Generator Sizing Questions

[jdereu]

So I just picked up my 2020 High Country. I have been researching generators and so stuck on different options to run the two 15k BTU Ac and the residential fridge…

Some options are
Champion 5500
Two of Champion or Predator 3500
Westinghouse or Cummins 4500

Does everyone have any recommendations or experience

[rames14]

Lots of questions to get the right answer, and even then it is your decision. Do you have soft start on your AC’s? Do you camp at altitude? Do you have lithium batteries? With soft starts, you can run both AC’s on 30 amp, unless you are camping above 5000 feet (you lose about 10% per 1000 feet of altitude gain).

We have two Honda 2000’s and they have been trouble free for the last 15 years. The advantage with any of the small generators is you can run one or both, depending on power need. With lithium batteries, they charge very quick. There are lots of options. The weight, versatility and reliability have been great - for us. Your needs may be different.

[Daryles]

Champion has a tool to help you with generator and parallel kit selection.
https://www.championpowerequipment.c...-kit-selector/
As Rames pointed out having two smaller, lighter generators that are easier to handle can be a better move. Also if one goes down for any reason you have a back up.
Adding SoftstartRV to your AC units will help regardless of which generator you choose.

[jdereu]

So I just have one stock battery currently but will be adding a 2nd. All of the rv use will be over 5000’ above sea level.

No I have not installed soft starts but will look into it

[mlh]

Generally speaking, an engine loses three percent of its rated power for every 1,000 feet of altitude gained. This is from a Google search

Two 3500 watt Predator generators are a lot to carry with you unless you plan to use them a lot. They are great generators. I have a Honda 3000 but would buy the Predator if I needed another generator. The 4500 watt generator should work great for you especially if you can get by with one AC. It probably will run 2 ACs with soft starts on them.
Lynwood

[rames14]

Lynwood, here in Colorado when we bought our Honda’s, they told us 10%. Based on trying to run AC in the past, I don’t believe it’s far off. At our altitude it isn’t an issue because it seldom gets warm enough to run air. Our high so far is 89 and usually gets into the 50’s at night. I would bet that the loss isn’t linear. Most people don’t camp much above 5000 feet anyway. Next week we’ll be at almost 10,000. Probably will need the furnace.

[Creeker]

Based on many years of ownership and heavy use. Both for personal and for my business use, I will buy nothing but Honda EU****Is series generators.

To run 2 A/C's and a resi fridge would require two Honda EU3000Is or the gold standard of gennies - The Honda EU7000Is. Buy once and forget it. They will likely outlast your camper and truck if properly maintained.

My Dad purchased the Predator 3500 two years ago. Thankfully he purchased the extended warranty as he already had to return the first one for replacement. Had less than 25 hrs on it. Carb issues.

[mlh]

Ron. I pulled a camper across the mountain on I80 just before you get to Laramie. I’m sure you have been there many times. It’s 8100 feet. My gasoline engine had 315 pound feet of torque. At 8100 feet it would have had only 60 pounds if you loose 10% per thousand feet. The engine would probably not run and certainly would pull my 7200 pound camper. The figure I have always heard for 40 years from Motor Trend, Car and Driver and others is 3, 3.5 or 3.6% and that depends on barometric pressure and temperature.
Lynwood

[mlh]

Originally Posted by Creeker

My Dad purchased the Predator 3500 two years ago. Thankfully he purchased the extended warranty as he already had to return the first one for replacement. Had less than 25 hrs on it. Carb issues.

He didn’t do quite as well as I did with my 4000 watt Micro Quiet Onan. I got 32 hours out of it before it had to be removed from my Motor Home completely tore down and repaired at a cost of almost what a Honda would cost.
Lynwood

[rames14]

Trucks and generators are two different animals. Your truck has a computer analyzing all of those factors such as barometric pressure, fuel/air ratios and compensates. Your generator isn’t near that sophisticated. Just relating our experience. My 15 year old Honda’s will be at almost 10,000 feet this next week. I couldn’t run both generators even with my soft starts. Maybe it’s just mine.

[mlh]

Ron at 10,000 feet if you lost 10% per thousand you would have zero power left. Check on what I have said. I’m positive I’m right. Just do a Google search.
Lynwood

[Last2Die]

Onan..?

[rames14]

Lynwood, if you read what I said, 10% above 5,000 feet which would be about 50% loss. Like I said earlier, I doubt that it is linear. They were probably rounding. Some say 3.5% starting at 500 ft, so that would be 35% vs 50%. Still a significant loss.

[mlh]

Ron I just copped this.
Do a Google search.
Lynwood

Higher Altitude Means Less Power
Reduced oxygen in high altitudes can lead to inefficient, sluggish engine performance because there is less air to feed the internal combustion engine. Generally speaking, an engine loses three percent of its rated power for every 1,000 feet of altitude gained. This means you could lose as much as 20% of your vehicle’s horsepower if you drive it from sea level to Big Bear Lake (with its 6,750 elevation).

