Design

This page will be a log of design decisions as this process evolves. I will also try to track major component purchases and why I picked the product I did.

At the top, here are some of the guiding principles:

  • Off-Grid Capable for 1-2 Weeks at a time
  • Sleep 2-4
  • 100% Electric (no LP, possible diesel hot water heater)
  • Full-size Lavatory (I hate tiny showers.)
  • Full-size refrigerator
  • Not likely to be used that much in cold weather (unless on shore power)
Bus Selection

I spent a good deal of time deciding which bus shell to start with. I pretty quickly had two lines of thought. I ruled out Prevost fairly early, mostly due to their design (boxcar on wheels) and cost of maintenance (They are VERY proud of their parts). So, to my mind, that left one classic bus model; the Silver Eagle Model 15/45, and one modern bus model; the MCI "Renaissance" 4500s (E or J series).

I seriously LOVE Silver Eagles. I think they are a beautiful classic bus and they have a smooth ride. However, the more I read about them, two big concerns came to mind:

  1. Rust - Eagles are known to rust pretty seriously (not uncommon on classic buses.) Almost every conversion story I found spoke of significant time spent repairing structural rust issues. For those who have metal working skills and tons of time, maybe that is not a big deal. But, for me, that translates to $$$, as I don't have the skills, the time, or the location to do that kind of work.
  2. Drivetrain - Silver Eagles were built with two-stroke diesel engines. There is nothing wrong with the older engines, but they have been out of charter/fleet use for some time. This means that finding qualified facilities/individuals to do repair work is getting harder and harder. If someone is a two-stroke expert and can do their own engine work, this is not a big issue. For me, again that translates to $$$. There are Eagles out there which have been upgraded to four-stroke diesels, but those are all aftermarket upgrades, which raises a whole different set of concerns. Plus, buying an Eagle which has been upgraded generally costs more than a bus 20+ years newer.

Another smaller concern is the fact that the manufacturer no longer exists. This means parts are no longer manufactured and are becoming more scarce all the time.

The other option I was considering was the MCI "Renaissance" 4500's. I think they are the most beautiful modern bus on the road. MCI has been building buses for a long time and, at one time, even sold this model as a factory shell. They originally had either a CAT or Detroit Diesel engine with either an Allison B500 or ZF Astronic transmission. Cummins engines were added to the lineup later on.

The J Series was originally designed as a "bare bones" workhorse model, while the E Series was designed as the "luxury" model. (In recent years, J Models have started adding many of the E Model features.) The J Series became a charter fleet favorite and is still heavily used. These differences actually factored into my decision. With all the "bells and whistles," the E Series buses have more complex electrical and mechanical systems which provide limited value towards conversion purposes, but added higher risk of repair costs down the road. So, all things being equal, my preference was the J Series.

There were also some concerns with the MCIs as well:

  1. Early iterations of the "MultiPlex" system (core electronic/wiring system, largely eliminating fuse boxes) were known to be fairly "buggy" and expensive to fix. The early "MultiPlex" models, known as "gold bricks," were used through the 2003 model year (from what I was told by MCI.) And, they cannot be upgraded, short of replacing the entire system and wiring harnesses -- a VERY cost-prohibitive "solution."
  2. Replacement parts can be either very affordable or extremely expensive. Take windows, for example. Replacing one of the windshields, as curved as they are, is generally a few hundred $$, labor included. Replacing one of the "pentagular" side windows (the first window on each side, behind the driver/entry door) will cost nearly $2500, just for the part.

The other consideration on the MCIs was the drivetrain. As I mentioned before, the first model years offered the CAT (C12 or C13) or the Detroit Diesel Series 60. The DD Series 60 became THE "go to" engine for the bus industry (and beyond), even despite recent inroads by Cummins. CAT, on the other hand, has gotten out of the bus market entirely.

Now, to be fair, I didn't hear many people speak ill of the CAT in terms of performance or reliability. My concern became one of future maintenance cost. The availability of DD mechanics FAR outstrips the availability of CAT mechanics, and that disparity will only grow. That translates into higher maintenance costs down the road.

(BTW, repowering is NOT a viable option, unless you have many, many $$$$$$$ laying around. It requires a replacement of the engine, ECM, wiring harness, and changing the gear ratio.) For the same money, you can get a VERY low mileage bus with the factory DD.

To me, that made for a pretty clear requirement for the DD S60 as the engine.

The transmission was a slightly different question. The ZF Astronic is, by all accounts, a very reliable transmission. I talked to a number of long-haul charter drivers who love it. When I looked around, I found service centers/qualified mechanics to be readily available.

However, the Allison B500 is simply everywhere. It has been the default automatic transmission in buses and RVs for a LONG time. The real difference was when I looked for service locations that did BOTH the DD and transmission service. The VAST majority were DD/Allison. It was far less common to find a place that did DD servicing and ZF Astronics. I also noticed parts for the ZF Astronics were marginally higher price than for the Allison B500.

