When you shop for a PV Solar Grid Tie inverter you are well advised to ensure the unit complies not only with UL testing, but also passes some form of Part 15 Class B test.

This gives you the best chance of not corrupting the communication ability of a licensed communications service such as FEMA and even Amateur Radio.

Even with Part 15 compliance there is a bit of risk involved with installing DC to AC inverters as they are inherently very noisy in radio communication bands. The better ones do their job and do it quietly.

It is absolutely possible for your new PV Solar Electric system to fully comply with Part 15 Class B requirements and still cause interference to a licensed communications service. It is up to you, the owner of the Part 15 equipment, to ensure you do not interfere. If you cannot terminate the interference during operation of your equipment you are obligated to cease use of your system as the licensed services have absolute priority.

It is a popular incorrect notion you have a right to operate any product you can legally purchase.

Checkout the language of the FCC’s Part 15 rules to learn more. Part 15 devices may not pollute the RF communication bands under any circumstances. Also they must accept any interference from primary users. Harsh, but true.

Many folks stumble into this issue often with 802.11 wireless LAN sharing bands with other services on a secondary basis.

Anyway, the point is investors of PV Solar are committing vast amounts of cash into their systems and are taking a big risk with the noise from their inverters. You are 100% responsible for any issues so be careful.

This following is a myth.

“JACK/PLUG – In electronics, a jack is a female part into which one inserts a plug, the male part.”

While often the case, the real definition is the jack is the more fixed of a connector pair and the plug is the less fixed connector of the same pair. Where two connectors are neither less or more fixed with respect to each other, both are a plug.

This was quite sensibly defined most recently in the IEEE-200-1975 standard. This standard was renewed in the 1980s and withdrawn in the 1990s. Even so it and IEEE-315-1975 form the basis on how to create reference designators in and around electrical equipment.

The notion Jack and Plug ever meant anything to do with a male or female contact, seems to have come about in the 1980s and 1990s. Somewhere in that time frame young engineers were not properly mentored by their elders in the way of good engineering practices. Bad habits leaked into the general population and now very few technical folks know how to properly annotate the references in harness designs and other electrical assemblies.

IEEE-200-1975 (also known as ANSI Y32.16-1975) serves as the last collection of knowledge dating all the way back to the 1950s in the MIL-STD-16 specification. UPDATE: See Below

Golden rules for harness reference designation from IEEE-200-1975 include:

  • The movable (less fixed) connector of a mating pair shall be designated P [where P means plug].
  • The stationary (more fixed) connector of a mating pair shall be designated J or X [where J means Jack].
  • If two cables are to be connected to each other, each of the mating cable connectors shall be designated P.

That last item is a mind blower for many. Yes this really means there is no such requirement to have J123 connect to P123. Efforts to try and achieve this are a notorious waste of time and such conventions are very easy to violate and, thus, break. A complete system on how to annotate an entire collection of electrical equipment is well defined in IEEE-200-1975. Despite it being withdrawn from active support in the IEEE, copies are still available from Tech Street and other standards suppliers.

Frequently heard statements:

“The fixed/less fixed distinction doesn’t work when both are unfixed, as is commonly the case when cables are being extended or split.”

This was never a problem since Plugs can connect to Plugs.

“Whatever IEEE may have wanted to establish, that’s not how it worked out…”

The IEEE did not establish anything. They documented what was once common knowledge, at least for technical folks, in the 1970s based on documentation dating back to at least the 1950s. It is clear the lack of mentoring is creating the break from tradition.

“Plugs always have male contacts while Jacks always have female contacts.”

No they don’t. Look at any PC (an older one) with a DB25 parallel and DE9 serial ports – all Jacks. Look at the AC power “Jack” on your PC – male for a very good reason. Still other connectors, aerospace connectors come to mind, have both male and female pins in the same body.

“Our engineers are from MIT so our custom annotation system is better.”

Perhaps, but the chance any super star engineer can outwit the collective knowledge of thousands of engineers and hundreds of thousands of man-hours documented in the standards… is laughable. Sure you may have the smartest team on planet Earth. Good for you. Keep their talents focused on the real engineering problems not engineering methods. Otherwise your A-Team will be in the unemployment lines after you miss your deadlines.

“We mandate each Pxyz to match up to the same Jxyz.”

This instantly breaks if you have two identical sub-assemblies in your assembly since each item will have the exact same series of J numbers on its housing. IEEE-200-1975 provides a very simple and elegant solution for this scenario; Buy a copy and read it.

“We ensure all the Jacks on all duplicate sub-assemblies are unique by writing new J numbers over top the ones printed by the manufacture.”

You just tripled the paperwork to track the “change” you made to an, otherwise simply identified, off the shelf item and must generate a whole new Control Drawing to track this change. Hopelessly ridiculous.

