1994 Diesel Pusher Land Yacht 34 ft.

[dscluchfc]

I am looking at this unit.
One of the things holding me back is the generator is fueled by propane.

1) How long will a 105 lb tank of propane last running the ACs in a boondocking situation?

2) Has anyone ever converted the coach to a diesel genset and plumbed in a diesel line to the fuel tank or a secondary diesel tank for the genset?

Only 40K miles on this coach...seems to be straight and has been under awning. Sides show some decal and paint fade.
Otherwise, the only thing I wish was different is that I could tap into about 60 gal of diesel before having to go get fuel for the genset instead of the propane unless the propane tank will last long enough.

Anyone have words of experience & wisdom?

[dscluchfc]

Apparently I have stumped the band with these two questions.....

[rmkrum]

Opinion follows:

My suspicion is that a diesel-fueled generator would be a rather big, heavy, and rather noisy beast. Gas or propane-powered units can be built fairly light and still have a large power output rating, with their own 'noise factor'.

You might look into a diesel-powered one, but it needs to be installed right, with a fuel pickup that does NOT go to the bottom of the main tank, so you have reserve diesel available to go get more fuel, if that makes sense... Also, it would probably be water-cooled, and that adds to bulk and weight.

Last diesel-fueled genset I worked with was on a largish yacht--had a 5-cylinder Mercedes/Benz engine and a rather heavy alternator. Was not something you could even fit into an RV, and was a pain to work on...lots of heavy cast-iron parts, even in the cooling system...

[dscluchfc]

Originally Posted by rmkrum

Opinion follows:

My suspicion is that a diesel-fueled generator would be a rather big, heavy, and rather noisy beast. Gas or propane-powered units can be built fairly light and still have a large power output rating, with their own 'noise factor'.

You might look into a diesel-powered one, but it needs to be installed right, with a fuel pickup that does NOT go to the bottom of the main tank, so you have reserve diesel available to go get more fuel, if that makes sense... Also, it would probably be water-cooled, and that adds to bulk and weight.

Last diesel-fueled genset I worked with was on a largish yacht--had a 5-cylinder Mercedes/Benz engine and a rather heavy alternator. Was not something you could even fit into an RV, and was a pain to work on...lots of heavy cast-iron parts, even in the cooling system...

rmkrum, thanks for the reply. I went looking for weights.

https://power.cummins.com/sites/defa...d=1172&elqat=2

After looking at the Cummins/Onan brochure, it appears the weight is double for a small diesel generator vs the current mounted LP Generator.

If I need more capacity, it would appear the easiest way to get that would be an additional LP tank mounted and plumbed in someplace.

So, I guess the final answer needed is how long does a stock 105 lb/ 24 gallon propane tank last running the AC?

[rmkrum]

How much propane you might burn is highly variable, based on ambient temperature, sun exposure, how often the A/C cycles on, and the efficiency of the generator setup. You could get a rough idea by running the A/C for a few hours on a 'full' tank, then refilling to see what you burned. It would be very hard to estimate that one...particularly if your tank does not have a gauge.

My usual practice is start with two full 20 pound tanks of propane on the front of the trailer, and 2-3 spares in the truck if I'm out in the cold...and refill when a set gets empty.

For running my single air conditioner, I have not had the opportunity to characterize my new Champion 3400 watt propane-powered inverter generator yet. I plan to try it this summer, just to see if the whole setup works after I get it fully rigged. I need to buy a flaring tool set before I get the AS propane tap-off install done.

[dscluchfc]

This is a 34 ft 1984 LandYacht motorhome I have not purchased yet.

Completely different considerations to a trailer.
Has a permanently mounted propane tank that is 105 lb/23 gallon.

I am thinking it is summer....it is HOT....might need to run one AC 24/7 and while going down the road.

So, if you figured 50% load consumption would be ????
Refill once a day?
Every other day?
Once a week?

And because it is permanently mounted, you're going to have to bring the motorhome to the pump, unlike my 31 ft trailer where I can just take the 30 lb aluminum worthingtons to the propane pump.

