DC/AC Power Distribution Panel Part 4

This is an entry in our current non-fiction writing contest  By DanW


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As I built this project there were many little details that had to be worked out. Stuff like laying out all the components, figuring out where they would best be situated, how the wiring might be affected, etc. I didn’t want to put this info into the article I submitted to the SurvivalistBlog as it would have made it too long. It also became apparent that those folks that knew just a little bit about electrical things might be intimidated by this project. I hope that perhaps you’ll find my comments below helpful.

General Thoughts:

last picBefore you build any type of enclosure for your Power Panel get all of the components you’re going to use on hand. While you can begin to “get a feel” for how they’ll be mounted and used, finalizing a design before you have the actual goodies in your hands will produce surprises. Nothing like having the part right next to you so you can make actual measurements, see how things will fit together on a mounting panel, and begin to look for any layout flaws.

1. Make a paper or cardboard template of your front panel layout. This step if well worth the time it will take and allows you a chance to view what the finished product will look like. Transferring the hole centers and meter rectangles to the aluminum is then a simple matter of using a sharp punch.

2. Design to enhance serviceability! As you layout your project and begin to decide on just how you’re going to put it all together, and what type of materials you’ll use, think about the assembly and disassembly of all the pieces. A design that allows you free accessibility without having to remove things to get to a component is the goal.

3. The old saying of “measuring twice and cutting once” is so true. While things can be built “on the fly”, designing as you go, the result is often less than satisfactory (or useable). Time spent at the drawing board will pay dividends when it comes time to actually build your project.

4. Be aware of “spatial” relationships. Just because things look like they’ll fit when you layout the front panel of your project doesn’t necessarily mean they’ll fit on the back side of the panel. For example: When mounting the switches they require a ½ “round hole and clearance for the toggle to move up and down properly. On the other side of the panel is the switch body. It takes up more space. If you drilled the mounting hole close enough to the meter so that the switch toggle had clearance to operate, there might not be room enough for the switch body to be installed because the meter body was in the way.

5. Allow some time to pass before you begin to build the project. Review your “final” design several times and look for the inevitable “oops”. It’s easier to correct things before holes are drilled or cuts are made than it is afterwards. Go through the steps of building the project in your mind and on paper ………… it will be time well spent!

6. Evaluate your needs. Be sure you have thought out just what it is you want to build and how it will be used. This may seem like an obvious thing to do but “a need” is, after all, the thing that has motivated you to build whatever it is your building in the first place. Be sure that what you build is what you need!

Comments and Suggestions: (These are not in any particular order)
1. If you are going to make this project utilizing a wooden box and two part front panel as I have done …… layout you components, measure the needed metal panel size ……… then build the box. Be sure that the metal panel will fit into the grooves properly and can be easily removed before you drill holes to add your components. Use metal screws instead of sheet rock screws, predrill the screw holes and use screws that will get the job done without being overly long. For future reference as you are installing components, and with the metal panel installed, use a pencil to mark the exposed edges of the metal panel where it is exposed. This establishes a boundary on the panel where nothing can be installed that will interfere with its installation.

2. The Tenma units, 10 Socket AC Panel, and the Inverter are all placed on the right side of the front panel. The other front panel components (switches, meters, fuses, and Accessory style sockets) are all positioned on the other side of the front panel. This was done on purpose to facilitate the internal wiring. The Tenma’s, Inverter and the 10 Socket Panel have rather large cables connecting them to the various components. You’ll note that my layout plan placed the main 12 VDC positive and negative cables and interconnect bars on the right upright 1 x 6 (as seen from the rear) of the wooden box.

3. I used ½” grommets to protect the Tenma power cables as they passed through the metal panel.

4. The 15 amp internal fuse of the Tenma units will be a pain to replace when it blows ……. and it will eventually! To get around this issue I installed a panel mount fuse holder in each unit. This fuse holder has a twist off cap and will hold a 3AG type glass fuse. Once you’ve removed the base plate screws and have the Tenma unit open you’ll see a heavy copper (not insulated) wire connecting the switch to a point on the small circuit board. This wire should be cut and the wires from the new fuse holder attached to each end of the cut. A piece of standard 12 or 14 ga. solid conductor “house” wire will work fine. Leave the insulation on it and strip the ends. Now the Tenma unit’s switched outputs are protected with your new fuse (in addition to the onboard 15 amp original fuse). For my application I have installed a 10 amp fuse in the new fuse holder which is adequate considering the limited current load that I will require.

