Archive for Understanding

RV Composting Toilet Thoughts

The Wynn’s YouTube channel has several videos about their RV composting toilet experience. Composting Toilet Secret Tips and Tricks is a good place to start if considering this option. Nature’s Head Dry Composting Toilet / Standard Crank Handle (Amazon affiliate link) is a popular example of the appliance. There are a few things to consider about composting toilets in an RV:

  • The RV composting toilet costs 3 times (or more) that of a typical RV toilet.
  • Proper composting requires aeration, 50F or better temperatures, 50% (+/- 10%) moisture content, and weeks to months of time.
  • Disposal of waste remains an issue. The Wynn’s experience is that they need to dump the urine bottle every 2 or 3 days and the compost bucket every 2 to 3 weeks.
  • The RV toilet needs a continuous electrical supply to keep its ventilation running. That is key to smell management, aeration, and moisture removal.
  • Water use may be a bit less. The typical RV toilet needs enough water to keep solid waste in the tank covered. A composting toilet only needs enough to clean the bowl.
  • A composting toilet needs to be ‘primed’ with peat moss or something like Worm Factory COIR250G10 Coconut Coir Growing Medium 250g – 10 pack (Amazon) to help aerate the feces and optimize decomposition.
  • Flushing the RV composting toilet involves cranking the aeration and maceration paddles.

Some cabin and house type composting toilets can get really sophisticated. The big issues that complicate the operation are that of removing moisture, allowing for a proper composting time, managing temperature, and facilitating final disposal.The RV toilet manages moisture by operator attention to separating feces and urine into separate containers, depending upon mild ambient temperatures, forced continuous ventilation, and removal of waste prior to complete decomposition. 

The comments I see indicate some of the same issues and attitudes regarding waste disposal as occur with gray water. With regulations and laws getting ever more strict, disposal of any biologic waste outside of specially designated places should be assumed to be prohibited. You might get away with dumping the urine bottle in a privy or toilet but the compost is another issue.

RV toilet compost should be handled and treated much the same way as cat litter. It should be considered dried out rather than composted. Some toilets allow rotating compost buckets to help further composting but the RV situation with a total bucket time of only a week or two with additions within a day or two of disposal isn’t going to do much other than start the initial phases of composting. The week or two does provide a good composting start and does remove a lot of moisture and that tends to reduce the volume and weight of the waste. The result isn’t the sort of thing to put in a privy or other toilet. It also isn’t the sort of thing to spread out in the open. That leaves bag and trash or shallow burying (if allowed).

There are a number of DIY composing projects out there. The RV provides a few opportunities for such a system. For example, the air feed for the toilet could come from the top of the refrigerator heat exchanger. That would help refrigerator efficiency as well as provide pre-warmed air for the compost pile. Both the compost pile air exhaust and the urine bottle could be routed into the RV black tank to reduce the necessary waste disposal intervals. 

The standard RV toilet works well for most RV needs and provides a fairly high barrier for competing technologies. What seems to give composting toilets an edge for some are ideological fantasies. These center on ‘green’ ideas like saving water or recycling or personalized waste handling. Perhaps the old style gopher hole should be considered for comparison. As with all waste, the issue is really more a problem of concentration than it is with where it goes.

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Cooking: knowing the why might help you adjust for the RV lifestyle

Fifty concepts stated, explained, and illustrated to show the how and why of cooking: The Science of Good Cooking (Cook’s Illustrated Cookbooks)

If you are into Alton Brown or are a Cook’s Illustrated subscriber or just interested in learning about such things as why Gentle Heat Prevents Overcooking, High Heat Develops Flavor, Some Proteins Are Best Cooked Twice, and more, this looks like a good resource.

(note: Amazon Affiliate Link: helps the site at no cost to you)

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Towel tech

There Is a Right and a Wrong Way to Use a Beach Towel — do you want to know why?

“That water-wicking blanket is actually an intricately designed instrument, fine-tuned to provide you with the best possible poolside experience. And here’s the thing: It’s entirely possible that you’ve been using it wrong all along.