“Do Engineers care about the proper use of reference designators?”

Engineers care. Engineeer wannabees don’t. Harsh, but true.

Other Standards?
I have searched the standards archives in depth to find any current standard that dictates a better approach than IEEE-200-1975. SAE AS50881 “Wiring Aerospace Vehicle” comes close, but really addresses how to identify the wires bundles themselves, not the connectors. UPDATE: See Below

The point is this. How to properly annotate electrical assemblies is nothing new. At some point the knowledge was dropped and chaos erupted causing, among other things, the bizarre concept of a plug meaning a male.

To Young Engineers:
If you are a young electrical engineer, you need to buy your own copies of IEEE-200-1975, IEEE-315-1975 and why not also IEEE-280-1985. Read them. Learn a great way to annotate. Amaze your boss by saying you will take responsibility for annotating your next project using a real standardized approach rather than home-brewing some half-baked method.

To Supervisors:
Supervisors, you need to find a way to pass on the knowledge stored in the above standards. If you don’t you are literally spending your project funding on the equivalent of learning how to read and write. Keep your engineers focused on the real problems to solve. Don’t spend time re-inventing the wheel.

To Contract and Specification Writers:
Make adherance to IEEE-200-1975 and IEEE-315-1975 a requirement. Save money.

If you do nothing else, please find a copy of IEEE-200-1975 and read it through once. It is very short.

Good luck.

UPDATE July 29, 2009

The commenter below discovered ASME, the mechanical engineering standards group, created a new standard to pick up where the withdrawn IEEE-200-1975 left off. It is called ASME Y14.44-2008. Apparently the void left by the removal of IEEE-200-1975 was felt by many so ASME came to the rescue with ASME Y14.44-2008. How embarrassing for the IEEE to have a mechanical engineering association pick up an electrical equipment standard.

I have ordered a copy from ASME and eagerly await its arrival for review and comparison. Stay tuned to this COSJWT post.

I was talking with a friend of mine who specifies battery technologies for a living. Our conversation drifted to the topic of electric vehicles and, more specifically, the batteries for them.

I suggested the idea that many times the good old lead acid battery is hard to beat for many applications, even ones with severe weight requirements because:

  • Joule for joule they are heavier than newer battery types include Lithium chemistry variants, but they are not an order of magnitude heavier
  • Most everyone knows how to deal with a lead acid battery
  • The recycling process is very mature – at least in the US
  • Within practical limits, lead acid batteries handle over charging
  • Vehicle electrical systems are most often designed with the expectation a lead acid battery is strapped across the bus to help regulate the voltage

My friend added some more thoughts on why it is, perhaps, folly to think Lithium batteries will fulfill the goal of replacing today’s vehicles with all electric versions…

  • There is only so much Lithium in the world
  • There is not enough Lithium to make enough batteries to replace even a fraction of today’s vehicles
  • With a couple of exceptions, Bolivia has a large share of the world’s Lithium reserves and may become the new OPEC leader of Lithium

The particular post came about after reading this interesting article…

Can Better Lead-Acid Batteries Compete in a Lithium-ion World?

…which describes some promising enhancements to the good old lead acid battery.

I wonder if Axion Power is publicly traded…

21 April 2009 · Topic: Energy · Tags: , ,

Recently my interests have turned again to alternative energy sources. Whenever I do this, I always find myself looking at the big picture of every energy sub-topic including sources, transmission and use.

For example…

Hybrid automobiles seem to be an interesting idea initially. However, if you take a step back and look at the entire energy equation you begin to see they don’t provide a benefit worth the extra costs frequently paid for the hybrid option. This benefit changes, of course, with the price of fuel, but generally, the market seems to price up the very benefit they claim to provide. We will examine more of this topic in another post. For now the point is the term “Hybrid Car” seems to be just a term the owner can brag about – even if the real benefit is not really there.

The same deal goes for electric cars. Time after time I hear folks who think they have zero emissions with their electric cars despite the fact they consume electricity to charge their vehicle which is provided largely by the burning of coal. If you take just one step back in the energy path, the zero emission car is a myth… so far.

Then there are the folks who take the bold action to obtain an all electric vehicle, an impressive photovoltaic array, storage batteries and the necessary gear to completely charge their vehicle from the Sun’s free energy. The return on investment of such a system is very long to be sure, but let’s assume the owner is creating this system for philanthropic reasons. This leaves the purchaser bragging rights of a truly zero emission system. Here again, we have to take a step back and view the energy equation. It took a lot of energy to manufacture the solar panels and the batteries. There are batteries in the car, too, which take energy to build. From what I have found on the Internet, it takes from one to four years for solar panels to generate the energy it took to build them with the good news this is getting better every year. The point is can this person claim to be saving the environment with this system? Maybe after many years.