5. Installing the small meters in the aluminum panel is an exercise in patience. Unless you’ve got access to a metal shop with the capability to use hole punches of the correct size you are going to have to use your drill, reciprocating saw, and some files. Once you’ve got the aluminum plate fitting into the “box” you’ve built to hold it, take a sanding sponge and lightly sand both sides of the plate to “clean” it off and remove any marks/scratches, etc. Next you’ll need to draw an accurate template of everything on the plate where each item will be installed. I drilled all of the switch mounting holes first then used a round file to clean up the edges of each hole. I addressed the rectangular meter mounting cutouts next. Each corner of the area to be cut out has a hole drilled in the inside of the template. Using the reciprocating saw I connected the holes by cutting inside my lines. Now the files come into play. Carefully file away the excess material until the meter will fit snugly in the hole.

6. I found out that the Main DCV/Ammeter would not measure current below 1 amp. This is not a big deal and is not a cause for concern. The Tenma units have analog meters so they will ready current loads below an amp.

7. The final finish for the aluminum panel is up to you. It can be spray painted, sanded with an orbital sander to make a nice smooth spiral effect or you can use a sanding sponge to carefully sand it lightly in a straight pattern. Whatever you decide will work. I chose to paint mine because the lettering of the switches, etc. looked better on a painted surface. I used clear address labels and my computer to print out the text, then cut the labels to size. Once they were in place on the aluminum panel I sprayed the entire surface with lacquer. This affixes the labels and will seal them so they last longer without peeling off. A coat of lacquer will also keep bare metal looking good if you chose that type of finish.

8. I suggest you use a drill press to drill the holes in your metal panel. While an electrical hand drill will work if you’re careful, a drill press will help to make the holes more accurately, cleaner, and is a safer way to work. Whichever tool you choose be sure to clamp the metal panel to a solid surface to prevent any uncontrolled “spinning” of the panel if the drill locks up during drilling.

9. I modified the 10 Socket Power Strip so that the input power cable is able to be fed through a hole drilled into the wooden panel. The 10 Socket Power Strip comes with a 15’ cord. Figure out how much cord you’ll need to connect it to the AC buss bars on the rear of the Power Panel (Hot, Neutral, and Ground), add a foot or so, then cut it off. The left over cord can be used for the AC input to the Power Panel and it’ll already have a three prong plug on it.

10. I thought I was through with the design phase but realized that it would be good if the Battery was protected from possible misconnections or other problems that might occur on the Panel. To accomplish this I added a standard 30 amp automotive style circuit breaker. This breaker is mounted on the inside of the box rather than try to make it accessible from the front of the Panel. It cannot be manually reset if it trips but it will reset itself and continue to trip until the high current problem is corrected. It is wired in series in the 12vdc Positive line between the battery and the Main 12vdc Switch (S1).

11. There are several things to keep in mind as you wire your Panel:
– Wire one circuit at a time.
– There are two basic types of circuitry in this project: Those that deal with the primary supply voltages and those that deal with the individual circuits. I suggest you wire the Supply type circuits first and, once this is done and verified, move on to wiring the individual circuits.
– Verify your work as you go. Double check what you’ve wired for accuracy and operational correctness.
– Keep the wires as short as possible yet maintain a little extra wire as a “service loop” at each connection point. Don’t compromise serviceability.
– Do not “bundle” the wires into neatly tied wiring harnesses. Sooner or later you’ll have to do some maintenance work on the panel. This may involve replacing a component with a similar but not exact duplicate of the defective part. No need to have to cut the bundle ties to reroute or replace an interconnecting wire.
– Use solid conductor wires for your DC devices and interconnections whenever possible. The main 12 vdc input wiring will be more than likely be multi-strand due to the desire to keep it somewhat flexible and the higher current involved. It would be good if your 12 vdc circuits can be wired with colors that match accepted standard for Positive (Red) and Negative (Black). Be careful when wiring the circuits not to confuse Black (AC Hot) with Black (DC Negative). I suggest you wire all of one type of circuit (AC/DC at a time.
– AC circuits can be wired with either solid or multi-strand wire.
– If you are using “slide-on” type connectors to attach the wiring to your switches I you solder those slide-on connectors to the wire. Crimping the connectors is okay, but a soldered connection is far superior and less problem prone.
– I don’t recommend the use of “wire nuts” for connections in this project. If you do use them be sure to use the right size and tape them with electrical tape to keep them from unscrewing.

