Silly A/C question

[jakegw2]

My generator is gas. Not sure why I have been thinking about propane generators for other posts.

[Davydd]

Originally Posted by avanti

After careful consideration, I have decided that my new rig is going to have a single 200W solar panel. Its purpose is not to extend my boon docking (it will be a drop in the bucket), but to power certain systems during storage. Such a setup now costs very little and in the center of the roof is visually unobtrusive. Also, don't forget that a panel is "portable shade" -- keeps a lot of solar heat away from the roof.

I basically concluded the same with a Class B but I store inside plugged into shore power and can't find a use for solar in any way, especially with a second alternator setup and high capacity lithium batteries and our historic RV habits of traveling most days. The middle of our van roof is taken up with two skylights, a Maxxfan, an air conditioner and a dome antenna. I doubt I could put much of any solar panel on our roof.

Solar is not an answer I can see to even extend air conditioning. An interesting attempt was made by the owner's of ARV's Solar Womp designed to take in Burning Man in the Nevada desert boondocking in August. They had 1200 watts covering the entire roof on a platform.

As for air conditioning, we have it obviously, but tend to avoid its use in where we go and when we go. It a year's time traveling those 16,500 miles new van, Mies, we haven't used it. In 17 years of travel I can probably count on one hand the times we used air conditioning. I also found air conditioning should be used periodically as we've had two compressors go bad from not using. I guess you would call that exercising.

[Urlauber]

Originally Posted by jakegw2

My generator is gas. Not sure why I have been thinking about propane generators for other posts.

Maybe because of the scenario in the OP?

[Urlauber]

Originally Posted by mloganusda

Did your MH come standard with propane for the generator? My Trend, based on the Pro Master, has the 2.8K generator using gas off of the gas tank, not propane. There is less power from the gen (2.5K) using propane instead of gas (2.8K).

Yes, standard Onan QG 2800i quiet propane generator.
It seems like running the generator off gasoline makes sense, except one still needs propane to cook and heat anyway, and my take is that propane generators are less iffy since they don't have degrading fuel in them and don't need to be "exercised" as frequently to keep them from fouling up.

[Urlauber]

Originally Posted by avanti

After careful consideration, I have decided that my new rig is going to have a single 200W solar panel. Its purpose is not to extend my boon docking (it will be a drop in the bucket), but to power certain systems during storage. Such a setup now costs very little and in the center of the roof is visually unobtrusive. Also, don't forget that a panel is "portable shade" -- keeps a lot of solar heat away from the roof.

I agree with most of this, except the "drop in the bucket". I very much enjoy that my 200W solar panel runs the compressor fridge, fan, lights, and water pump. Keeps me from having to run the genny or go for a drive to re-charge the batteries, extending boon-docking very much... As long as there is sun hitting it for most of the day, obviously.

And, of course, while parked (in the sun, in my case) it keeps chassis and coach batteries more than topped off, and allows running the roof van to keep airflow and temps more or less close to ambient. Plus adds some shade.

[Urlauber]

Originally Posted by Rlum

Shade and insulation makes a whole of difference for vans. Embassy RV is not a big fan of solar because who want to park in sun to get electricity? Terry wants his clients to spend money for better batteries, AC units, 7 layers of airplane insulation and dedicated alternators. Park in shade and enjoy comfort of AC.

Dunno... You don't always have the option to park in the shade. And, except for Summer months, parking in the sun is often preferable.

[avanti]

Originally Posted by Urlauber

And, of course, while parked (in the sun, in my case) it keeps chassis and coach batteries more than topped off

This is actually a minor negative with a lithium house system. Not good for the batteries to store them fully-charged. My automation system will deal with this automatically, but I need a way to "burn off" the excess charge if I return from a trip fully-charged (which will happen unless I remember to take special measures). I will probably use the 120VAC aux heat coil in the Rixen's expansion tank. Will need to experiment.

I am thinking of using one of the Transit's four center-console "upfitter switches" as a "heading home" control, that I can turn on for the last day of a trip, so the van will know not to fully charge. I can't think of a practical fully-automatic solution.

[Urlauber]

Yep, seems like nothing is perfectly perfect. I still prefer AGM batteries over Li as they are less finicky and cheaper.
Getting a huge, expensive row of Li batteries just to run it down in a few hours of A/C or heating and some electric cooking seems odd to me.

A lot of folks don't know much about Li batteries and are surprised that their tools and vacuum cleaners etc don't last... even though they are plugged in all the time! With RVs, this can get a bit expensive I guess, unless you monitor and blow off some of the charge as you say before storing.

Not only that, but running them down too much hurts them too. I remember looking at campers and some of them had the famous EcoTrek batteries and I guess they ran them down too much and could not figure out how to start them up again.

Of course, everyone is different, and some just like to say they don't use propane.

[Davydd]

In storage ARV regulates the battery charging while on shore power by charging the batteries up to 99% and then turns off the charging until I think 40% before it charges again. I haven't figured out the low % yet as I do not get out to my remote garage that frequently to determine it. I can visually see whether it is charging or discharging and by how much on my touch screen monitor. It discharges at less than 1% per hour in storage. I have my autogen (second alternator and engine start up on high idle) set to go off when on the road when the batteries hit 40% discharged or any other % I want to set and run for an hour or when I want to stop it. Batteries shut down at 20% and you have to start the engine and hold a button down for about 1 minute for the batteries to come online again. It is also set to not run regardless between 10 PM and 6 AM. Setting at 40% means never to have batteries hard shut down with a 20% reserve in that 8 hour period. It's pretty sophisticated and failsafe.

