Dumb newbie generator question--tanks freezing - RV-Dreams Community Forum

cheryls-other-half · RV-Dreams Family Member

Dumb newbie generator question--tanks freezing

Lonney Wade · RV-Dreams Family Member

When you are using 2 AC units at the same time you are putting a big load on the generator, when you pull that much propane out of a tank that fast it will get iced up. The faster it comes out of the tank the colder the lines and fittings get, than ICE becomes your friend.
Solution, turn one AC off, You can do it !!!!!

Lonney

TRAILERKING · RV-Dreams Family Member

Joys of propane...................But as said, run one A/C, I do all the time and it's sufficient. I guess it depends on how hot you're at.

Joe_Camper · RV-Dreams Family Member

Yup, as said, you are pulling too much propane out of the tank too quickly. There's another issue that this will cause. It is called empty tanks! :) The diesel motor home folks have the best scenario because their generators run off of the motor home fuel tank and the diesel generators are more efficient than the propane generators.

Terry and Jo · RV-Dreams Family Member

Mitch,

Also, talk to some LPG folks. Back years ago, I used to haul and deliver LPG to farms and homes. On occasion, someone's LP regulator would freeze up. When that happened, we'd pour a smidgen of alcohol (not the drinking kind) into the lines ahead of the regulator. If moisture gets into the regulator, that is what freezes and the alcohol "dries" out the little moisture that is there and lets the gas flow again.

Terry

Bill and Linda · RV-Dreams Family Member

Terry's on the right path. If properly installed with a large enough LP line to the generator (assumption here) a 5500 watt generator will easily run two AC units. However in very cold or humid conditions you can get a freeze up. As regulators are not all that expensive and easy to change, if this continues I would change out the regulator. Summer and Wal-Marts are no place to be without full generator power, to run both AC’s, if you paid for it.

But, it could be a low tank, not just an empty tank and there just isn’t enough LP in the tank to turn into enough gas fast enough. Try a full tank and see what happens first as was suggested.

(I’ve actually had to put a heat gun on a gas generator in very humid conditions when the carburetor would freeze up. It can happen to gas and LP. Not so much to diesel, they do other annoying things when it gets cold outside.)

-- Edited by Bill and Linda on Sunday 6th of July 2014 09:16:24 AM

The Junkman · RV-Dreams Family Member

Can the lines be heated ? maybe with heat tape? I have heat cable used on roofs in my inventory.. I better grab a 100ft box of it..

I like it cold, and I expect my ac to be on all the time..

cheryls-other-half · RV-Dreams Family Member

Thanks, y'all.. the propane was filled Tuesday and this started Wednesday.. so I guess it is just too fast too quick..

Bill and Linda · RV-Dreams Family Member

cheryls-other-half wrote:
Thanks, y'all.. the propane was filled Tuesday and this started Wednesday.. so I guess it is just too fast too quick..

Mitch:

LP generators (5,500 watt version) burn about 1 gallon of LP per hour. That’s a good rule of thumb. They do burn more under full load than at idle but the 1 gallon / hour is a good operating number. (Diesels a bit less, yes more efficient, but there are other factors to consider in a 5er.)

Anyway – a 40lb LP tank contains about 9 ½ gallons of LP. So do the math. In 9 hours a full tank is going to be empty running a generator give or take and sooner if your using LP for other things. (Fridge uses very little so don't worry about that in the 1 tank = ~ 9 operating hour thing.)

So there ya go.

-- Edited by Bill and Linda on Sunday 6th of July 2014 12:30:51 PM

Sushidog · RV-Dreams Family Member

Around here propane runs about $3.50/gallon, so at a gallon per hour for 24 hours/day that's $84/day to run that genny! It's usually much cheaper to pay for a camp site at a campground for a night with electricity included in the daily rate, especially if you have a discount club membership.

I currently camp with an Aliner with a tiny 5,000 BTU AC. My little 1,200 watt/1,600 watt genny will run it for about 8 hours on a gallon of gas. At $4/gallon that's about $12/day for a cool camper. Of course it's only about 90 sq ft inside. ;)

For the size genny you need, diesel is the most efficient fuel. The general rule of thumb for smaller diesel generators, fuel consumption is 7% of the rated generator output (Example: 5 kW x 7% = .35 gallon per hour at full load). So .35 x 24 = 8.4 gallons x $3.65/gallon = about $30/day to operate - still expensive if you need to run both ac units 24/7, but only 35-40% of the cost to operate a propane genny. Now realistically, you probably only need to run one AC unit for 8 hrs while sleeping (now that you know what running both are going to cost) bringing your operation cost down some.

Chip

Camper Chronicles · RV-Dreams Family Member

Great thread guys...thanks for all the info

Bill and Linda · RV-Dreams Family Member

Chip:

You got me to thinking and so I went and double checked the manual for the Onan 5500 LP genset commonly used in 5er’s when built-in from the factory. The diesel use specs vs. LP use specs shows the diesel about 20-25%% more efficient; i.e. burns about 20-25% less fuel per hour than the LP under nominal loads. In this area on the country LP is less expensive than diesel. In other areas, not so much as you point out.

