[Dick]

No, you don’t…..Can’t thank you enough.

[Roscoeapproved]

The generator uses 1/10 gal per hour foreach kw of demand. Plus 1/10 gal per hour efficency loss, friction, etc. So using the generator only costs you 1/10 per hour to run. The engine uses the same amount of fuel to turn the alternator and that takes that HP away from the driveline. Meaning a reduction in available power for the driveline. As saiod above there is no frre electricity or lunch… chuckle.

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Jeff and Lindsay

91 Marathon XL

[Larry & Diane]

so Mikee, Does that mean it only uses 1/10 gal per hour at speed with no load? Jeff

[Archived]

Volts X Amps = Watts

12 X 270 = 3240

120 X 27 = 3240

Theoretically the 12 volt/270 amp 50DN can create only 3,240 watts of power, which is only 27 amps at 120 volts. All this is done with the 50DN alternator drawing its biggiest load on the bus engine and creating the maximum amount of heat.

There should be some loss of efficiency as the electricity goes through the inverters and maybe due to the length of the wires from the back of the coach to the house batteries and over to the Cruise-Air, so its likely that there is less than 27 amps available to the coach 120 volt system. If that efficiency factor is 90%, then the available 120 volt amps drops down to 24.3. I don’t know off hand what a Cruise-Air draws after start-up. Keep in mind that if the C-A is running off the inverter, its competing for “watts” with everything else tied into the 120 volt system and “on” as you go down the road. All of my assumptions presume that everything is work in a “perfect state”, there has been no system or component degradation.

I’m not an electrician nor an electrical engineer. I likely learned the electrical formula above in a physics class many years ago when I learned about electricity. Hopefully one or more of the experts on the Forum will validate or correct what I’ve written.

[Dick]

All kidding aside the decision regarding the use of generator or inverters is to a large extent determined by how the coach was set up originally.

According to Inverter Services the inverters of today (pure sine wave) are not well designed to handle the initial inrush as the older inverters were. But the converters who use shells not equipped with OTR and who realize the use of inverters for A/C is likely, are getting shells with multiple alternators, 24V house systems, and multiple inverters so the loads on alternators and inverters is less of an issue.

Older coaches, especially with 12V systems may be able to run an A/C from the inverter but as owners it is important to look at the entire system, and not just the inverters. Some systems are set up so the inverters are handling dedicated circuits so that means the A/C load is all on one inverter. Some are set up with inverters piggy backed so you have the load spread out. But if the coach has only one alternator dedicated to the house regardless of how many inverters or batteries that single alternator shoulders the entire load.

So in some cases it makes perfect sense to run the generator, in others it is less clear. What is important is that if the generator is running as a matter of course there is no problem running every A/C and device and enjoying all the features of the coach. Just as a point of reference if we want to conservatively estimate our engine hours we can use 50 MPH. It is likely less, but that is a good number. If you drive the coach 10,000 miles annually you are using the generator about 200 hours. Throw in another 100 hours just to cover the time you dry camp or run it while waiting for a campsite. If your total annual generator use is 300 hours, you can plan on replacing it in 100 years.

If you go wild and crazy and use it 600 hours annually you better start saving because now you might have to consider replacing it in 50 years. Entertainer coaches typically start a generator at the beginning of a tour and run one of the two on board until it needs service and then switches to the other. It is not unusual for those to have 30,000 to 40,000 hours and still be performing very well.

So my point is we are all better off running our generators long and hard.

[Kim]

Marius, I think you made the wise decision. Let me share my experience with the 1990 CC generator layout, assuming yours is the same as mine was. The gen is cooled by air sucked through the radiator via a fiberglass shroud over the radiator with its opening at the bottom on the passenger side. Cooling air is sucked though the complartment, and thus the radiator, by a large squirrel cage fan which exhausts out the bottom of the bus on the driver side. I found that over time my gen started running hotter and hotter, to the point that it would shut down on super hot days while in motion. Radiator flush and service did not fix it. We eventually realized that either the squirrel cage was not as effective as it had been, or air was somehow being sucked into the compartment without going through the radiator. The fan checked out ok and we could not find any obvious air leaks. We solved the problem by mounting a couple of electric automotive cooling fans on the inside of the radiator, which assisted the squirrel cage and assured that air was going through the radiator. Something to consider if yours runs hot.

[Harry]

Thank you, definitely will be looking into that. Have not been running it much, it is already in the building getting the interior redone and then moving onto the outside things.

When I tried it out, it looked to me that the Squarel Cage fan on the driver side was the one sucking the air into the compartment, pressurizing it and the hot air expelled after being channeled through the radiator, into the shroud and expelled at the bottom on passenger side. I can see where some electric fans on the radiator would help create the flow through the radiator.

I have to find the rubber/foam/blanket material to re-line the whole compartment and sort out this electrical Stop issue I have.

Noticed today that if I engage the Generator boost switch (to help start it when the Gen battery is weak), the main 12V ressetable fuse pops due to overload. After a few seconds 12v power comes back on and everythin works. That tells me that I may have a short or a problem in the 12v boost cable that goes directly to the Gen battery…..never ending issues to sort out….Fun !