As for storing it used to not be that sophisticated but I haven't observed battery performance drop off in my previous ARV van of 6 years (800ah lithium batteries) to be concerned about what percentage to store them at. Now I have a different brand of lithium batteries but for just one year with the more sophisticated monitoring. I did reduce my batteries to 552ah based on my observable and practicing experience, saving weight and make better use of storage and still have a peace of mind. Don't get me wrong. You pay for all that peace of mind. My van is all electric with no propane.

ARV has a higher capacity 56v Volta battery system. They are developing I think a 24v battery system to save weight, space and reduce wiring. Don't quote me on that as I didn't take notes because they to my knowledge have't built one yet and I doubt I will ever need to buy one.

Back to air conditioning. I suppose I could get a couple of hours boon docking but as I said I don't use it, and if I did, I wouldn't turn away seeking a shore power campsite. You can stay in many state parks with electrical hookups pretty cheap. My last campground at a state park in Ohio I paid a $6 premium at $28 because it was a better located site, had a level concrete pad and then I didn't bother to plug in.

[otr]

If it has not already been mentioned, make sure your CO monitor is working!

[JPMcG]

Originally Posted by jakegw2

Well let's see:

Promaster Chassis
From this post I am going to use the value of 0.54 Gal/Hr @ idle for the Promaster. This gets you the dash air conditioning with probably in excess of 18k BTU at idle (at cruising speed this rises up to something like 60k BTU). Since these are estimates I will go ahead and estimate that using the AC increases idle fuel consumption by 10% bringing it to 0.59 Gal / Hr for 18k BTU of cooling.

Roof AC
The roof AC draws 13.6A at full load.

The Onan produces about 23A at full power, or 11.5A at half-load. At half-load it consumes 0.31 Gal / Hr for the propane model. By interpolation we get about 0.35 Gal / Hr to support a continuous 13.6A load for 13.5k BTU of cooling.

Comparison
I'm on shaky ground here as I'm not really sure how to do comparison adjustments for different BTU ratings, but I'll take a stab at using a linear comparison. In a very hot environment the roof AC will be under-powered and cannot be increased to 18K. Most of the gas consumption from the dash AC is from the engine idle, so it can't be decreased. That makes this comparison entirely theoretical, but here it goes:

scaling 13.5k to 18k is a 30% increase in cooling, so using a linear approach we would get to a power consumption increase to 18.1A. Using that same increase and interpolating between half-load and full load consumption we get to 0.45 Gal / Hr of propane for equivalent cooling.

I'll skip the energy density comparison and go right to the price comparison:

I am using data for Rapid City, SD in the link, choose your own adventure here if you wish.
Propane: $4.10 / Gal
Gas: $4.70 / Gal

Conclusion:
Propane $1.44 / hr of operation ($1.85 / hr of operation for equivalent cooling performance)
Gas $2.77 / hr of operation

Very interesting. Not even fully understanding the calculation aI can see in summer of 2022 Propane at $3.90 vs Diesel at $6.99 running propane seems to win by a long shot. Not even considering the engine heat or not good idling diesel with DEF for that long.

[jeana]

Originally Posted by Urlauber

Nothing serious, just out of curiosity... lets say you are in the Summer desert somewhere and want to hang out for an hour or two in the van, so you need to run A/C... which would be cheaper?

1) Running the 2800i Onan Propane Generator to power the roof A/C
2) Idling the 3.6l Ram engine while blasting the dashboard A/C

Propane being more expensive and less energy-dense than gas?

(I do not know how much propane is used /hr to run the genny under load... nor do I know how much an hour of idling takes out in terms of gas. Hey... that's why the post.)

gas and propane even are fossil fuels
Get a jackery/ yeti and use the solar panels Use fan PUt insulating panels on the rv over the windows

[horacecupp@gmail.com]

Urlauber
Not a good idea to idle a diesel for prolonged periods of time, anyway.

[Urlauber]

Originally Posted by jeana

gas and propane even are fossil fuels
Get a jackery/ yeti and use the solar panels Use fan PUt insulating panels on the rv over the windows

Good luck with that when traveling in Arizona in Summer. Some don't have the options to choose perfect time and climate.

[Urlauber]

Originally Posted by horacecupp@gmail.com

Urlauber
Not a good idea to idle a diesel for prolonged periods of time, anyway.

Absolutely! Looks like even idling the Promaster gas engine is not such a good choice.

[Macodiva]

Not an answer to your question but....
Be very careful with Death valley. The temps there this time of year are no joke.
Check out the slot canyons in Page they're amazing

[Urlauber]

Originally Posted by Macodiva

Not an answer to your question but....
Be very careful with Death valley. The temps there this time of year are no joke.
Check out the slot canyons in Page they're amazing

Yeah, DV in Summer is definitely a stress test, for man and machine. From where I start to the places in Utah it's just part of the route... If you stay hydrated, covered, and in the shade its not all that bad. There are folks who like running marathons there... Planning to arrive in the afternoon, doing some stuff in the evening and next morning and then heading further east.

Antelope Canyon (both Lower and Upper) is definitely something one should see at least once. Super commercial, get in line, don't stray from the group, but amazing nonetheless. We'll bypass Page this time and go to explore the Valley of the Gods instead where there is also a number of slot canyons, maybe not quite as overrun with tourists and their guides.