For those reading along: If you going to use the generator a lot in a 5er, diesel is certainly worth consideration. But for me the hassle, maintenance and space required for diesel fuel to use a diesel generator in a 5er isn’t worth it unless you’re going to use it a lot. This goes for the “average” user much like many of us who do want it when we need it, but don’t really use it for long periods of time.

Unlike motorhomes which commonly run the generator a lot when traveling, few 5ers tend to put many hours on their built-in 5.5K-ish units. I wouldn’t be without one but have found LP to be the way to go for so many reasons. Your mileage may vary. Just info – not trying to sell a thing either way. It just depends on your situation, and naturally Terry’s relatively small dual portables are very economical but don’t have the same capacity. It just depends on what you think you need and what you are willing to spend.

Happy puttering. . .

Sushidog · RV-Dreams Family Member

Bill and Linda wrote:

Chip:

You got me to thinking and so I went and double checked the manual for the Onan 5500 LP genset commonly used in 5er’s when built-in from the factory. The diesel use specs vs. LP use specs shows the diesel about 20-25%% more efficient; i.e. burns about 20-25% less fuel per hour than the LP under nominal loads. In this area on the country LP is less expensive than diesel. In other areas, not so much as you point out.

For those reading along: If you going to use the generator a lot in a 5er, diesel is certainly worth consideration. But for me the hassle, maintenance and space required for diesel fuel to use a diesel generator in a 5er isn’t worth it unless you’re going to use it a lot. This goes for the “average” user much like many of us who do want it when we need it, but don’t really use it for long periods of time.

Unlike motorhomes which commonly run the generator a lot when traveling, few 5ers tend to put many hours on their built-in 5.5K-ish units. I wouldn’t be without one but have found LP to be the way to go for so many reasons. Your mileage may vary. Just info – not trying to sell a thing either way. It just depends on your situation, and naturally Terry’s relatively small dual portables are very economical but don’t have the same capacity. It just depends on what you think you need and what you are willing to spend.
Happy puttering. . .

Everyone's needs are different, so there is no one "right choice" that fits everyone. One thing those deciding on a generator should consider is that a generator configured for diesel fuel (or gasoline) will produce more wattage than the exact size (displacement) genny running off of less energetic propane. High elevation makes this difference even more pronounced, especially under max load conditions. Diesel fuel has 128,000 BTU/gallon, while propane only has 84,000 BTU/gallon. Not only is diesel more energetic, but it burns more efficiently than gas too. For an equal engine displacement (generator size), a diesel will produce more power (torque) with a 20% increase in fuel economy, vs a gasoline engine. Propane burns very clean, but produces about a 25% less power than diesel, though has 1/3rd less energy (BTUs) than diesel. Natural gas burns cleanest, though it suffers another 10% loss in power vs propane.

So propane produces 25% less power than diesel and natural gas produces about 35% less. However, comparing it to gasoline for a generator fuel, propane is only at a 5% disadvantage. A friend of mine has an EU2000 Honda that he converted to natural gas. It only produces about 1,200 watts when he runs it on natural gas. Had he converted it to propane it would probably produce around 1,500 watts (100 watts less than its rated power output).

Yes, diesels are generally noisier, dirtier burning, and diesel fuel only stores about a year vs propane which stores indefinitely, and is very convenient, as you already have some on hand, and it is piped in ready to go with no messy fuel to transfer, but like you said everything in life is a trade-off. The current price of propane would have to drop substantially to make it attractive for me to use as a generator fuel, all other considerations aside. I know I can't afford to burn through a tank or two of propane a day, though I guess there are many who can, and the convenience and cleanliness far outweighs the added expense. I just thought that from my perspective, those boondocking at Walmart valued economy over convenience, though I may be mistaken.

Chip

Terry and Jo · RV-Dreams Family Member

Something I'll mention here for Mitch and others to consider. We do have a Honda generator, but it is the single EU3000IS model, not two smaller units. When we were simply camping for a week in Colorado in the past, I learned that at higher elevations, the gas engines will run richer on fuel due to less oxygen, thus leading to fouling of the spark plugs. I was running our Honda about 5 or 6 hours per day and after only about 3 days, the engine wouldn't start, thus it took a new spark plug to make it run again. I learned that lesson the had way because in the area where we were, not every auto parts store had the tools I needed to accomplish the simple task of reaching and removing the spark plug. It took three different stores in two different towns to find all I needed in a ratchet, an extension, a pivot joint adapter, and the spark plug socket with insert to hold the spark plug.

So, first of all, if you have a gasoline motor on your generators, see what tools you might need to change the plugs.

When I was considering an on-board generator for our Mobile Suites, I looked at the Onan 5500. What the one I saw had that impressed me was an adjustment "lever" that would allow one to adjust the carburetor to an approximate altitude. While the LP systems won't necessarily require that adjustment lever, any gasoline system will or at least, have another way to adjust the carburetor.

We chose to not get the Onan because of its cost. For what the Onan cost, I could buy an awful lot of spark plugs, although it would be a pain to keep changing plugs.

Terry