The beach towel is not just an oversized, elaborately patterned bathroom towel, used to dry you off any which way. It has two distinct sides, designed for two very different purposes—and one side has absolutely no business in the bathroom.”

Gizmodo‘s Rachel Swaby provides some insight into the technology behind towels and why a bath towel and a beach towel are different. Who knew?

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Understanding the price of gasoline

Already the headlines are working on fears of $5/gallon gasoline this summer. You may have also seen stories about the North Dakota oil boom or the political fracas about an oil pipeline. It’s all about what kind of oil is where. Casey Research has a nice story to help explain things: It’s All about Differentials.

We’re talking about oil price differentials, which means the different prices paid for crude oil in different parts of the world. People often talk about “the price of oil” as though there is just one price, when really there are dozens of crude blends that each has a different valuation. Sure, some blends are much more prevalent and therefore important than others.

If you want to skip right to the bottom line, it is this: location matters. Bakken producers are getting hammered on pricing because they struggle to get their oil to the nearest refinery and storage hub – in Cushing, Oklahoma. Then, in a cruel feedback cycle, once the oil reaches Cushing it actually pushes its own value down by adding to a supply glut – there isn’t enough refinery capacity in Cushing to process rising output from the Bakken and the Canadian oil sands, and there are only a few small pipes available to ease the glut by moving oil from Cushing to the big, sophisticated refineries on the Gulf Coast.

The right kind of oil has to get to the right kind of refinery to distil to the right kind of gasoline (or diesel) you need to get your rig on down the road. The price you pay at the pump reflects all of this and much more.

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RB energy supply considerations: Sean replaces his batteries and considers the issues

Sean has a bank of eight 8D sized batteries that he is replacing. That’s 22 kilowatt hours of total energy storage weighing more than 1300 pounds. His blog post takes a look at costs and options.

When all is said and done, there is not a single one-size-fits-all answer for the right balance among batteries, inverters, generators, solar, and power-pole usage for all RVers. Our set of choices is almost the right balance for us. If I were in the market for a generator today, I would buy a 6.5 kW as opposed to the 15+ kW unit we have now (and which came with the bus). But I would definitely not trade in my large battery bank, and the flexibility it buys us, even though it costs us about a grand a year.

His post takes a look at cycle life considerations, charge cost effectiveness, use profile variations and its implications, and what it really costs. It provides a good basis for looking at your options for meeting your RV household energy needs.

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Automotive tech: they don’t build them like they used to.

Popular Mechanics lists 23 Ways Your Car Is Better Than Your Dad’s – Auto Industry News – Popular Mechanics and Wired lists ten examples of Hidden Tech That Makes Modern Driving Better. A lot of these items increase comfort and reduce fatigue and are in tow vehicles as well as the everyday automobile.

Active noise canceling systems and acoustic glass help make for a quieter ride. Direct and minutely controlled fuel injection along with turbo charging systems provide more power for less engine at better fuel efficiencies. Integrated GPS is being used to determine sun angle and adjust climate control. Magnetorheological dampers adapt the suspension for driving conditions. Security is improved making vehicles a more difficult target for thieves. Sound systems make the stereo of yesteryear, even the home ones, look rather anemic and low-fi.

The reliability is also a target. Engine alternators are producing 1.6 kw and fan belt driven pumps are moving to electrical. Tires get better traction, are less prone to damage from road hazards, and last longer. Engines and drive trains often come with warranties up to five times (or more) as long as they did in the past.

They don’t build them like they used to and much of the improvement is behind the scenes and stuff we take for granted.

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Nitrogen for the tires?

Costco does it. Airplane tires require it. What does pure nitrogen in tires do that simple compressed air doesn’t?

Charles Day says it all boils down to moisture. Nitrogen in your car tires at Physics Today tells some of the story.

Pure nitrogen has other advantages over air besides its dryness. When tires get very hot, oxygen, the second most abundant component of air, can react with volatile chemicals in the rubber and cause an explosion. Even at lower, everyday temperatures, oxygen reacts with rubber, weakening it.

So will I refill my tires with nitrogen? Not if it costs more than a few dollars. Having owned the same car for 18 years, I know that worn treads will prompt me to replace the tires long before oxidation sets in.

