How long will A/C run on a #20 propane cylinder?

[keepitlow]

Using a propane powered generator, about how long would the A/C run before it runs a 20 pounder dry? (Interested in smaller class c size units as discussion.)

Thanks

[Alie&Jim's Carrilite]

This depends on the size of the generator you're running.

[keepitlow]

Just an average gen that comes with a smaller size class c.

[The Quiet Assassin]

A 3000w lpg running at 75% load will burn a 20 lb cylinder in 5 -6 hours.

[Kirk W]

Most onboard generator sets burn about 1/2 gallon of fuel per hour when under load. Idling it would be less so the temperature outside will determine how much the compressor will run to push max load. Since propane weighs about 4.6#/gallon so you have about 4.5 gallons and that will give you somewhere between 8 and 20 hours of generator time, depending on the load.

[trailertraveler]

2 hours ago, keepitlow said:

...C in the 25 foot area? I'd like to get Ford gas powered and bedroom slide out...

A gasoline powered Class C will most likely have a gasoline generator that runs off the main fuel tank setup so that it can not run the fuel tank empty. The diesel C's have an LP generator or possibly a diesel generator.

[Kirk W]

1 hour ago, trailertraveler said:

A gasoline powered Class C will most likely have a gasoline generator that runs off the main fuel tank setup so that it can not run the fuel tank empty. The diesel C's have an LP generator or possibly a diesel generator.

A very good point. I have seen diesel RVs with a propane generator and also trailers but I can't recall ever seeing a gasoline powered motorhome that had a propane generator. And I also consider that to be a good thing since our gasoline class A had a 75-gallon tank and we could use the generator for several days without fuel worries. 

[Yarome]

You can't compare dino fuel vs. LP consumption in gal/lbs per hr. LP requires approximately 25-35% more fuel (quantity) for about 90% output of a comparable dino fuel genset.

Without knowing the type of size of your genset and A/C it's difficult to give much in the way of ballpark runtime numbers.

[chirakawa]

4 hours ago, Yarome said:

You can't compare dino fuel vs. LP consumption in gal/lbs per hr. LP requires approximately 25-35% more fuel (quantity) for about 90% output of a comparable dino fuel genset.

Without knowing the type of size of your genset and A/C it's difficult to give much in the way of ballpark runtime numbers.

I think LPG is dino fuel.

[Darryl&Rita]

5 hours ago, Yarome said:

You can't compare dino fuel vs. LP consumption in gal/lbs per hr. LP requires approximately 25-35% more fuel (quantity) for about 90% output of a comparable dino fuel genset.

Without knowing the type of size of your genset and A/C it's difficult to give much in the way of ballpark runtime numbers.

Whaat? 

[keepitlow]

Thanks for all the replies. 

I didn't know that C gens run off the main gas tank. That saves a lot of worries about running out of LP. 

[markandkim]

17 hours ago, keepitlow said:

Using a propane powered generator, about how long would the A/C run before it runs a 20 pounder dry? (Interested in smaller class c size units as discussion.)

Thanks

 

 

[Yarome]

I stand corrected. 😄

LP is a by-product of oil refining or extracted from natural gas. Technically, "dino fuel" for those that don't recognize "dino fuels" to typically refer to products directly refined from crude oil (gasoline & diesel) and used as fuel source options in standard combustion engines found in typical RV's and portable generators.

The facts remain. To be crystal clear... LP contains approximately 25% less energy per lb of fuel than gasoline and 35% less than diesel and cannot be compared pound for pound/gallon for gallon when it comes to genset output. Energy conversion rates also come into play. LP being the lowest... overall genset output will also be affected.

Gensets range in fuel consumption, under A/C load, between 1/4 - 1gal/hr. A 13.5k BTU A/C... typically installed on "smaller class c" RV's... can have power consumption rates that vary by 4-5amps.

