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Old 10-29-2013, 09:59 AM   #1
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Engine driven generator

I am fairly new on this forum as well as new to the airstream interstate and my English is not the best so excuse me if I address something what was already somewhere else and for my little awkward
I follow the threads on electricity with Solar upgrades and battery problems as well the unique and intelligent solutions of the participants.
I was wondering if a engine driven generator like the one from Fabco BELT DRIVEN GENERATOR | POWER MITE | UNDER HOOD GENERATOR | FABCO POWER would be a good solution special if you want to use the AC while driving. Would like to get some input form the forum on a solution like this as it seams to me something what would solve a lot of problems and could lead to the elimination of the onboard gas generator.
Looking forward to all your responses.
Thanks
Peter
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Old 10-29-2013, 10:27 AM   #2
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It would have to be a small air conditioner. That unit is 2500 Watt max output. I would expect it to get hot running an AC unit but it is definately better than trying to run something big on an inverter. I would contact the manufacturer and ask them if will run an air conditioner. What are the power requirements of your particular air conditioner?

Perry
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Old 10-29-2013, 10:56 AM   #3
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IIRC, the Onan generator is a 2,500W one the Airstream Interstate and runs a 15,000 BTU A/C unit.
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Old 10-29-2013, 11:00 AM   #4
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Should be doable. The all-electric Roadtrek has an engine-driven generator installed. But the generator is a bit of a parasite; you'll lose a goodly amount of horsepower to the generator that won't be able to go to driving the rear wheels. That could make your Sprinter kind of wimpy with regard to acceleration (more than it already is), and make it less fuel-efficient as well. Not sure I'd like that tradeoff just for the sake of using the rooftop A/C while underway.

Not to mention that with an engine-powered generator in place of the Onan propane generator, you'll have to run your engine any time you want to charge your house batteries. Not the most efficient use of a V-6 diesel engine. And potentially unsafe as well; I can just see someone accidentally knocking into the gearshift while trying to swivel the driver's seat and putting the unit into reverse gear when it should be securely parked.

There's no shortage of small 12vDC air conditioners, especially for boats, that could easily be adapted to an Interstate and tied into the house batteries. Dometic makes one that might fit in an overhead locker, or in that under-floor storage compartment behind the rear seat of an Extended Interstate.
http://www.marineair.com/QBank/EPiSe...-Web_13156.pdf
It's only 3500 BTU, but that would still be 3500 BTU more of cooling than you already have with just your Sprinter's dashboard A/C.
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Old 10-29-2013, 11:32 AM   #5
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is there room to mount it?

read the specs carefully, and compare them to your "normal" engine speed while driving and idling. the table quotes those wattage ratings at 3600 rpm - is that real life for an Interstate?

a real life performance curve from idle speed to road speed will give you a better idea of posssible performance.

I believe that you'll also be needing the optional voltage regulator.

just my opinion, but I think that you could easily chew up an a/c compressor with one of these belt-driven generators.

what does the manufacturer have to say about your application and vehicle?

best,
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Old 10-29-2013, 12:23 PM   #6
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Maybe a better option would be to add another AC compressor to drive a second roof mounted air conditioning unit.
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Old 10-29-2013, 12:57 PM   #7
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That is a good point. This thing produces 2500 W at a certain RPM. It is not like it is hooked to a motor that is always at the same speed. I also question if something that small could maintain that power without overheating.

Perry

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is there room to mount it?

read the specs carefully, and compare them to your "normal" engine speed while driving and idling. the table quotes those wattage ratings at 3600 rpm - is that real life for an Interstate?

a real life performance curve from idle speed to road speed will give you a better idea of posssible performance.

