Generator Sizing

[aguablanco]

I have been looking for a generator for our TT for a while now and I have a question I hope I can get some answers to. My trailer will most likely need around 3.5k watts to run everything including AC. My question is, if I buy say 4k watts and run everything at once, the generator will run at full RPM to make that happen. 3600 RPM would be fairly noisy as I am not going to buy the Honda's etc. So, if I were to buy say a 6000-7000 watt generator wouldn't that then run at around half the RPM's and be somewhat quieter? Also a little better gas consumption rate? How far off is my thinking?
Thanks,
RichH

[alexleblanc]

I love running my twin 2000I Honda's with the Link kit, on eco mode you can be 10ft away and have a conversation at a normal level. Provides a full 26.6A 120v source. Much quieter running than my fathers 3000w Honda running the same load while we're at the race track.

[aguablanco]

Good morning,
First, I will apologize for posting this on the 5th wheel forum. I need to look closer before posting. Second, thanks to everyone for the great replies, especially Rusty and smkettner for the specific info I needed. I will be buying 2 2000w inverters and the parallel kit to mate them. Seems like the best alternative.
RichH

[aguablanco]

2oldman wrote:
bait post

What is a bait post?
RichH

[RustyJC]

laknox wrote:
Rich, there are generators and there are inverters. A generator runs at full RPM all the time (unless it's one that idles down with no load); an inverter runs at an RPM needed to support the load demanded.

Actually, both are generators. One is a synchronous AC (alternating current) generator that runs at a fixed (synchronous) speed determined by the number of poles in the generator and the desired AC frequency (50Hz or 60Hz). Synchronous speed is calculated as cycles per minute (3000 for 50Hz; 3600 for 60Hz) divided by the number of poles in the generator. For a single pole 60Hz synchronous generator, synchronous speed would be 3600 cycles per minute divided by 1 pole = 3600 RPM.

The other is an inverter generator that inverts DC into PSW AC at a fixed frequency (50Hz or 60Hz), leaving the engine RPM to float with load.

50Hz AC is generally used in many European and Asian countries - North America uses 60Hz AC as a standard.

Rusty

[laknox]

aguablanco wrote:
I have been looking for a generator for our TT for a while now and I have a question I hope I can get some answers to. My trailer will most likely need around 3.5k watts to run everything including AC. My question is, if I buy say 4k watts and run everything at once, the generator will run at full RPM to make that happen. 3600 RPM would be fairly noisy as I am not going to buy the Honda's etc. So, if I were to buy say a 6000-7000 watt generator wouldn't that then run at around half the RPM's and be somewhat quieter? Also a little better gas consumption rate? How far off is my thinking?
Thanks,
RichH

Rich, there are generators and there are inverters. A generator runs at full RPM all the time (unless it's one that idles down with no load); an inverter runs at an RPM needed to support the load demanded. The Yamaha 4k generator runs at a slow 2600 RPM, so makes it more quiet than other standard generators; IIRC, there are several others that are the same way, but they are straight generators, not inverters. Inverters are also a lot more efficient than straight generators.

You might think about 2 3k inverters, paralleled together. Several companies make them.

Lyle

[TGPILOT]

I have an older Honda 3000C, it ran my a/c and a few things on the RV, some of it not all at once. My thinking because it was a bit nosey was maybe a new Honda 300IS would be less nosey (it was) and maybe put out more juice.

Wrong, I was only able to run it about fifteen minutes as it kept going into overload and shut down. Took it to a dealer he said it was running fine, yet it was not doing what my old one was. So, I traded it in on a new Honda 5000IS. Finally got to use it on the way home one night. Plugged it in and it ran twelve hours and ran the a/c, TV, sat. dish and everything else that I had turned on. Love it, yes it's heavier and sits in the back of my truck between the fifth wheel hitch and a tool box chained down. Now have a winch set up to load/unload it. Everything works great.

[Mile_High]

ol Bombero-JC wrote:

Oasisbob wrote:
Please stay with a quiet quality unit. I maybecamping nesxt to you oneday.

And - note spacing between words!

.

hahahah - Mr. fragmenented incomplete sentences giving editing lessons! :R

[ol_Bombero-JC]

Oasisbob wrote:
Please stay with a quiet quality unit. I maybecamping nesxt to you oneday.

Drivel...:R

Maybe you might try to answer his questions...:S

If your hangup is noise - address the issue!

And - note spacing between words!

OP - great GENERATOR info on the *Tech Issues* forum.

Try a search on generator brands, ratings, etc. for more (useful) immediate information.

.

[time2roll]

Only an inverter generator is going to slow down to save fuel and noise at part throttle.

[RustyJC]

pianotuna wrote:
Hi, There are very few 6000 watt inverter generators.

Here's the Honda eu7000is inverter generator rated for 7kW peak, 5.5kW continuous. 60db @ rated load, 52db @ 1/4 throttle. It's fuel injected for excellent fuel efficiency (6.5-18 hours on 5.1 gallons of fuel, depending on load). That's one example.

And I'm not even a Honda user - we run 2 each Yamaha EF2000iS inverter generators in parallel in the bed of the truck to power one of the 5th wheel's A/Cs on the road.

Rusty

[pianotuna]

Hi, There are very few 6000 watt inverter generators. The Yamaha 3000 and the Honda even running flat out are fairly quiet. The 6000 may be louder at 1/4 throttle, which is generally where the eco switch moves the speed to under low load. If the 6k unit is rack mounted (and they are HEAVY) the noise will transmit through the frame of the trailer to the interior.

The lower weight 3000 watt units can be deployed on the ground so that no noise is transmitted via the frame.

Cost of operation may be higher on the 6k units.

I'd add a hybrid inverter and run on the eco setting of the 3k generator.

[RustyJC]

edhensley wrote:
No the speed is set to deliver the proper line frequency, 60 cycles per second, 60 times 60 = 3600 RPM.

True for a synchronous AC generator - speed is constant and torque varies with amperage. Depending on the number of poles in the generator, 60Hz synchronous speed can be 3600, 1800, 1200, 900, 720, 600, 514, 450, 400, 360, 327, etc. RPM.

If you want RPM to vary with amperage, get an adequately sized inverter generator and run it on the Econ setting.

Rusty

[2oldman]

bait post

[Mile_High]

You are asking on the 5th wheel forum, which are folks that typically have provisions for built in gen systems using LP. You probably would have better responses from the TT folks under Travel Trailer.