So....I don't know if I want to purchase the motorhome or not if it doesn't really get me the freedom from hookups in an RV Park and ability to boondock better than my trailer.

[rmkrum]

What is the rating of the generator at full load in watts or kilowatts?

[dscluchfc]

Originally Posted by rmkrum

What is the rating of the generator at full load in watts or kilowatts?

I believe it is an Onan 6.5 KW that is LP powered.

[rmkrum]

OK, then the question to ask is how many pounds of propane per hour the Onan consumes at rated load...possibly a spec sheet or listing on their site...

Then estimate "normal" usage based on say 50% of running time at full load, if the spec is at full load.

Sometimes gensets specify fuel consumption at only 50% load--either way a spec sheet for a similar Onan genset will provide a clue.

EDIT: a quick search for a 6.5 KW Onan reveals 0.7 gallons per hour at 50% load. So a look in the calculator gets me roughly 32 generator run hours for a full tank of propane at half load.

So yeah, if you run the A/C 8 hours a day, maybe 3-4 days run time. I'd be thinking more available propane if you are out in the heat, and since you are in Texas, I'd bet its going to take more than 8 hours running in the heat to stay cool without hookups...

Then, as an engineer, I would figure about 80% of propane capacity dedicated to the generator on average, saving some for fridge and cooking, whatever...

A little math, and you have a rough idea of runtime.

Does the coach have one or two air conditioners? Some are set up to only run one off the generator, because it can be a big load.

[dscluchfc]

Originally Posted by rmkrum

OK, then the question to ask is how many pounds of propane per hour the Onan consumes at rated load...possibly a spec sheet or listing on their site...

Then estimate "normal" usage based on say 50% of running time at full load, if the spec is at full load.

Sometimes gensets specify fuel consumption at only 50% load--either way a spec sheet for a similar Onan genset will provide a clue.

Then, as an engineer, I would figure about 80% of propane capacity dedicated to the generator on average, saving some for fridge and cooking, whatever...

A little math, and you have a rough idea of runtime.

Does the coach have one or two air conditioners? Some are set up to only run one off the generator, because it can be a big load.

It has 2 AC units, but can only run one at a time on genset.

[Al and Missy]

This is all theoretical, so take it for what it is worth (what you paid for it):

For two AC units, I'd figure about 3 kW. Guessing at a 50% duty cycle, that averages to 1.5 kW. Converting to BTU/h that's 5000 BTU/h. In 24 hours, that's 120,000 BTU. A pound of propane has roughly 21,000 BTU, so say 6 pounds per day. Since this is based on 100% efficiency conversion factors, derate it 50%, so maybe 12 pounds per day.

Coming at it another way,
1500 watts for a day is 36kwh. A gallon of propane is 26.8 kWh. so roughly 1.3 gallons at 4.24 lb./gal = 5.5#. Double that to take into account efficiency.

Another way of looking at it is a gallon of gasoline has roughly 1.24 times the energy of a gallon of propane or 5.25 times the energy of a pound of propane. Figure out your load, look up the gallons per hour for a gasoline generator and multiply by 5.25 to get the pounds of propane.

Probably more than you wanted to know.....

Al

[dscluchfc]

https://power.cummins.com/sites/defa...d=1172&elqat=2

This is the closest specifications pdf I can find from Onan.
At .8 gal consumption per hour, it would mean a trip to a town for propane, and having to spend about $60 a day at current prices to refill a 24 gal propane tank almost daily unless you can figure a way to do without the AC for a while.

That makes the whole thing a lot less attractive than just biting the bullet for hookups.

[55AS]

Running AC units full time in a big rig while boondocking is a pricey proposition in any case. In terms of convenience, the best option would be to install a much larger LP tank in a basement compartment to allow you to run longer between fill ups. That was the route I chose when I had a Class A SOB several years ago. Hookups are cheaper if you are running the AC 24/7 (as one must in the Texas summer heat). Summertime boondocking was only done if there was no other option.

[55AS]

On the plus side, LP generators are lighter, cheaper, quieter, require less maintenance and avoid the "old fuel" issues of diesels.

