and we hoped to do the same for the headset charger.

USB Standards

A USB port can supply 100mA at 4.75 to 5.25volts. A higher current, to a maximum of 500mA, can be drawn if the port follows a particular handshaking protocol.

USB Pin-Out
















Voyager 510 Charging Requirements

The headset charger has a barrel type plug with diameter 3.0mm and only 3.5mm in length. Notice that the barrel has a reduced diameter region near the end to help the headset “grip” the plug.

The open-circuit voltage measures 5.5V, and the charging current was 63.8mA. This is within the 100mA current limit of USB, and the voltage is close enough to the USB supply voltage that we suspect a direct connection to the VBus and Gnd conductors of a USB cable will successfully keep the headset charged. See the “Design and Experiment” section of a previous article for more in-depth hand-waving.


Usual Disclaimer: Use this information at your own risk. We are not responsible for damage to your headset or computer.

We couldn’t find a similar connector anywhere on Digikey or other electronics parts vendors we searched. (If anyone has found a source, let us know.) Reluctantly we purchased a spare charger on Ebay for less than $5, just to salvage the connector.

Take a spare USB cord and cut off the series “A” type plug, leaving a few centimeters of cable. Remove a centimeter of outer insulation and shield, exposing four wires. You can cut off the green (D+) and white (D-) wires– they are not needed here.

Cut the spare charger cable 10cm from the connector end, and remove one cm of outer insulation, exposing a red and yellow wire. The red connects to the inner conductor of the plug, 5V, and the yellow connects to outer GND.

Strip insulation 0.5cm from the wires. Thread a length of shrink-wrap tubing on the cable, and twist the red wires together and solder. Twist the yellow wire from the charger plug to the black wire from the USB plug, and solder.

Use a bit of electrician tape to insulate the conductors, and wrap more around both wires for strain relief.

Check continuity with a meter. Slip the shrink wrap tubing over the solder joints and apply gentle heat until snug.


It works!

Related Posts: V176 Cell Phone USB Charger, Power to the Programmers

OS Wars Film Festival

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Related Posts: Tech Support Film Festival, Theremoid FilmFest, Theremin Video Film Festival

Solar 2: Mounting the Panel

  • December 31, 2008
  • General

[This is the second in a series of articles describing installation of a solar hot water system.]

The solar panel was not in stock at AAASolar, so we had to wait a couple of weeks for it to be freighted to the shop. We have access to a truck, so we could pick up the goodies at the shop and not have it delivered.

We could have transported the solar panel and storage tank in one trip, but decided to truck them separately to avoid any possibility of damaging the panel. Cracked glazing would have made me very sad.

Here is the storage tank protected for the trip:

The solar panel is solid and heavy, approximately 150lbs, too massive for one or two people to carry up a ladder. In retrospect, the easiest way to get this panel onto a flat roof is crowd-sourcing: get six good friends or family members with ropes pulling and pushing the panel together. Sadly this particular day I was (almost) friendless, so cleverness was in order. Phil and I fastened a 4×4 crossbar between two ladders, affixed a pulley in the middle, and tied a rope harness around the panel. We parked Phil’s jeep with electric winch in the garage underneath the ladders (barely seen in this photo because the dark-colored vehicle is in shadow).

The winch and pulley pulled the panel up to the roof, while one person on the roof steadied the panel using ropes. Again, this technique worked but is overly complex– use crowd-sourcing instead.

I could not work out how the mounting hardware fastened to the panel, and no documentation was included. AAASolar had no instructions for this particular model, and recommended we contact the panel manufacturer SunEarth. No instructions were found on the web site– a helpful person on the phone faxed us the drawings we needed.

One thing apparent from the drawings is that the panel is mounted  with the shorter side along the roof, unlike most panels we see installed in this part of the country: Good to know!

We needed to bolt the panel mounting hardware to the roof with long lag bolts sunk into roof joists. The problem was finding the roof joists! Two different stud finders gave no consistent readings on the roof (and yes, we did try the trick of using cardboard over this rough surface), and we drilled two or three holes that totally missed a joist. It’s bad enough to be drilling into a perfectly nice roof, but to miss the timber beneath and have to patch the hole is most embarrassing.

Finally, we hit upon the trick of drilling a test hole at a shallow angle, and then using a coat hanger wire as a probe to test for where the joist is located.

Once we know where one joist is, we should be able to find the next one, assuming the joist spacing is the same as over the garage, where joists are visible. One final indignity: the joist spacing was different on this section of the roof, so we had to drill another shallow angle test hole as before and patch it afterward. We used 2×4 boards as footers to help spread the weight on the roof surface, and screwed long lag bolts through the metal mounting block, the wood footer, and into the roof joist.

Albuquerque has a 35 degree latitude. We elevated the panel to 55 degrees, to give more sun in the winter when the panel needs it most.

Related Posts: Solar 1, Power to the Programmers

Solar 1

  • December 29, 2008
  • General

Sagebrush Systems “world headquarters” is fortunate to be located in a building with passive solar heating. A large expanse of south-facing windows direct sunlight onto adobe walls and bare brick floors for heat storage.

