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Old 06-25-2020, 09:51 AM   #1
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Generator Sizing

I flipped through over 500 threads within multiple forums on this site and didn't find an explanation for my below question. I apologize in advance if this is posted in the wrong section/location.
My TT utilizes 30 amp service.
If I go by the equation 30(A) x 120(V) = 3600(W) I should only need an inverter generator with a minimum running watts rating of 3600(W).
My question is; If I purchase an inverter generator (pure sine wave) with a starting/surge rating of 4500 watts and a run rating of 3700 watts, that has a NEMA TT-30 RV outlet (120V/30A) and does not split wattage rating between outlets, will I be able to run/operate my TT as if it were plugged into shore power? Of do I need to look into a 5500watts or higher inverter generator?

I am not looking for an inverter that only allows a bare minimum of appliances to be used or just big enough to run the A/C. I want something big enough to act as though plugged into shore power but not so big I'm wasting wattage that would never be used.

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Old 06-25-2020, 09:54 AM   #2
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Yes, you will be able to. If you are constantly running higher loads (though I doubt you will be with a 30A unit, which I assume is single AC) you will be adding more stress to that generator than you would a higher wattage model running at a lower percent of its capacity. At least with some simplified assumptions about the two generators. And altitude will affect the ratings, as paul65k noted below. Roughly 3% of power output per 1000ft.

I think you would be safe with the generator you are talking about and wouldn't worry too much about it.

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Old 06-25-2020, 09:59 AM   #3
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Buying the larger generator is a good idea if it will work for you physically!

Generators are less efficient as you go up in altitude so that 4500W generator rated at 3700W is likely to only produce ~3000K or less above 5000'.

5500 is a bit of overkill IMO but if I could make one recommendation it would be to ONLY consider an inverter type generator. The predator 3500 for ~$700 at HF is currently the best bang for the buck and will absolutely be one of the quietest in that size range. Honda and Yamaha are certainly quality generators but this particular Predator has been around for almost 3 years and the reviews are almost universally positive.....and less than 1/2 the price of the other 2 mentioned, it's probably worth a look.
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Old 06-25-2020, 10:26 AM   #4
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I am currently looking at the Briggs & Stratton P4500 from Home Depot.

Operating dB is 60 vs HF Predator (57 dB)
Weight is 115 Lbs. vs HF Predator (100 - 110 Lbs.)
Amps is listed as 30A vs HF Predator (25A)
Runtime @ 1/4 load is 16-hours vs HF Predator (11-hours)
Warranty is 1yr Parts/labor and 2nd/3rd year parts only vs HF Predator (90-days).
Dimensional wise they are about the same size.
Newly released so not many reviews vs HF Predator (3148 reviews - 4.8 stars)

As for the type, I am ONLY considering the inverter type generators. Sound levels and clean power being the two biggest driving points.
If I can determine that the 3000 watts at 25A can handle my TT needs, I might go with the Predator.
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Old 06-25-2020, 11:52 AM   #5
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My 30 amp motor home came with a 4000 watt generator. It runs everything.

Anything more then that, running, not surge rating, would be a waste.

The RV breaker will trip over 30 amps anyway.
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Old 06-25-2020, 12:20 PM   #6
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I found that sizing the generator to my load produces the best fuel efficiency. I mostly run just my computer equipment off of a Yamaha 2000.

But when it is cold, I also want to power a 7/15 amp space heater and the smaller generator is too inefficient at max throttle and I have to dumb down my gear power usage.

The bigger generator (Yamaha 2200) will power the space heater and all computer gear at a better fuel rate.

On the flip-side, running just the computer gear off the Yamaha 2200 uses more gas than my smaller generator. The extra fuel usage adds up over the week(s).

Size the generator to your normal load if you care about fuel efficiency.

BTW, if you go with the Yamaha, they may last much longer. The Yamaha has a 3 year commercial warranty. That is a theoretical 26,280 hour warranty.
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Old 06-25-2020, 01:14 PM   #7
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No matter what generator you buy here's a recommendation:

GET A RUNNING TIME METER AND USE IT (sometimes called an hour meter). An RTM is CHEAP and very easy to install.

Generator maintenance is performed based on running hours. Gennys live and die on their maintenance (or lack of it)... example: 99% of the gennys out there don't have oil filters and depend on oil changes to keep the oil clean.

If you don't have a RTM then you will be guessing on what maintenance is needed and when. And most people under-guess on the running hours.

Here's just one of the youtube videos on RTMs... In it he says that the RTM was under $15 (on amazon).

Here's another video on what looks like the same hour meter...

https: // hobotech.tv/blog/how-to-install-a-cheap-digital-hour-meter-to-any-generator-and-track-run-time

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Old 06-25-2020, 06:28 PM   #8
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I have a firman 3000watt 3300 starting and I can run everything in my 5th wheel just fine, I only have propane water heater. I have tested turning everything on and works fine. The newer models are 3300/3600 which I think would be better. I think a 4500 would be more than enough. Almost got but didnt the remote start, which would be nice but easy enough to step outside and pull a rope.
A factor to consider if you start getting a bigger one. I can pick mine up and fit behind the hitch and it clears the tongue, some bigger ones i had looked out would get crushed back there.
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Old 06-25-2020, 07:49 PM   #9
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Predator has an hour meter, and now mine has a remote wireless start and stop.....
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Old 06-25-2020, 09:04 PM   #10
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My Champion 3100 remote start runs everything I need. I have one a/c and not two.

I do carry a little 1000 watt Sportsman inverter (Home Depot-$199) to charge my batteries and run light loads.

The HFT Predator is a fine and quiet generator also.
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Old 06-26-2020, 06:08 PM   #11
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Ok, so you know you can run any size generator from 100 watts all the way up to 7000 watts. It's just a matter of how much stuff you want to run. My Motorhome came with Onan 4000 watt and it runs everything just fine. However, you do need at least 3100 watts to start an AC......notice I said "start"......the start up surge of power to get it going is much higher then to run it. Running, it uses around 1800 watts. So you can install a SOFT START device in the AC unit so in a sense you can start it AND run it with a 2000 watt generator. You won't run much else though. If you have a SOFT START and larger generator you can start it AND run more things at the same time. Most everyone that has a Travel Trailer or RV with no built in generator use a 3500 watt generator, and there are plenty of those out there......what's the best HONDA, YAMAHA, CHAMPION and on and on. Set your budget, check the prices then watch a YouTube of what you like and if it all looks good.....then go purchase it. I have my onboard 4000 watt Onan and I also carry a backup Honda 2000 watt. Good luck and Happy Trails
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Old 06-29-2020, 08:15 PM   #12
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How about a parallel of honda eu2200i, It gives you flexibility and they are relatively light.
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Old 07-03-2020, 01:10 PM   #13
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I have had 4 Honda generators, a 1000, a 2000, a 3000 and a 6500, all being inverter. I still have the 6500 as it will do what the 1k, 2k, and 3k will do and the other 3 wont do what it will. Its quieter than the other 3 and has more gas capacity.
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Old 07-03-2020, 05:41 PM   #14
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Originally Posted by bob caldwell View Post
Predator has an hour meter, and now mine has a remote wireless start and stop.....
how did you manage that? I have the HF 3500 and may want to take a look at remote start.

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