So if we move the topic towards powering the needs of a typical home what can be said of the possible alternative energy sources? Solar, wind and hydro seem to be the big three. Not many folks can benefit from hydro so let’s constrain the discussion to Solar and Wind Alternative Energy Sources.


Photovoltaic solar panels cost about $4-$6 per watt installed (much less if you use Ebay cells in your DIY panels). Then there are additional pieces of equipment depending if you have a storage or grid-tie system.

When you add up the costs, calculate the expected energy and compute the net benefit based on the cost of electricity (my current cost is 12.1 cents per kWhr) the return on investment (ROI) is something like 23 years. This will, of course, improve if electricity prices rise beyond inflationary rates, but it will be very difficult to bring the ROI down to the practical limit of 3-5 years.

Let me repeat that.

If saving money is your aim your ROI should be within five years or it is not worth doing. Remember… if your solar installer presents figures showing ROI based on anything longer than 5 years all the potential financial benefits flow to his bank account using your funding as the source and yields you little to nothing. This is basic business common sense and, yes, you, the average homeowner, are an individual business.

So photovoltaic solar is difficult to justify in the financial sense. Let’s assume you want to be environmental friendly and any cost. Hey that’s great. The world needs more people like you. Really. So what does it take to recoup the “energy” needed to manufacturer the products.

The answer appears to be a around one to four years for current technologies and perhaps longer for the older style PV arrays.

So the point is this. If you are trying to go good things for the environment and plan on installing a PV array, consider the energy payback period needed. A lot depends on the type of PV you specify and the good news is things are getting better with the latest technologies.

So Energy Payback is getting better with PV Solar. Utilizing second hand PV cells available from many sources on Ebay may negate the Energy Payback issue entirely if you make use of otherwise unsellable “cosmetically blemished” cells that roll off the assembly lines. ROI remains an immense problem though.


So we move towards wind power as an alternative source of power.

Here again we have many available off-the-shelf systems which run, from what I can see, about $3 to $7 per watt installed.

Wind has its merits, but once again the return on investment is staggering.

The DIY wind power crowd offsets this ROI issue pretty well. If you have your own labor to contribute, the material costs are not too hard to swallow.

Remember this is electricity and care is needed to ensure you don’t hurt yourself or others. You can also wipe out your entire electrical system if you don’t know what you are doing. A licensed electrician should be consulted before messing with anything electrical in your system.


Now more than ever alternative energy sources deserve a good hard look for use in any energy offsetting system.

If you have a lot of spare cash and want to make an investment in “green” then a professionally installed Wind or Solar solution is a great thing to do. Understand you are supporting an industry that cannot survive without philanthropists like you as the financial justification is simply not there.

If you are a DIY person, you may well be able to lower the ROI to five years or less. Alternative energy then becomes the financially, as well as environmentally, responsible thing to do. Your hours of labor you donate to your system becomes YOUR investment in YOUR future gains (savings).

The analysis of Energy and Financial payback need consideration in any Alternative Energy system you desire for your situation. Alternative Energy systems are a good thing to add, but be sure you understand who really benefits and where the ROI line is drawn. I very much want to offset my energy consumption, but will not needlessly support ridiculous financial transactions with my money to do so. Neither should you unless you are a rich philanthropist.

Control Your Liability

Remember to always use licensed professionals when connecting anything to your plumbing, electrical and/or structural systems. The liability exposure is too great otherwise.

Recently I turned my attention to alternative energy including solar, wind and hydro.

I gave no hydro possibility, but still researched some of the offerings since many of the techniques apply to wind also.

This leaves solar and wind as possible sources of energy.

Solar can be further split into two categories: thermal and photovoltaic.

In this post I will summarize the findings applicable to my own situation.

More »

If you have an old fashioned open fireplace and have always wondered “there has got to be a better way to ‘do’ fire” here is your answer.
More »

31 August 2008 · Topic: Appliances · Tags: , ,

While doing research for a new front loader clothes washing machine, my wife and I looked closely at the offerings manufactured by LG. We saw models at Sears and Home Depot. The models and their features are very nice.

While at Home Depot we asked about differences between all the various models including LG. The saleslady spoke about this and that, but was particularly careful to understand where we would be placing the new clothes washer and dryer in our home.

We said we desired to move our laundry upstairs to the closet of our bedroom. The sales lady warned us that the LG clothes washer has a particular need to be on a very sturdy surface such as concrete. She went on the inquire where our current laundry is located. We said on the middle floor between the garage and the kitchen which is a very typical location in the U.S. She was concerned the LG would not work there either since this was not a concrete floor.

We visited consumer reports and find their ratings for the LG to be some of the highest, but they never mention anything about location restrictions. If this issue is true, LG products won’t work well in the majority of homes.