The question then is how much filling an RV tire with nitrogen might expand its life beyond the 5 to 7 year timeline. That looks to be one of those questions where the data is weak or nonexistent that make for good myth-mongering in order to sell tires…

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US93 improvements north of Kingman

The big news was the bypass around Hoover Dam but the big improvement for travelers included the Arizona side access. That upgraded the road to near freeway spec. What you might notice on that stretch includes a number of overpasses out in the middle of nowhere that are too small to serve as the typical road overpass and don’t seem to connect to anything.

Those strange overpasses are a part of the new highway design paradigm. They are for wildlife. It seems that bighorn sheep can be a traffic hazard along this stretch of highway and it is hoped that providing the sheep their own overpass will reduce that hazard. The Daily Miner reports that “The Arizona Game and Fish Department has its first confirmed sheep crossing.” It’s a $4.8M project that is hoped to reduce the ten or more sheep hits per year by vehicles near Hoover Dam as well as reduce herd fragmentation. That area holds one of the largest contiguous bighorn populations in the nation.

The bridges cost almost $2m each and were built because the sheep didn’t seem to like underpasses. It appears the effort was supported by a good deal of research and consideration of factors involved.  There is more at the AG&F Department website, pictures too.

The NV DOT says traffic crashes involving wildlife cost an estimated $5B to $8B nationally every year. They provide a bit of history and some selling points for animal crossings.

The Canada Safety council says “Collisions with wildlife are a hazard throughout the year, but they start to peak in the summer and fall. The majority of these crashes occur between dusk and dawn, when visibility is low.”

Leslie Linthicum has a mea culpa that cites the effectiveness of efforts to reduce animal collisions. Her column provides an description of some of the methods and techniques that have been tried.

The FHA has a book on Best Practices Manual: Wildlife Vehicle Collision Reduction Study if you really want to get into vehicle and animal collisions.

There are also some interesting comparisons. The vehicle and wildlife crash incidence rate is increasing yet the crash rate per million miles is decreasing while actual miles driven is not increasing. That would indicate that wildlife conservation efforts are succeeding.

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Making ice cream or aging batteries – they have similarities

Serious Eats took after making ice cream without any special equipment. The problem is one that is very similar to how you keep your lead acid batteries from sulfating. How do you keep those crystals from growing into “something more akin to a wet concrete with shards of broken glass.”

With ice cream, you need to agitate it while it freezes to keep the crystallization under control. With lead acid batteries, you also need to keep the electrolyte stirred to keep the crystals from growing large and hardy.

In the quest for making ice cream without the usual equipment, Kenji experimented with the chemistry – much as lead acid battery manufacturers do for their product. After that it was materials prep – like batteries with the red lead paste. Then was the final construction phase and technique. Flash freezing was the key for smooth ice cream.

If you want to make some ice cream in your RV in small amounts without specialized equipment, ice, and rock salt, you might check out the recipe for Real Ice Cream Without the Machine ».

Then you can put on your physical chemist’s hat and think about how crystallization is important in your RV experience whether it is ice cream or lead acid batteries or, come to think of it, the cooling process your refrigerator uses. The absorption refrigerator in RV’s often fail because the ammonia solution crystallizes and blocks the flow that carries heat out of the fridge. What else might there be like this?

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How much can I tow?

One of the questions trailer owners ask is about what they need in a tow vehicle for their trailer. This has been a very subjective matter with a lot of sales hype and FUD mongering thrown in. The SAE has put together a committee to provide a standard against which towing issues can be compared. Automobile Magazine says

There are five engineering characteristics that strongly influence any tow vehicle’s performance:

* The engine’s power and torque characteristics.
* The powertrain’s cooling capacity.
* The durability of the powertrain and chassis.
* Handling characteristics during cornering and braking
* maneuvers. The structural characteristics of the vehicle’s hitch attachment area.

Standard J2807 spells out test procedures and performance requirements that must be meant for a manufacturer to assign a maximum tow rating to a particular vehicle.

