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Generator Use
At the Autofest Carlisle event some of us opted to park on a taxiway and run our generators for the duration of the show. We decided on 6 AM to 10 PM operating hours. I had previously determined my generator fuel consumption and I wanted to refigure it to see if it is staying about the same. The problem this time was I couldn’t fuel near the venue so I had to consider a blend of driving and generator use for the calculations.
I had a total of 504 miles of driving to and from the truck stop. I had 83 total generator hours. My historical mileage for the last year is 6.5 MPG. I took on 100.8 gallons and using my mileage I should have used about 77.5 gallons to drive the 504 miles. that leaves about 23 gallons to run the generator 83 hours. My math tells me that is about .28 gallons per hour, compared to my previous .41 gallons per hour. I don’t believe it but have no way of verifying or refuting the numbers.
I couldn’t add another tenth of a gallon of fuel. I tried. I doubt if my mileage was greater than my historical average that I used because I was towing a 6700 pound Hummer and was using OTR on the southbound leg. I would expect the fuel consumption of the generator to be better than the previous calculation because while we were running at least three of our Cruisairs the temps were lower and the AC units were not always cooling the coach.
My conclusion however is that the fuel cost of running our generators is cheap. At todays prices it is not unreasonable to anticipate a cost of $.74 to $1.08 per hour. That is cheap comfort especially compared to my cost per hour of driving of about $25 just for the fuel I burn each hour.
I am not usually an advocate of Walmart camping when an RV park is nearby and available, but since PV park costs have risen to $35 or more being normal running a generator 16 hours daily not only saves us money, it gives our generators badly needed exercise.
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17 Replies
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I am with you, Jon.
When fuel was $4-5 per gallon I exercised my generator 3-4 hours each month and ran when needed but I avoided using it over night. As diesel prices fell I used it more and more. Since we are usually on a straight path to get from point A to point B with as little stopping as possible, we hardly ever spend a night in a $30-50 campground any more.
It is much cheaper and convenient for us to stop at Flying J, a rest area or Walmart and run the generator all night than to pay for an overnight spot in a roadside RV park. Plus I am pleased to miss the hassle of narrow roads, low trees and flakey power. I can also drive later and leave earlier without worrying about waking up my neighbors at a campground.
There are times when an overnight place makes sense. Sometimes we need to take on water, empty our tanks, use free wifi or do laundry. However, most times we crank the generator and enjoy the ambience of an RV spot in the front of a Flying J. My daughter says she knows she is at home when she hears, “Shower number 5 is now ready.”
Davy
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I hope this give comfort and inspiration for folks who might need to run air conditioners to do it from their generator instead of inverters. We were told by the folks from Inverter Service Center that we can run AC units on inverters, but it is hard on them. This is a good excuse to just start generators at the start of a trip, turn on all breakers on our electric panels and live large using all the electric we need.
It was nice at Autofest to not be concerned about power management and being able to have all four AC’s working, along with the washer and dryer, the outside grill and not worry about what would happen if the water pump, aux compressor or the HW tank kicked on all at once. If Tom was nicer to me I would have let him hook up to my buddy plug.
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Wow Jon!
.28 gallons per hour is unbelieveable if you’re running all four A/C’s. When I did that for a 15-hour stretch, I averaged .82. I’ve averaged .25, but I didn’t run my A/C’s.
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I had them all on, but I think my Cruiseairs were cycled off most of the time because the temps were never hot outside. On several days it took a long time for sun to appear either due to fog or cloudy skies.
On the trip that gave me the data to come up with .41 GPH it was a different story. Daytime temps were in the 90’s and the skies were sunny. I don’t believe the .28 GPH, but I cannot come up with a reason other than the bus did not get filled all the way. I think if the fuel island slopes even a little it has a big affect on how much can be put in the tank.
To have a fuel consumption equal to the previous one however I would have had to add 11 gallons more fuel and I don’t think a slight tip to one side on the fuel island would skew the contents that much. My conclusion is our greatest loads are the AC units and if they are not operating as much as they must have been when I got the .41 GPH fuel burn then it is possible our generators are not burning a lot of fuel.
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jon,
thanks fpr sharing . Always good to know. What generator are you running on your rig? Is it the Kabota or Kohler engine ? -
Jon,
I run my generator at any time and exercise it completely. I am concerned if, at night for example, the a/c’s are not on and it is running without a draw on the generator. What is your thought about this?
Pres
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I run mine all the time five days at a time and 24 hours a day and and most of the time it’s 1/2 gallon a hour but my point is who cares we have it and it needs to run , if you can’t afford a gallon a hour maybe something is wrong a pop up camper is in order with solar panels
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As much as I want to load my generator while it is running the harsh reality is there are going to be times when it has almost no load. I have not altered how I use my generators for 27 years and so far I have never had any issues with my generators. My experience per coach is 15 years, 8 1/2 years and 5 years. The reason for more years is I have been a member of the two bus club twice so there is overlap.
When we park overnight our usual practice is to start the generator as soon as we are stopped. Unless it is going to be cold or hot we shut down the generator at bed time. When we get up we restart the generator. Depending on how long it has been since shut down our morning voltage is somewhere between 24.4 to 25 volts. If we plan to drive soon after getting up we do not restart the generator. We run the generator all night, regardless of loads if it is hot so we can keep the whole coach cool, and if it is cold so we can use the Webasto all night. The Webasto, its circulating pump and all the heat exchanger fans draw a lot of DC power so the generator is keeping the batteries charged. Not much of a load, but I have not had issues despite light loads.