During the past several months, Home Depot is selling many more models of LG clothes washers which, I suppose, still have this “sturdy floor” need.

If you are looking at the LG front loader products, you are well advised to ask about floor sturdiness requirements.

I would consider this an urban legend if it weren’t a sales lady from Home Depot telling me about this.

Your mileage may vary.

31 August 2008 · Topic: Appliances · Tags: ,

My family and I stopped by Sears and Home Depot after Church this morning to take another look at front loader clothes washing machines. Our current top loader won’t rinse well and both my wife and I consider the front loader method superior to the top load for a variety of reasons which some may find debatable. That’s not the point of this post, however.

All the front loader clothes washer offerings from Whirlpool (Duet), LG, Kenmore, etc. have a companion dryer to match the style. Of course my wife is all over that and desires both a new washer and dryer so they will “match.” I just want to replace the broken appliance and get the washer.

My wife and I disagree about this, but we don’t disagree on the startling discovery about the matching dryers. When you compare feature for feature between the matching dryers and the stand alone dryers you will see they are pretty much the same thing.

  • They both front load
  • The both have high, medium and low heat settings
  • They both have the “touch clothes” moisture sensor as opposed to the older air outlet humidity sensor

The huge difference is the price. Stand alone dryers cost about $300 to $700. The dryers that match the front load washers cost about $800 – $1600.

In other words, the premium you pay to have a matched set of a washer and dryer is about 120% on the cost of the dryer… over twice as much.

That is a lot of money to pay for “looks” of appliances that, quite likely, are hidden away in a back room. The only operational difference I could find between the two kinds of dryers is the “matched” units have the see through front door to compliment the see through front load washer.

So buyer beware. For the typical mid-level dryer you are going to pay $600 or more for no extra benefits if you just have to have the matching set of washer and dryer. That is $600 for home decor.

If you want to spend this on looks that’s great, but now you know the full story.

I ordered a PowerCost Meter from Blueline Innovations in an effort to better demonstrate to my family the overall power consumption of everyday things in a home.

The hope is by seeing the cost per hour as things are turn on and off, increased awareness will suggest to turn things off. That’s the hope of the Power Cost meter it seems.

Please understand this meter does not save you any money on your power bill. It does not do any quack technique of saving energy. It simply reports your energy usage so you will be understand where your waste might be. It is up to you to do the actual saving.

There are several different meters available, but the Blue Line model seems to be a good mix of capabilities.

Several aspects of this meter appealed to me including:

  • Measures the power use by sensing the wheel or window of the power companies meter – The meter’s power is the same as what the electric company measures
  • Portable display unit – to place where your family can see it
  • Ability to show energy consumed per unit time or dollars per unit time
  • Can handle tiered rates
  • RF link between sensor and display unit

I eagerly took the parts home and immediately set about going through the very good instructions in the manuals. I put two batteries into the display unit, two in the remote unit and then headed outside to continue installation onto the power meter. Things were going great…

…and then…

The hidden wheel in my power meter.

The hidden wheel in my power meter.

…disaster. Of all the various meters this Power Cost sensor supports, and it is many, I had to have the one kind of meter that won’t work with this sensor. Look close and you will see the problem. My meter does have the spinning wheel, but there is a metal shroud covering the front portion of it thereby blocking any view from the front for the sensor.


I sent an email to the support at Blue Line Innovations and they promptly confirmed my finding that my meter just won’t work.

I am not giving up yet, though. This meter system and the way it displays data is just too cool to pass up.

My next task will be to create a substitute power meter that will tick off either one tick per 7.2 watt-hours or one tick per watt-hour both of which appear compatible with the Power Cost meter. Stay tuned.

The pictures below show the unveiling of the Blue Line Innovations Power Cost Meter as received from Northern Tool Company.

BatteryThe 12 volt lead-acid battery for my backup sump pump does not seem to last for more than about one year. There is a “maintenance” battery charger that is, supposedly, designed to keep a battery topped off and ready to go should the backup power be needed.

I have heard the rumor putting batteries on the concrete floor will shorten their life. Research on the net suggests a few theories why this is or was true. Thoughts include:

  • Batteries on cold concrete floors develop a thermal gradient with the plate near the floor slightly colder than the top. This creates a slightly different potential which can mess with the balance of that cell. The idea that backs up this claim is the notion that submarine batteries bubble air through their battery’s electrolyte liquid thereby maintaining flow of the liquid which stabilizes the liquid’s temperature via mixing.
  • Battery housings use to be made of materials that conduct heat more thus making them more susceptible to the previous issue.

Perhaps I should use a flooded battery so I can top it off. Perhaps putting it on the shelf will make a difference. Then again, this battery and the one before it are from Wal-Mart.

Guess it is time to search out Solar Energy suppliers for their design guidance for systems that require batteries.

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