12. Installing the switches, fuse holder, and meter in the wooden section of the front panel
can be difficult if you use a piece of ¾” thick wood. These components are not really designed to be installed in anything over ½” thickness. I decided to stay with a ¾” thick piece of oak for the wooden panel as it offers more strength plus it’s thick enough to cut a groove that the metal panel will fit into. To solve this thickness problem I used a Forstner bit to produce an area of reduced thickness on the backside of the board. I marked out the area where I wanted the oak to be thinner (¼”) using the template and, a drill press for accuracy, removed the excess wood. A little touch up work with a sharp chisel cleaned up the edges of the one rectangular cut.

13. I made the box frame using 1” x 6” oak boards. Since these are actually ¾” thick by 5 ½” wide I was concerned that the Inverter would not easily fit in the configuration I wanted. To resolve this minor problem I cut a 3/8” deep slot in the rear bottom of the wooden front panel. The flat mounting plate on the Inverter could be inserted in this slot leaving enough room to use two screws on the outboard side on the plate to hold the Inverter in place. The Inverter fits nicely without protruding to far from the back of the box.

14. I was going to use some dry transfer lettering to make the labels for everything but found that these were very difficult to use and have them turn out looking good. Instead I used clear address labels (printed with a computer printer) to make the labels for the switches, fuses, etc. This is a fairly cheap way to make good looking lettering to give your finished project a touch of class! These are self-stick labels and work well on the metal and wood panels. A trick that will keep the labels in place so that they don’t peel up after years of use is to apply a thin spray coat of polyurethane or lacquer to the surface after installing the labels. Allow a few hours for everything to set up and then put on another thin spray coat. This technique works equally well on a metal surface.

15. I tried very hard to ensure that the rectangular cutouts for the meters and the holes for the small meter switches were sized accurately. Nonetheless, there was some play and these components wiggled around a bit. To solve this problem (it might cause the slide-on wire connectors to loosen) I placed a dab or two of clear silicone caulk on the back-side edge of each component to hold it securely in place. If the component ever has to be removed it is still easy to do.

Prizes for this round (ends May 24 2014) in our non fiction writing contest include…

  1. First place winner will receive –  A $150 gift certificate for Hornady Ammo  courtesy of LuckyGunner, a Wonder Junior Deluxe grain millcourtesy of Kitchen Neads, a one year subscription to the Personal VPN service courtesy of unspyable and Three Survival Seed Vaults courtesy of LPC Survival.
  2. Second place winner will receive – Brand New, Sealed Case of Military MREs (Meal, Ready-To-Eat)  a $119 value courtesy ofCampingsurvival.com and a Survival Puck  courtesy of Innovation Industries.
  3. Third place winner will receive – a copy of my book ”31 Days to Survival: A Complete Plan for Emergency Preparedness“ and “Dirt Cheap Survival Retreat” courtesy of TheSurvivalistBlog.net a copy of “The Survival Medicine Handbook” courtesy of www.doomandbloom.net and a copy Herbal Antivirals and Herbal Antibiotics .


  1. JP in MT says:

    Thanks for all the work!

  2. Big Bear says:

    Thanks JP,
    Just sent an email to MD. The schematic was not included in this part (or the other parts 1-3) and it’s really more important than the photos that were posted. I’m sure MD will make it happen!

    Big Bear aka DanW

  3. Hi Dan,

    I’m happy to see the use of fuses in your design because they save a lot of blown equipment. This seems well thought out. Personally, I’m a fan of the old Western Electric power equipment. It was built heavy duty and designed for the worst you could throw at it. What is, or was your profession?

  4. Doug Pearson says:

    Great article, Big Bear! This is EXACTLY the style of article I need to actually build this: I’m not quite an electrical moron, but I’m no electrician either. This is just right for me. Kudos!

    On another note, I have two unrelated questions both of which are not directly connected to the present project of yours. These arise from comments in your earlier articles. I will send you a private email if you contact me at dougpearson[NO space here]31415 – at – gmail – dot – com. Note that the first part (prior to the -at- sign) has NO spaces.

    Thanks again for the great article! I WILL

    • Big Bear says:

      Thank you for your interest in the project. Doug, I’ve been burned before by unscrupulous people that cruise weblogs with bad intentions. Don’t mean any insult to you but I would prefer that you respond here, on this blog, to give me some idea of your “unrelated questions”. If I feel a measure of comfort then we’ll figure out a way to connect.

      • Doug Pearson says:

        OK, no problem.

