How much power do I need from my generator?

[stimm]

Hi all,

We have a 2013 Flying Cloud 27. We currently have a 2,200 (peak) Chinese brand generator that is useless. We are looking to get a generator (or two in parallel) powerful enough to run the AC and maybe the microwave or other appliances at the same time. According to Honda's website, we would need one with approximately 4,500 starting watts and around 3,000 - 3,500 running watts.

What sizes are others using? Any recommendations? Looking at the champions at Costco as well as running a couple Briggs and Strattons in parallel.

Thanks!

[sgschwend]

The starting watts is referring to the power available to start the AC compressor. A common rule of thumb is your need four times the running current to start a AC unit's compressor. So if the AC draws 10 amps then you would need 40 amps at the beginning to handle the startup load (very short period of time, but necessary to protect the compressor from being over-stressed).

The generator you select would need a good size flywheel effect on the generator engine to accomplish this.

[J. Morgan]

The consensus is generally that a Honda or a Yamaha 3,000 watt "inverter" generator is more than capable of running an air conditioner and all other non heat making loads at the same time.

Most folks seem to use two Honda 2,000 watt inverter generators wired together with a parallel kit.

I use a Yamaha 2,400 inverter generator.


Superat stultitia.

[ROBERTSUNRUS]

Hi, one Yamaha 2400 works for me. My main concern is to run my air conditioner. If you need to use the micro wave, turn your air conditioner off or set it at a low temperature to shut the compressor off until you are done with the micro wave.

[paiceman]

We have run two Honda 2,000 in parallel but not often as we seldom are without electric when camping. By using two 2,000 we have the option of running just one for lights and the televisions when we want just those items. But, as Robertsunrus stated if on generators we have not even tried the microwave with the AC running.

Bud

[CRH]

I have a Champion 3500/4000. It runs my AC with no problems. I paid less than 300 bucks for it. It is not Honda quiet. It is also not Briggs and Stratton loud.... If I were buying new, I would try one of their 3k inverters. They are about 700 bucks...I have had good luck with them. I have a Champion at another piece of property that I run 15 to 20 hours a month. I have been using it 3.5 years with no troubles.

[J. Morgan]

Originally Posted by ROBERTSUNRUS

Hi, one Yamaha 2400 works for me. My main concern is to run my air conditioner. If you need to use the micro wave, turn your air conditioner off or set it at a low temperature to shut the compressor off until you are done with the micro wave.

Bingo!

Me too.


Superat stultitia.

[J. Morgan]

Originally Posted by CRH

I have a Champion 3500/4000. It runs my AC with no problems. I paid less than 300 bucks for it. It is not Honda quiet. It is also not Briggs and Stratton loud.... If I were buying new, I would try one of their 3k inverters. They are about 700 bucks...I have had good luck with them. I have a Champion at another piece of property that I run 15 to 20 hours a month. I have been using it 3.5 years with no troubles.

I think I have the same Champion 3500/4000, it is a good and reliable unit that was cheap. It was a little noisy for parking lot use where I wanted to keep it close though.



Superat stultitia.

[jcwall]

I have the Honda Handi 3,000. It runs the A/C just fine. Until you get to altitude. We were outside of Grand Lake in Colorado and I fired it up to run the generator and it couldn't handle the load. It turns out it really doesn't put out 3.000 watts. It is actually rated lower. Maybe 2,700. Then it loses 3% for every 1,000 feet in altitude. Since we were around 11,000 we were loosing 33% of our power. But needing A/C at a altitude is pretty rare. Works just fine at sea level. So if you are going to be in the mountains you might consider the dual 2,000 Hondas wired together. Then you can just run one to charge up the batteries or run everything but the A/C.

[McDave]

With 2 Yamaha 2kw generators run in parallel, and I believe with the Honda generators as well, you can either run the generators in efficiency mode or full out. Efficiency mode is a lot quieter, and burns less gas. It seems to work well with the microwave, and you can hear the generator revving up when you turn on the microwave. However, I've been told not to run the generator in efficiency mode when starting the A/C, so I always have it full on when I do that. What I'm wondering is whether I can switch the generators to efficiency mode after the A/C starts running? Of course, at some point the A/C will switch itself off and then back on again when the temperature rises. Does this mean I can never safely switch the generators to efficiency mode, because I never know when the A/C is going to cycle off and on?

[Gamehawkers]

Depends on how much of your trailer you want to run at the same time. If you're set on having 50 amps available then take out your wallet and buy a 9000 to 11000 watt unit that runs on diesel. They cost about 75 cents a watt. They are big and will weigh several hundred pounds and will take up a lot of room.
If you want to spend the least and still run at least one of the air conditioning units then two Honda or Yamaha inverter generators connected in parallel is the way to go. Total cost less than $2500.

[stimm]

Hi all,

Thanks for the replies. I checked the specs for what I believe is our AC unit (a Dometic Penguin II 15k BTU) and the compressor is rated with a load of approximately 13 amps. Does this mean I would need 52 amps for starting?

Another idea I had was mounting a 4k Onan in the back of the tow vehicle (pickup) on its own platform.

[ROBERTSUNRUS]

Originally Posted by stimm

Hi all,

Thanks for the replies. I checked the specs for what I believe is our AC unit (a Dometic Penguin II 15k BTU) and the compressor is rated with a load of approximately 13 amps. Does this mean I would need 52 amps for starting?

Another idea I had was mounting a 4k Onan in the back of the tow vehicle (pickup) on its own platform.

Hi, this was one of my thoughts too. I was going to mount an Onan where the spare tire is.

[lewster]

Originally Posted by stimm

Hi all,

Thanks for the replies. I checked the specs for what I believe is our AC unit (a Dometic Penguin II 15k BTU) and the compressor is rated with a load of approximately 13 amps. Does this mean I would need 52 amps for starting?

Another idea I had was mounting a 4k Onan in the back of the tow vehicle (pickup) on its own platform.

Running load for the compressor is 13 amps. You have to add the blower motor to that, which is another 3 or so amps for a total of 16 amps. This is at the standard industry rated reference temperature of 95ºF. If the ambient temperatures are greater than that, it will draw more amperage and if lower, less amperage.

There is a formula for this calculation, but it is approximately 0.1 amps per degree F.

If you look at your data tag on the unit, you will find a rating for LRA or locked rotor amps. This is a good approximation for the required transient load to start the unit. Running amps are what is stated as RLA or 'running load amps' which will be lore in line with the numbers above.

A Yamaha 2400 inverter generator will start and run a 13.5K A/C. You will need a pair of 2000s or a single 3000 watt unit to run a 15K............

Or go lithium with a 300 amp/hour + battery pack, adequate solar charging system and a Magnum 3000 watt hybrid inverter and you can start and run a 15K roof A/C with a single 2000 watt generator all day long!!!

[sgschwend]

Thanks, Lewster. Folks should understand that a lower powered generator will still likely start and run their AC but it will be hard on the AC unit, and also the circuit breaker that may trip in a nuisance way.