Most of the issues, concerns, and questions that have come up over the years in the ‘what can I tow?’ question have been addressed in the standard. For instance, a tow vehicle must be able to go forward and backward 16 feet on a 12% grade five times in five minutes as well as meet acceleration times over a set of defined speed ranges commonly encountered in driving. The Davis Dam run on 68 and 163 in Arizona is used as a criterion where the rig has to keep up a minimum cruising speed when temperatures are over 100F and the AC is on full. Handling is also considered. Turns up to .3g or so must not exhibit oversteer and panic stops need to stay in lane and be accomplished in specified distances at various speeds.

These criteria will not only help choosing a tow vehicle but can also be used to understand what the ‘experts’ think is necessary for proper and safe towing. Starting with 2013 models, you may see the claim that the vehicle meets J2807 SAE standards and that will provide some assurance about the claims for what the vehicle will tow.

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Phone options

If you live on your phone, the unlimited cell phone minutes plan is something you might try to hold on to. They may not be available for long.

If you don’t need your telephone with you 24×7 and reducing costs is a consideration, WiseBread has some ideas in Kick that Cell Phone Contract: Save with a Prepaid Plan.

There are two basic cell phone networks. You may have seen the advertisements about who has the best coverage. One network uses CDMA and its major provider is Verizon. The other uses GSM and its major provider is AT&T. They are not compatible with each other and phones for one will not work on the other.

Some of the pre-paid cell phone providers contract with Verizon, AT&T, and other network providers. Tracfone, for instance, will sell you a GSM or a CDMA phone depending upon where you say you want to use it. If you are in Reno, Tracfone prefers a GSM phone. If in Gerlach or Doyle, the choices are CDMA phones. Verizon has better coverage in the less populated areas, it seems but AT&T better coverage in town.

Another factor to consider is that GSM phones use a SIM card and CDMA phones don’t. The SIM card is a little memory card that you plug into your phone that contains the service information from your cell phone provider. It is a lot easier to plug that into the phone for both you and the phone company than having to type in long strings of numbers on a CDMA phone to do the same thing. That is why the CDMA folks are looking at A RUIM card (also R-UIM) or Re-Usable Identification Module as a means to control service more easily.

Note that pre-paid cell phone service is often very basic. The phones are inexpensive and don’t have a lot of the bells and whistles the contract providers offer. You will usually have to look for other options for I’net access.

A pre-paid cell service can be a very inexpensive option as a part of a more complete plan. If you wait until you find a wifi hotspot, you can use Skype or MagicJack to the long calls and keep the pre-paid calls short.

The market is in a turmoil and things are changing quite rapidly. There are many different ways to do things. That provides opportunities for meeting your needs at low cost but it also means it is easy to miss something. Keep your options and your eyes open. It can be fun.

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Sway control and modern vehicles

Controlling trailer sway is often a hot topic in discussions. It is often difficult to figure out what to do to make sure the trailer stays behind the tow vehicle or why trailer sway happens. The recent labeling of the Lexus GX as a ‘do not buy’ by Consumer Reports (CR) has related causes. Why the Lexus GX may be rollover-prone (and the 4Runner isn’t) covers a number of issues that will help those towing trailers understand what is involved in rig stability and what modern vehicles do about it.

The first item is about oversteer. Trailers tend to exaggerate this because they push the rear out in when turning. “Cornering oversteer is something automakers try to avoid, except on high-performance sports cars. On SUVs with a high center of gravity, this is an especially serious problem”. Coupled with oversteer is that of lifting the throttle that CR uses in its tests to aggravate problems. Lifting throttle and failing to compensate for oversteer are primary contributions to trailer sway problems.

Electronic Stability Control Systems (ESC) were first adopted in the late 1990’s to combat the problem. “ESC relies on signals such as steering angle, lateral and longitudinal acceleration, yaw rate (the rate of rotation around the vertical axis), brake and throttle position, among others.” These systems can make your RV experience safer and more pleasant but, as in the Lexus case, they may not be tuned quite right and that may create problems.

It would be easy to read this article and just write off the problem as a technical, even computer, issue. That would be to miss what is being said about SUV’s, typical vehicle stability factors, and the implications of CR’s tests that are intended to bring out typical vehicle behavior problems. There are some things to learn that you can use to enhance your RV driving experience and comfort and safety.