So, I decided I preferred the Allison B500 over the ZF, but it wouldn't be a deal-breaker. When it came time to decide, I was actually looking at one of each. I ended up going with the B500, and paid a little more, but the bus was also two years newer and had around half the miles on it.

Here are the specs on the J4500: J4500 Specs

Electrical Design

Here is my current thinking on electrical:

  1. I definitely want to be 100% electric on the consumption side, with the possible exception of a diesel hot water heater. I have no interest in dealing with the storage and safety factors of LP. This is one of those things that has changed with the advance of technology. Modern RV stoves/microwaves/convection ovens are getting extremely efficient at pretty decent prices (especially with induction cooktops.) So, I just don't see a need to mess with LP. This removes a safety concern and simplifies the design.
  2. I am going to invest some $$$ in solar and Lithium batteries. This is not something everyone is willing to do or able to do, but I think the tech has progressed to the point that it makes sense. This is also an area where I plan on getting skilled. I will likely get some help in the planning and some of the installation, but I want to be able to maintain/repair the system myself.
  3. I will do the rough electrical and fixture installation myself, but I will hire someone to do the "heavy" connections (power sources, battery linkage, etc.) and wire the breaker panels. I could probably do these, but, to me, the safety factor is worth having a professional involved.
  4. I am currently planning on using concealed duct mini-splits for HVAC.  I HATE the look of roof "warts" and I plan on having most of the roof covered with solar panels anyway.  My current thought is to have 3 separate units with separate zones (bedroom, bath/kitchen, and living room,) each at 12,000 BTU.  (You can get some pretty high SEER units very reasonably.) This allows for a number of things. First, I can limit use as needed (only cool the living room and bath/kitchen during the day, and only cool the bedroom at night).  Second, this means I don't need any 220V on the power supply side, which simplifies things.  It will cost a little more up front, but I think it will work.  I may also add an additional unit for the driver's air, but it would likely run off the alternator, not the battery. I have to do something for the driver's air, but haven't solved for it yet.
  5. I know many people setup their system to run some components direct from the power source and not through the battery, and I generally understand why.  (There is some energy loss when converting power and charging batteries.) However, I still don't know if it is enough of a concern to warrant the additional complexity.  So, for now, the plan is to run everything through the batteries.  As more details are ironed out, this may change.  Also, this concept is only viable with recent technology advances in Lithium batteries.  Older battery technology would not handle this well.

My current electrical plan is here: Electrical Design.  It is by no means a schematic and not yet complete.  I know there are more "grid" components to add.  But it is enough to get things started and run my house wiring.  As I select specific devices, I will update it with details.  I will also update this page with specific product choices as I move along.

Plumbing Design

Here is my current thinking on plumbing:

  1. I will be doing fresh and black tanks (as large as I can fit in the footprint).  Grey tanks used to be a big deal, but from what I have learned, there is just no reason for the extra plumbing and dumping anymore.
  2. The decision on whether or not to use a macerating toilet will be driven by where the toilet ends up in relation to the black tank.  I will either have a macerating toilet or a macerating pump for dumping.  I may even do both.  I'm just not a fan of the "slinky," even though I will have the connection and hose as a backup.
  3. I am putting a thermostat valve on all hot water distro lines with a diversion back to the fresh tank, so water is not wasted waiting for hot water to get to the tap.  I will be using an on-demand hot water heater and none of the runs is super long, so the waste would not be huge.  But, again, it is a pretty cheap solution to conserve a limited resource when off grid.
  4. I am installing redundant fresh water pumps, just for simplicity.  They are not that expensive, so having the backup in place makes sense.
  5. I am installing "isolation" valves EVERYWHERE so I can replace components (and isolate leaks) more easily.  Again, it is pretty cheap investment in simplicity down the road.
  6. I have not yet decided on the hot water heater, tying it to the engine coolant system, and/or tying the hot water heater to the HVAC for heat.  In some ways, I like the idea for efficiency purposes. But, in practicality, is it worth the complexity and tying the house systems to the vehicle system?  How often will someone take a shower while the engine is running?  How often will we be in cold enough weather to warrant using the hot water heater as an engine heater?  Do I really want to mess with the enclosed HVAC units to plumb in the heat source?  All questions TBD...
  7. I will be using PEX for all component supply lines.
  8. I will have the ability to pump water directly from the fresh tank to the black tank so I can rinse it out when needed.
  9. I have heard different opinions on the whether or not I need an accumulator.  Accumulators used to be a necessary part of the system, both to build/hold water pressure and mitigate surge from the water pump.  However, with more modern pumps in the mix, some people seem to be fine without them.  So, there is still more research to be done before I make a final decision.  At this point, I'm leaning towards having one, simply because they are pretty cheap and I have yet to hear of a downside to having one.

My current plumbing plan is here: Plumbing Design. It is definitely not a real schematic and it is still a work in progress.  But, it is enough to move forward.  I will update it as more decisions are made.  I will also add details as I select specific components.  I will also update this page with specific product choices as I move along.