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Old 04-22-2016, 04:58 AM   #1
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5.5 or 6.5 Onan

Need some input. I'm going to add an Onan to a 2015 GK. The unit has 2-ACs with heat pump/ residential fridge / induction cook top / fireplace / dishwasher / washer - dryer. These are the big electricity consumers. Does anyone out there have a 5.5 and feels at times it just is not keeping up when you are in a full demand load. Onan of Elkahrt suggests any coach over 36' needs a 6.5 and especially a unit that is classified as a full time unit. The different in cost is about $880-$1000 more. They are the same size and the same weight. the only difference is the consumption of gas. Any input would be a help as I want to do it wright the first time.
Here is a second part. Seeing as the truck is a diesel would you install an LP or Diesel. And run a connection from the truck.
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Old 04-22-2016, 11:18 AM   #2
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Personally, I'd go with the 6.5. I have the 5.5 LP version and it will trip a generator breaker when both A/Cs kick in at the same time, but otherwise the 5.5 does fine.

If you are traveling, how would you get the diesel supply? I would think the only choice for a non-toy hauler is LP. I did switch my 30# LPs to 40# cylinders, LP does go fast. (I miss my toy-hauler with the 60 gallons of gas for my old Onan 5.5 gas generator. But at least you won't have to worry about stale fuel with the LP)
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Old 04-22-2016, 02:57 PM   #3
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I had the 5.5 and it did everything I needed it to do. With that said.....if you could run a diesel generator in the bed of your truck (off the trucks fuel tank), I think that could be a very effective setup. That way you wouldn't have to contend with the LP and the diesel fuel wouldn't get stale from lack of use.
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Old 04-22-2016, 05:40 PM   #4
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I haven't added a generator yet. But I am in the process of adding an auxiliary fuel tank to the truck. I will have almost 90 gallons. My plan then is to get a diesel generator, ether portable or in the RW.

I much rather have to find diesel then LP. From what I read on these posts, the generator goes through the LP quickly.

One more thought, before I get the generator, I am trying to decide if I spend the same amount of money on batteries and solar if that would be a better option. Knowing full well that I wouldn't be able to run the AC's on that set up. But then, most nights in many areas get cool enough.

Lithium batteries are starting to come down in price. So may questions.
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Old 04-22-2016, 06:30 PM   #5
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Just as an fyi, there is apparently an option on the Onan generators to have 30/30 Amp breakers; mine are 30/20 and the 20 amp is the one that throws when both A/Cs start up at the same time; but I have learned to wait for a few minutes before turning the other one on.
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Old 04-22-2016, 10:43 PM   #6
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My rig was pre wired for a generator and I had the dealer install the Onan when I made the original purchase. They said the factory would only allow the installation the 5.5 LP. It works fine. I don't have a washer/dryer but everything else and use the generator often when we stop for lunch. Never a problem.
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Old 04-22-2016, 11:09 PM   #7
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Onan makes a 6500 Diesel generator that is the same size and footprint as the gas ones. It is around $7.4 k depending on source and is actually quite ran the gas one.
If I go to a gen set it will be either this one or one mounted in the truck with an umbilical cord to the coach. There is more than enough room to build a mount and put a 15-20 gal diesel tank above the gen.
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Old 04-23-2016, 01:12 AM   #8
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We have the 5.5 with the 30/30 breakers and have run both ACs without a problem. You have to really look at your big loads and guess how many you would ever have running at the same time.
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Old 04-23-2016, 02:11 AM   #9
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We have the 5.5 and last week during PDI, I turned on everything I could to test the generator capacity. Granted the weather wasn't overly warm, but the generator ran everything both A/C's, fireplace, microwave, every light, TV's plus moved the slides in and out. Assuming you turn the A/C's on independently, you shouldn't have a problem with the 5.5. The LP version is surprising quiet, not sure about the DB rating on the diesel version.
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Old 04-23-2016, 03:24 AM   #10
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Ugh, picture how loud an Onan generator is in the bed of a truck with no exhaust - even with one! You need a generator when you can't plug in... like boondocking in state parks or beach campgrounds. Doesn't "sound" practical.
When Redwood OEMs only the LP version, that tells you something...
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