We also run it on hot days when we pull into a rest area for lunch. I shut the engine and OTR down and put on several Cruiseairs just to get 1/2 hour or so of run time under load.
My first coach had a 12.5 KW Universal with a Kubota, and the last two coaches have been 20 KW Kohler with Yanmar engines. I have been doing 100 to 150 hour service intervals (depends on usage before we return from a trip) and no issues so far. I do not use auto-start. I do not need to rely on that based on how we use our coach and I do not want to discharge my house batteries as deeply as is required for auto-start to function.
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Jon,
Why not just leave the gen autostart on … in case of an emergency.
For example, you leave your bus for the day, the campground loses power, and you have two A/C’s running. If you’re gone all day, it will only take a couple hours for your A/C’s to totally drain your batteries. If you have the autostart selected, this would save your batteries from totally being discharged.
Where am I going wrong?
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You’re not wrong Tim, I choose to manually operate my gen, but leave the autostart on for the reason you stated. While at Autofest, we left for half the day and I forgot to turn off the salon AC button. Got back about 5 hrs later, gen was running and AC was purring away. Even if I didn’t have the autostart active, my inverters would have shut everything down at 12 volts saving the batteries, but the fridge would be without power.
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You are not wrong Tim, but because of our pup we don’t leave the coach for long periods. If the power were to shut down everything would start drawing the batteries down, but I estimate our longest period away (3 hours) would mean the inverters shut down about an hour before we got back.
I have to test to see if our Cruiseairs will restart if power is temporarily disconnected. They would not on the two previous buses.
At Autofest we had no hookups so the issue is the same if the generator shuts down, but there is no backup then.
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FWIW,
Most of You probably know this already , But for those of You who Don’t ?A generator is supposed to be started with No Load. Then Load it up gradually until You get to Max . And in certain situations like cooler temps. It is better to let the Gen Engine come up to operating Temp before applying Heavy Loads. Think About Your Coach engine , You would not start up cold , And Take off and Put heavy loads on it until it is up to Temp ? Reverse order for Gen Shutdown. Decrease loads until You get to Zero , Let run for a few Minutes to rest. Then shut down. Starting Your Generator with a Load on it will Reduce the Life span of its Engine.
I will engage Autostart ( YAY , It Works ) if I am going to be away for several Hours. For the Groceries in the Fridge. And just have House Battery chargers and Fridge turned on. Therefore applying A Small load to Gen on Startup. It does not take very long to cool My Coach down even on a Hot day . By Starting Engine and Running OTR Air and Turning on 3 Cruise Airs. 30 Minutes maybe to get comfortable ? Depending on Ambient Temp. And Yes I know that drawing the Batteries down to Autostart Voltage will cost Me a few Charging cycles in the life of the House Batteries. But A Cold Beer and fresh Groceries are Priority ! Eat , Drink and Be Merry < Buy More Batteries Later ! Safe Travels,
Rocky -
I found Jon’s post interesting and containing valuable information. I’ve often wondered how much fuel the generator takes, now I know. Consistent with other reports I’ve heard. It would be nice if the generator procvided some kind of indication of its fuel consumption.
I rarely if ever turn the WatchDog off. The reason for this is that we dry camp at race tracks, rest areas, Wal-Marts, etc. and I don’t want to run the house batteries down too far. The WatchDog is the only way to ensure the batteries don’t go down too far in spite of me trying to be diligent about managing them. We can’t run our Cruise-Airs off the house batteries, so we don’t have to deal with that. Cruise-Airs are shore power or generator only.
I’ve come up to the coach with the generator unexpectedly running (as a result of the WatchDog kicking in) …
1. At the race track after someone left the coach with all the lights on (only partically converted to LED) and probably not running the generator long enough in the morning after getting up. If there are other campers/RVer’s near the coach I’m very mindful of their comfort and use the generator sparingly.
2. After coming home at night when its dark and raining, parking the coach, getting the “stuff” out of the coach and into the house, and forgetting to plug the shore power in … next morning I walk outside the house and can hear the generator singing away.
All that said, I’ve learned some things about the WatchDog and the various charging systems on the coach from the various posters on the PC Forum (specifically Jon and Tom):
1. The alternator(s) on the Detroit Diesel is not capable of bringing the 8D AGM LifeLine house batteries up to full voltage. I can’t offhand remember the max voltage available from the DD alternator, but only the onboard 20kW generator and the invertors using shore power can take the 8D’s to full charge. So after driving the coach all day from 9am to 9pm or 10pm the house batteries should be topped off using the generator before retiring for the night when dry camping at the track, Wal-Mart, or a rest stop.
2. The WatchDog starts the generator to recharge the 8D house batteries at too low of voltage. Again I can’t remember the actual number that WatchDog starts the generator at, but it’s below the voltage recommended by AGM battery expert Tom Chilcotte. Its my understanding that the WatchDog genny start voltage is not adjustable, but a resistor in the WatchDog can be changed out to increase the house battery voltage that the genny will fire up. I’m looking to make this change.
So that’s how I manage the generator and the batteries.
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Dick is proving there is no right way to do things and based on how he uses his coach his methods work for him.
And Rocky is right that starting or stopping the generator under loads is not the best thing in the world to be doing, and that also applies to plugging into shore power. Remove all loads when connecting or disconnecting from shore power.
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A rule of thumb you can use for generator fuel consumption is 1/10 per hour no load, this is for friction loss, etc of the generator itself. After that add 1/10 gallon per hour per KW of load. Using this rule a 5 KW load would be .5 gph.
Hope this helps.
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