The furnace hasn’t been turned on for over a decade, so we save a good deal on heating costs. (In full disclosure, the solar adobe construction of our building does not provide complete warmth at our latitude at 5000 feet elevation, but we throw on an extra sweater and become accustomed to somewhat lower temperatures than the 70 degree F office workers expect. For a couple of weeks each year we get consecutive days of overcast weather, requiring the fireplace to be used.)

We plan further energy independence, with solar hot water, possibly a supplemental solar hot air heater, and eventually a grid-tied photovoltaic system to supply all electricity needed by Sagebrush.

Our latest energy project was to install a solar hot water heating system. The area is blessed with plenty of solar exposure, averaging over 300 days of sunshine a year. A few periods in winter might have cloudy days extending for a solid week or two. We do have hard freezes, so a glycol system is necessary. (A drain-back system might work here, but based on the number of burst water lines we needed to fix in supposedly drained water lines running up to our evaporative cooler, we decided to use a glycol system.)

Active glycol systems can use an electronic controller to monitor temperatures and turn the circulating pump on and off, or use a pump connected to a photo-voltaic (PV) panel which runs the pump only when the sun shines. We wanted a PV system, based on the experience of a friend with a system installed a few decades ago, whose original manufacturer no longer exists and has difficulty getting the controller serviced. We also confess to a pyschological satisfaction of using no utility energy, even the minimal amount needed to run a circulating pump.

We wanted a kit-based system, so we could participate in installation and learn better how to maintain and use the equipment– and because it’s a challenge. Someday perhaps one could go to a big-box “home improvement” store and buy a solar hot water system in kit form or completely installed, but that day is not here, so we have to shop on the Internet. This system from looks well-engineered for do-it-yourselfers, with a complete step-by-step installation manual and no soldering required. Their solar panels are also extremely light-weight, which should be an advantage for high slanted rooftop installations. Ultimately we decided against this system because of the plastic glazing: We get a LOT of UV radiation here, hard on plastics, and we recently replaced an acrylic sun roof that was thoroughly destroyed after twenty years of sun exposure. Perhaps these solar panel glazings have superior UV resistance, but how can a buyer prove that?

Ultimately we purchased a solar kit with tempered glass panel glazing, ordered from the venerable AAASolar, located in nearby Albuquerque. It doesn’t come with a complete install manual like the system above, but they did offer to provide reprints of articles from Home Power magazine dealing with installation. The article “DWHW Installation Basics Part 2” from June 2003 was particularly helpful. We also save on shipping charges, since they are so close, allow local pickup, and we have a truck available. The kit includes solar panel, storage tank, PV panel, pump, assorted valves and gauges. You supply plumbing available from your local hardware store. Propylene glycol and pipe insulation are extra.

In future posts we document our adventures (and minor missteps) in installing the system:

Solar 2: Installing the panel.
Solar 3: Connecting everything.
Solar 4: Starting up and running, lesson, and future.

Related Posts: Power to the Programmers

No Way

  • December 16, 2008
  • General

Noism: the practice of referring to oneself in the
plural as “we”.

“Only kings, presidents, editors, and people with tapeworms have
the right to use the editorial ‘we’.” Mark Twain

(image courtesy Wikimedia Commons)

We do this a lot when blogging…


  • December 11, 2008
  • General

How do you read QR codes if you don’t have a mobile phone handy? This on-line reader will run on your JVM (Java Virtual Machine).

Untangled Web

  • December 10, 2008
  • General

With a web site maintained for several years now, we had fallen behind somewhat in best web practices. We only made limited use of CSS cascading style sheets, and relied on tables with lots of ALIGN and BGCOLOR parameters for layout. (At least we didn’t use tiny invisible GIFs for layout. What a hack.) With cruft accumulating over the years in our HTML, it was time for a makeover.

Strange Banana showed us how a random CSS generator could radically change the appearance of a web site with no changes to the XHTML files. Zen Garden showcases many elegant CSS designs for the same site. Delving further, we discover A List Apart, with a wealth of articles on CSS tricks and web design best practice.

We grabbed the HTML Validator add-on to Firefox (based on Dave Raggett’s Tidy, also available as a web service), which displays a check-box icon on the bottom-right corner of the browser window when a page has no markup errors.

How surprised we were to see so many errors on our own web site! Hold on, are we not coders? Do we not revile syntax errors? This must not stand!  We resolve to correct our mistakes and earn that cute little W3 code correct icons.

Other Firefox add-ons we found useful included IE Tab (for previewing HTML in IE while staying in the Firefox browser) and also Firebug.

AOLPress, the ancient WYSIWYG HTML editor we used was set aside for something with better CSS support. The open source multi-platform Amaya has reasonable WYSIWYG capabilities (although we now tend to use it with split pane web view/source view mode and edit the source code directly). Amaya also includes the Tidy code, to automate some HMTL clean-up and automatically check for valid code with a similar icon to the Firefox add-on mentioned above.

Once we converted the main web site pages, we still needed to work on this blog, which uses WordPress non-hosted. We switched to the Fluid Blue theme which conforms to strict XHTML, but we still got errors whenever a video was present. using the pb-embedFlash Media Manager fixed this last problem and we now get correct XHTML code.

Now if I could only learn good website layout design…