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Your auto is becoming a robot

The march of progress often goes by with little notice. CB radio was the primary option for in-vehicle communications only forty years ago and cell phones didn’t become a real option until about ten years ago. Fuel injection for vehicles really only become common something like twenty years ago and now the automotive computers carefully control engine fuel use in harmony with transmission gearing and other factors. Suspensions have also improved.

The last stage in developing robot capabilities in the automobile is in driving. Personal Navigation Systems are one step in this. TGDaily describes research that allows the automobile to stay in its lane without human control.

Already in cars are automatic parallel parking features, braking assistance, collision alarms, and trailer sway control. Being able to stay in line means being able to determine if the current vehicle path is staying in lane. That ability could be used to wake up a drowsy driver who might be driving off the road or into oncoming traffic – which is a major cause of traffic crashes in Nevada.

Maybe, one of these days, the joke about the new moho driver who sets the cruise control and then heads back to the bathroom won’t be such an odd absurdity. Perhaps the joke will be the moho doing a panic stop while on autopilot and what that does to the driver back in the bathroom.

Just you wait. We live in interesting times and driving is not like what it was just a few years ago – and will likely change just as much a few years hence.

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High speed I’net

The I’net is creeping into the RV lifestyle. The access to the world wide network is becoming a necessary link for everything from paying bills to chatting with friends. The government thinks it is so important that they have allocated some of the old UHF TV channels to be used for I’net access and even allocated funding. The website Welcome to
has been set up with explanations and speed tests as a part of this governmental effort.

It used to be that you’d have to use satellite for I’net access on the road. This was slow, especially for uploads, and there was a latency that made it impractical for voice communications. Nowadays, you’ll find wifi access points at many RV parks and at some rest areas as well as at libraries, fast food and coffee joints, and other places. Cell phones are also moving to I’net integration. You may have seen the adds where the two major cell phone networks are fighting about coverage maps. DataJack is a way to access a cell phone network on a monthly basis without any longer term commitment.

A network telephone, called voip or voice over ip, can be a convenient and inexpensive alternative to a cell phone. Examples include Ooma, available at Costco. It uses a standard network device to make the connection between standard telephone and I’net. Magicjack is available at Radio Shack and uses a dongle for your computer that has I’net access. Both provide complete telephony services that you can use anywhere you can get a decent I’net connection.

Speed measures can be a bit confusing. You will hear terms like bits and bytes and have no idea how to figure out what it means for what you want to do. There is a table of these numbers at Network Connection Speeds Reference  for a start. Cell phone I’net access provides from 2 to 7 times dialup speeds. Bluetooth, used most often for those wireless cell phone earplugs, runs at a bit more than 12 times dialup. Wifi can run from 200 to 1,000 times dialup speeds. Home networks usually run at about 1800 times dialup speed. DSL, the connection that uses telephone wires, runs about 18 times dialup and cable, using the TV coaxial network, can run up to 100 times dialup speeds.

What speed do you need? Voice calls over the I’net need only 2 times dialup data speeds so Cell and wifi access will do just fine. Satellite would also do OK but the second or two lag in the link can require some adjustment. The need for speed will likely only be evident if you want to watch video or look at a lot of pictures. The base for that pushes cell phone technologies. The only choice for a true video nut is going to be cable at this time.

To find your connection speeds, you can use the government site or which need a Java plugin. Other speed test sites include
audit my pc (good speed chart by connection type, too) and  CNET Bandwidth Meter.

All of this is fine as long as you are somewhat near civilization – major highways or cities and towns. That doesn’t include some of the best RV spots, especially west of the Rockies. You can still get away from it all if you want but beware, technology is creeping up on you.

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Battery maintenance concepts

Spring is coming and that means its time to get the rig out of storage mode. That often means finding out what didn’t make it through the winter. The cooler temperatures are usually a good thing for your batteries because they reduce the self discharge rate but the long periods of sitting are not so good for the batteries.

Venkat Srinivasan, who works with the Lawrence Berkely National Lab, started a blog about batteries and an entry described the problem with lead acid battery life.