        First, I am VERY interested in your future project of making a system to provide some heat for chickens and rabbits and their watering systems. I don’t have my coop set up yet, but I remember my grandmother having to go out each morning and provide new, warmer water for the hens. Gets very cold in Nebraska in January. So I really, REALLY want in on that project.

        Second, I was intrigued by your mention of putting your Power Panel in your faraday cage. What do you use that would hold such a thing? You seem more than adequately knowledgeable, so do you ground your cage or not? (From what I’ve read, faraday cages do not need to be grounded, but I’d like your opinion.) I have plans on converting an old granary in our old barn (about 6′ x 8′ x about 7′ tall) into a faraday cage with gavanized sheet metal, sheet metal screws, conductive copper tape, etc. . . . well, we’ll see how it goes . . . Just wondering what you’ve done.

        Both of these are quite off topic for the matter at hand, but I’d sure like to know.

        Doug Pearson

        P.S. I hit the wrong button on the above note. I meant to finish the note with “I WILL be using these plans!”

        Thanks again for a great article!

        • Good Morning Doug,
          Glad you understand my hesitation to divulge my personal data ………. you’ve got to buy me dinner first!!!

          Anyway, I’m about 75% finished with the initial design workup for an automated solar powered low voltage water freeze preventer suitable for use with chickens, rabbits, and perhaps even livestock. Ordered the parts last evening and once they are here I’ll begin testing the design. Don’t want to give too much away until I am certain it’ll work as planned. I will post a write up with drawings, schematics, photos, etc. once it’s ready.

          As to Faraday Cages or shields: There’s a lot of discussion about whether or not they should be grounded. Good and valid arguments for yes and no. I am a proponent of grounding the cage or shield. My opinion is based on my belief that protection from an EMP/CME will be better provided using a grounded shield than by using an ungrounded shield ………. that plus 50 years experience in the electronics industry. Currents induced within the metal of an enclosure by an EMP or CME can be allowed to dissipate or they can be shunted to ground. What causes the damage to sensitive electronics components is the standing currents induced within metal and crystalline structures. These standing currents are produced by an EMP or CME. I would prefer if those standing currents were directed to ground rather than have them slowly dissipate (slow is a relative term here as we’re talking about microseconds). So, I purchased a standard office type metal cabinet. Took a standard AC three prong power cable, stripped the end and isolated the hot and neutral wires. Took the ground wire, soldered a ring lug to it and connected it to the cabinet …… then plugged it in to the wall outlet. Viola! Grounded Faraday Cage! Whether grounded or ungrounded, your metal granary will make a great Faraday Cage. Hope this helps. By my posting this I’m sure you’ll see responses arguing the “ungrounded” side of the discussion.

  5. Big Bear says:

    Still working with MD to get the schematic posted! Thanks for your comments.

    Harry, I spent my entire working life in electronics. Joined the Navy at age 17 1/2 went through A,B, and many, many C schools. B School in Great Lakes was a year long. It was the University of IL. Engineering 4 year course (without the Humanities and unrelated studies) and was adapted to be taught in a very condensed manner. Started in electronics back when most everything was tubes and transistors were new. Was taught computer theory when torroidal cores were being used for memory storage devices! That alone should tell you how old I am ……. got into field service for Varian, KLA Instruments, Icore, SemiTool, and eventually moved into Service Management for the last 15 years I worked. Retired 19 years ago at age 48 but still enjoy designing and building things.

    Fuses are so important that I wouldn’t consider building a project like this without including plenty of them. Cheap Insurance!

  6. DanW:
    Excellent project, I have no doubt you were educated in the U.S.N. The Navy has always had an excellent track record of training personnel very well in electronics, avionics and electricity.
    My brother is USN retired and his MOS was as an AET, he doesn’t do anything any longer but I’m glad that you’re keeping busy with work projects like the one presented here.

    Excellent post!!!!!

  7. Another tool (along with the tapered reamer, LOL) that can be handy is a Nibbling Tool like this one http://www.parts-express.com/nickel-plated-nibbling-tool–360-022?utm_source=google&utm_medium=cpc&utm_campaign=pla

    Guess I’m just a sucker for hard work, and I happen to have these tools around from a day when they were all I could afford.

  8. Jersey Drifter says:

    Big Bear
    Nice Job !
    Glad to see it all come together and thanks for the comments at the end of part 4. They will be a help in how to approach things, what to watch out for, and thoughts for work layouts.

    Got to admirer a squared away project from a squared away guy!

  9. thanks again for this

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