[dscluchfc]

Originally Posted by BambiTex

Running AC units full time in a big rig while boondocking is a pricey proposition in any case. In terms of convenience, the best option would be to install a much larger LP tank in a basement compartment to allow you to run longer between fill ups. That was the route I chose when I had a Class A SOB several years ago. Hookups are cheaper if you are running the AC 24/7 (as one must in the Texas summer heat). Summertime boondocking was only done if there was no other option.

Pretty much makes me think I like my 1984 31 ft Excella trailer a lot more than dealing with the inherent issues that go with motorhomes at this point.

[rmkrum]

True that. However, now you see how "group think" can answer a lot of engineering and other questions on the forums...

And from the data you get, answers, although not the ones you thought might come up, spring forth...

Do let us know what ends up happening, and if you chose NOT to go with the motorhome, let us know where it was being sold--there are threads here that just love to resurrect old motorhomes--some are quite addicted to the process, to put it mildly...

[dscluchfc]

Originally Posted by rmkrum

True that. However, now you see how "group think" can answer a lot of engineering and other questions on the forums...

And from the data you get, answers, although not the ones you thought might come up, spring forth...

Do let us know what ends up happening, and if you chose NOT to go with the motorhome, let us know where it was being sold--there are threads here that just love to resurrect old motorhomes--some are quite addicted to the process, to put it mildly...

This is a 1994 slope nose, 34 ft LandYacht Diesel Pusher Spartan Chassis, 5.9 Cummins/Allison Transmission, with 39,000 miles on it and a new Allison push button controller installed, in need of 6 tires, fluids and filters, belts and hoses, and one of the two AC's isn't working and needs serviced or replaced....and there is some sun fade/cracking to the decals, but it has been parked under awning so only routine maintenance needs to be done on roof seams and window seams, although the sides need buffed out.

This is NOT the unit, but it looks a lot like this one I found by googling images:
http://vsquare.com/blkmagikca/1107/motorhome/

Anybody got an idea what would be Fair Market Value for such a motorhome?
Book value and Fair Market Value are often in different zip codes/solar systems on anything Airstream.

EDIT:
I would add, I have known the owner for over 30 years, and he hasn't used it much the past 3-4 years, but he does go start it up and drive it 3-4 miles about once a month to get it warm and keep things lubricated.

[Mike1997]

David, read through your responses and guess I am the only one who actually owns and uses an identical 1997 Airstream Landyacht motorhome.

My generator is the Marquis 6500LP.
Model #6.5NHMFA26115G
Ser#J9636054492

As of today the unit has 597hours on the meter.

Like you, I would prefer it was diesel but the unit does perform excellent and I have never had problems. As far as usage, it just depends on how and where you use it. It WILL run both AC units and can be started with either the coach batteries or the engine batteries when the transfer switch is used on the dash.

My rig was kept in dry storage for over 15 years when I bought it in excellent condition. Biggest expense was tires, belts, hoses that were all original 1997.

I spent almost a month at the Navy Campground in Key West last year and was in dry camping over 25 days. During that time I ran the generator an hour each morning (while fixing breakfast with microwave) which allowed it to charge the coach batteries. It also has a small solar charger but highly recommend you replace with a larger new panel (on my wish list). Then ran generator at night for about 2 hours. In meantime my frig was on propane and used the water heater a few times. I never needed the AC as it was March in Key West so weather was cool and breezy. At night used both ceiling fans (12v) and it kept the interior cool.

My propane tank is 105lbs or about 26 gals. Using under conditions described, I refilled it in 10 days. Had I used the AC regularly, my run time would have been half.

Onan estimates this unit to use approximately 0.7gals per hour under half load or 1.2gals per hour full load. Hope this info helps. If you have other questions about this rig, please feel free to contact me directly. I know 2 other Landyacht owners and we have solved problems together. Most recently I finally got my dash AC working as designed, problem was with a bad ground wire and defective pressure valve. Repair cost was $70 for new valve found online.

Let me know if I can answer any other questions. Drove mine to the Airstream Rally in Michigan last year but staying on east coast this summer.
Regards, Mike