I believe that you'll also be needing the optional voltage regulator.

just my opinion, but I think that you could easily chew up an a/c compressor with one of these belt-driven generators.

what does the manufacturer have to say about your application and vehicle?

best,
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Old 10-29-2013, 01:32 PM   #8
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Maybe a better option would be to add another AC compressor to drive a second roof mounted air conditioning unit.
That might be slightly more efficient than a belt driven generator but in the final analysis 13,500 BTU of cooling is going to take roughly the same amount of energy no matter how it is generated.
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Old 10-29-2013, 01:35 PM   #9
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That might be slightly more efficient than a belt driven generator but in the final analysis 13,500 BTU of cooling is going to take roughly the same amount of energy no matter how it is generated.
But the second roof-mounted A/C doesn't have to be 13,500 BTU if it is to work in conjunction with the dashboard A/C unit while driving down the road. My first post on this thread included a link to product literature for a Dometic 12vDC marine air conditioner that puts out 3,500 BTU and is small enough to fit in a battery box.
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Old 10-29-2013, 02:07 PM   #10
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The blue max has 3000w continues with a max of 4500w. 37amps peak on the blue max and a 29amps on the standard continues and the set up is with the belt driven system that the generator runs 3600rpm and the engine between 1200 and 1800 rpm.
It takes about 7hp under full load and I agree an voltage regulator is a must which they offer as an option. If it is not on it does not draw the power.
I did contact the manufacturer but did not hear back yet.
There is plenty of room in the engine bay and I may have to install a high idle device to prevent engine damage.
Running the AC is only one benefit as you also could have your tank heater on as well as your hot water heater if you want to use the Interstate in the winter time. You could also run a electrical heat at night with the quite engine running and not the noisy onboard generator.
I understand definitely not an efficient way of using the engine but better then lying awake all night with the generator running. Or having to run AC for a few hours to cool the inside down.
It is also nice for a quick stop to use the microwave without having to start the generator just as an addition to the generator.
If I look at a Solar upgrade and this from the cost it is about the same but I think the engine generator is more versatile.
Thanks for all the good opinions and I will report on what the manufacturer is saying.
Thanks
Peter
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Old 10-29-2013, 03:03 PM   #11
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I haven't looked closely at the link, but I looked at something similar for the B190 and rejected it because it works by running the engine at a certain speed - i.e., you can't use it while driving. This one might be different, but definitely check that.
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Old 10-29-2013, 04:06 PM   #12
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Thanks Skater I will defiantly check into this. This is one of my question I had to the manufacturer and I waiting for a replay.
it is used with ambulances and fire trucks and Roadtrek uses something similar too which make me think it could work.
But I guess that what the forum is all about getting all the different opinion to help to make the best decision.
thanks
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Old 10-30-2013, 06:25 AM   #13
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I'm not an expert on this, but I think the issue is that generators produce 60 Hz based on the speed at which they're running. If the speed can vary independently of the load on the generator, then there would need to be a fairly complex device (an inverter) to ensure you still get 60 Hz out, which adds cost - this is why the Honda/Yamaha inverter generators are so expensive compared to the "industrial" generators you can buy for a couple hundred bucks.

However, if you can predetermine the speed at which the generator will be running, you can set it up so that it produces 60 Hz. It's not as "clean" as power from the power plant or an inverter generator, but most devices you'd be running won't care - it's only electronic devices like laptops that start to get funky.

I think. There are people here who understand generators far better than I do - hopefully one will jump in and correct this post.

I went through this kind of research when my Onan 2600 in the B190 died. I came to the conclusion the best solution was another Onan 2600. Unfortunately I was never totally thrilled with that solution - it was often hard to start, used oil, and would sometimes stall - but it was still the best solution.
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Old 10-30-2013, 09:25 AM   #14
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Generators are typically designed to run at a fixed speed in order to produce the 60 cycles. We are talking about standard mechanical generators, not inverter generators.
A 2 pole generator must run at 3,600 RPM; a 4 pole generator must run at 1,800 RPM.
Any variance will cause the frequency to change in proportion to the speed.
The voltage will also change in proportion to the speed.
For example: if you were to run a 2 pole 120 volt generator at 1,800 rpm. The output would be 60 volts at 30 Hz. If it were a 1,000 watt generator at speed; at half speed it will produce 1/2 of the power or 500 watts.
Motors run by a generator would typically not be damaged, because the volts per cycle ratio remains the same. The motor would not produce the full HP at a lower speed.
Chances are good, that anything electronic would be damaged, or at least not function properly because of the low voltage
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