For a lead-acid car battery, the failure mechanism is called sulfation, where the discharged material undergoes a phase transformation after which it can’t recharge.

But, keeping a lead acid completely charged also leads to other problems (like grid corrosion) which would be lessened if you let the voltage decrease a bit. Moreover sulfation takes a few days. So one could do something complicated like let the battery charge, and then let it discharge a bit, but come back the next day and charge it back up before sulfation kicks in.

These two competing phenomena, sulfation and grid corrosion, may explain why keeping a float or trickle charge on the battery is not optimum. Float charging keeps a top charge to prevent sulfation but promotes grid corrosion. Solar charging systems may also tend this way as they spend perhaps a quarter of the time keeping a top charge. This may be why RV converters like the Progressive Dynamics with Charge Wizard do so well. Those maintain a reduced float level which keeps gassing and grid corrosion down. Every day or so, they bump the charge up for just a few minutes to inhibit sulfation.

There is a progression here. Float keeps the batteries always at top charge. Solar provides a top charge for maybe a quarter of the time. A good battery maintainer prevents discharge but puts a top charge on the battery only about 1% of the time.

For your spring time battery checks, make sure to your battery water levels of OK (unless you have sealed batteries), Disconnect the charger and maintainer (unplug the rig), turn on a load like a few incandescent lights (5 or 10 amps or about 100 watts) for an hour or two, then let the batteries rest with no load or charging for an hour or so. Check the battery voltage. If the batteries are good, they should show about 12.6v to 12.8v. If in doubt, consider replacement. Batteries often cost less than a tank of fuel for the RV and that cost may be good insurance against a dead battery on a cool spring morning.

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Watch out for supposed experts

Whenever someone thinks they know more than the manufacturer of a device or about the codes involved, you need to be very careful that you really know what is going on before doing anything. Howard falls into this trap in the February Blue Beret when he suggests modifying Honda gensets to implement neutral to ground bonding when the small Honda 120v gensets do not have a neutral to start with.

The lesson is that you need to be very careful in listening to recommendations from ‘experts’ and make sure you really understand what is going on. Be especially careful when the experts starting tossing around ‘safety’ as the primary reason for their recommendations.

There is no need or reason for an earth ground with a portable genset. The chassis grounds of the genset and the RV are connected together by the cord and plug ground wires and that is sufficient to provide a proper frame of reference for the fault detection circuits required in modern equipment. The reason for earth grounding is with grid attached power where the earth ground, chassis ground, and neutral are connected together only at the service entrance. This is why your RV circuit box does not connect these together as it is a sub panel and not a service entrance. The grid has long transmission lines that couple it to the earth which is why it needs careful earth ground considerations. Your RV on its own, off-grid and local, power systems does not have that problem and, hence does not need earth grounding for power safety.

You do not have a safety hazard as long as the power circuit is isolated from your RV frame and the earth ground, despite what Howard says. This is why the code is as it is for small gensets or other power supply devices (like battery powered inverters).

Your 3 light circuit indicator is designed for grid power. When using small gensets with plugs, it is entirely proper for it to not show a light for hot to ground voltage as the hot and neutral sides of the power may be isolated from everything else. Like with the voltmeter, you need to use the proper test equipment and properly interpret their readings in the context of what you are doing.

The column also gets into the problem of a genset not being able to power things such as air conditioners and microwave ovens. The lesson here is to watch out for oversimplification. The reasons why a 3kW genset might not power a 1.5 kw microwave include many factors. Altitude effects on genset performance is one. The appliance power factor is another. Power startup surge might be another. Hidden loads (the fridge going to electric is a common one) can be a source of failure. Even the type and length of extension cord you use between the genset and the RV can be a factor.

When you have larger gensets or wired in gensets, then you should have a transfer switch that will automatically make the proper connections.

Note that circumstances determine how things are done. Single phase small 120v portable gensets that use plugs are not the same as house backup systems or contractor power. Sometimes you know the generator is completely independent of any other power source or not. Sometimes, especially with portable equipment, you do not know for sure it is really a ‘separately derived system.’