[mlh]

This is from Garret turbo chargers

As a general rule, a naturally aspirated combustion engine will lose 3% of its power for every 1,000 ft of elevation gain. If you have 100 horsepower at sea level by the time you get to 5,000 feet of elevation your engine is making 85 horsepower.

At 10,000 feet of elevation your engine will make 70 horsepower.
At 15,000 feet of elevation your engine will make 55 horsepower.
At 15,000 feet of elevation your engine will lose 45% of its power due to lower air density.

[rames14]

My guess is they have improved over the last 15 years, which is the age of mine. Honda states 3.5%. Again, whether it’s 35% or 50%, not worth arguing over. The point remains the same, altitude equals decreased output.

From Honda:
CARBURETOR JETTING FOR HIGH ELEVATIONS
Honda Power Equipment
At high elevations, an engine’s performance will decrease, and fuel consumption will increase due to the air being less dense. If a Honda engine will be used at an elevation above 2,000 feet (610 meters), its performance and exhaust emissions can be improved by making a modification to the carburetor to correct the air-fuel mixture.
Even with carburetor modifications, engine horsepower will decrease around 3.5% for each 1,000-foot (300 meter) increase in elevation. When the carburetor is modified for high elevation operation, the air-fuel mixture will be too lean for low elevation use. Operation at elevations below 2,000 feet (610 meters) with a modified carburetor may cause the engine to overheat, and result in serious engine damage.
To have your engine’s carburetor modified for high elevation use, contact an authorized Honda Power Equipment Dealer near you for assistance. To find a dealer near you, go to powerequipment.honda.com or call Honda Customer Relations at 770-497-6400. Modifying the carburetor for high elevation use is not covered under the Distributor’s Limited Warranty.

[bshgto]

Originally Posted by jdereu

So I just picked up my 2020 High Country. I have been researching generators and so stuck on different options to run the two 15k BTU Ac and the residential fridge…

Some options are
Champion 5500
Two of Champion or Predator 3500
Westinghouse or Cummins 4500

Does everyone have any recommendations or experience

Back to the original question, THe large campers can`t run just 1 A/C and get comfortable at any higher outside temperature. Or lower temps with a lot of humidity. I tried with 2 2000`s a couple of times when I first got the beast, doesn`t work and have any power left for other things. And with just 1 A/C running the wife gets hot and cranky and we all know what that means she`ll look at you and say "don`t even think about it sport". So the only thing you can do to run both A/C`s and make a cup of coffee is go big, I went with 2 Westinghouse 4500`S and never looked back. Both A/C`s can run and all the other stuff you might want even at altitude. Yep, 200 lbs in the bed of the truck, 50 amp paralleled cord to the front of the camper with a transfer switch, but what is cost for comfort?

[432bartman]

The best improvement is to put soft starts on your A/C units, and then get your generator. I'm looking at getting this Duromax generator. It is made in the good ole U.S.A. and right around the corner from where I live in Ontario, California.

https://www.lowes.com/pd/DuroMax-Dur...tor/5005423355

[bshgto]

Originally Posted by 432bartman

The best improvement is to put soft starts on your A/C units, and then get your generator. I'm looking at getting this Duromax generator. It is made in the good ole U.S.A. and right around the corner from where I live in Ontario, California.

https://www.lowes.com/pd/DuroMax-Dur...tor/5005423355

I put the soft starts when I had 2 2000`s it helped but still could only run one A/C at a time. Just out of curiosity I went out today and ran a power test on my propane powered 4500 Westinghouse units with both A/C`s, the converter( pulling 4 amps constant) the refrigerator 3.5 amps off an on and was pulling 30.5 amps. A single 4500 is not going to manage this or adding else. If the out door temps are high amps will rise slightly on the A/C`s. Added the microwave for my coffee or the wife`s coffee pot it brought it up to 43 amps completely out of the single 4500 range. Most manufactures will tell you not to run a generator more than 78% of it`s power or risk self detonation. LOL turned on the water heater and it ran up to 54 amps then the voltage started to drop so I backed off on that. Turned on several lights and 1 TV and it added a couple of amps to the 43 amp load. Checked the power gage on the gens and it said at 45 amps was running at both 4500 gens at 70% load and still had 121 volts. That` going to really suck the gas or propane. On paper I should be able to pull 54 amps with both running at 100% on propane but not recommended by the voltage starting to drop.
\ A fun test so I know what I can and cannot do at any given time.

[mlh]

Quote
Most manufactures will tell you not to run a generator more than 78% of it`s power or risk self detonation.

I believe this is true. My Onan had a major repair at 34 hours. The guy who fixed it said it had been run with too much load. He suggested I look at the air conditioner and sure enough it was pulling way too many amps but it still cooled.

He made his living repairing generators usually Onan. Onan generators have a set of small brushes deep inside that excites the armature. The more power that is called for the higher the voltage on the brushes and the faster they wear out.
Lynwood