Without knowing the make/size/model of genset and A/C unit it's difficult to give any meaningful ballpark number of hours of runtime off a #20 LP tank (assuming it's an actually full #20'er and not one from an LP tank exchange program that typically only has #14-#16 of LP in em.). At least... somewhere between 5 and 20... wouldn't help me do much advanced planning. 😉

While we're clarifying... also be aware that you will get "zero" hours of A/C from any genset unless it is in the "on" and engine continuously running configuration. 😁

Of course... to confuse matters... we're not even talking about a "generator" since they don't produce 120vac current. 🤣

[Yarome]

56 minutes ago, keepitlow said:

I didn't know that C gens run off the main gas tank. 

Not all do. That's why it would be important to find out exactly what you have installed. If it is in fact an LP generator then that wouldn't be the case... but "may" be plumbed directly into an onboard LP tank, if so equipped. That tank may or may not have an exterior tank adapter installed which will accept an auxillary #20 tank or larger.

If it is a gas or diesel genset.. and you have a cooresponding gas or diesel chassis... then it's likely that it IS fed directly from your chassis fuel tank... if the genset was in fact a factory installed option.

When you asked about an LP genset... I made the assumption that you knew it was an LP genset... where it would, naturally, not be fed from your chassis fuel tank. 😉

[The Quiet Assassin]

If the genset uses the main fuel tank then it is common to have a fuel pickup for it that only reaches to 1/4 full level. Thus the genset can not completely empty the tank. 

[keepitlow]

22 hours ago, Yarome said:

Not all do. That's why it would be important to find out exactly what you have installed. If it is in fact an LP generator then that wouldn't be the case... but "may" be plumbed directly into an onboard LP tank, if so equipped. That tank may or may not have an exterior tank adapter installed which will accept an auxillary #20 tank or larger.

If it is a gas or diesel genset.. and you have a cooresponding gas or diesel chassis... then it's likely that it IS fed directly from your chassis fuel tank... if the genset was in fact a factory installed option.

When you asked about an LP genset... I made the assumption that you knew it was an LP genset... where it would, naturally, not be fed from your chassis fuel tank. 😉

I'm just learning about them now. I never had AC in my rig. I'm getting sick of 98 degree heat inside. If I cook it goes to 106.

I thought that AC was either electric or propane gen run. I boondock a lot, so having an AC that would drain the propane in a few days would not be good. Gas fed is the way to go, so I will have to make sure that is what I get. 

[Kirk W]

21 minutes ago, keepitlow said:

I thought that AC was either electric or propane gen run. I boondock a lot, so having an AC that would drain the propane in a few days would not be good. Gas fed is the way to go, so I will have to make sure that is what I get. 

While propane powered generators are very rare in gasoline chassis motorhomes, it is worth checking to be sure. I have never seen a factory installed generator that burned propane from a special tank for the purpose but all of them have drawn from the same propane supply as the RV appliances. It is important to keep in mind that your air conditioning will require 120V power so you will need to have either shore power or the generator running for it to work. Even if the generator does use gasoline from the main fuel tank, it will still get very expensive to use for long periods. You will go through 6 to 10 gallons of gasoline per day, so that makes it cost somewhere around $15 to $40 per day for fuel alone. If you are running an air conditioner, it is usually less costly to spend the time in an RV park. 

[markandkim]

My Champion dual fuel unit powers my 15K a/c for about 12 hours on a 20lb bottle of propane.

I can see that you're talking about portable generators since you mentioned propane bottles.

I love the Champion, since you don't have to carry gasoline. I can connect it to my installed propane system, where I have 2-30lb bottles available.

[2gypsies]

4 hours ago, keepitlow said:

I'm just learning about them now. I never had AC in my rig. I'm getting sick of 98 degree heat inside. If I cook it goes to 106.

I thought that AC was either electric or propane gen run. I boondock a lot, so having an AC that would drain the propane in a few days would not be good. Gas fed is the way to go, so I will have to make sure that is what I get. 

You'd save a lot of money if you just move to cooler areas.

[noteven]

Cummins/ Onan publishes fuel use rates for Onan gensets on their website. 

I’ve found the numbers to be quite accurate for country work but maybe not detailed enough for forum debates...