A 2-wire 120 volt system has no neutral and therefore bonding is optional. Recall that neither side of a 2-wire derived system is a neutral and when one grounds either side, it becomes a grounded terminal or conductor, but it is not a neutral. (OSHA 1993 clarifying letter)

Definitions of terms such as neutral and ground confuse people, too. A neutral is halfway between the two sides of a split phase 240v system, not an arbitrarily selected side of a 120v system. Chassis grounds and earth grounds are two separate things. Unless you and the expert are very careful with terms, confusion can result.

There is a lot of bad advice out there. Forums and discussion boards are particularly poor sources as they don’t do any filtering. Magazine columnists can also go astray. It is up to you to properly qualify what you find by using sound logic, gaining a proper understanding, and using multiple sources of information.

See Also

see OSHA Grounding Requirements for Portable Generators and Using Portable Generators Safely

PORTABLE GENERATORS AND OSHA CONSTRUCTION REGULATIONS is by “Grizzy” Grzywacs at the OSHA National Training Institute. He had a ‘discussion’ on RV.NET where he very patiently went over the genset grounding issues with some recalcitrant objectors and that provided a good tutorial that is summarized in the paper linked here. (the RV,NET blog has the same bad advice as the Blue Beret, though)

Solid Grounding For Your Generator thinks through some of the issues. Another EC&M column on this is about how you should treat the neutral conductor. Mike Holt also talks about the National Electric Code on Neutral to Ground connections to describe what the code says.

The IMSA describes Generator Grounding and when ground rods are required at portable generators. The article carefully describes what a “separately derived system” is with illustrations. Also note

“Portable generators are covered in Section 250.34 Portable and Vehicle-Mounted Generators. This section allows the generator or vehicle frame to serve as the grounding electrode when:
(1) The generator supplies only equipment mounted on the generator, cord-and-plug-connected equipment through receptacles mounted on the generator, or both, and
(2) The non–current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator frame.

If the generator neutral is grounded then the generator can only be used with a transfer switch that transfers the neutral, or as a stand alone generator for a carnival or special even, and then ground rods are required.”

Generator Joe also has some good ideas for the proper operation of your portable generator.

With I’net searching, it is easy to find good resources to use to understand technical issues. Don’t get caught by bad advice, even if it does have the imprimateur of print in a journal or magazine. Electrical power is nothing to mess with so don’t think you know more than the NEC, OSHA, and the OEM unless you have the background and the resources to outweigh those authorities.

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When it gets cold

Marks RV has an interesting page about the properties of LP gases including both propane and butane. Near the bottom of the page is a table that provides information about the BTU per hour as a function of temperature and tank type. It tells the story of why keeping warm in cold weather gets difficult from many directions.

For the typical RV with 30# propane bottles and a 30 kBTU/hr furnace, the furnace is going to be fuel starved when temperatures get below 10F or your tank gets below 20% full. The factors behind this include the surface area of the liquid in the tank and the fact that it is tougher to get from liquid to vapor when the temperature decreases. A chart on the page puts propane vapor pressure at 0F at only a quarter of its value at 70F. If you have a lot of Butane in the mix, which might happen if the tanks were filled in warm climes, then getting vapor will be even more difficult as butane has to get to 100F to have the same vapor pressure propane has at 0F.

The bottle size is one reason for getting a large, rented, bottle when parked for the winter. From the tables, a 20# tank nearly full could just barely fuel the furnace at 20F and a 65# under mounted tank could be 30% full and keep the furnace going down to 0F.

The website also has a good rundown on troubleshooting your RV furnace that will help you learn how it works.

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State parks and budget crunches

Coyote Blog has Total Frustration With Arizona Parks. He runs a business of privatizing public recreation and knows how to keep state parks and similar recreation areas financially viable yet cannot convince the authorities to act on his knowledge.

Of course, I am not completely naive. I know there is a tried and true kabuki dance here where parks departments threaten to close down the Washington Monument in a bid for public sympathy that will either deflect budget cuts or spur new taxes. I also know that state parks directors have sworn a blood oath together never to let private concessionaires run whole parks, even if the parks have to be shut down

The places we like to visit in our RV’s make for good symbols because they are ‘recreational’ and, hence, luxuries that are not critical to the state and they are visible. When times are good, that is why they get a lot of extras and fancy geegaws and RV spaces with utilities and fancy trails and facilities. When times are not so good, …

The observations in the commentary are worth considering. They touch on how government and social ideology influence our access to outdoor opportunities with our RV’s.

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The RV ammonia based refrigerator

When you try to find out how an RV refrigerator works, it can get you to wondering how on earth somebody could invent it. RV Mobile has a good rundown on the process using ammonia, also known as refrigerant 717.

The process occurs in a sealed pressurized set of tubes that has enough pressure in it to liquify ammonia at room temperatures. It has a hot side where ammonia is separated from water and a cool side where the ammonia gas is mixed with hydrogen to change its partial pressure and allow it to evaporate and provide cooling The hot and cold sides are separated by liquids with liquid ammonia in the condenser at the top and a water and ammonia solution in an absorber at the bottom.

Three chemicals are needed for the refrigerator: ammonia, chosen because of the amount of heat it can carry and its boiling temperature; water, chosen because it will dissolve a lot of ammonia and be a liquid when ammonia is a gas; and hydrogen because it can take up space in a gas providing a partial pressure and won’t dissolve in either liquid ammonia or water.

A key to how it works is Solubility of Ammonia – NH3 – in Water. Ammonia gas is readily dissolvable in water but how much is temperature dependent. Going from room temperature to body temperature water, the amount of ammonia that can be dissolved decreases by nearly half. That’s a range from about a pound to a half pound of ammonia in a quart so adding a bit of heat can release a good amount of ammonia.

When heat is applied to an ammonia solution in the percolation (perc) tube, three things are happening at once. One is that ammonia gas is released as the solution with water heats up. A second is that water is separated out of the ammonia vapor. A third is a concentration of the ammonia in solution going up the tube. Ammonia gas comes out the top and any water that tries to escape with it is shaken out and sent back to the absorber tank. The heating that pushes gas out the top of the perc tube is also what drives the cycle.

The condenser cools the ammonia gas which allows it to liquify. This is where the heat is removed from the refrigerator. Ammonia drips out of the condenser into the evaporator which has hydrogen trapped between the water below and the ammonia above. That gives the ammonia room to evaporate to share space with the hydrogen. This evaporation is what provides the cooling. As the ammonia drips on down the evaporator, more and more of it evaporates and that means its portion of the space shared with hydrogen increases. That means that the boiling point increases. So the higher part of the evaporator is used to cool the freezer compartment and the lower part is for the refrigerator. As the ammonia gas mixes with the hydrogen gas, it makes for a heavier mixed gas that settles down towards the absorber tank. That exposes it to water which dissolves the ammonia and leaves the hydrogen, which, being a light gas, rises back up to the evaporator.

The whole thing depends upon heat rising and stuff sliding down tubes of various sizes to control the flow of the chemicals in a way to provide cooling. That is why the refrigerator in your RV needs to be fairly level to function efficiently.

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Crash fears

Several discussions have come up on the forums about safety and risk. There are those who are very worried about hitch rigging or travel weight and other things being unsafe. The Nevada Crash report for 2006 (big PDF) indicates that worries are misplaced.

In the table about types of vehicles involved in all property damage, injury, and fatal collisions, 162 “motorized homes’ crashes included only 3 fatalities. Golf carts were in 3 crashes and tent trailers and travel trailers in 2 each with no fatalities in any of these. This is out of 114,632 crashes reported. That puts travel trailers at one percent of RV crashes in Nevada in 2006 or at a rate of about 17 per million of all vehicle crashes.

There are reasons for this that include driver maturity and a tendency to avoid traffic congestion. At just single digit events in a year it would be very difficult to accumulate meaningful numbers about causes and risks.

The bottom line is that the risk is very very small for the RV community. When you see someone on the forums spouting off about how some hitch is a safety hazard or expressing a desire to leave the state if someone dares to get on the road with some rig that isn’t on their approval list, write them off as a blowhard who has lost touch with reality.

Continue to take care of your rig and pay attention when driving. Enjoy the Sierra Nevada and Great Basin RV experience.

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